feat(mpc-system): integrate reliability mechanisms and enable party-driven architecture

- Enable SubscribeSessionEvents for automatic session participation
- Integrate heartbeat mechanism with pending message count
- Add ACK sending after message receipt for reliable delivery
- Add party activity tracking in session coordinator
- Add CountPendingByParty for heartbeat response
- Add retry package with exponential backoff for gRPC clients
- Add memory-based message broker and event publisher adapters
- Add account service integration for keygen completion
- Add party timeout checking background job
- Add notification service stub for future implementation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/.claude/settings.local.json

@@ -16,7 +16,9 @@
       "Bash(powershell -Command:*)",
       "Bash(go build:*)",
       "Bash(git add:*)",
-      "Bash(git commit:*)"
+      "Bash(git commit:*)",
+      "Bash(git push:*)",
+      "Bash(git pull:*)"
     ],
     "deny": [],
     "ask": []

backend/mpc-system/api/grpc/coordinator/v1/session_coordinator.pb.go

@@ -1,7 +1,7 @@
 // Code generated by protoc-gen-go. DO NOT EDIT.
 // versions:
 // 	protoc-gen-go v1.36.10
-// 	protoc        v3.12.4
+// 	protoc        v6.33.1
 // source: api/proto/session_coordinator.proto
 
 package coordinator
@@ -24,12 +24,13 @@ const (
 // CreateSessionRequest creates a new MPC session
 type CreateSessionRequest struct {
 	state            protoimpl.MessageState `protogen:"open.v1"`
-	SessionType      string                 `protobuf:"bytes,1,opt,name=session_type,json=sessionType,proto3" json:"session_type,omitempty"` // "keygen" or "sign"
+	SessionType      string                 `protobuf:"bytes,1,opt,name=session_type,json=sessionType,proto3" json:"session_type,omitempty"`                   // "keygen" or "sign"
-	ThresholdN       int32                  `protobuf:"varint,2,opt,name=threshold_n,json=thresholdN,proto3" json:"threshold_n,omitempty"`   // Total number of parties
+	ThresholdN       int32                  `protobuf:"varint,2,opt,name=threshold_n,json=thresholdN,proto3" json:"threshold_n,omitempty"`                     // Total number of parties
-	ThresholdT       int32                  `protobuf:"varint,3,opt,name=threshold_t,json=thresholdT,proto3" json:"threshold_t,omitempty"`   // Minimum required parties
+	ThresholdT       int32                  `protobuf:"varint,3,opt,name=threshold_t,json=thresholdT,proto3" json:"threshold_t,omitempty"`                     // Minimum required parties
-	Participants     []*ParticipantInfo     `protobuf:"bytes,4,rep,name=participants,proto3" json:"participants,omitempty"`
+	Participants     []*ParticipantInfo     `protobuf:"bytes,4,rep,name=participants,proto3" json:"participants,omitempty"`                                    // Optional: if empty, coordinator selects automatically
 	MessageHash      []byte                 `protobuf:"bytes,5,opt,name=message_hash,json=messageHash,proto3" json:"message_hash,omitempty"`                   // Required for sign sessions
 	ExpiresInSeconds int64                  `protobuf:"varint,6,opt,name=expires_in_seconds,json=expiresInSeconds,proto3" json:"expires_in_seconds,omitempty"` // Session expiration time
+	PartyComposition *PartyComposition      `protobuf:"bytes,7,opt,name=party_composition,json=partyComposition,proto3" json:"party_composition,omitempty"`    // Optional: party composition requirements for auto-selection
 	unknownFields    protoimpl.UnknownFields
 	sizeCache        protoimpl.SizeCache
 }
@@ -106,6 +107,74 @@ func (x *CreateSessionRequest) GetExpiresInSeconds() int64 {
 	return 0
 }
 
+func (x *CreateSessionRequest) GetPartyComposition() *PartyComposition {
+	if x != nil {
+		return x.PartyComposition
+	}
+	return nil
+}
+
+// PartyComposition specifies requirements for automatic party selection
+type PartyComposition struct {
+	state           protoimpl.MessageState `protogen:"open.v1"`
+	PersistentCount int32                  `protobuf:"varint,1,opt,name=persistent_count,json=persistentCount,proto3" json:"persistent_count,omitempty"` // Number of persistent parties (store shares in DB)
+	DelegateCount   int32                  `protobuf:"varint,2,opt,name=delegate_count,json=delegateCount,proto3" json:"delegate_count,omitempty"`       // Number of delegate parties (return shares to user)
+	TemporaryCount  int32                  `protobuf:"varint,3,opt,name=temporary_count,json=temporaryCount,proto3" json:"temporary_count,omitempty"`    // Number of temporary parties
+	unknownFields   protoimpl.UnknownFields
+	sizeCache       protoimpl.SizeCache
+}
+
+func (x *PartyComposition) Reset() {
+	*x = PartyComposition{}
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[1]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *PartyComposition) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*PartyComposition) ProtoMessage() {}
+
+func (x *PartyComposition) ProtoReflect() protoreflect.Message {
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[1]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use PartyComposition.ProtoReflect.Descriptor instead.
+func (*PartyComposition) Descriptor() ([]byte, []int) {
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{1}
+}
+
+func (x *PartyComposition) GetPersistentCount() int32 {
+	if x != nil {
+		return x.PersistentCount
+	}
+	return 0
+}
+
+func (x *PartyComposition) GetDelegateCount() int32 {
+	if x != nil {
+		return x.DelegateCount
+	}
+	return 0
+}
+
+func (x *PartyComposition) GetTemporaryCount() int32 {
+	if x != nil {
+		return x.TemporaryCount
+	}
+	return 0
+}
+
 // ParticipantInfo contains information about a participant
 type ParticipantInfo struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
@@ -117,7 +186,7 @@ type ParticipantInfo struct {
 
 func (x *ParticipantInfo) Reset() {
 	*x = ParticipantInfo{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[1]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[2]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -129,7 +198,7 @@ func (x *ParticipantInfo) String() string {
 func (*ParticipantInfo) ProtoMessage() {}
 
 func (x *ParticipantInfo) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[1]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[2]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -142,7 +211,7 @@ func (x *ParticipantInfo) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use ParticipantInfo.ProtoReflect.Descriptor instead.
 func (*ParticipantInfo) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{1}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{2}
 }
 
 func (x *ParticipantInfo) GetPartyId() string {
@@ -172,7 +241,7 @@ type DeviceInfo struct {
 
 func (x *DeviceInfo) Reset() {
 	*x = DeviceInfo{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[2]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[3]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -184,7 +253,7 @@ func (x *DeviceInfo) String() string {
 func (*DeviceInfo) ProtoMessage() {}
 
 func (x *DeviceInfo) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[2]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[3]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -197,7 +266,7 @@ func (x *DeviceInfo) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use DeviceInfo.ProtoReflect.Descriptor instead.
 func (*DeviceInfo) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{2}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{3}
 }
 
 func (x *DeviceInfo) GetDeviceType() string {
@@ -230,17 +299,19 @@ func (x *DeviceInfo) GetAppVersion() string {
 
 // CreateSessionResponse contains the created session info
 type CreateSessionResponse struct {
-	state         protoimpl.MessageState `protogen:"open.v1"`
+	state           protoimpl.MessageState `protogen:"open.v1"`
-	SessionId     string                 `protobuf:"bytes,1,opt,name=session_id,json=sessionId,proto3" json:"session_id,omitempty"`
+	SessionId       string                 `protobuf:"bytes,1,opt,name=session_id,json=sessionId,proto3" json:"session_id,omitempty"`
-	JoinTokens    map[string]string      `protobuf:"bytes,2,rep,name=join_tokens,json=joinTokens,proto3" json:"join_tokens,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"` // party_id -> join_token
+	JoinTokens      map[string]string      `protobuf:"bytes,2,rep,name=join_tokens,json=joinTokens,proto3" json:"join_tokens,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"` // party_id -> join_token
-	ExpiresAt     int64                  `protobuf:"varint,3,opt,name=expires_at,json=expiresAt,proto3" json:"expires_at,omitempty"`                                                                             // Unix timestamp milliseconds
+	ExpiresAt       int64                  `protobuf:"varint,3,opt,name=expires_at,json=expiresAt,proto3" json:"expires_at,omitempty"`                                                                             // Unix timestamp milliseconds
-	unknownFields protoimpl.UnknownFields
+	SelectedParties []string               `protobuf:"bytes,4,rep,name=selected_parties,json=selectedParties,proto3" json:"selected_parties,omitempty"`                                                            // List of selected party IDs
-	sizeCache     protoimpl.SizeCache
+	DelegatePartyId string                 `protobuf:"bytes,5,opt,name=delegate_party_id,json=delegatePartyId,proto3" json:"delegate_party_id,omitempty"`                                                          // The delegate party ID (if any)
+	unknownFields   protoimpl.UnknownFields
+	sizeCache       protoimpl.SizeCache
 }
 
 func (x *CreateSessionResponse) Reset() {
 	*x = CreateSessionResponse{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[3]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[4]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -252,7 +323,7 @@ func (x *CreateSessionResponse) String() string {
 func (*CreateSessionResponse) ProtoMessage() {}
 
 func (x *CreateSessionResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[3]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[4]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -265,7 +336,7 @@ func (x *CreateSessionResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use CreateSessionResponse.ProtoReflect.Descriptor instead.
 func (*CreateSessionResponse) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{3}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{4}
 }
 
 func (x *CreateSessionResponse) GetSessionId() string {
@@ -289,6 +360,20 @@ func (x *CreateSessionResponse) GetExpiresAt() int64 {
 	return 0
 }
 
+func (x *CreateSessionResponse) GetSelectedParties() []string {
+	if x != nil {
+		return x.SelectedParties
+	}
+	return nil
+}
+
+func (x *CreateSessionResponse) GetDelegatePartyId() string {
+	if x != nil {
+		return x.DelegatePartyId
+	}
+	return ""
+}
+
 // JoinSessionRequest allows a participant to join a session
 type JoinSessionRequest struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
@@ -302,7 +387,7 @@ type JoinSessionRequest struct {
 
 func (x *JoinSessionRequest) Reset() {
 	*x = JoinSessionRequest{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[4]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[5]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -314,7 +399,7 @@ func (x *JoinSessionRequest) String() string {
 func (*JoinSessionRequest) ProtoMessage() {}
 
 func (x *JoinSessionRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[4]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[5]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -327,7 +412,7 @@ func (x *JoinSessionRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use JoinSessionRequest.ProtoReflect.Descriptor instead.
 func (*JoinSessionRequest) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{4}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{5}
 }
 
 func (x *JoinSessionRequest) GetSessionId() string {
@@ -370,7 +455,7 @@ type JoinSessionResponse struct {
 
 func (x *JoinSessionResponse) Reset() {
 	*x = JoinSessionResponse{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[5]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[6]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -382,7 +467,7 @@ func (x *JoinSessionResponse) String() string {
 func (*JoinSessionResponse) ProtoMessage() {}
 
 func (x *JoinSessionResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[5]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[6]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -395,7 +480,7 @@ func (x *JoinSessionResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use JoinSessionResponse.ProtoReflect.Descriptor instead.
 func (*JoinSessionResponse) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{5}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{6}
 }
 
 func (x *JoinSessionResponse) GetSuccess() bool {
@@ -434,7 +519,7 @@ type SessionInfo struct {
 
 func (x *SessionInfo) Reset() {
 	*x = SessionInfo{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[6]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[7]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -446,7 +531,7 @@ func (x *SessionInfo) String() string {
 func (*SessionInfo) ProtoMessage() {}
 
 func (x *SessionInfo) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[6]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[7]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -459,7 +544,7 @@ func (x *SessionInfo) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use SessionInfo.ProtoReflect.Descriptor instead.
 func (*SessionInfo) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{6}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{7}
 }
 
 func (x *SessionInfo) GetSessionId() string {
@@ -516,7 +601,7 @@ type PartyInfo struct {
 
 func (x *PartyInfo) Reset() {
 	*x = PartyInfo{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[7]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[8]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -528,7 +613,7 @@ func (x *PartyInfo) String() string {
 func (*PartyInfo) ProtoMessage() {}
 
 func (x *PartyInfo) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[7]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[8]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -541,7 +626,7 @@ func (x *PartyInfo) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use PartyInfo.ProtoReflect.Descriptor instead.
 func (*PartyInfo) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{7}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{8}
 }
 
 func (x *PartyInfo) GetPartyId() string {
@@ -575,7 +660,7 @@ type GetSessionStatusRequest struct {
 
 func (x *GetSessionStatusRequest) Reset() {
 	*x = GetSessionStatusRequest{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[8]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[9]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -587,7 +672,7 @@ func (x *GetSessionStatusRequest) String() string {
 func (*GetSessionStatusRequest) ProtoMessage() {}
 
 func (x *GetSessionStatusRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[8]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[9]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -600,7 +685,7 @@ func (x *GetSessionStatusRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use GetSessionStatusRequest.ProtoReflect.Descriptor instead.
 func (*GetSessionStatusRequest) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{8}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{9}
 }
 
 func (x *GetSessionStatusRequest) GetSessionId() string {
@@ -624,7 +709,7 @@ type GetSessionStatusResponse struct {
 
 func (x *GetSessionStatusResponse) Reset() {
 	*x = GetSessionStatusResponse{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[9]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[10]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -636,7 +721,7 @@ func (x *GetSessionStatusResponse) String() string {
 func (*GetSessionStatusResponse) ProtoMessage() {}
 
 func (x *GetSessionStatusResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[9]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[10]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -649,7 +734,7 @@ func (x *GetSessionStatusResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use GetSessionStatusResponse.ProtoReflect.Descriptor instead.
 func (*GetSessionStatusResponse) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{9}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{10}
 }
 
 func (x *GetSessionStatusResponse) GetStatus() string {
@@ -700,7 +785,7 @@ type ReportCompletionRequest struct {
 
 func (x *ReportCompletionRequest) Reset() {
 	*x = ReportCompletionRequest{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[10]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[11]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -712,7 +797,7 @@ func (x *ReportCompletionRequest) String() string {
 func (*ReportCompletionRequest) ProtoMessage() {}
 
 func (x *ReportCompletionRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[10]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[11]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -725,7 +810,7 @@ func (x *ReportCompletionRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use ReportCompletionRequest.ProtoReflect.Descriptor instead.
 func (*ReportCompletionRequest) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{10}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{11}
 }
 
 func (x *ReportCompletionRequest) GetSessionId() string {
@@ -767,7 +852,7 @@ type ReportCompletionResponse struct {
 
 func (x *ReportCompletionResponse) Reset() {
 	*x = ReportCompletionResponse{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[11]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[12]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -779,7 +864,7 @@ func (x *ReportCompletionResponse) String() string {
 func (*ReportCompletionResponse) ProtoMessage() {}
 
 func (x *ReportCompletionResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[11]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[12]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -792,7 +877,7 @@ func (x *ReportCompletionResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use ReportCompletionResponse.ProtoReflect.Descriptor instead.
 func (*ReportCompletionResponse) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{11}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{12}
 }
 
 func (x *ReportCompletionResponse) GetSuccess() bool {
@@ -819,7 +904,7 @@ type CloseSessionRequest struct {
 
 func (x *CloseSessionRequest) Reset() {
 	*x = CloseSessionRequest{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[12]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[13]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -831,7 +916,7 @@ func (x *CloseSessionRequest) String() string {
 func (*CloseSessionRequest) ProtoMessage() {}
 
 func (x *CloseSessionRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[12]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[13]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -844,7 +929,7 @@ func (x *CloseSessionRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use CloseSessionRequest.ProtoReflect.Descriptor instead.
 func (*CloseSessionRequest) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{12}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{13}
 }
 
 func (x *CloseSessionRequest) GetSessionId() string {
@@ -864,7 +949,7 @@ type CloseSessionResponse struct {
 
 func (x *CloseSessionResponse) Reset() {
 	*x = CloseSessionResponse{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[13]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[14]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -876,7 +961,7 @@ func (x *CloseSessionResponse) String() string {
 func (*CloseSessionResponse) ProtoMessage() {}
 
 func (x *CloseSessionResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[13]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[14]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -889,7 +974,7 @@ func (x *CloseSessionResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use CloseSessionResponse.ProtoReflect.Descriptor instead.
 func (*CloseSessionResponse) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{13}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{14}
 }
 
 func (x *CloseSessionResponse) GetSuccess() bool {
@@ -910,7 +995,7 @@ type MarkPartyReadyRequest struct {
 
 func (x *MarkPartyReadyRequest) Reset() {
 	*x = MarkPartyReadyRequest{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[14]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[15]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -922,7 +1007,7 @@ func (x *MarkPartyReadyRequest) String() string {
 func (*MarkPartyReadyRequest) ProtoMessage() {}
 
 func (x *MarkPartyReadyRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[14]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[15]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -935,7 +1020,7 @@ func (x *MarkPartyReadyRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use MarkPartyReadyRequest.ProtoReflect.Descriptor instead.
 func (*MarkPartyReadyRequest) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{14}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{15}
 }
 
 func (x *MarkPartyReadyRequest) GetSessionId() string {
@@ -965,7 +1050,7 @@ type MarkPartyReadyResponse struct {
 
 func (x *MarkPartyReadyResponse) Reset() {
 	*x = MarkPartyReadyResponse{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[15]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[16]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -977,7 +1062,7 @@ func (x *MarkPartyReadyResponse) String() string {
 func (*MarkPartyReadyResponse) ProtoMessage() {}
 
 func (x *MarkPartyReadyResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[15]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[16]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -990,7 +1075,7 @@ func (x *MarkPartyReadyResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use MarkPartyReadyResponse.ProtoReflect.Descriptor instead.
 func (*MarkPartyReadyResponse) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{15}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{16}
 }
 
 func (x *MarkPartyReadyResponse) GetSuccess() bool {
@@ -1031,7 +1116,7 @@ type StartSessionRequest struct {
 
 func (x *StartSessionRequest) Reset() {
 	*x = StartSessionRequest{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[16]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[17]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -1043,7 +1128,7 @@ func (x *StartSessionRequest) String() string {
 func (*StartSessionRequest) ProtoMessage() {}
 
 func (x *StartSessionRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[16]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[17]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -1056,7 +1141,7 @@ func (x *StartSessionRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use StartSessionRequest.ProtoReflect.Descriptor instead.
 func (*StartSessionRequest) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{16}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{17}
 }
 
 func (x *StartSessionRequest) GetSessionId() string {
@@ -1077,7 +1162,7 @@ type StartSessionResponse struct {
 
 func (x *StartSessionResponse) Reset() {
 	*x = StartSessionResponse{}
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[17]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[18]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -1089,7 +1174,7 @@ func (x *StartSessionResponse) String() string {
 func (*StartSessionResponse) ProtoMessage() {}
 
 func (x *StartSessionResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_session_coordinator_proto_msgTypes[17]
+	mi := &file_api_proto_session_coordinator_proto_msgTypes[18]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -1102,7 +1187,7 @@ func (x *StartSessionResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use StartSessionResponse.ProtoReflect.Descriptor instead.
 func (*StartSessionResponse) Descriptor() ([]byte, []int) {
-	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{17}
+	return file_api_proto_session_coordinator_proto_rawDescGZIP(), []int{18}
 }
 
 func (x *StartSessionResponse) GetSuccess() bool {
@@ -1123,7 +1208,7 @@ var File_api_proto_session_coordinator_proto protoreflect.FileDescriptor
 
 const file_api_proto_session_coordinator_proto_rawDesc = "" +
 	"\n" +
-	"#api/proto/session_coordinator.proto\x12\x12mpc.coordinator.v1\"\x95\x02\n" +
+	"#api/proto/session_coordinator.proto\x12\x12mpc.coordinator.v1\"\xe8\x02\n" +
 	"\x14CreateSessionRequest\x12!\n" +
 	"\fsession_type\x18\x01 \x01(\tR\vsessionType\x12\x1f\n" +
 	"\vthreshold_n\x18\x02 \x01(\x05R\n" +
@@ -1132,7 +1217,12 @@ const file_api_proto_session_coordinator_proto_rawDesc = "" +
 	"thresholdT\x12G\n" +
 	"\fparticipants\x18\x04 \x03(\v2#.mpc.coordinator.v1.ParticipantInfoR\fparticipants\x12!\n" +
 	"\fmessage_hash\x18\x05 \x01(\fR\vmessageHash\x12,\n" +
-	"\x12expires_in_seconds\x18\x06 \x01(\x03R\x10expiresInSeconds\"m\n" +
+	"\x12expires_in_seconds\x18\x06 \x01(\x03R\x10expiresInSeconds\x12Q\n" +
+	"\x11party_composition\x18\a \x01(\v2$.mpc.coordinator.v1.PartyCompositionR\x10partyComposition\"\x8d\x01\n" +
+	"\x10PartyComposition\x12)\n" +
+	"\x10persistent_count\x18\x01 \x01(\x05R\x0fpersistentCount\x12%\n" +
+	"\x0edelegate_count\x18\x02 \x01(\x05R\rdelegateCount\x12'\n" +
+	"\x0ftemporary_count\x18\x03 \x01(\x05R\x0etemporaryCount\"m\n" +
 	"\x0fParticipantInfo\x12\x19\n" +
 	"\bparty_id\x18\x01 \x01(\tR\apartyId\x12?\n" +
 	"\vdevice_info\x18\x02 \x01(\v2\x1e.mpc.coordinator.v1.DeviceInfoR\n" +
@@ -1144,14 +1234,16 @@ const file_api_proto_session_coordinator_proto_rawDesc = "" +
 	"\tdevice_id\x18\x02 \x01(\tR\bdeviceId\x12\x1a\n" +
 	"\bplatform\x18\x03 \x01(\tR\bplatform\x12\x1f\n" +
 	"\vapp_version\x18\x04 \x01(\tR\n" +
-	"appVersion\"\xf0\x01\n" +
+	"appVersion\"\xc7\x02\n" +
 	"\x15CreateSessionResponse\x12\x1d\n" +
 	"\n" +
 	"session_id\x18\x01 \x01(\tR\tsessionId\x12Z\n" +
 	"\vjoin_tokens\x18\x02 \x03(\v29.mpc.coordinator.v1.CreateSessionResponse.JoinTokensEntryR\n" +
 	"joinTokens\x12\x1d\n" +
 	"\n" +
-	"expires_at\x18\x03 \x01(\x03R\texpiresAt\x1a=\n" +
+	"expires_at\x18\x03 \x01(\x03R\texpiresAt\x12)\n" +
+	"\x10selected_parties\x18\x04 \x03(\tR\x0fselectedParties\x12*\n" +
+	"\x11delegate_party_id\x18\x05 \x01(\tR\x0fdelegatePartyId\x1a=\n" +
 	"\x0fJoinTokensEntry\x12\x10\n" +
 	"\x03key\x18\x01 \x01(\tR\x03key\x12\x14\n" +
 	"\x05value\x18\x02 \x01(\tR\x05value:\x028\x01\"\xae\x01\n" +
@@ -1245,55 +1337,57 @@ func file_api_proto_session_coordinator_proto_rawDescGZIP() []byte {
 	return file_api_proto_session_coordinator_proto_rawDescData
 }
 
-var file_api_proto_session_coordinator_proto_msgTypes = make([]protoimpl.MessageInfo, 19)
+var file_api_proto_session_coordinator_proto_msgTypes = make([]protoimpl.MessageInfo, 20)
 var file_api_proto_session_coordinator_proto_goTypes = []any{
 	(*CreateSessionRequest)(nil),     // 0: mpc.coordinator.v1.CreateSessionRequest
-	(*ParticipantInfo)(nil),          // 1: mpc.coordinator.v1.ParticipantInfo
+	(*PartyComposition)(nil),         // 1: mpc.coordinator.v1.PartyComposition
-	(*DeviceInfo)(nil),               // 2: mpc.coordinator.v1.DeviceInfo
+	(*ParticipantInfo)(nil),          // 2: mpc.coordinator.v1.ParticipantInfo
-	(*CreateSessionResponse)(nil),    // 3: mpc.coordinator.v1.CreateSessionResponse
+	(*DeviceInfo)(nil),               // 3: mpc.coordinator.v1.DeviceInfo
-	(*JoinSessionRequest)(nil),       // 4: mpc.coordinator.v1.JoinSessionRequest
+	(*CreateSessionResponse)(nil),    // 4: mpc.coordinator.v1.CreateSessionResponse
-	(*JoinSessionResponse)(nil),      // 5: mpc.coordinator.v1.JoinSessionResponse
+	(*JoinSessionRequest)(nil),       // 5: mpc.coordinator.v1.JoinSessionRequest
-	(*SessionInfo)(nil),              // 6: mpc.coordinator.v1.SessionInfo
+	(*JoinSessionResponse)(nil),      // 6: mpc.coordinator.v1.JoinSessionResponse
-	(*PartyInfo)(nil),                // 7: mpc.coordinator.v1.PartyInfo
+	(*SessionInfo)(nil),              // 7: mpc.coordinator.v1.SessionInfo
-	(*GetSessionStatusRequest)(nil),  // 8: mpc.coordinator.v1.GetSessionStatusRequest
+	(*PartyInfo)(nil),                // 8: mpc.coordinator.v1.PartyInfo
-	(*GetSessionStatusResponse)(nil), // 9: mpc.coordinator.v1.GetSessionStatusResponse
+	(*GetSessionStatusRequest)(nil),  // 9: mpc.coordinator.v1.GetSessionStatusRequest
-	(*ReportCompletionRequest)(nil),  // 10: mpc.coordinator.v1.ReportCompletionRequest
+	(*GetSessionStatusResponse)(nil), // 10: mpc.coordinator.v1.GetSessionStatusResponse
-	(*ReportCompletionResponse)(nil), // 11: mpc.coordinator.v1.ReportCompletionResponse
+	(*ReportCompletionRequest)(nil),  // 11: mpc.coordinator.v1.ReportCompletionRequest
-	(*CloseSessionRequest)(nil),      // 12: mpc.coordinator.v1.CloseSessionRequest
+	(*ReportCompletionResponse)(nil), // 12: mpc.coordinator.v1.ReportCompletionResponse
-	(*CloseSessionResponse)(nil),     // 13: mpc.coordinator.v1.CloseSessionResponse
+	(*CloseSessionRequest)(nil),      // 13: mpc.coordinator.v1.CloseSessionRequest
-	(*MarkPartyReadyRequest)(nil),    // 14: mpc.coordinator.v1.MarkPartyReadyRequest
+	(*CloseSessionResponse)(nil),     // 14: mpc.coordinator.v1.CloseSessionResponse
-	(*MarkPartyReadyResponse)(nil),   // 15: mpc.coordinator.v1.MarkPartyReadyResponse
+	(*MarkPartyReadyRequest)(nil),    // 15: mpc.coordinator.v1.MarkPartyReadyRequest
-	(*StartSessionRequest)(nil),      // 16: mpc.coordinator.v1.StartSessionRequest
+	(*MarkPartyReadyResponse)(nil),   // 16: mpc.coordinator.v1.MarkPartyReadyResponse
-	(*StartSessionResponse)(nil),     // 17: mpc.coordinator.v1.StartSessionResponse
+	(*StartSessionRequest)(nil),      // 17: mpc.coordinator.v1.StartSessionRequest
-	nil,                              // 18: mpc.coordinator.v1.CreateSessionResponse.JoinTokensEntry
+	(*StartSessionResponse)(nil),     // 18: mpc.coordinator.v1.StartSessionResponse
+	nil,                              // 19: mpc.coordinator.v1.CreateSessionResponse.JoinTokensEntry
 }
 var file_api_proto_session_coordinator_proto_depIdxs = []int32{
-	1,  // 0: mpc.coordinator.v1.CreateSessionRequest.participants:type_name -> mpc.coordinator.v1.ParticipantInfo
+	2,  // 0: mpc.coordinator.v1.CreateSessionRequest.participants:type_name -> mpc.coordinator.v1.ParticipantInfo
-	2,  // 1: mpc.coordinator.v1.ParticipantInfo.device_info:type_name -> mpc.coordinator.v1.DeviceInfo
+	1,  // 1: mpc.coordinator.v1.CreateSessionRequest.party_composition:type_name -> mpc.coordinator.v1.PartyComposition
-	18, // 2: mpc.coordinator.v1.CreateSessionResponse.join_tokens:type_name -> mpc.coordinator.v1.CreateSessionResponse.JoinTokensEntry
+	3,  // 2: mpc.coordinator.v1.ParticipantInfo.device_info:type_name -> mpc.coordinator.v1.DeviceInfo
-	2,  // 3: mpc.coordinator.v1.JoinSessionRequest.device_info:type_name -> mpc.coordinator.v1.DeviceInfo
+	19, // 3: mpc.coordinator.v1.CreateSessionResponse.join_tokens:type_name -> mpc.coordinator.v1.CreateSessionResponse.JoinTokensEntry
-	6,  // 4: mpc.coordinator.v1.JoinSessionResponse.session_info:type_name -> mpc.coordinator.v1.SessionInfo
+	3,  // 4: mpc.coordinator.v1.JoinSessionRequest.device_info:type_name -> mpc.coordinator.v1.DeviceInfo
-	7,  // 5: mpc.coordinator.v1.JoinSessionResponse.other_parties:type_name -> mpc.coordinator.v1.PartyInfo
+	7,  // 5: mpc.coordinator.v1.JoinSessionResponse.session_info:type_name -> mpc.coordinator.v1.SessionInfo
-	2,  // 6: mpc.coordinator.v1.PartyInfo.device_info:type_name -> mpc.coordinator.v1.DeviceInfo
+	8,  // 6: mpc.coordinator.v1.JoinSessionResponse.other_parties:type_name -> mpc.coordinator.v1.PartyInfo
-	0,  // 7: mpc.coordinator.v1.SessionCoordinator.CreateSession:input_type -> mpc.coordinator.v1.CreateSessionRequest
+	3,  // 7: mpc.coordinator.v1.PartyInfo.device_info:type_name -> mpc.coordinator.v1.DeviceInfo
-	4,  // 8: mpc.coordinator.v1.SessionCoordinator.JoinSession:input_type -> mpc.coordinator.v1.JoinSessionRequest
+	0,  // 8: mpc.coordinator.v1.SessionCoordinator.CreateSession:input_type -> mpc.coordinator.v1.CreateSessionRequest
-	8,  // 9: mpc.coordinator.v1.SessionCoordinator.GetSessionStatus:input_type -> mpc.coordinator.v1.GetSessionStatusRequest
+	5,  // 9: mpc.coordinator.v1.SessionCoordinator.JoinSession:input_type -> mpc.coordinator.v1.JoinSessionRequest
-	14, // 10: mpc.coordinator.v1.SessionCoordinator.MarkPartyReady:input_type -> mpc.coordinator.v1.MarkPartyReadyRequest
+	9,  // 10: mpc.coordinator.v1.SessionCoordinator.GetSessionStatus:input_type -> mpc.coordinator.v1.GetSessionStatusRequest
-	16, // 11: mpc.coordinator.v1.SessionCoordinator.StartSession:input_type -> mpc.coordinator.v1.StartSessionRequest
+	15, // 11: mpc.coordinator.v1.SessionCoordinator.MarkPartyReady:input_type -> mpc.coordinator.v1.MarkPartyReadyRequest
-	10, // 12: mpc.coordinator.v1.SessionCoordinator.ReportCompletion:input_type -> mpc.coordinator.v1.ReportCompletionRequest
+	17, // 12: mpc.coordinator.v1.SessionCoordinator.StartSession:input_type -> mpc.coordinator.v1.StartSessionRequest
-	12, // 13: mpc.coordinator.v1.SessionCoordinator.CloseSession:input_type -> mpc.coordinator.v1.CloseSessionRequest
+	11, // 13: mpc.coordinator.v1.SessionCoordinator.ReportCompletion:input_type -> mpc.coordinator.v1.ReportCompletionRequest
-	3,  // 14: mpc.coordinator.v1.SessionCoordinator.CreateSession:output_type -> mpc.coordinator.v1.CreateSessionResponse
+	13, // 14: mpc.coordinator.v1.SessionCoordinator.CloseSession:input_type -> mpc.coordinator.v1.CloseSessionRequest
-	5,  // 15: mpc.coordinator.v1.SessionCoordinator.JoinSession:output_type -> mpc.coordinator.v1.JoinSessionResponse
+	4,  // 15: mpc.coordinator.v1.SessionCoordinator.CreateSession:output_type -> mpc.coordinator.v1.CreateSessionResponse
-	9,  // 16: mpc.coordinator.v1.SessionCoordinator.GetSessionStatus:output_type -> mpc.coordinator.v1.GetSessionStatusResponse
+	6,  // 16: mpc.coordinator.v1.SessionCoordinator.JoinSession:output_type -> mpc.coordinator.v1.JoinSessionResponse
-	15, // 17: mpc.coordinator.v1.SessionCoordinator.MarkPartyReady:output_type -> mpc.coordinator.v1.MarkPartyReadyResponse
+	10, // 17: mpc.coordinator.v1.SessionCoordinator.GetSessionStatus:output_type -> mpc.coordinator.v1.GetSessionStatusResponse
-	17, // 18: mpc.coordinator.v1.SessionCoordinator.StartSession:output_type -> mpc.coordinator.v1.StartSessionResponse
+	16, // 18: mpc.coordinator.v1.SessionCoordinator.MarkPartyReady:output_type -> mpc.coordinator.v1.MarkPartyReadyResponse
-	11, // 19: mpc.coordinator.v1.SessionCoordinator.ReportCompletion:output_type -> mpc.coordinator.v1.ReportCompletionResponse
+	18, // 19: mpc.coordinator.v1.SessionCoordinator.StartSession:output_type -> mpc.coordinator.v1.StartSessionResponse
-	13, // 20: mpc.coordinator.v1.SessionCoordinator.CloseSession:output_type -> mpc.coordinator.v1.CloseSessionResponse
+	12, // 20: mpc.coordinator.v1.SessionCoordinator.ReportCompletion:output_type -> mpc.coordinator.v1.ReportCompletionResponse
-	14, // [14:21] is the sub-list for method output_type
+	14, // 21: mpc.coordinator.v1.SessionCoordinator.CloseSession:output_type -> mpc.coordinator.v1.CloseSessionResponse
-	7,  // [7:14] is the sub-list for method input_type
+	15, // [15:22] is the sub-list for method output_type
-	7,  // [7:7] is the sub-list for extension type_name
+	8,  // [8:15] is the sub-list for method input_type
-	7,  // [7:7] is the sub-list for extension extendee
+	8,  // [8:8] is the sub-list for extension type_name
-	0,  // [0:7] is the sub-list for field type_name
+	8,  // [8:8] is the sub-list for extension extendee
+	0,  // [0:8] is the sub-list for field type_name
 }
 
 func init() { file_api_proto_session_coordinator_proto_init() }
@@ -1307,7 +1401,7 @@ func file_api_proto_session_coordinator_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: unsafe.Slice(unsafe.StringData(file_api_proto_session_coordinator_proto_rawDesc), len(file_api_proto_session_coordinator_proto_rawDesc)),
 			NumEnums:      0,
-			NumMessages:   19,
+			NumMessages:   20,
 			NumExtensions: 0,
 			NumServices:   1,
 		},

backend/mpc-system/api/grpc/coordinator/v1/session_coordinator_grpc.pb.go

@@ -1,7 +1,7 @@
 // Code generated by protoc-gen-go-grpc. DO NOT EDIT.
 // versions:
-// - protoc-gen-go-grpc v1.3.0
+// - protoc-gen-go-grpc v1.6.0
-// - protoc             v3.12.4
+// - protoc             v6.33.1
 // source: api/proto/session_coordinator.proto
 
 package coordinator
@@ -15,8 +15,8 @@ import (
 
 // This is a compile-time assertion to ensure that this generated file
 // is compatible with the grpc package it is being compiled against.
-// Requires gRPC-Go v1.32.0 or later.
+// Requires gRPC-Go v1.64.0 or later.
-const _ = grpc.SupportPackageIsVersion7
+const _ = grpc.SupportPackageIsVersion9
 
 const (
 	SessionCoordinator_CreateSession_FullMethodName    = "/mpc.coordinator.v1.SessionCoordinator/CreateSession"
@@ -31,6 +31,8 @@ const (
 // SessionCoordinatorClient is the client API for SessionCoordinator service.
 //
 // For semantics around ctx use and closing/ending streaming RPCs, please refer to https://pkg.go.dev/google.golang.org/grpc/?tab=doc#ClientConn.NewStream.
+//
+// SessionCoordinator service manages MPC sessions
 type SessionCoordinatorClient interface {
 	// Session management
 	CreateSession(ctx context.Context, in *CreateSessionRequest, opts ...grpc.CallOption) (*CreateSessionResponse, error)
@@ -51,8 +53,9 @@ func NewSessionCoordinatorClient(cc grpc.ClientConnInterface) SessionCoordinator
 }
 
 func (c *sessionCoordinatorClient) CreateSession(ctx context.Context, in *CreateSessionRequest, opts ...grpc.CallOption) (*CreateSessionResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
 	out := new(CreateSessionResponse)
-	err := c.cc.Invoke(ctx, SessionCoordinator_CreateSession_FullMethodName, in, out, opts...)
+	err := c.cc.Invoke(ctx, SessionCoordinator_CreateSession_FullMethodName, in, out, cOpts...)
 	if err != nil {
 		return nil, err
 	}
@@ -60,8 +63,9 @@ func (c *sessionCoordinatorClient) CreateSession(ctx context.Context, in *Create
 }
 
 func (c *sessionCoordinatorClient) JoinSession(ctx context.Context, in *JoinSessionRequest, opts ...grpc.CallOption) (*JoinSessionResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
 	out := new(JoinSessionResponse)
-	err := c.cc.Invoke(ctx, SessionCoordinator_JoinSession_FullMethodName, in, out, opts...)
+	err := c.cc.Invoke(ctx, SessionCoordinator_JoinSession_FullMethodName, in, out, cOpts...)
 	if err != nil {
 		return nil, err
 	}
@@ -69,8 +73,9 @@ func (c *sessionCoordinatorClient) JoinSession(ctx context.Context, in *JoinSess
 }
 
 func (c *sessionCoordinatorClient) GetSessionStatus(ctx context.Context, in *GetSessionStatusRequest, opts ...grpc.CallOption) (*GetSessionStatusResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
 	out := new(GetSessionStatusResponse)
-	err := c.cc.Invoke(ctx, SessionCoordinator_GetSessionStatus_FullMethodName, in, out, opts...)
+	err := c.cc.Invoke(ctx, SessionCoordinator_GetSessionStatus_FullMethodName, in, out, cOpts...)
 	if err != nil {
 		return nil, err
 	}
@@ -78,8 +83,9 @@ func (c *sessionCoordinatorClient) GetSessionStatus(ctx context.Context, in *Get
 }
 
 func (c *sessionCoordinatorClient) MarkPartyReady(ctx context.Context, in *MarkPartyReadyRequest, opts ...grpc.CallOption) (*MarkPartyReadyResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
 	out := new(MarkPartyReadyResponse)
-	err := c.cc.Invoke(ctx, SessionCoordinator_MarkPartyReady_FullMethodName, in, out, opts...)
+	err := c.cc.Invoke(ctx, SessionCoordinator_MarkPartyReady_FullMethodName, in, out, cOpts...)
 	if err != nil {
 		return nil, err
 	}
@@ -87,8 +93,9 @@ func (c *sessionCoordinatorClient) MarkPartyReady(ctx context.Context, in *MarkP
 }
 
 func (c *sessionCoordinatorClient) StartSession(ctx context.Context, in *StartSessionRequest, opts ...grpc.CallOption) (*StartSessionResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
 	out := new(StartSessionResponse)
-	err := c.cc.Invoke(ctx, SessionCoordinator_StartSession_FullMethodName, in, out, opts...)
+	err := c.cc.Invoke(ctx, SessionCoordinator_StartSession_FullMethodName, in, out, cOpts...)
 	if err != nil {
 		return nil, err
 	}
@@ -96,8 +103,9 @@ func (c *sessionCoordinatorClient) StartSession(ctx context.Context, in *StartSe
 }
 
 func (c *sessionCoordinatorClient) ReportCompletion(ctx context.Context, in *ReportCompletionRequest, opts ...grpc.CallOption) (*ReportCompletionResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
 	out := new(ReportCompletionResponse)
-	err := c.cc.Invoke(ctx, SessionCoordinator_ReportCompletion_FullMethodName, in, out, opts...)
+	err := c.cc.Invoke(ctx, SessionCoordinator_ReportCompletion_FullMethodName, in, out, cOpts...)
 	if err != nil {
 		return nil, err
 	}
@@ -105,8 +113,9 @@ func (c *sessionCoordinatorClient) ReportCompletion(ctx context.Context, in *Rep
 }
 
 func (c *sessionCoordinatorClient) CloseSession(ctx context.Context, in *CloseSessionRequest, opts ...grpc.CallOption) (*CloseSessionResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
 	out := new(CloseSessionResponse)
-	err := c.cc.Invoke(ctx, SessionCoordinator_CloseSession_FullMethodName, in, out, opts...)
+	err := c.cc.Invoke(ctx, SessionCoordinator_CloseSession_FullMethodName, in, out, cOpts...)
 	if err != nil {
 		return nil, err
 	}
@@ -115,7 +124,9 @@ func (c *sessionCoordinatorClient) CloseSession(ctx context.Context, in *CloseSe
 
 // SessionCoordinatorServer is the server API for SessionCoordinator service.
 // All implementations must embed UnimplementedSessionCoordinatorServer
-// for forward compatibility
+// for forward compatibility.
+//
+// SessionCoordinator service manages MPC sessions
 type SessionCoordinatorServer interface {
 	// Session management
 	CreateSession(context.Context, *CreateSessionRequest) (*CreateSessionResponse, error)
@@ -128,32 +139,36 @@ type SessionCoordinatorServer interface {
 	mustEmbedUnimplementedSessionCoordinatorServer()
 }
 
-// UnimplementedSessionCoordinatorServer must be embedded to have forward compatible implementations.
+// UnimplementedSessionCoordinatorServer must be embedded to have
-type UnimplementedSessionCoordinatorServer struct {
+// forward compatible implementations.
-}
+//
+// NOTE: this should be embedded by value instead of pointer to avoid a nil
+// pointer dereference when methods are called.
+type UnimplementedSessionCoordinatorServer struct{}
 
 func (UnimplementedSessionCoordinatorServer) CreateSession(context.Context, *CreateSessionRequest) (*CreateSessionResponse, error) {
-	return nil, status.Errorf(codes.Unimplemented, "method CreateSession not implemented")
+	return nil, status.Error(codes.Unimplemented, "method CreateSession not implemented")
 }
 func (UnimplementedSessionCoordinatorServer) JoinSession(context.Context, *JoinSessionRequest) (*JoinSessionResponse, error) {
-	return nil, status.Errorf(codes.Unimplemented, "method JoinSession not implemented")
+	return nil, status.Error(codes.Unimplemented, "method JoinSession not implemented")
 }
 func (UnimplementedSessionCoordinatorServer) GetSessionStatus(context.Context, *GetSessionStatusRequest) (*GetSessionStatusResponse, error) {
-	return nil, status.Errorf(codes.Unimplemented, "method GetSessionStatus not implemented")
+	return nil, status.Error(codes.Unimplemented, "method GetSessionStatus not implemented")
 }
 func (UnimplementedSessionCoordinatorServer) MarkPartyReady(context.Context, *MarkPartyReadyRequest) (*MarkPartyReadyResponse, error) {
-	return nil, status.Errorf(codes.Unimplemented, "method MarkPartyReady not implemented")
+	return nil, status.Error(codes.Unimplemented, "method MarkPartyReady not implemented")
 }
 func (UnimplementedSessionCoordinatorServer) StartSession(context.Context, *StartSessionRequest) (*StartSessionResponse, error) {
-	return nil, status.Errorf(codes.Unimplemented, "method StartSession not implemented")
+	return nil, status.Error(codes.Unimplemented, "method StartSession not implemented")
 }
 func (UnimplementedSessionCoordinatorServer) ReportCompletion(context.Context, *ReportCompletionRequest) (*ReportCompletionResponse, error) {
-	return nil, status.Errorf(codes.Unimplemented, "method ReportCompletion not implemented")
+	return nil, status.Error(codes.Unimplemented, "method ReportCompletion not implemented")
 }
 func (UnimplementedSessionCoordinatorServer) CloseSession(context.Context, *CloseSessionRequest) (*CloseSessionResponse, error) {
-	return nil, status.Errorf(codes.Unimplemented, "method CloseSession not implemented")
+	return nil, status.Error(codes.Unimplemented, "method CloseSession not implemented")
 }
 func (UnimplementedSessionCoordinatorServer) mustEmbedUnimplementedSessionCoordinatorServer() {}
+func (UnimplementedSessionCoordinatorServer) testEmbeddedByValue()                            {}
 
 // UnsafeSessionCoordinatorServer may be embedded to opt out of forward compatibility for this service.
 // Use of this interface is not recommended, as added methods to SessionCoordinatorServer will
@@ -163,6 +178,13 @@ type UnsafeSessionCoordinatorServer interface {
 }
 
 func RegisterSessionCoordinatorServer(s grpc.ServiceRegistrar, srv SessionCoordinatorServer) {
+	// If the following call panics, it indicates UnimplementedSessionCoordinatorServer was
+	// embedded by pointer and is nil.  This will cause panics if an
+	// unimplemented method is ever invoked, so we test this at initialization
+	// time to prevent it from happening at runtime later due to I/O.
+	if t, ok := srv.(interface{ testEmbeddedByValue() }); ok {
+		t.testEmbeddedByValue()
+	}
 	s.RegisterService(&SessionCoordinator_ServiceDesc, srv)
 }
 

backend/mpc-system/api/grpc/router/v1/message_router.pb.go

@@ -419,19 +419,83 @@ func (x *GetPendingMessagesResponse) GetMessages() []*MPCMessage {
 	return nil
 }
 
+// NotificationChannel represents a notification channel for offline parties
+// If a party has notification channels, it operates in offline mode (24h async)
+// If no notification channels, it operates in real-time mode (Message Router push)
+type NotificationChannel struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	Email         string                 `protobuf:"bytes,1,opt,name=email,proto3" json:"email,omitempty"`                          // Optional: email address for notifications
+	Phone         string                 `protobuf:"bytes,2,opt,name=phone,proto3" json:"phone,omitempty"`                          // Optional: phone number for SMS notifications
+	PushToken     string                 `protobuf:"bytes,3,opt,name=push_token,json=pushToken,proto3" json:"push_token,omitempty"` // Optional: push notification token (FCM/APNs)
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *NotificationChannel) Reset() {
+	*x = NotificationChannel{}
+	mi := &file_api_proto_message_router_proto_msgTypes[6]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *NotificationChannel) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*NotificationChannel) ProtoMessage() {}
+
+func (x *NotificationChannel) ProtoReflect() protoreflect.Message {
+	mi := &file_api_proto_message_router_proto_msgTypes[6]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use NotificationChannel.ProtoReflect.Descriptor instead.
+func (*NotificationChannel) Descriptor() ([]byte, []int) {
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{6}
+}
+
+func (x *NotificationChannel) GetEmail() string {
+	if x != nil {
+		return x.Email
+	}
+	return ""
+}
+
+func (x *NotificationChannel) GetPhone() string {
+	if x != nil {
+		return x.Phone
+	}
+	return ""
+}
+
+func (x *NotificationChannel) GetPushToken() string {
+	if x != nil {
+		return x.PushToken
+	}
+	return ""
+}
+
 // RegisterPartyRequest registers a party with the router
 type RegisterPartyRequest struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
 	PartyId       string                 `protobuf:"bytes,1,opt,name=party_id,json=partyId,proto3" json:"party_id,omitempty"`       // Unique party identifier
 	PartyRole     string                 `protobuf:"bytes,2,opt,name=party_role,json=partyRole,proto3" json:"party_role,omitempty"` // persistent, delegate, or temporary
 	Version       string                 `protobuf:"bytes,3,opt,name=version,proto3" json:"version,omitempty"`                      // Party software version
+	Notification  *NotificationChannel   `protobuf:"bytes,4,opt,name=notification,proto3" json:"notification,omitempty"`            // Optional: notification channel for offline mode
 	unknownFields protoimpl.UnknownFields
 	sizeCache     protoimpl.SizeCache
 }
 
 func (x *RegisterPartyRequest) Reset() {
 	*x = RegisterPartyRequest{}
-	mi := &file_api_proto_message_router_proto_msgTypes[6]
+	mi := &file_api_proto_message_router_proto_msgTypes[7]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -443,7 +507,7 @@ func (x *RegisterPartyRequest) String() string {
 func (*RegisterPartyRequest) ProtoMessage() {}
 
 func (x *RegisterPartyRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_message_router_proto_msgTypes[6]
+	mi := &file_api_proto_message_router_proto_msgTypes[7]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -456,7 +520,7 @@ func (x *RegisterPartyRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use RegisterPartyRequest.ProtoReflect.Descriptor instead.
 func (*RegisterPartyRequest) Descriptor() ([]byte, []int) {
-	return file_api_proto_message_router_proto_rawDescGZIP(), []int{6}
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{7}
 }
 
 func (x *RegisterPartyRequest) GetPartyId() string {
@@ -480,6 +544,13 @@ func (x *RegisterPartyRequest) GetVersion() string {
 	return ""
 }
 
+func (x *RegisterPartyRequest) GetNotification() *NotificationChannel {
+	if x != nil {
+		return x.Notification
+	}
+	return nil
+}
+
 // RegisterPartyResponse confirms party registration
 type RegisterPartyResponse struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
@@ -492,7 +563,7 @@ type RegisterPartyResponse struct {
 
 func (x *RegisterPartyResponse) Reset() {
 	*x = RegisterPartyResponse{}
-	mi := &file_api_proto_message_router_proto_msgTypes[7]
+	mi := &file_api_proto_message_router_proto_msgTypes[8]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -504,7 +575,7 @@ func (x *RegisterPartyResponse) String() string {
 func (*RegisterPartyResponse) ProtoMessage() {}
 
 func (x *RegisterPartyResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_message_router_proto_msgTypes[7]
+	mi := &file_api_proto_message_router_proto_msgTypes[8]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -517,7 +588,7 @@ func (x *RegisterPartyResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use RegisterPartyResponse.ProtoReflect.Descriptor instead.
 func (*RegisterPartyResponse) Descriptor() ([]byte, []int) {
-	return file_api_proto_message_router_proto_rawDescGZIP(), []int{7}
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{8}
 }
 
 func (x *RegisterPartyResponse) GetSuccess() bool {
@@ -552,7 +623,7 @@ type SubscribeSessionEventsRequest struct {
 
 func (x *SubscribeSessionEventsRequest) Reset() {
 	*x = SubscribeSessionEventsRequest{}
-	mi := &file_api_proto_message_router_proto_msgTypes[8]
+	mi := &file_api_proto_message_router_proto_msgTypes[9]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -564,7 +635,7 @@ func (x *SubscribeSessionEventsRequest) String() string {
 func (*SubscribeSessionEventsRequest) ProtoMessage() {}
 
 func (x *SubscribeSessionEventsRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_message_router_proto_msgTypes[8]
+	mi := &file_api_proto_message_router_proto_msgTypes[9]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -577,7 +648,7 @@ func (x *SubscribeSessionEventsRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use SubscribeSessionEventsRequest.ProtoReflect.Descriptor instead.
 func (*SubscribeSessionEventsRequest) Descriptor() ([]byte, []int) {
-	return file_api_proto_message_router_proto_rawDescGZIP(), []int{8}
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{9}
 }
 
 func (x *SubscribeSessionEventsRequest) GetPartyId() string {
@@ -613,7 +684,7 @@ type SessionEvent struct {
 
 func (x *SessionEvent) Reset() {
 	*x = SessionEvent{}
-	mi := &file_api_proto_message_router_proto_msgTypes[9]
+	mi := &file_api_proto_message_router_proto_msgTypes[10]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -625,7 +696,7 @@ func (x *SessionEvent) String() string {
 func (*SessionEvent) ProtoMessage() {}
 
 func (x *SessionEvent) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_message_router_proto_msgTypes[9]
+	mi := &file_api_proto_message_router_proto_msgTypes[10]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -638,7 +709,7 @@ func (x *SessionEvent) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use SessionEvent.ProtoReflect.Descriptor instead.
 func (*SessionEvent) Descriptor() ([]byte, []int) {
-	return file_api_proto_message_router_proto_rawDescGZIP(), []int{9}
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{10}
 }
 
 func (x *SessionEvent) GetEventId() string {
@@ -721,7 +792,7 @@ type PublishSessionEventRequest struct {
 
 func (x *PublishSessionEventRequest) Reset() {
 	*x = PublishSessionEventRequest{}
-	mi := &file_api_proto_message_router_proto_msgTypes[10]
+	mi := &file_api_proto_message_router_proto_msgTypes[11]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -733,7 +804,7 @@ func (x *PublishSessionEventRequest) String() string {
 func (*PublishSessionEventRequest) ProtoMessage() {}
 
 func (x *PublishSessionEventRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_message_router_proto_msgTypes[10]
+	mi := &file_api_proto_message_router_proto_msgTypes[11]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -746,7 +817,7 @@ func (x *PublishSessionEventRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use PublishSessionEventRequest.ProtoReflect.Descriptor instead.
 func (*PublishSessionEventRequest) Descriptor() ([]byte, []int) {
-	return file_api_proto_message_router_proto_rawDescGZIP(), []int{10}
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{11}
 }
 
 func (x *PublishSessionEventRequest) GetEvent() *SessionEvent {
@@ -767,7 +838,7 @@ type PublishSessionEventResponse struct {
 
 func (x *PublishSessionEventResponse) Reset() {
 	*x = PublishSessionEventResponse{}
-	mi := &file_api_proto_message_router_proto_msgTypes[11]
+	mi := &file_api_proto_message_router_proto_msgTypes[12]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -779,7 +850,7 @@ func (x *PublishSessionEventResponse) String() string {
 func (*PublishSessionEventResponse) ProtoMessage() {}
 
 func (x *PublishSessionEventResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_message_router_proto_msgTypes[11]
+	mi := &file_api_proto_message_router_proto_msgTypes[12]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -792,7 +863,7 @@ func (x *PublishSessionEventResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use PublishSessionEventResponse.ProtoReflect.Descriptor instead.
 func (*PublishSessionEventResponse) Descriptor() ([]byte, []int) {
-	return file_api_proto_message_router_proto_rawDescGZIP(), []int{11}
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{12}
 }
 
 func (x *PublishSessionEventResponse) GetSuccess() bool {
@@ -820,7 +891,7 @@ type GetRegisteredPartiesRequest struct {
 
 func (x *GetRegisteredPartiesRequest) Reset() {
 	*x = GetRegisteredPartiesRequest{}
-	mi := &file_api_proto_message_router_proto_msgTypes[12]
+	mi := &file_api_proto_message_router_proto_msgTypes[13]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -832,7 +903,7 @@ func (x *GetRegisteredPartiesRequest) String() string {
 func (*GetRegisteredPartiesRequest) ProtoMessage() {}
 
 func (x *GetRegisteredPartiesRequest) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_message_router_proto_msgTypes[12]
+	mi := &file_api_proto_message_router_proto_msgTypes[13]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -845,7 +916,7 @@ func (x *GetRegisteredPartiesRequest) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use GetRegisteredPartiesRequest.ProtoReflect.Descriptor instead.
 func (*GetRegisteredPartiesRequest) Descriptor() ([]byte, []int) {
-	return file_api_proto_message_router_proto_rawDescGZIP(), []int{12}
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{13}
 }
 
 func (x *GetRegisteredPartiesRequest) GetRoleFilter() string {
@@ -870,13 +941,14 @@ type RegisteredParty struct {
 	Online        bool                   `protobuf:"varint,3,opt,name=online,proto3" json:"online,omitempty"`                                 // Whether party is currently connected
 	RegisteredAt  int64                  `protobuf:"varint,4,opt,name=registered_at,json=registeredAt,proto3" json:"registered_at,omitempty"` // Unix timestamp milliseconds
 	LastSeenAt    int64                  `protobuf:"varint,5,opt,name=last_seen_at,json=lastSeenAt,proto3" json:"last_seen_at,omitempty"`     // Unix timestamp milliseconds
+	Notification  *NotificationChannel   `protobuf:"bytes,6,opt,name=notification,proto3" json:"notification,omitempty"`                      // Optional: notification channel (if set, party is offline mode)
 	unknownFields protoimpl.UnknownFields
 	sizeCache     protoimpl.SizeCache
 }
 
 func (x *RegisteredParty) Reset() {
 	*x = RegisteredParty{}
-	mi := &file_api_proto_message_router_proto_msgTypes[13]
+	mi := &file_api_proto_message_router_proto_msgTypes[14]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -888,7 +960,7 @@ func (x *RegisteredParty) String() string {
 func (*RegisteredParty) ProtoMessage() {}
 
 func (x *RegisteredParty) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_message_router_proto_msgTypes[13]
+	mi := &file_api_proto_message_router_proto_msgTypes[14]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -901,7 +973,7 @@ func (x *RegisteredParty) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use RegisteredParty.ProtoReflect.Descriptor instead.
 func (*RegisteredParty) Descriptor() ([]byte, []int) {
-	return file_api_proto_message_router_proto_rawDescGZIP(), []int{13}
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{14}
 }
 
 func (x *RegisteredParty) GetPartyId() string {
@@ -939,6 +1011,13 @@ func (x *RegisteredParty) GetLastSeenAt() int64 {
 	return 0
 }
 
+func (x *RegisteredParty) GetNotification() *NotificationChannel {
+	if x != nil {
+		return x.Notification
+	}
+	return nil
+}
+
 // GetRegisteredPartiesResponse returns registered parties
 type GetRegisteredPartiesResponse struct {
 	state         protoimpl.MessageState `protogen:"open.v1"`
@@ -950,7 +1029,7 @@ type GetRegisteredPartiesResponse struct {
 
 func (x *GetRegisteredPartiesResponse) Reset() {
 	*x = GetRegisteredPartiesResponse{}
-	mi := &file_api_proto_message_router_proto_msgTypes[14]
+	mi := &file_api_proto_message_router_proto_msgTypes[15]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -962,7 +1041,7 @@ func (x *GetRegisteredPartiesResponse) String() string {
 func (*GetRegisteredPartiesResponse) ProtoMessage() {}
 
 func (x *GetRegisteredPartiesResponse) ProtoReflect() protoreflect.Message {
-	mi := &file_api_proto_message_router_proto_msgTypes[14]
+	mi := &file_api_proto_message_router_proto_msgTypes[15]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -975,7 +1054,7 @@ func (x *GetRegisteredPartiesResponse) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use GetRegisteredPartiesResponse.ProtoReflect.Descriptor instead.
 func (*GetRegisteredPartiesResponse) Descriptor() ([]byte, []int) {
-	return file_api_proto_message_router_proto_rawDescGZIP(), []int{14}
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{15}
 }
 
 func (x *GetRegisteredPartiesResponse) GetParties() []*RegisteredParty {
@@ -992,6 +1071,449 @@ func (x *GetRegisteredPartiesResponse) GetTotalCount() int32 {
 	return 0
 }
 
+// AcknowledgeMessageRequest acknowledges message receipt
+type AcknowledgeMessageRequest struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	MessageId     string                 `protobuf:"bytes,1,opt,name=message_id,json=messageId,proto3" json:"message_id,omitempty"`          // ID of the message being acknowledged
+	PartyId       string                 `protobuf:"bytes,2,opt,name=party_id,json=partyId,proto3" json:"party_id,omitempty"`                // ID of the party acknowledging
+	SessionId     string                 `protobuf:"bytes,3,opt,name=session_id,json=sessionId,proto3" json:"session_id,omitempty"`          // Session the message belongs to
+	Success       bool                   `protobuf:"varint,4,opt,name=success,proto3" json:"success,omitempty"`                              // True if message was processed successfully
+	ErrorMessage  string                 `protobuf:"bytes,5,opt,name=error_message,json=errorMessage,proto3" json:"error_message,omitempty"` // Error message if processing failed
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *AcknowledgeMessageRequest) Reset() {
+	*x = AcknowledgeMessageRequest{}
+	mi := &file_api_proto_message_router_proto_msgTypes[16]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *AcknowledgeMessageRequest) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*AcknowledgeMessageRequest) ProtoMessage() {}
+
+func (x *AcknowledgeMessageRequest) ProtoReflect() protoreflect.Message {
+	mi := &file_api_proto_message_router_proto_msgTypes[16]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use AcknowledgeMessageRequest.ProtoReflect.Descriptor instead.
+func (*AcknowledgeMessageRequest) Descriptor() ([]byte, []int) {
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{16}
+}
+
+func (x *AcknowledgeMessageRequest) GetMessageId() string {
+	if x != nil {
+		return x.MessageId
+	}
+	return ""
+}
+
+func (x *AcknowledgeMessageRequest) GetPartyId() string {
+	if x != nil {
+		return x.PartyId
+	}
+	return ""
+}
+
+func (x *AcknowledgeMessageRequest) GetSessionId() string {
+	if x != nil {
+		return x.SessionId
+	}
+	return ""
+}
+
+func (x *AcknowledgeMessageRequest) GetSuccess() bool {
+	if x != nil {
+		return x.Success
+	}
+	return false
+}
+
+func (x *AcknowledgeMessageRequest) GetErrorMessage() string {
+	if x != nil {
+		return x.ErrorMessage
+	}
+	return ""
+}
+
+// AcknowledgeMessageResponse confirms acknowledgment
+type AcknowledgeMessageResponse struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	Success       bool                   `protobuf:"varint,1,opt,name=success,proto3" json:"success,omitempty"`
+	Message       string                 `protobuf:"bytes,2,opt,name=message,proto3" json:"message,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *AcknowledgeMessageResponse) Reset() {
+	*x = AcknowledgeMessageResponse{}
+	mi := &file_api_proto_message_router_proto_msgTypes[17]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *AcknowledgeMessageResponse) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*AcknowledgeMessageResponse) ProtoMessage() {}
+
+func (x *AcknowledgeMessageResponse) ProtoReflect() protoreflect.Message {
+	mi := &file_api_proto_message_router_proto_msgTypes[17]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use AcknowledgeMessageResponse.ProtoReflect.Descriptor instead.
+func (*AcknowledgeMessageResponse) Descriptor() ([]byte, []int) {
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{17}
+}
+
+func (x *AcknowledgeMessageResponse) GetSuccess() bool {
+	if x != nil {
+		return x.Success
+	}
+	return false
+}
+
+func (x *AcknowledgeMessageResponse) GetMessage() string {
+	if x != nil {
+		return x.Message
+	}
+	return ""
+}
+
+// GetMessageStatusRequest requests message delivery status
+type GetMessageStatusRequest struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	MessageId     string                 `protobuf:"bytes,1,opt,name=message_id,json=messageId,proto3" json:"message_id,omitempty"`
+	SessionId     string                 `protobuf:"bytes,2,opt,name=session_id,json=sessionId,proto3" json:"session_id,omitempty"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *GetMessageStatusRequest) Reset() {
+	*x = GetMessageStatusRequest{}
+	mi := &file_api_proto_message_router_proto_msgTypes[18]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *GetMessageStatusRequest) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*GetMessageStatusRequest) ProtoMessage() {}
+
+func (x *GetMessageStatusRequest) ProtoReflect() protoreflect.Message {
+	mi := &file_api_proto_message_router_proto_msgTypes[18]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use GetMessageStatusRequest.ProtoReflect.Descriptor instead.
+func (*GetMessageStatusRequest) Descriptor() ([]byte, []int) {
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{18}
+}
+
+func (x *GetMessageStatusRequest) GetMessageId() string {
+	if x != nil {
+		return x.MessageId
+	}
+	return ""
+}
+
+func (x *GetMessageStatusRequest) GetSessionId() string {
+	if x != nil {
+		return x.SessionId
+	}
+	return ""
+}
+
+// MessageDeliveryStatus represents delivery status to a single party
+type MessageDeliveryStatus struct {
+	state          protoimpl.MessageState `protogen:"open.v1"`
+	PartyId        string                 `protobuf:"bytes,1,opt,name=party_id,json=partyId,proto3" json:"party_id,omitempty"`
+	Status         string                 `protobuf:"bytes,2,opt,name=status,proto3" json:"status,omitempty"`                                        // pending, delivered, acknowledged, failed
+	DeliveredAt    int64                  `protobuf:"varint,3,opt,name=delivered_at,json=deliveredAt,proto3" json:"delivered_at,omitempty"`          // Unix timestamp milliseconds
+	AcknowledgedAt int64                  `protobuf:"varint,4,opt,name=acknowledged_at,json=acknowledgedAt,proto3" json:"acknowledged_at,omitempty"` // Unix timestamp milliseconds
+	RetryCount     int32                  `protobuf:"varint,5,opt,name=retry_count,json=retryCount,proto3" json:"retry_count,omitempty"`             // Number of delivery retries
+	unknownFields  protoimpl.UnknownFields
+	sizeCache      protoimpl.SizeCache
+}
+
+func (x *MessageDeliveryStatus) Reset() {
+	*x = MessageDeliveryStatus{}
+	mi := &file_api_proto_message_router_proto_msgTypes[19]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *MessageDeliveryStatus) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*MessageDeliveryStatus) ProtoMessage() {}
+
+func (x *MessageDeliveryStatus) ProtoReflect() protoreflect.Message {
+	mi := &file_api_proto_message_router_proto_msgTypes[19]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use MessageDeliveryStatus.ProtoReflect.Descriptor instead.
+func (*MessageDeliveryStatus) Descriptor() ([]byte, []int) {
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{19}
+}
+
+func (x *MessageDeliveryStatus) GetPartyId() string {
+	if x != nil {
+		return x.PartyId
+	}
+	return ""
+}
+
+func (x *MessageDeliveryStatus) GetStatus() string {
+	if x != nil {
+		return x.Status
+	}
+	return ""
+}
+
+func (x *MessageDeliveryStatus) GetDeliveredAt() int64 {
+	if x != nil {
+		return x.DeliveredAt
+	}
+	return 0
+}
+
+func (x *MessageDeliveryStatus) GetAcknowledgedAt() int64 {
+	if x != nil {
+		return x.AcknowledgedAt
+	}
+	return 0
+}
+
+func (x *MessageDeliveryStatus) GetRetryCount() int32 {
+	if x != nil {
+		return x.RetryCount
+	}
+	return 0
+}
+
+// GetMessageStatusResponse returns message delivery status
+type GetMessageStatusResponse struct {
+	state           protoimpl.MessageState   `protogen:"open.v1"`
+	MessageId       string                   `protobuf:"bytes,1,opt,name=message_id,json=messageId,proto3" json:"message_id,omitempty"`
+	SessionId       string                   `protobuf:"bytes,2,opt,name=session_id,json=sessionId,proto3" json:"session_id,omitempty"`
+	Deliveries      []*MessageDeliveryStatus `protobuf:"bytes,3,rep,name=deliveries,proto3" json:"deliveries,omitempty"`
+	AllAcknowledged bool                     `protobuf:"varint,4,opt,name=all_acknowledged,json=allAcknowledged,proto3" json:"all_acknowledged,omitempty"` // True if all recipients acknowledged
+	unknownFields   protoimpl.UnknownFields
+	sizeCache       protoimpl.SizeCache
+}
+
+func (x *GetMessageStatusResponse) Reset() {
+	*x = GetMessageStatusResponse{}
+	mi := &file_api_proto_message_router_proto_msgTypes[20]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *GetMessageStatusResponse) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*GetMessageStatusResponse) ProtoMessage() {}
+
+func (x *GetMessageStatusResponse) ProtoReflect() protoreflect.Message {
+	mi := &file_api_proto_message_router_proto_msgTypes[20]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use GetMessageStatusResponse.ProtoReflect.Descriptor instead.
+func (*GetMessageStatusResponse) Descriptor() ([]byte, []int) {
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{20}
+}
+
+func (x *GetMessageStatusResponse) GetMessageId() string {
+	if x != nil {
+		return x.MessageId
+	}
+	return ""
+}
+
+func (x *GetMessageStatusResponse) GetSessionId() string {
+	if x != nil {
+		return x.SessionId
+	}
+	return ""
+}
+
+func (x *GetMessageStatusResponse) GetDeliveries() []*MessageDeliveryStatus {
+	if x != nil {
+		return x.Deliveries
+	}
+	return nil
+}
+
+func (x *GetMessageStatusResponse) GetAllAcknowledged() bool {
+	if x != nil {
+		return x.AllAcknowledged
+	}
+	return false
+}
+
+// HeartbeatRequest sends a heartbeat to keep the party alive
+type HeartbeatRequest struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	PartyId       string                 `protobuf:"bytes,1,opt,name=party_id,json=partyId,proto3" json:"party_id,omitempty"`
+	Timestamp     int64                  `protobuf:"varint,2,opt,name=timestamp,proto3" json:"timestamp,omitempty"` // Unix timestamp milliseconds
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *HeartbeatRequest) Reset() {
+	*x = HeartbeatRequest{}
+	mi := &file_api_proto_message_router_proto_msgTypes[21]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *HeartbeatRequest) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*HeartbeatRequest) ProtoMessage() {}
+
+func (x *HeartbeatRequest) ProtoReflect() protoreflect.Message {
+	mi := &file_api_proto_message_router_proto_msgTypes[21]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use HeartbeatRequest.ProtoReflect.Descriptor instead.
+func (*HeartbeatRequest) Descriptor() ([]byte, []int) {
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{21}
+}
+
+func (x *HeartbeatRequest) GetPartyId() string {
+	if x != nil {
+		return x.PartyId
+	}
+	return ""
+}
+
+func (x *HeartbeatRequest) GetTimestamp() int64 {
+	if x != nil {
+		return x.Timestamp
+	}
+	return 0
+}
+
+// HeartbeatResponse confirms heartbeat receipt
+type HeartbeatResponse struct {
+	state           protoimpl.MessageState `protogen:"open.v1"`
+	Success         bool                   `protobuf:"varint,1,opt,name=success,proto3" json:"success,omitempty"`
+	ServerTimestamp int64                  `protobuf:"varint,2,opt,name=server_timestamp,json=serverTimestamp,proto3" json:"server_timestamp,omitempty"` // Server timestamp for clock sync
+	PendingMessages int32                  `protobuf:"varint,3,opt,name=pending_messages,json=pendingMessages,proto3" json:"pending_messages,omitempty"` // Number of pending messages for this party
+	unknownFields   protoimpl.UnknownFields
+	sizeCache       protoimpl.SizeCache
+}
+
+func (x *HeartbeatResponse) Reset() {
+	*x = HeartbeatResponse{}
+	mi := &file_api_proto_message_router_proto_msgTypes[22]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *HeartbeatResponse) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*HeartbeatResponse) ProtoMessage() {}
+
+func (x *HeartbeatResponse) ProtoReflect() protoreflect.Message {
+	mi := &file_api_proto_message_router_proto_msgTypes[22]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use HeartbeatResponse.ProtoReflect.Descriptor instead.
+func (*HeartbeatResponse) Descriptor() ([]byte, []int) {
+	return file_api_proto_message_router_proto_rawDescGZIP(), []int{22}
+}
+
+func (x *HeartbeatResponse) GetSuccess() bool {
+	if x != nil {
+		return x.Success
+	}
+	return false
+}
+
+func (x *HeartbeatResponse) GetServerTimestamp() int64 {
+	if x != nil {
+		return x.ServerTimestamp
+	}
+	return 0
+}
+
+func (x *HeartbeatResponse) GetPendingMessages() int32 {
+	if x != nil {
+		return x.PendingMessages
+	}
+	return 0
+}
+
 var File_api_proto_message_router_proto protoreflect.FileDescriptor
 
 const file_api_proto_message_router_proto_rawDesc = "" +
@@ -1035,12 +1557,18 @@ const file_api_proto_message_router_proto_rawDesc = "" +
 	"\bparty_id\x18\x02 \x01(\tR\apartyId\x12'\n" +
 	"\x0fafter_timestamp\x18\x03 \x01(\x03R\x0eafterTimestamp\"S\n" +
 	"\x1aGetPendingMessagesResponse\x125\n" +
-	"\bmessages\x18\x01 \x03(\v2\x19.mpc.router.v1.MPCMessageR\bmessages\"j\n" +
+	"\bmessages\x18\x01 \x03(\v2\x19.mpc.router.v1.MPCMessageR\bmessages\"`\n" +
+	"\x13NotificationChannel\x12\x14\n" +
+	"\x05email\x18\x01 \x01(\tR\x05email\x12\x14\n" +
+	"\x05phone\x18\x02 \x01(\tR\x05phone\x12\x1d\n" +
+	"\n" +
+	"push_token\x18\x03 \x01(\tR\tpushToken\"\xb2\x01\n" +
 	"\x14RegisterPartyRequest\x12\x19\n" +
 	"\bparty_id\x18\x01 \x01(\tR\apartyId\x12\x1d\n" +
 	"\n" +
 	"party_role\x18\x02 \x01(\tR\tpartyRole\x12\x18\n" +
-	"\aversion\x18\x03 \x01(\tR\aversion\"p\n" +
+	"\aversion\x18\x03 \x01(\tR\aversion\x12F\n" +
+	"\fnotification\x18\x04 \x01(\v2\".mpc.router.v1.NotificationChannelR\fnotification\"p\n" +
 	"\x15RegisterPartyResponse\x12\x18\n" +
 	"\asuccess\x18\x01 \x01(\bR\asuccess\x12\x18\n" +
 	"\amessage\x18\x02 \x01(\tR\amessage\x12#\n" +
@@ -1080,23 +1608,66 @@ const file_api_proto_message_router_proto_rawDesc = "" +
 	"\vrole_filter\x18\x01 \x01(\tR\n" +
 	"roleFilter\x12\x1f\n" +
 	"\vonly_online\x18\x02 \x01(\bR\n" +
-	"onlyOnline\"\x9f\x01\n" +
+	"onlyOnline\"\xe7\x01\n" +
 	"\x0fRegisteredParty\x12\x19\n" +
 	"\bparty_id\x18\x01 \x01(\tR\apartyId\x12\x12\n" +
 	"\x04role\x18\x02 \x01(\tR\x04role\x12\x16\n" +
 	"\x06online\x18\x03 \x01(\bR\x06online\x12#\n" +
 	"\rregistered_at\x18\x04 \x01(\x03R\fregisteredAt\x12 \n" +
 	"\flast_seen_at\x18\x05 \x01(\x03R\n" +
-	"lastSeenAt\"y\n" +
+	"lastSeenAt\x12F\n" +
+	"\fnotification\x18\x06 \x01(\v2\".mpc.router.v1.NotificationChannelR\fnotification\"y\n" +
 	"\x1cGetRegisteredPartiesResponse\x128\n" +
 	"\aparties\x18\x01 \x03(\v2\x1e.mpc.router.v1.RegisteredPartyR\aparties\x12\x1f\n" +
 	"\vtotal_count\x18\x02 \x01(\x05R\n" +
-	"totalCount2\xd0\x05\n" +
+	"totalCount\"\xb3\x01\n" +
+	"\x19AcknowledgeMessageRequest\x12\x1d\n" +
+	"\n" +
+	"message_id\x18\x01 \x01(\tR\tmessageId\x12\x19\n" +
+	"\bparty_id\x18\x02 \x01(\tR\apartyId\x12\x1d\n" +
+	"\n" +
+	"session_id\x18\x03 \x01(\tR\tsessionId\x12\x18\n" +
+	"\asuccess\x18\x04 \x01(\bR\asuccess\x12#\n" +
+	"\rerror_message\x18\x05 \x01(\tR\ferrorMessage\"P\n" +
+	"\x1aAcknowledgeMessageResponse\x12\x18\n" +
+	"\asuccess\x18\x01 \x01(\bR\asuccess\x12\x18\n" +
+	"\amessage\x18\x02 \x01(\tR\amessage\"W\n" +
+	"\x17GetMessageStatusRequest\x12\x1d\n" +
+	"\n" +
+	"message_id\x18\x01 \x01(\tR\tmessageId\x12\x1d\n" +
+	"\n" +
+	"session_id\x18\x02 \x01(\tR\tsessionId\"\xb7\x01\n" +
+	"\x15MessageDeliveryStatus\x12\x19\n" +
+	"\bparty_id\x18\x01 \x01(\tR\apartyId\x12\x16\n" +
+	"\x06status\x18\x02 \x01(\tR\x06status\x12!\n" +
+	"\fdelivered_at\x18\x03 \x01(\x03R\vdeliveredAt\x12'\n" +
+	"\x0facknowledged_at\x18\x04 \x01(\x03R\x0eacknowledgedAt\x12\x1f\n" +
+	"\vretry_count\x18\x05 \x01(\x05R\n" +
+	"retryCount\"\xc9\x01\n" +
+	"\x18GetMessageStatusResponse\x12\x1d\n" +
+	"\n" +
+	"message_id\x18\x01 \x01(\tR\tmessageId\x12\x1d\n" +
+	"\n" +
+	"session_id\x18\x02 \x01(\tR\tsessionId\x12D\n" +
+	"\n" +
+	"deliveries\x18\x03 \x03(\v2$.mpc.router.v1.MessageDeliveryStatusR\n" +
+	"deliveries\x12)\n" +
+	"\x10all_acknowledged\x18\x04 \x01(\bR\x0fallAcknowledged\"K\n" +
+	"\x10HeartbeatRequest\x12\x19\n" +
+	"\bparty_id\x18\x01 \x01(\tR\apartyId\x12\x1c\n" +
+	"\ttimestamp\x18\x02 \x01(\x03R\ttimestamp\"\x83\x01\n" +
+	"\x11HeartbeatResponse\x12\x18\n" +
+	"\asuccess\x18\x01 \x01(\bR\asuccess\x12)\n" +
+	"\x10server_timestamp\x18\x02 \x01(\x03R\x0fserverTimestamp\x12)\n" +
+	"\x10pending_messages\x18\x03 \x01(\x05R\x0fpendingMessages2\xf0\a\n" +
 	"\rMessageRouter\x12W\n" +
 	"\fRouteMessage\x12\".mpc.router.v1.RouteMessageRequest\x1a#.mpc.router.v1.RouteMessageResponse\x12Y\n" +
 	"\x11SubscribeMessages\x12'.mpc.router.v1.SubscribeMessagesRequest\x1a\x19.mpc.router.v1.MPCMessage0\x01\x12i\n" +
-	"\x12GetPendingMessages\x12(.mpc.router.v1.GetPendingMessagesRequest\x1a).mpc.router.v1.GetPendingMessagesResponse\x12Z\n" +
+	"\x12GetPendingMessages\x12(.mpc.router.v1.GetPendingMessagesRequest\x1a).mpc.router.v1.GetPendingMessagesResponse\x12i\n" +
-	"\rRegisterParty\x12#.mpc.router.v1.RegisterPartyRequest\x1a$.mpc.router.v1.RegisterPartyResponse\x12e\n" +
+	"\x12AcknowledgeMessage\x12(.mpc.router.v1.AcknowledgeMessageRequest\x1a).mpc.router.v1.AcknowledgeMessageResponse\x12c\n" +
+	"\x10GetMessageStatus\x12&.mpc.router.v1.GetMessageStatusRequest\x1a'.mpc.router.v1.GetMessageStatusResponse\x12Z\n" +
+	"\rRegisterParty\x12#.mpc.router.v1.RegisterPartyRequest\x1a$.mpc.router.v1.RegisterPartyResponse\x12N\n" +
+	"\tHeartbeat\x12\x1f.mpc.router.v1.HeartbeatRequest\x1a .mpc.router.v1.HeartbeatResponse\x12e\n" +
 	"\x16SubscribeSessionEvents\x12,.mpc.router.v1.SubscribeSessionEventsRequest\x1a\x1b.mpc.router.v1.SessionEvent0\x01\x12l\n" +
 	"\x13PublishSessionEvent\x12).mpc.router.v1.PublishSessionEventRequest\x1a*.mpc.router.v1.PublishSessionEventResponse\x12o\n" +
 	"\x14GetRegisteredParties\x12*.mpc.router.v1.GetRegisteredPartiesRequest\x1a+.mpc.router.v1.GetRegisteredPartiesResponseB;Z9github.com/rwadurian/mpc-system/api/grpc/router/v1;routerb\x06proto3"
@@ -1113,7 +1684,7 @@ func file_api_proto_message_router_proto_rawDescGZIP() []byte {
 	return file_api_proto_message_router_proto_rawDescData
 }
 
-var file_api_proto_message_router_proto_msgTypes = make([]protoimpl.MessageInfo, 16)
+var file_api_proto_message_router_proto_msgTypes = make([]protoimpl.MessageInfo, 24)
 var file_api_proto_message_router_proto_goTypes = []any{
 	(*RouteMessageRequest)(nil),           // 0: mpc.router.v1.RouteMessageRequest
 	(*RouteMessageResponse)(nil),          // 1: mpc.router.v1.RouteMessageResponse
@@ -1121,41 +1692,58 @@ var file_api_proto_message_router_proto_goTypes = []any{
 	(*MPCMessage)(nil),                    // 3: mpc.router.v1.MPCMessage
 	(*GetPendingMessagesRequest)(nil),     // 4: mpc.router.v1.GetPendingMessagesRequest
 	(*GetPendingMessagesResponse)(nil),    // 5: mpc.router.v1.GetPendingMessagesResponse
-	(*RegisterPartyRequest)(nil),          // 6: mpc.router.v1.RegisterPartyRequest
+	(*NotificationChannel)(nil),           // 6: mpc.router.v1.NotificationChannel
-	(*RegisterPartyResponse)(nil),         // 7: mpc.router.v1.RegisterPartyResponse
+	(*RegisterPartyRequest)(nil),          // 7: mpc.router.v1.RegisterPartyRequest
-	(*SubscribeSessionEventsRequest)(nil), // 8: mpc.router.v1.SubscribeSessionEventsRequest
+	(*RegisterPartyResponse)(nil),         // 8: mpc.router.v1.RegisterPartyResponse
-	(*SessionEvent)(nil),                  // 9: mpc.router.v1.SessionEvent
+	(*SubscribeSessionEventsRequest)(nil), // 9: mpc.router.v1.SubscribeSessionEventsRequest
-	(*PublishSessionEventRequest)(nil),    // 10: mpc.router.v1.PublishSessionEventRequest
+	(*SessionEvent)(nil),                  // 10: mpc.router.v1.SessionEvent
-	(*PublishSessionEventResponse)(nil),   // 11: mpc.router.v1.PublishSessionEventResponse
+	(*PublishSessionEventRequest)(nil),    // 11: mpc.router.v1.PublishSessionEventRequest
-	(*GetRegisteredPartiesRequest)(nil),   // 12: mpc.router.v1.GetRegisteredPartiesRequest
+	(*PublishSessionEventResponse)(nil),   // 12: mpc.router.v1.PublishSessionEventResponse
-	(*RegisteredParty)(nil),               // 13: mpc.router.v1.RegisteredParty
+	(*GetRegisteredPartiesRequest)(nil),   // 13: mpc.router.v1.GetRegisteredPartiesRequest
-	(*GetRegisteredPartiesResponse)(nil),  // 14: mpc.router.v1.GetRegisteredPartiesResponse
+	(*RegisteredParty)(nil),               // 14: mpc.router.v1.RegisteredParty
-	nil,                                   // 15: mpc.router.v1.SessionEvent.JoinTokensEntry
+	(*GetRegisteredPartiesResponse)(nil),  // 15: mpc.router.v1.GetRegisteredPartiesResponse
+	(*AcknowledgeMessageRequest)(nil),     // 16: mpc.router.v1.AcknowledgeMessageRequest
+	(*AcknowledgeMessageResponse)(nil),    // 17: mpc.router.v1.AcknowledgeMessageResponse
+	(*GetMessageStatusRequest)(nil),       // 18: mpc.router.v1.GetMessageStatusRequest
+	(*MessageDeliveryStatus)(nil),         // 19: mpc.router.v1.MessageDeliveryStatus
+	(*GetMessageStatusResponse)(nil),      // 20: mpc.router.v1.GetMessageStatusResponse
+	(*HeartbeatRequest)(nil),              // 21: mpc.router.v1.HeartbeatRequest
+	(*HeartbeatResponse)(nil),             // 22: mpc.router.v1.HeartbeatResponse
+	nil,                                   // 23: mpc.router.v1.SessionEvent.JoinTokensEntry
 }
 var file_api_proto_message_router_proto_depIdxs = []int32{
 	3,  // 0: mpc.router.v1.GetPendingMessagesResponse.messages:type_name -> mpc.router.v1.MPCMessage
-	15, // 1: mpc.router.v1.SessionEvent.join_tokens:type_name -> mpc.router.v1.SessionEvent.JoinTokensEntry
+	6,  // 1: mpc.router.v1.RegisterPartyRequest.notification:type_name -> mpc.router.v1.NotificationChannel
-	9,  // 2: mpc.router.v1.PublishSessionEventRequest.event:type_name -> mpc.router.v1.SessionEvent
+	23, // 2: mpc.router.v1.SessionEvent.join_tokens:type_name -> mpc.router.v1.SessionEvent.JoinTokensEntry
-	13, // 3: mpc.router.v1.GetRegisteredPartiesResponse.parties:type_name -> mpc.router.v1.RegisteredParty
+	10, // 3: mpc.router.v1.PublishSessionEventRequest.event:type_name -> mpc.router.v1.SessionEvent
-	0,  // 4: mpc.router.v1.MessageRouter.RouteMessage:input_type -> mpc.router.v1.RouteMessageRequest
+	6,  // 4: mpc.router.v1.RegisteredParty.notification:type_name -> mpc.router.v1.NotificationChannel
-	2,  // 5: mpc.router.v1.MessageRouter.SubscribeMessages:input_type -> mpc.router.v1.SubscribeMessagesRequest
+	14, // 5: mpc.router.v1.GetRegisteredPartiesResponse.parties:type_name -> mpc.router.v1.RegisteredParty
-	4,  // 6: mpc.router.v1.MessageRouter.GetPendingMessages:input_type -> mpc.router.v1.GetPendingMessagesRequest
+	19, // 6: mpc.router.v1.GetMessageStatusResponse.deliveries:type_name -> mpc.router.v1.MessageDeliveryStatus
-	6,  // 7: mpc.router.v1.MessageRouter.RegisterParty:input_type -> mpc.router.v1.RegisterPartyRequest
+	0,  // 7: mpc.router.v1.MessageRouter.RouteMessage:input_type -> mpc.router.v1.RouteMessageRequest
-	8,  // 8: mpc.router.v1.MessageRouter.SubscribeSessionEvents:input_type -> mpc.router.v1.SubscribeSessionEventsRequest
+	2,  // 8: mpc.router.v1.MessageRouter.SubscribeMessages:input_type -> mpc.router.v1.SubscribeMessagesRequest
-	10, // 9: mpc.router.v1.MessageRouter.PublishSessionEvent:input_type -> mpc.router.v1.PublishSessionEventRequest
+	4,  // 9: mpc.router.v1.MessageRouter.GetPendingMessages:input_type -> mpc.router.v1.GetPendingMessagesRequest
-	12, // 10: mpc.router.v1.MessageRouter.GetRegisteredParties:input_type -> mpc.router.v1.GetRegisteredPartiesRequest
+	16, // 10: mpc.router.v1.MessageRouter.AcknowledgeMessage:input_type -> mpc.router.v1.AcknowledgeMessageRequest
-	1,  // 11: mpc.router.v1.MessageRouter.RouteMessage:output_type -> mpc.router.v1.RouteMessageResponse
+	18, // 11: mpc.router.v1.MessageRouter.GetMessageStatus:input_type -> mpc.router.v1.GetMessageStatusRequest
-	3,  // 12: mpc.router.v1.MessageRouter.SubscribeMessages:output_type -> mpc.router.v1.MPCMessage
+	7,  // 12: mpc.router.v1.MessageRouter.RegisterParty:input_type -> mpc.router.v1.RegisterPartyRequest
-	5,  // 13: mpc.router.v1.MessageRouter.GetPendingMessages:output_type -> mpc.router.v1.GetPendingMessagesResponse
+	21, // 13: mpc.router.v1.MessageRouter.Heartbeat:input_type -> mpc.router.v1.HeartbeatRequest
-	7,  // 14: mpc.router.v1.MessageRouter.RegisterParty:output_type -> mpc.router.v1.RegisterPartyResponse
+	9,  // 14: mpc.router.v1.MessageRouter.SubscribeSessionEvents:input_type -> mpc.router.v1.SubscribeSessionEventsRequest
-	9,  // 15: mpc.router.v1.MessageRouter.SubscribeSessionEvents:output_type -> mpc.router.v1.SessionEvent
+	11, // 15: mpc.router.v1.MessageRouter.PublishSessionEvent:input_type -> mpc.router.v1.PublishSessionEventRequest
-	11, // 16: mpc.router.v1.MessageRouter.PublishSessionEvent:output_type -> mpc.router.v1.PublishSessionEventResponse
+	13, // 16: mpc.router.v1.MessageRouter.GetRegisteredParties:input_type -> mpc.router.v1.GetRegisteredPartiesRequest
-	14, // 17: mpc.router.v1.MessageRouter.GetRegisteredParties:output_type -> mpc.router.v1.GetRegisteredPartiesResponse
+	1,  // 17: mpc.router.v1.MessageRouter.RouteMessage:output_type -> mpc.router.v1.RouteMessageResponse
-	11, // [11:18] is the sub-list for method output_type
+	3,  // 18: mpc.router.v1.MessageRouter.SubscribeMessages:output_type -> mpc.router.v1.MPCMessage
-	4,  // [4:11] is the sub-list for method input_type
+	5,  // 19: mpc.router.v1.MessageRouter.GetPendingMessages:output_type -> mpc.router.v1.GetPendingMessagesResponse
-	4,  // [4:4] is the sub-list for extension type_name
+	17, // 20: mpc.router.v1.MessageRouter.AcknowledgeMessage:output_type -> mpc.router.v1.AcknowledgeMessageResponse
-	4,  // [4:4] is the sub-list for extension extendee
+	20, // 21: mpc.router.v1.MessageRouter.GetMessageStatus:output_type -> mpc.router.v1.GetMessageStatusResponse
-	0,  // [0:4] is the sub-list for field type_name
+	8,  // 22: mpc.router.v1.MessageRouter.RegisterParty:output_type -> mpc.router.v1.RegisterPartyResponse
+	22, // 23: mpc.router.v1.MessageRouter.Heartbeat:output_type -> mpc.router.v1.HeartbeatResponse
+	10, // 24: mpc.router.v1.MessageRouter.SubscribeSessionEvents:output_type -> mpc.router.v1.SessionEvent
+	12, // 25: mpc.router.v1.MessageRouter.PublishSessionEvent:output_type -> mpc.router.v1.PublishSessionEventResponse
+	15, // 26: mpc.router.v1.MessageRouter.GetRegisteredParties:output_type -> mpc.router.v1.GetRegisteredPartiesResponse
+	17, // [17:27] is the sub-list for method output_type
+	7,  // [7:17] is the sub-list for method input_type
+	7,  // [7:7] is the sub-list for extension type_name
+	7,  // [7:7] is the sub-list for extension extendee
+	0,  // [0:7] is the sub-list for field type_name
 }
 
 func init() { file_api_proto_message_router_proto_init() }
@@ -1169,7 +1757,7 @@ func file_api_proto_message_router_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: unsafe.Slice(unsafe.StringData(file_api_proto_message_router_proto_rawDesc), len(file_api_proto_message_router_proto_rawDesc)),
 			NumEnums:      0,
-			NumMessages:   16,
+			NumMessages:   24,
 			NumExtensions: 0,
 			NumServices:   1,
 		},

backend/mpc-system/api/grpc/router/v1/message_router_grpc.pb.go

@@ -22,7 +22,10 @@ const (
 	MessageRouter_RouteMessage_FullMethodName           = "/mpc.router.v1.MessageRouter/RouteMessage"
 	MessageRouter_SubscribeMessages_FullMethodName      = "/mpc.router.v1.MessageRouter/SubscribeMessages"
 	MessageRouter_GetPendingMessages_FullMethodName     = "/mpc.router.v1.MessageRouter/GetPendingMessages"
+	MessageRouter_AcknowledgeMessage_FullMethodName     = "/mpc.router.v1.MessageRouter/AcknowledgeMessage"
+	MessageRouter_GetMessageStatus_FullMethodName       = "/mpc.router.v1.MessageRouter/GetMessageStatus"
 	MessageRouter_RegisterParty_FullMethodName          = "/mpc.router.v1.MessageRouter/RegisterParty"
+	MessageRouter_Heartbeat_FullMethodName              = "/mpc.router.v1.MessageRouter/Heartbeat"
 	MessageRouter_SubscribeSessionEvents_FullMethodName = "/mpc.router.v1.MessageRouter/SubscribeSessionEvents"
 	MessageRouter_PublishSessionEvent_FullMethodName    = "/mpc.router.v1.MessageRouter/PublishSessionEvent"
 	MessageRouter_GetRegisteredParties_FullMethodName   = "/mpc.router.v1.MessageRouter/GetRegisteredParties"
@@ -40,8 +43,15 @@ type MessageRouterClient interface {
 	SubscribeMessages(ctx context.Context, in *SubscribeMessagesRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[MPCMessage], error)
 	// GetPendingMessages retrieves pending messages (polling alternative)
 	GetPendingMessages(ctx context.Context, in *GetPendingMessagesRequest, opts ...grpc.CallOption) (*GetPendingMessagesResponse, error)
+	// AcknowledgeMessage acknowledges receipt of a message
+	// Must be called after processing a message to confirm delivery
+	AcknowledgeMessage(ctx context.Context, in *AcknowledgeMessageRequest, opts ...grpc.CallOption) (*AcknowledgeMessageResponse, error)
+	// GetMessageStatus gets the delivery status of a message
+	GetMessageStatus(ctx context.Context, in *GetMessageStatusRequest, opts ...grpc.CallOption) (*GetMessageStatusResponse, error)
 	// RegisterParty registers a party with the message router (party actively connects)
 	RegisterParty(ctx context.Context, in *RegisterPartyRequest, opts ...grpc.CallOption) (*RegisterPartyResponse, error)
+	// Heartbeat sends a heartbeat to keep the party alive
+	Heartbeat(ctx context.Context, in *HeartbeatRequest, opts ...grpc.CallOption) (*HeartbeatResponse, error)
 	// SubscribeSessionEvents subscribes to session lifecycle events (session start, etc.)
 	SubscribeSessionEvents(ctx context.Context, in *SubscribeSessionEventsRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[SessionEvent], error)
 	// PublishSessionEvent publishes a session event (called by Session Coordinator)
@@ -97,6 +107,26 @@ func (c *messageRouterClient) GetPendingMessages(ctx context.Context, in *GetPen
 	return out, nil
 }
 
+func (c *messageRouterClient) AcknowledgeMessage(ctx context.Context, in *AcknowledgeMessageRequest, opts ...grpc.CallOption) (*AcknowledgeMessageResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(AcknowledgeMessageResponse)
+	err := c.cc.Invoke(ctx, MessageRouter_AcknowledgeMessage_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *messageRouterClient) GetMessageStatus(ctx context.Context, in *GetMessageStatusRequest, opts ...grpc.CallOption) (*GetMessageStatusResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(GetMessageStatusResponse)
+	err := c.cc.Invoke(ctx, MessageRouter_GetMessageStatus_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 func (c *messageRouterClient) RegisterParty(ctx context.Context, in *RegisterPartyRequest, opts ...grpc.CallOption) (*RegisterPartyResponse, error) {
 	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
 	out := new(RegisterPartyResponse)
@@ -107,6 +137,16 @@ func (c *messageRouterClient) RegisterParty(ctx context.Context, in *RegisterPar
 	return out, nil
 }
 
+func (c *messageRouterClient) Heartbeat(ctx context.Context, in *HeartbeatRequest, opts ...grpc.CallOption) (*HeartbeatResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(HeartbeatResponse)
+	err := c.cc.Invoke(ctx, MessageRouter_Heartbeat_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 func (c *messageRouterClient) SubscribeSessionEvents(ctx context.Context, in *SubscribeSessionEventsRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[SessionEvent], error) {
 	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
 	stream, err := c.cc.NewStream(ctx, &MessageRouter_ServiceDesc.Streams[1], MessageRouter_SubscribeSessionEvents_FullMethodName, cOpts...)
@@ -158,8 +198,15 @@ type MessageRouterServer interface {
 	SubscribeMessages(*SubscribeMessagesRequest, grpc.ServerStreamingServer[MPCMessage]) error
 	// GetPendingMessages retrieves pending messages (polling alternative)
 	GetPendingMessages(context.Context, *GetPendingMessagesRequest) (*GetPendingMessagesResponse, error)
+	// AcknowledgeMessage acknowledges receipt of a message
+	// Must be called after processing a message to confirm delivery
+	AcknowledgeMessage(context.Context, *AcknowledgeMessageRequest) (*AcknowledgeMessageResponse, error)
+	// GetMessageStatus gets the delivery status of a message
+	GetMessageStatus(context.Context, *GetMessageStatusRequest) (*GetMessageStatusResponse, error)
 	// RegisterParty registers a party with the message router (party actively connects)
 	RegisterParty(context.Context, *RegisterPartyRequest) (*RegisterPartyResponse, error)
+	// Heartbeat sends a heartbeat to keep the party alive
+	Heartbeat(context.Context, *HeartbeatRequest) (*HeartbeatResponse, error)
 	// SubscribeSessionEvents subscribes to session lifecycle events (session start, etc.)
 	SubscribeSessionEvents(*SubscribeSessionEventsRequest, grpc.ServerStreamingServer[SessionEvent]) error
 	// PublishSessionEvent publishes a session event (called by Session Coordinator)
@@ -185,9 +232,18 @@ func (UnimplementedMessageRouterServer) SubscribeMessages(*SubscribeMessagesRequ
 func (UnimplementedMessageRouterServer) GetPendingMessages(context.Context, *GetPendingMessagesRequest) (*GetPendingMessagesResponse, error) {
 	return nil, status.Error(codes.Unimplemented, "method GetPendingMessages not implemented")
 }
+func (UnimplementedMessageRouterServer) AcknowledgeMessage(context.Context, *AcknowledgeMessageRequest) (*AcknowledgeMessageResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method AcknowledgeMessage not implemented")
+}
+func (UnimplementedMessageRouterServer) GetMessageStatus(context.Context, *GetMessageStatusRequest) (*GetMessageStatusResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method GetMessageStatus not implemented")
+}
 func (UnimplementedMessageRouterServer) RegisterParty(context.Context, *RegisterPartyRequest) (*RegisterPartyResponse, error) {
 	return nil, status.Error(codes.Unimplemented, "method RegisterParty not implemented")
 }
+func (UnimplementedMessageRouterServer) Heartbeat(context.Context, *HeartbeatRequest) (*HeartbeatResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method Heartbeat not implemented")
+}
 func (UnimplementedMessageRouterServer) SubscribeSessionEvents(*SubscribeSessionEventsRequest, grpc.ServerStreamingServer[SessionEvent]) error {
 	return status.Error(codes.Unimplemented, "method SubscribeSessionEvents not implemented")
 }
@@ -265,6 +321,42 @@ func _MessageRouter_GetPendingMessages_Handler(srv interface{}, ctx context.Cont
 	return interceptor(ctx, in, info, handler)
 }
 
+func _MessageRouter_AcknowledgeMessage_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(AcknowledgeMessageRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(MessageRouterServer).AcknowledgeMessage(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: MessageRouter_AcknowledgeMessage_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(MessageRouterServer).AcknowledgeMessage(ctx, req.(*AcknowledgeMessageRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _MessageRouter_GetMessageStatus_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(GetMessageStatusRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(MessageRouterServer).GetMessageStatus(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: MessageRouter_GetMessageStatus_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(MessageRouterServer).GetMessageStatus(ctx, req.(*GetMessageStatusRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
 func _MessageRouter_RegisterParty_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
 	in := new(RegisterPartyRequest)
 	if err := dec(in); err != nil {
@@ -283,6 +375,24 @@ func _MessageRouter_RegisterParty_Handler(srv interface{}, ctx context.Context,
 	return interceptor(ctx, in, info, handler)
 }
 
+func _MessageRouter_Heartbeat_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(HeartbeatRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(MessageRouterServer).Heartbeat(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: MessageRouter_Heartbeat_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(MessageRouterServer).Heartbeat(ctx, req.(*HeartbeatRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
 func _MessageRouter_SubscribeSessionEvents_Handler(srv interface{}, stream grpc.ServerStream) error {
 	m := new(SubscribeSessionEventsRequest)
 	if err := stream.RecvMsg(m); err != nil {
@@ -345,10 +455,22 @@ var MessageRouter_ServiceDesc = grpc.ServiceDesc{
 			MethodName: "GetPendingMessages",
 			Handler:    _MessageRouter_GetPendingMessages_Handler,
 		},
+		{
+			MethodName: "AcknowledgeMessage",
+			Handler:    _MessageRouter_AcknowledgeMessage_Handler,
+		},
+		{
+			MethodName: "GetMessageStatus",
+			Handler:    _MessageRouter_GetMessageStatus_Handler,
+		},
 		{
 			MethodName: "RegisterParty",
 			Handler:    _MessageRouter_RegisterParty_Handler,
 		},
+		{
+			MethodName: "Heartbeat",
+			Handler:    _MessageRouter_Heartbeat_Handler,
+		},
 		{
 			MethodName: "PublishSessionEvent",
 			Handler:    _MessageRouter_PublishSessionEvent_Handler,

backend/mpc-system/api/proto/message_router.proto

@@ -15,9 +15,19 @@ service MessageRouter {
   // GetPendingMessages retrieves pending messages (polling alternative)
   rpc GetPendingMessages(GetPendingMessagesRequest) returns (GetPendingMessagesResponse);
 
+  // AcknowledgeMessage acknowledges receipt of a message
+  // Must be called after processing a message to confirm delivery
+  rpc AcknowledgeMessage(AcknowledgeMessageRequest) returns (AcknowledgeMessageResponse);
+
+  // GetMessageStatus gets the delivery status of a message
+  rpc GetMessageStatus(GetMessageStatusRequest) returns (GetMessageStatusResponse);
+
   // RegisterParty registers a party with the message router (party actively connects)
   rpc RegisterParty(RegisterPartyRequest) returns (RegisterPartyResponse);
 
+  // Heartbeat sends a heartbeat to keep the party alive
+  rpc Heartbeat(HeartbeatRequest) returns (HeartbeatResponse);
+
   // SubscribeSessionEvents subscribes to session lifecycle events (session start, etc.)
   rpc SubscribeSessionEvents(SubscribeSessionEventsRequest) returns (stream SessionEvent);
 
@@ -74,11 +84,21 @@ message GetPendingMessagesResponse {
   repeated MPCMessage messages = 1;
 }
 
+// NotificationChannel represents a notification channel for offline parties
+// If a party has notification channels, it operates in offline mode (24h async)
+// If no notification channels, it operates in real-time mode (Message Router push)
+message NotificationChannel {
+  string email = 1;                          // Optional: email address for notifications
+  string phone = 2;                          // Optional: phone number for SMS notifications
+  string push_token = 3;                     // Optional: push notification token (FCM/APNs)
+}
+
 // RegisterPartyRequest registers a party with the router
 message RegisterPartyRequest {
   string party_id = 1;                       // Unique party identifier
   string party_role = 2;                     // persistent, delegate, or temporary
   string version = 3;                        // Party software version
+  NotificationChannel notification = 4;     // Optional: notification channel for offline mode
 }
 
 // RegisterPartyResponse confirms party registration
@@ -132,6 +152,7 @@ message RegisteredParty {
   bool online = 3;                           // Whether party is currently connected
   int64 registered_at = 4;                   // Unix timestamp milliseconds
   int64 last_seen_at = 5;                    // Unix timestamp milliseconds
+  NotificationChannel notification = 6;     // Optional: notification channel (if set, party is offline mode)
 }
 
 // GetRegisteredPartiesResponse returns registered parties
@@ -139,3 +160,54 @@ message GetRegisteredPartiesResponse {
   repeated RegisteredParty parties = 1;
   int32 total_count = 2;
 }
+
+// AcknowledgeMessageRequest acknowledges message receipt
+message AcknowledgeMessageRequest {
+  string message_id = 1;                     // ID of the message being acknowledged
+  string party_id = 2;                       // ID of the party acknowledging
+  string session_id = 3;                     // Session the message belongs to
+  bool success = 4;                          // True if message was processed successfully
+  string error_message = 5;                  // Error message if processing failed
+}
+
+// AcknowledgeMessageResponse confirms acknowledgment
+message AcknowledgeMessageResponse {
+  bool success = 1;
+  string message = 2;
+}
+
+// GetMessageStatusRequest requests message delivery status
+message GetMessageStatusRequest {
+  string message_id = 1;
+  string session_id = 2;
+}
+
+// MessageDeliveryStatus represents delivery status to a single party
+message MessageDeliveryStatus {
+  string party_id = 1;
+  string status = 2;                         // pending, delivered, acknowledged, failed
+  int64 delivered_at = 3;                    // Unix timestamp milliseconds
+  int64 acknowledged_at = 4;                 // Unix timestamp milliseconds
+  int32 retry_count = 5;                     // Number of delivery retries
+}
+
+// GetMessageStatusResponse returns message delivery status
+message GetMessageStatusResponse {
+  string message_id = 1;
+  string session_id = 2;
+  repeated MessageDeliveryStatus deliveries = 3;
+  bool all_acknowledged = 4;                 // True if all recipients acknowledged
+}
+
+// HeartbeatRequest sends a heartbeat to keep the party alive
+message HeartbeatRequest {
+  string party_id = 1;
+  int64 timestamp = 2;                       // Unix timestamp milliseconds
+}
+
+// HeartbeatResponse confirms heartbeat receipt
+message HeartbeatResponse {
+  bool success = 1;
+  int64 server_timestamp = 2;                // Server timestamp for clock sync
+  int32 pending_messages = 3;                // Number of pending messages for this party
+}

backend/mpc-system/api/proto/message_router_grpc.pb.go

@@ -0,0 +1,496 @@
+// Code generated by protoc-gen-go-grpc. DO NOT EDIT.
+// versions:
+// - protoc-gen-go-grpc v1.6.0
+// - protoc             v6.33.1
+// source: api/proto/message_router.proto
+
+package router
+
+import (
+	context "context"
+	grpc "google.golang.org/grpc"
+	codes "google.golang.org/grpc/codes"
+	status "google.golang.org/grpc/status"
+)
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the grpc package it is being compiled against.
+// Requires gRPC-Go v1.64.0 or later.
+const _ = grpc.SupportPackageIsVersion9
+
+const (
+	MessageRouter_RouteMessage_FullMethodName           = "/mpc.router.v1.MessageRouter/RouteMessage"
+	MessageRouter_SubscribeMessages_FullMethodName      = "/mpc.router.v1.MessageRouter/SubscribeMessages"
+	MessageRouter_GetPendingMessages_FullMethodName     = "/mpc.router.v1.MessageRouter/GetPendingMessages"
+	MessageRouter_AcknowledgeMessage_FullMethodName     = "/mpc.router.v1.MessageRouter/AcknowledgeMessage"
+	MessageRouter_GetMessageStatus_FullMethodName       = "/mpc.router.v1.MessageRouter/GetMessageStatus"
+	MessageRouter_RegisterParty_FullMethodName          = "/mpc.router.v1.MessageRouter/RegisterParty"
+	MessageRouter_Heartbeat_FullMethodName              = "/mpc.router.v1.MessageRouter/Heartbeat"
+	MessageRouter_SubscribeSessionEvents_FullMethodName = "/mpc.router.v1.MessageRouter/SubscribeSessionEvents"
+	MessageRouter_PublishSessionEvent_FullMethodName    = "/mpc.router.v1.MessageRouter/PublishSessionEvent"
+	MessageRouter_GetRegisteredParties_FullMethodName   = "/mpc.router.v1.MessageRouter/GetRegisteredParties"
+)
+
+// MessageRouterClient is the client API for MessageRouter service.
+//
+// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://pkg.go.dev/google.golang.org/grpc/?tab=doc#ClientConn.NewStream.
+//
+// MessageRouter service handles MPC message routing
+type MessageRouterClient interface {
+	// RouteMessage routes a message from one party to others
+	RouteMessage(ctx context.Context, in *RouteMessageRequest, opts ...grpc.CallOption) (*RouteMessageResponse, error)
+	// SubscribeMessages subscribes to messages for a party (streaming)
+	SubscribeMessages(ctx context.Context, in *SubscribeMessagesRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[MPCMessage], error)
+	// GetPendingMessages retrieves pending messages (polling alternative)
+	GetPendingMessages(ctx context.Context, in *GetPendingMessagesRequest, opts ...grpc.CallOption) (*GetPendingMessagesResponse, error)
+	// AcknowledgeMessage acknowledges receipt of a message
+	// Must be called after processing a message to confirm delivery
+	AcknowledgeMessage(ctx context.Context, in *AcknowledgeMessageRequest, opts ...grpc.CallOption) (*AcknowledgeMessageResponse, error)
+	// GetMessageStatus gets the delivery status of a message
+	GetMessageStatus(ctx context.Context, in *GetMessageStatusRequest, opts ...grpc.CallOption) (*GetMessageStatusResponse, error)
+	// RegisterParty registers a party with the message router (party actively connects)
+	RegisterParty(ctx context.Context, in *RegisterPartyRequest, opts ...grpc.CallOption) (*RegisterPartyResponse, error)
+	// Heartbeat sends a heartbeat to keep the party alive
+	Heartbeat(ctx context.Context, in *HeartbeatRequest, opts ...grpc.CallOption) (*HeartbeatResponse, error)
+	// SubscribeSessionEvents subscribes to session lifecycle events (session start, etc.)
+	SubscribeSessionEvents(ctx context.Context, in *SubscribeSessionEventsRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[SessionEvent], error)
+	// PublishSessionEvent publishes a session event (called by Session Coordinator)
+	PublishSessionEvent(ctx context.Context, in *PublishSessionEventRequest, opts ...grpc.CallOption) (*PublishSessionEventResponse, error)
+	// GetRegisteredParties returns all registered parties (for Session Coordinator party discovery)
+	GetRegisteredParties(ctx context.Context, in *GetRegisteredPartiesRequest, opts ...grpc.CallOption) (*GetRegisteredPartiesResponse, error)
+}
+
+type messageRouterClient struct {
+	cc grpc.ClientConnInterface
+}
+
+func NewMessageRouterClient(cc grpc.ClientConnInterface) MessageRouterClient {
+	return &messageRouterClient{cc}
+}
+
+func (c *messageRouterClient) RouteMessage(ctx context.Context, in *RouteMessageRequest, opts ...grpc.CallOption) (*RouteMessageResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(RouteMessageResponse)
+	err := c.cc.Invoke(ctx, MessageRouter_RouteMessage_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *messageRouterClient) SubscribeMessages(ctx context.Context, in *SubscribeMessagesRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[MPCMessage], error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	stream, err := c.cc.NewStream(ctx, &MessageRouter_ServiceDesc.Streams[0], MessageRouter_SubscribeMessages_FullMethodName, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	x := &grpc.GenericClientStream[SubscribeMessagesRequest, MPCMessage]{ClientStream: stream}
+	if err := x.ClientStream.SendMsg(in); err != nil {
+		return nil, err
+	}
+	if err := x.ClientStream.CloseSend(); err != nil {
+		return nil, err
+	}
+	return x, nil
+}
+
+// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
+type MessageRouter_SubscribeMessagesClient = grpc.ServerStreamingClient[MPCMessage]
+
+func (c *messageRouterClient) GetPendingMessages(ctx context.Context, in *GetPendingMessagesRequest, opts ...grpc.CallOption) (*GetPendingMessagesResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(GetPendingMessagesResponse)
+	err := c.cc.Invoke(ctx, MessageRouter_GetPendingMessages_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *messageRouterClient) AcknowledgeMessage(ctx context.Context, in *AcknowledgeMessageRequest, opts ...grpc.CallOption) (*AcknowledgeMessageResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(AcknowledgeMessageResponse)
+	err := c.cc.Invoke(ctx, MessageRouter_AcknowledgeMessage_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *messageRouterClient) GetMessageStatus(ctx context.Context, in *GetMessageStatusRequest, opts ...grpc.CallOption) (*GetMessageStatusResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(GetMessageStatusResponse)
+	err := c.cc.Invoke(ctx, MessageRouter_GetMessageStatus_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *messageRouterClient) RegisterParty(ctx context.Context, in *RegisterPartyRequest, opts ...grpc.CallOption) (*RegisterPartyResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(RegisterPartyResponse)
+	err := c.cc.Invoke(ctx, MessageRouter_RegisterParty_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *messageRouterClient) Heartbeat(ctx context.Context, in *HeartbeatRequest, opts ...grpc.CallOption) (*HeartbeatResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(HeartbeatResponse)
+	err := c.cc.Invoke(ctx, MessageRouter_Heartbeat_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *messageRouterClient) SubscribeSessionEvents(ctx context.Context, in *SubscribeSessionEventsRequest, opts ...grpc.CallOption) (grpc.ServerStreamingClient[SessionEvent], error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	stream, err := c.cc.NewStream(ctx, &MessageRouter_ServiceDesc.Streams[1], MessageRouter_SubscribeSessionEvents_FullMethodName, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	x := &grpc.GenericClientStream[SubscribeSessionEventsRequest, SessionEvent]{ClientStream: stream}
+	if err := x.ClientStream.SendMsg(in); err != nil {
+		return nil, err
+	}
+	if err := x.ClientStream.CloseSend(); err != nil {
+		return nil, err
+	}
+	return x, nil
+}
+
+// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
+type MessageRouter_SubscribeSessionEventsClient = grpc.ServerStreamingClient[SessionEvent]
+
+func (c *messageRouterClient) PublishSessionEvent(ctx context.Context, in *PublishSessionEventRequest, opts ...grpc.CallOption) (*PublishSessionEventResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(PublishSessionEventResponse)
+	err := c.cc.Invoke(ctx, MessageRouter_PublishSessionEvent_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *messageRouterClient) GetRegisteredParties(ctx context.Context, in *GetRegisteredPartiesRequest, opts ...grpc.CallOption) (*GetRegisteredPartiesResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(GetRegisteredPartiesResponse)
+	err := c.cc.Invoke(ctx, MessageRouter_GetRegisteredParties_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+// MessageRouterServer is the server API for MessageRouter service.
+// All implementations must embed UnimplementedMessageRouterServer
+// for forward compatibility.
+//
+// MessageRouter service handles MPC message routing
+type MessageRouterServer interface {
+	// RouteMessage routes a message from one party to others
+	RouteMessage(context.Context, *RouteMessageRequest) (*RouteMessageResponse, error)
+	// SubscribeMessages subscribes to messages for a party (streaming)
+	SubscribeMessages(*SubscribeMessagesRequest, grpc.ServerStreamingServer[MPCMessage]) error
+	// GetPendingMessages retrieves pending messages (polling alternative)
+	GetPendingMessages(context.Context, *GetPendingMessagesRequest) (*GetPendingMessagesResponse, error)
+	// AcknowledgeMessage acknowledges receipt of a message
+	// Must be called after processing a message to confirm delivery
+	AcknowledgeMessage(context.Context, *AcknowledgeMessageRequest) (*AcknowledgeMessageResponse, error)
+	// GetMessageStatus gets the delivery status of a message
+	GetMessageStatus(context.Context, *GetMessageStatusRequest) (*GetMessageStatusResponse, error)
+	// RegisterParty registers a party with the message router (party actively connects)
+	RegisterParty(context.Context, *RegisterPartyRequest) (*RegisterPartyResponse, error)
+	// Heartbeat sends a heartbeat to keep the party alive
+	Heartbeat(context.Context, *HeartbeatRequest) (*HeartbeatResponse, error)
+	// SubscribeSessionEvents subscribes to session lifecycle events (session start, etc.)
+	SubscribeSessionEvents(*SubscribeSessionEventsRequest, grpc.ServerStreamingServer[SessionEvent]) error
+	// PublishSessionEvent publishes a session event (called by Session Coordinator)
+	PublishSessionEvent(context.Context, *PublishSessionEventRequest) (*PublishSessionEventResponse, error)
+	// GetRegisteredParties returns all registered parties (for Session Coordinator party discovery)
+	GetRegisteredParties(context.Context, *GetRegisteredPartiesRequest) (*GetRegisteredPartiesResponse, error)
+	mustEmbedUnimplementedMessageRouterServer()
+}
+
+// UnimplementedMessageRouterServer must be embedded to have
+// forward compatible implementations.
+//
+// NOTE: this should be embedded by value instead of pointer to avoid a nil
+// pointer dereference when methods are called.
+type UnimplementedMessageRouterServer struct{}
+
+func (UnimplementedMessageRouterServer) RouteMessage(context.Context, *RouteMessageRequest) (*RouteMessageResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method RouteMessage not implemented")
+}
+func (UnimplementedMessageRouterServer) SubscribeMessages(*SubscribeMessagesRequest, grpc.ServerStreamingServer[MPCMessage]) error {
+	return status.Error(codes.Unimplemented, "method SubscribeMessages not implemented")
+}
+func (UnimplementedMessageRouterServer) GetPendingMessages(context.Context, *GetPendingMessagesRequest) (*GetPendingMessagesResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method GetPendingMessages not implemented")
+}
+func (UnimplementedMessageRouterServer) AcknowledgeMessage(context.Context, *AcknowledgeMessageRequest) (*AcknowledgeMessageResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method AcknowledgeMessage not implemented")
+}
+func (UnimplementedMessageRouterServer) GetMessageStatus(context.Context, *GetMessageStatusRequest) (*GetMessageStatusResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method GetMessageStatus not implemented")
+}
+func (UnimplementedMessageRouterServer) RegisterParty(context.Context, *RegisterPartyRequest) (*RegisterPartyResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method RegisterParty not implemented")
+}
+func (UnimplementedMessageRouterServer) Heartbeat(context.Context, *HeartbeatRequest) (*HeartbeatResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method Heartbeat not implemented")
+}
+func (UnimplementedMessageRouterServer) SubscribeSessionEvents(*SubscribeSessionEventsRequest, grpc.ServerStreamingServer[SessionEvent]) error {
+	return status.Error(codes.Unimplemented, "method SubscribeSessionEvents not implemented")
+}
+func (UnimplementedMessageRouterServer) PublishSessionEvent(context.Context, *PublishSessionEventRequest) (*PublishSessionEventResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method PublishSessionEvent not implemented")
+}
+func (UnimplementedMessageRouterServer) GetRegisteredParties(context.Context, *GetRegisteredPartiesRequest) (*GetRegisteredPartiesResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method GetRegisteredParties not implemented")
+}
+func (UnimplementedMessageRouterServer) mustEmbedUnimplementedMessageRouterServer() {}
+func (UnimplementedMessageRouterServer) testEmbeddedByValue()                       {}
+
+// UnsafeMessageRouterServer may be embedded to opt out of forward compatibility for this service.
+// Use of this interface is not recommended, as added methods to MessageRouterServer will
+// result in compilation errors.
+type UnsafeMessageRouterServer interface {
+	mustEmbedUnimplementedMessageRouterServer()
+}
+
+func RegisterMessageRouterServer(s grpc.ServiceRegistrar, srv MessageRouterServer) {
+	// If the following call panics, it indicates UnimplementedMessageRouterServer was
+	// embedded by pointer and is nil.  This will cause panics if an
+	// unimplemented method is ever invoked, so we test this at initialization
+	// time to prevent it from happening at runtime later due to I/O.
+	if t, ok := srv.(interface{ testEmbeddedByValue() }); ok {
+		t.testEmbeddedByValue()
+	}
+	s.RegisterService(&MessageRouter_ServiceDesc, srv)
+}
+
+func _MessageRouter_RouteMessage_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(RouteMessageRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(MessageRouterServer).RouteMessage(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: MessageRouter_RouteMessage_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(MessageRouterServer).RouteMessage(ctx, req.(*RouteMessageRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _MessageRouter_SubscribeMessages_Handler(srv interface{}, stream grpc.ServerStream) error {
+	m := new(SubscribeMessagesRequest)
+	if err := stream.RecvMsg(m); err != nil {
+		return err
+	}
+	return srv.(MessageRouterServer).SubscribeMessages(m, &grpc.GenericServerStream[SubscribeMessagesRequest, MPCMessage]{ServerStream: stream})
+}
+
+// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
+type MessageRouter_SubscribeMessagesServer = grpc.ServerStreamingServer[MPCMessage]
+
+func _MessageRouter_GetPendingMessages_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(GetPendingMessagesRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(MessageRouterServer).GetPendingMessages(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: MessageRouter_GetPendingMessages_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(MessageRouterServer).GetPendingMessages(ctx, req.(*GetPendingMessagesRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _MessageRouter_AcknowledgeMessage_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(AcknowledgeMessageRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(MessageRouterServer).AcknowledgeMessage(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: MessageRouter_AcknowledgeMessage_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(MessageRouterServer).AcknowledgeMessage(ctx, req.(*AcknowledgeMessageRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _MessageRouter_GetMessageStatus_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(GetMessageStatusRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(MessageRouterServer).GetMessageStatus(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: MessageRouter_GetMessageStatus_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(MessageRouterServer).GetMessageStatus(ctx, req.(*GetMessageStatusRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _MessageRouter_RegisterParty_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(RegisterPartyRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(MessageRouterServer).RegisterParty(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: MessageRouter_RegisterParty_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(MessageRouterServer).RegisterParty(ctx, req.(*RegisterPartyRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _MessageRouter_Heartbeat_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(HeartbeatRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(MessageRouterServer).Heartbeat(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: MessageRouter_Heartbeat_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(MessageRouterServer).Heartbeat(ctx, req.(*HeartbeatRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _MessageRouter_SubscribeSessionEvents_Handler(srv interface{}, stream grpc.ServerStream) error {
+	m := new(SubscribeSessionEventsRequest)
+	if err := stream.RecvMsg(m); err != nil {
+		return err
+	}
+	return srv.(MessageRouterServer).SubscribeSessionEvents(m, &grpc.GenericServerStream[SubscribeSessionEventsRequest, SessionEvent]{ServerStream: stream})
+}
+
+// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
+type MessageRouter_SubscribeSessionEventsServer = grpc.ServerStreamingServer[SessionEvent]
+
+func _MessageRouter_PublishSessionEvent_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(PublishSessionEventRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(MessageRouterServer).PublishSessionEvent(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: MessageRouter_PublishSessionEvent_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(MessageRouterServer).PublishSessionEvent(ctx, req.(*PublishSessionEventRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _MessageRouter_GetRegisteredParties_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(GetRegisteredPartiesRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(MessageRouterServer).GetRegisteredParties(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: MessageRouter_GetRegisteredParties_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(MessageRouterServer).GetRegisteredParties(ctx, req.(*GetRegisteredPartiesRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+// MessageRouter_ServiceDesc is the grpc.ServiceDesc for MessageRouter service.
+// It's only intended for direct use with grpc.RegisterService,
+// and not to be introspected or modified (even as a copy)
+var MessageRouter_ServiceDesc = grpc.ServiceDesc{
+	ServiceName: "mpc.router.v1.MessageRouter",
+	HandlerType: (*MessageRouterServer)(nil),
+	Methods: []grpc.MethodDesc{
+		{
+			MethodName: "RouteMessage",
+			Handler:    _MessageRouter_RouteMessage_Handler,
+		},
+		{
+			MethodName: "GetPendingMessages",
+			Handler:    _MessageRouter_GetPendingMessages_Handler,
+		},
+		{
+			MethodName: "AcknowledgeMessage",
+			Handler:    _MessageRouter_AcknowledgeMessage_Handler,
+		},
+		{
+			MethodName: "GetMessageStatus",
+			Handler:    _MessageRouter_GetMessageStatus_Handler,
+		},
+		{
+			MethodName: "RegisterParty",
+			Handler:    _MessageRouter_RegisterParty_Handler,
+		},
+		{
+			MethodName: "Heartbeat",
+			Handler:    _MessageRouter_Heartbeat_Handler,
+		},
+		{
+			MethodName: "PublishSessionEvent",
+			Handler:    _MessageRouter_PublishSessionEvent_Handler,
+		},
+		{
+			MethodName: "GetRegisteredParties",
+			Handler:    _MessageRouter_GetRegisteredParties_Handler,
+		},
+	},
+	Streams: []grpc.StreamDesc{
+		{
+			StreamName:    "SubscribeMessages",
+			Handler:       _MessageRouter_SubscribeMessages_Handler,
+			ServerStreams: true,
+		},
+		{
+			StreamName:    "SubscribeSessionEvents",
+			Handler:       _MessageRouter_SubscribeSessionEvents_Handler,
+			ServerStreams: true,
+		},
+	},
+	Metadata: "api/proto/message_router.proto",
+}

backend/mpc-system/api/proto/session_coordinator.proto

@@ -21,9 +21,17 @@ message CreateSessionRequest {
   string session_type = 1;               // "keygen" or "sign"
   int32 threshold_n = 2;                 // Total number of parties
   int32 threshold_t = 3;                 // Minimum required parties
-  repeated ParticipantInfo participants = 4;
+  repeated ParticipantInfo participants = 4;  // Optional: if empty, coordinator selects automatically
   bytes message_hash = 5;                // Required for sign sessions
   int64 expires_in_seconds = 6;          // Session expiration time
+  PartyComposition party_composition = 7; // Optional: party composition requirements for auto-selection
+}
+
+// PartyComposition specifies requirements for automatic party selection
+message PartyComposition {
+  int32 persistent_count = 1;            // Number of persistent parties (store shares in DB)
+  int32 delegate_count = 2;              // Number of delegate parties (return shares to user)
+  int32 temporary_count = 3;             // Number of temporary parties
 }
 
 // ParticipantInfo contains information about a participant
@@ -45,6 +53,8 @@ message CreateSessionResponse {
   string session_id = 1;
   map<string, string> join_tokens = 2;   // party_id -> join_token
   int64 expires_at = 3;                  // Unix timestamp milliseconds
+  repeated string selected_parties = 4;  // List of selected party IDs
+  string delegate_party_id = 5;          // The delegate party ID (if any)
 }
 
 // JoinSessionRequest allows a participant to join a session

backend/mpc-system/api/proto/session_coordinator_grpc.pb.go

@@ -0,0 +1,355 @@
+// Code generated by protoc-gen-go-grpc. DO NOT EDIT.
+// versions:
+// - protoc-gen-go-grpc v1.6.0
+// - protoc             v6.33.1
+// source: api/proto/session_coordinator.proto
+
+package coordinator
+
+import (
+	context "context"
+	grpc "google.golang.org/grpc"
+	codes "google.golang.org/grpc/codes"
+	status "google.golang.org/grpc/status"
+)
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the grpc package it is being compiled against.
+// Requires gRPC-Go v1.64.0 or later.
+const _ = grpc.SupportPackageIsVersion9
+
+const (
+	SessionCoordinator_CreateSession_FullMethodName    = "/mpc.coordinator.v1.SessionCoordinator/CreateSession"
+	SessionCoordinator_JoinSession_FullMethodName      = "/mpc.coordinator.v1.SessionCoordinator/JoinSession"
+	SessionCoordinator_GetSessionStatus_FullMethodName = "/mpc.coordinator.v1.SessionCoordinator/GetSessionStatus"
+	SessionCoordinator_MarkPartyReady_FullMethodName   = "/mpc.coordinator.v1.SessionCoordinator/MarkPartyReady"
+	SessionCoordinator_StartSession_FullMethodName     = "/mpc.coordinator.v1.SessionCoordinator/StartSession"
+	SessionCoordinator_ReportCompletion_FullMethodName = "/mpc.coordinator.v1.SessionCoordinator/ReportCompletion"
+	SessionCoordinator_CloseSession_FullMethodName     = "/mpc.coordinator.v1.SessionCoordinator/CloseSession"
+)
+
+// SessionCoordinatorClient is the client API for SessionCoordinator service.
+//
+// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://pkg.go.dev/google.golang.org/grpc/?tab=doc#ClientConn.NewStream.
+//
+// SessionCoordinator service manages MPC sessions
+type SessionCoordinatorClient interface {
+	// Session management
+	CreateSession(ctx context.Context, in *CreateSessionRequest, opts ...grpc.CallOption) (*CreateSessionResponse, error)
+	JoinSession(ctx context.Context, in *JoinSessionRequest, opts ...grpc.CallOption) (*JoinSessionResponse, error)
+	GetSessionStatus(ctx context.Context, in *GetSessionStatusRequest, opts ...grpc.CallOption) (*GetSessionStatusResponse, error)
+	MarkPartyReady(ctx context.Context, in *MarkPartyReadyRequest, opts ...grpc.CallOption) (*MarkPartyReadyResponse, error)
+	StartSession(ctx context.Context, in *StartSessionRequest, opts ...grpc.CallOption) (*StartSessionResponse, error)
+	ReportCompletion(ctx context.Context, in *ReportCompletionRequest, opts ...grpc.CallOption) (*ReportCompletionResponse, error)
+	CloseSession(ctx context.Context, in *CloseSessionRequest, opts ...grpc.CallOption) (*CloseSessionResponse, error)
+}
+
+type sessionCoordinatorClient struct {
+	cc grpc.ClientConnInterface
+}
+
+func NewSessionCoordinatorClient(cc grpc.ClientConnInterface) SessionCoordinatorClient {
+	return &sessionCoordinatorClient{cc}
+}
+
+func (c *sessionCoordinatorClient) CreateSession(ctx context.Context, in *CreateSessionRequest, opts ...grpc.CallOption) (*CreateSessionResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(CreateSessionResponse)
+	err := c.cc.Invoke(ctx, SessionCoordinator_CreateSession_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *sessionCoordinatorClient) JoinSession(ctx context.Context, in *JoinSessionRequest, opts ...grpc.CallOption) (*JoinSessionResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(JoinSessionResponse)
+	err := c.cc.Invoke(ctx, SessionCoordinator_JoinSession_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *sessionCoordinatorClient) GetSessionStatus(ctx context.Context, in *GetSessionStatusRequest, opts ...grpc.CallOption) (*GetSessionStatusResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(GetSessionStatusResponse)
+	err := c.cc.Invoke(ctx, SessionCoordinator_GetSessionStatus_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *sessionCoordinatorClient) MarkPartyReady(ctx context.Context, in *MarkPartyReadyRequest, opts ...grpc.CallOption) (*MarkPartyReadyResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(MarkPartyReadyResponse)
+	err := c.cc.Invoke(ctx, SessionCoordinator_MarkPartyReady_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *sessionCoordinatorClient) StartSession(ctx context.Context, in *StartSessionRequest, opts ...grpc.CallOption) (*StartSessionResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(StartSessionResponse)
+	err := c.cc.Invoke(ctx, SessionCoordinator_StartSession_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *sessionCoordinatorClient) ReportCompletion(ctx context.Context, in *ReportCompletionRequest, opts ...grpc.CallOption) (*ReportCompletionResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(ReportCompletionResponse)
+	err := c.cc.Invoke(ctx, SessionCoordinator_ReportCompletion_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+func (c *sessionCoordinatorClient) CloseSession(ctx context.Context, in *CloseSessionRequest, opts ...grpc.CallOption) (*CloseSessionResponse, error) {
+	cOpts := append([]grpc.CallOption{grpc.StaticMethod()}, opts...)
+	out := new(CloseSessionResponse)
+	err := c.cc.Invoke(ctx, SessionCoordinator_CloseSession_FullMethodName, in, out, cOpts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+// SessionCoordinatorServer is the server API for SessionCoordinator service.
+// All implementations must embed UnimplementedSessionCoordinatorServer
+// for forward compatibility.
+//
+// SessionCoordinator service manages MPC sessions
+type SessionCoordinatorServer interface {
+	// Session management
+	CreateSession(context.Context, *CreateSessionRequest) (*CreateSessionResponse, error)
+	JoinSession(context.Context, *JoinSessionRequest) (*JoinSessionResponse, error)
+	GetSessionStatus(context.Context, *GetSessionStatusRequest) (*GetSessionStatusResponse, error)
+	MarkPartyReady(context.Context, *MarkPartyReadyRequest) (*MarkPartyReadyResponse, error)
+	StartSession(context.Context, *StartSessionRequest) (*StartSessionResponse, error)
+	ReportCompletion(context.Context, *ReportCompletionRequest) (*ReportCompletionResponse, error)
+	CloseSession(context.Context, *CloseSessionRequest) (*CloseSessionResponse, error)
+	mustEmbedUnimplementedSessionCoordinatorServer()
+}
+
+// UnimplementedSessionCoordinatorServer must be embedded to have
+// forward compatible implementations.
+//
+// NOTE: this should be embedded by value instead of pointer to avoid a nil
+// pointer dereference when methods are called.
+type UnimplementedSessionCoordinatorServer struct{}
+
+func (UnimplementedSessionCoordinatorServer) CreateSession(context.Context, *CreateSessionRequest) (*CreateSessionResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method CreateSession not implemented")
+}
+func (UnimplementedSessionCoordinatorServer) JoinSession(context.Context, *JoinSessionRequest) (*JoinSessionResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method JoinSession not implemented")
+}
+func (UnimplementedSessionCoordinatorServer) GetSessionStatus(context.Context, *GetSessionStatusRequest) (*GetSessionStatusResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method GetSessionStatus not implemented")
+}
+func (UnimplementedSessionCoordinatorServer) MarkPartyReady(context.Context, *MarkPartyReadyRequest) (*MarkPartyReadyResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method MarkPartyReady not implemented")
+}
+func (UnimplementedSessionCoordinatorServer) StartSession(context.Context, *StartSessionRequest) (*StartSessionResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method StartSession not implemented")
+}
+func (UnimplementedSessionCoordinatorServer) ReportCompletion(context.Context, *ReportCompletionRequest) (*ReportCompletionResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method ReportCompletion not implemented")
+}
+func (UnimplementedSessionCoordinatorServer) CloseSession(context.Context, *CloseSessionRequest) (*CloseSessionResponse, error) {
+	return nil, status.Error(codes.Unimplemented, "method CloseSession not implemented")
+}
+func (UnimplementedSessionCoordinatorServer) mustEmbedUnimplementedSessionCoordinatorServer() {}
+func (UnimplementedSessionCoordinatorServer) testEmbeddedByValue()                            {}
+
+// UnsafeSessionCoordinatorServer may be embedded to opt out of forward compatibility for this service.
+// Use of this interface is not recommended, as added methods to SessionCoordinatorServer will
+// result in compilation errors.
+type UnsafeSessionCoordinatorServer interface {
+	mustEmbedUnimplementedSessionCoordinatorServer()
+}
+
+func RegisterSessionCoordinatorServer(s grpc.ServiceRegistrar, srv SessionCoordinatorServer) {
+	// If the following call panics, it indicates UnimplementedSessionCoordinatorServer was
+	// embedded by pointer and is nil.  This will cause panics if an
+	// unimplemented method is ever invoked, so we test this at initialization
+	// time to prevent it from happening at runtime later due to I/O.
+	if t, ok := srv.(interface{ testEmbeddedByValue() }); ok {
+		t.testEmbeddedByValue()
+	}
+	s.RegisterService(&SessionCoordinator_ServiceDesc, srv)
+}
+
+func _SessionCoordinator_CreateSession_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(CreateSessionRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(SessionCoordinatorServer).CreateSession(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: SessionCoordinator_CreateSession_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(SessionCoordinatorServer).CreateSession(ctx, req.(*CreateSessionRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _SessionCoordinator_JoinSession_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(JoinSessionRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(SessionCoordinatorServer).JoinSession(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: SessionCoordinator_JoinSession_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(SessionCoordinatorServer).JoinSession(ctx, req.(*JoinSessionRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _SessionCoordinator_GetSessionStatus_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(GetSessionStatusRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(SessionCoordinatorServer).GetSessionStatus(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: SessionCoordinator_GetSessionStatus_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(SessionCoordinatorServer).GetSessionStatus(ctx, req.(*GetSessionStatusRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _SessionCoordinator_MarkPartyReady_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(MarkPartyReadyRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(SessionCoordinatorServer).MarkPartyReady(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: SessionCoordinator_MarkPartyReady_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(SessionCoordinatorServer).MarkPartyReady(ctx, req.(*MarkPartyReadyRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _SessionCoordinator_StartSession_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(StartSessionRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(SessionCoordinatorServer).StartSession(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: SessionCoordinator_StartSession_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(SessionCoordinatorServer).StartSession(ctx, req.(*StartSessionRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _SessionCoordinator_ReportCompletion_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(ReportCompletionRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(SessionCoordinatorServer).ReportCompletion(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: SessionCoordinator_ReportCompletion_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(SessionCoordinatorServer).ReportCompletion(ctx, req.(*ReportCompletionRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+func _SessionCoordinator_CloseSession_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(CloseSessionRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(SessionCoordinatorServer).CloseSession(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: SessionCoordinator_CloseSession_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(SessionCoordinatorServer).CloseSession(ctx, req.(*CloseSessionRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
+// SessionCoordinator_ServiceDesc is the grpc.ServiceDesc for SessionCoordinator service.
+// It's only intended for direct use with grpc.RegisterService,
+// and not to be introspected or modified (even as a copy)
+var SessionCoordinator_ServiceDesc = grpc.ServiceDesc{
+	ServiceName: "mpc.coordinator.v1.SessionCoordinator",
+	HandlerType: (*SessionCoordinatorServer)(nil),
+	Methods: []grpc.MethodDesc{
+		{
+			MethodName: "CreateSession",
+			Handler:    _SessionCoordinator_CreateSession_Handler,
+		},
+		{
+			MethodName: "JoinSession",
+			Handler:    _SessionCoordinator_JoinSession_Handler,
+		},
+		{
+			MethodName: "GetSessionStatus",
+			Handler:    _SessionCoordinator_GetSessionStatus_Handler,
+		},
+		{
+			MethodName: "MarkPartyReady",
+			Handler:    _SessionCoordinator_MarkPartyReady_Handler,
+		},
+		{
+			MethodName: "StartSession",
+			Handler:    _SessionCoordinator_StartSession_Handler,
+		},
+		{
+			MethodName: "ReportCompletion",
+			Handler:    _SessionCoordinator_ReportCompletion_Handler,
+		},
+		{
+			MethodName: "CloseSession",
+			Handler:    _SessionCoordinator_CloseSession_Handler,
+		},
+	},
+	Streams:  []grpc.StreamDesc{},
+	Metadata: "api/proto/session_coordinator.proto",
+}

backend/mpc-system/docker-compose.yml

@@ -39,48 +39,6 @@ services:
     networks:
       - mpc-network
     restart: unless-stopped
-    # 生产环境不暴露端口到主机，仅内部网络可访问
-    # ports:
-    #   - "5432:5432"
-
-  # Redis Cache
-  redis:
-    image: redis:7-alpine
-    container_name: mpc-redis
-    command: redis-server --appendonly yes --maxmemory 512mb --maxmemory-policy allkeys-lru ${REDIS_PASSWORD:+--requirepass $REDIS_PASSWORD}
-    volumes:
-      - redis-data:/data
-    healthcheck:
-      test: ["CMD", "redis-cli", "ping"]
-      interval: 10s
-      timeout: 5s
-      retries: 5
-    networks:
-      - mpc-network
-    restart: unless-stopped
-
-  # RabbitMQ Message Broker
-  rabbitmq:
-    image: rabbitmq:3-management-alpine
-    container_name: mpc-rabbitmq
-    environment:
-      RABBITMQ_DEFAULT_USER: ${RABBITMQ_USER:-mpc_user}
-      RABBITMQ_DEFAULT_PASS: ${RABBITMQ_PASSWORD:?RABBITMQ_PASSWORD must be set in .env}
-      RABBITMQ_DEFAULT_VHOST: /
-    volumes:
-      - rabbitmq-data:/var/lib/rabbitmq
-    healthcheck:
-      test: ["CMD", "rabbitmq-diagnostics", "-q", "ping"]
-      interval: 30s
-      timeout: 10s
-      retries: 5
-      start_period: 30s
-    networks:
-      - mpc-network
-    restart: unless-stopped
-    # 生产环境管理界面仅开发时使用
-    # ports:
-    #   - "15672:15672"
 
   # ============================================
   # MPC Core Services
@@ -104,23 +62,12 @@ services:
       MPC_DATABASE_PASSWORD: ${POSTGRES_PASSWORD:?POSTGRES_PASSWORD must be set}
       MPC_DATABASE_DBNAME: mpc_system
       MPC_DATABASE_SSLMODE: disable
-      MPC_REDIS_HOST: redis
-      MPC_REDIS_PORT: 6379
-      MPC_REDIS_PASSWORD: ${REDIS_PASSWORD:-}
-      MPC_RABBITMQ_HOST: rabbitmq
-      MPC_RABBITMQ_PORT: 5672
-      MPC_RABBITMQ_USER: ${RABBITMQ_USER:-mpc_user}
-      MPC_RABBITMQ_PASSWORD: ${RABBITMQ_PASSWORD:?RABBITMQ_PASSWORD must be set}
       MPC_JWT_SECRET_KEY: ${JWT_SECRET_KEY}
       MPC_JWT_ISSUER: mpc-system
       MESSAGE_ROUTER_ADDR: message-router:50051
     depends_on:
       postgres:
         condition: service_healthy
-      redis:
-        condition: service_healthy
-      rabbitmq:
-        condition: service_healthy
       message-router:
         condition: service_healthy
     healthcheck:
@@ -151,15 +98,9 @@ services:
       MPC_DATABASE_PASSWORD: ${POSTGRES_PASSWORD:?POSTGRES_PASSWORD must be set}
       MPC_DATABASE_DBNAME: mpc_system
       MPC_DATABASE_SSLMODE: disable
-      MPC_RABBITMQ_HOST: rabbitmq
-      MPC_RABBITMQ_PORT: 5672
-      MPC_RABBITMQ_USER: ${RABBITMQ_USER:-mpc_user}
-      MPC_RABBITMQ_PASSWORD: ${RABBITMQ_PASSWORD:?RABBITMQ_PASSWORD must be set}
     depends_on:
       postgres:
         condition: service_healthy
-      rabbitmq:
-        condition: service_healthy
     healthcheck:
       test: ["CMD", "curl", "-sf", "http://localhost:8080/health"]
       interval: 30s
@@ -342,13 +283,6 @@ services:
       MPC_DATABASE_PASSWORD: ${POSTGRES_PASSWORD:?POSTGRES_PASSWORD must be set}
       MPC_DATABASE_DBNAME: mpc_system
       MPC_DATABASE_SSLMODE: disable
-      MPC_REDIS_HOST: redis
-      MPC_REDIS_PORT: 6379
-      MPC_REDIS_PASSWORD: ${REDIS_PASSWORD:-}
-      MPC_RABBITMQ_HOST: rabbitmq
-      MPC_RABBITMQ_PORT: 5672
-      MPC_RABBITMQ_USER: ${RABBITMQ_USER:-mpc_user}
-      MPC_RABBITMQ_PASSWORD: ${RABBITMQ_PASSWORD:?RABBITMQ_PASSWORD must be set}
       MPC_COORDINATOR_URL: session-coordinator:50051
       MPC_JWT_SECRET_KEY: ${JWT_SECRET_KEY}
       # API 认证密钥 (与 mpc-service 配置的 MPC_API_KEY 一致)
@@ -359,10 +293,6 @@ services:
     depends_on:
       postgres:
         condition: service_healthy
-      redis:
-        condition: service_healthy
-      rabbitmq:
-        condition: service_healthy
       session-coordinator:
         condition: service_healthy
     healthcheck:
@@ -388,7 +318,3 @@ networks:
 volumes:
   postgres-data:
     driver: local
-  redis-data:
-    driver: local
-  rabbitmq-data:
-    driver: local

backend/mpc-system/pkg/grpcutil/client.go

@@ -0,0 +1,249 @@
+package grpcutil
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"github.com/rwadurian/mpc-system/pkg/logger"
+	"go.uber.org/zap"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/connectivity"
+	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/keepalive"
+)
+
+// ClientConfig holds configuration for gRPC client connections
+type ClientConfig struct {
+	// Connection settings
+	Address            string
+	ConnectTimeout     time.Duration
+	BlockingConnect    bool
+
+	// Keepalive settings
+	KeepaliveTime      time.Duration // How often to send pings
+	KeepaliveTimeout   time.Duration // How long to wait for ping ack
+	PermitWithoutStream bool         // Allow pings even without active streams
+
+	// Reconnection settings
+	EnableReconnect    bool
+	ReconnectBackoff   time.Duration
+	MaxReconnectBackoff time.Duration
+}
+
+// DefaultClientConfig returns a sensible default configuration
+func DefaultClientConfig(address string) ClientConfig {
+	return ClientConfig{
+		Address:             address,
+		ConnectTimeout:      10 * time.Second,
+		BlockingConnect:     true,
+		KeepaliveTime:       30 * time.Second,
+		KeepaliveTimeout:    10 * time.Second,
+		PermitWithoutStream: true,
+		EnableReconnect:     true,
+		ReconnectBackoff:    1 * time.Second,
+		MaxReconnectBackoff: 30 * time.Second,
+	}
+}
+
+// ResilientConn wraps a gRPC connection with automatic reconnection
+type ResilientConn struct {
+	config    ClientConfig
+	conn      *grpc.ClientConn
+	mu        sync.RWMutex
+	closed    bool
+	closeChan chan struct{}
+}
+
+// NewResilientConn creates a new resilient gRPC connection
+func NewResilientConn(config ClientConfig) (*ResilientConn, error) {
+	rc := &ResilientConn{
+		config:    config,
+		closeChan: make(chan struct{}),
+	}
+
+	// Initial connection
+	conn, err := rc.dial()
+	if err != nil {
+		return nil, err
+	}
+	rc.conn = conn
+
+	// Start connection monitor if reconnection is enabled
+	if config.EnableReconnect {
+		go rc.monitorConnection()
+	}
+
+	return rc, nil
+}
+
+// dial creates a new gRPC connection with keepalive settings
+func (rc *ResilientConn) dial() (*grpc.ClientConn, error) {
+	// Build dial options
+	opts := []grpc.DialOption{
+		grpc.WithTransportCredentials(insecure.NewCredentials()),
+		grpc.WithKeepaliveParams(keepalive.ClientParameters{
+			Time:                rc.config.KeepaliveTime,
+			Timeout:             rc.config.KeepaliveTimeout,
+			PermitWithoutStream: rc.config.PermitWithoutStream,
+		}),
+	}
+
+	if rc.config.BlockingConnect {
+		opts = append(opts, grpc.WithBlock())
+	}
+
+	// Create context with timeout for connection
+	ctx, cancel := context.WithTimeout(context.Background(), rc.config.ConnectTimeout)
+	defer cancel()
+
+	conn, err := grpc.DialContext(ctx, rc.config.Address, opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	logger.Info("gRPC connection established",
+		zap.String("address", rc.config.Address),
+		zap.Duration("keepalive_time", rc.config.KeepaliveTime))
+
+	return conn, nil
+}
+
+// monitorConnection monitors the connection state and reconnects if needed
+func (rc *ResilientConn) monitorConnection() {
+	backoff := rc.config.ReconnectBackoff
+
+	for {
+		select {
+		case <-rc.closeChan:
+			return
+		default:
+		}
+
+		rc.mu.RLock()
+		conn := rc.conn
+		closed := rc.closed
+		rc.mu.RUnlock()
+
+		if closed {
+			return
+		}
+
+		// Wait for state change
+		state := conn.GetState()
+		if state == connectivity.TransientFailure || state == connectivity.Shutdown {
+			logger.Warn("gRPC connection lost, attempting reconnection",
+				zap.String("address", rc.config.Address),
+				zap.String("state", state.String()))
+
+			// Attempt reconnection with backoff
+			for {
+				select {
+				case <-rc.closeChan:
+					return
+				case <-time.After(backoff):
+				}
+
+				newConn, err := rc.dial()
+				if err != nil {
+					logger.Error("Reconnection failed, retrying",
+						zap.String("address", rc.config.Address),
+						zap.Duration("backoff", backoff),
+						zap.Error(err))
+
+					// Increase backoff
+					backoff = backoff * 2
+					if backoff > rc.config.MaxReconnectBackoff {
+						backoff = rc.config.MaxReconnectBackoff
+					}
+					continue
+				}
+
+				// Successfully reconnected
+				rc.mu.Lock()
+				oldConn := rc.conn
+				rc.conn = newConn
+				rc.mu.Unlock()
+
+				// Close old connection
+				if oldConn != nil {
+					oldConn.Close()
+				}
+
+				logger.Info("gRPC connection restored",
+					zap.String("address", rc.config.Address))
+
+				// Reset backoff
+				backoff = rc.config.ReconnectBackoff
+				break
+			}
+		}
+
+		// Wait for next state change or check periodically
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		conn.WaitForStateChange(ctx, state)
+		cancel()
+	}
+}
+
+// GetConn returns the current connection
+func (rc *ResilientConn) GetConn() *grpc.ClientConn {
+	rc.mu.RLock()
+	defer rc.mu.RUnlock()
+	return rc.conn
+}
+
+// IsConnected returns true if the connection is ready
+func (rc *ResilientConn) IsConnected() bool {
+	rc.mu.RLock()
+	defer rc.mu.RUnlock()
+	if rc.conn == nil {
+		return false
+	}
+	state := rc.conn.GetState()
+	return state == connectivity.Ready || state == connectivity.Idle
+}
+
+// WaitForReady waits for the connection to be ready
+func (rc *ResilientConn) WaitForReady(ctx context.Context) bool {
+	for {
+		rc.mu.RLock()
+		conn := rc.conn
+		rc.mu.RUnlock()
+
+		if conn == nil {
+			return false
+		}
+
+		state := conn.GetState()
+		if state == connectivity.Ready {
+			return true
+		}
+		if state == connectivity.Shutdown {
+			return false
+		}
+
+		// Wait for state change
+		if !conn.WaitForStateChange(ctx, state) {
+			return false // Context cancelled
+		}
+	}
+}
+
+// Close closes the connection and stops the monitor
+func (rc *ResilientConn) Close() error {
+	rc.mu.Lock()
+	defer rc.mu.Unlock()
+
+	if rc.closed {
+		return nil
+	}
+
+	rc.closed = true
+	close(rc.closeChan)
+
+	if rc.conn != nil {
+		return rc.conn.Close()
+	}
+	return nil
+}

backend/mpc-system/pkg/middleware/auth.go

@@ -0,0 +1,186 @@
+package middleware
+
+import (
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+	"github.com/rwadurian/mpc-system/pkg/jwt"
+	"github.com/rwadurian/mpc-system/pkg/logger"
+	"go.uber.org/zap"
+)
+
+// AuthConfig holds configuration for authentication middleware
+type AuthConfig struct {
+	JWTService      *jwt.JWTService
+	SkipPaths       []string // Paths to skip authentication (e.g., /health, /auth/*)
+	AllowAnonymous  bool     // If true, allow requests without token (user info will be nil)
+}
+
+// ContextKey is a custom type for context keys to avoid collisions
+type ContextKey string
+
+const (
+	// UserContextKey is the key for storing user info in gin context
+	UserContextKey ContextKey = "user"
+	// ClaimsContextKey is the key for storing JWT claims in gin context
+	ClaimsContextKey ContextKey = "claims"
+)
+
+// UserInfo represents authenticated user information
+type UserInfo struct {
+	UserID   string
+	Username string
+}
+
+// BearerAuth creates a middleware that validates Bearer tokens
+// Extracts token from Authorization header: "Bearer <token>"
+func BearerAuth(config AuthConfig) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		// Check if path should be skipped
+		path := c.Request.URL.Path
+		for _, skipPath := range config.SkipPaths {
+			if matchPath(skipPath, path) {
+				c.Next()
+				return
+			}
+		}
+
+		// Extract token from Authorization header
+		authHeader := c.GetHeader("Authorization")
+		if authHeader == "" {
+			if config.AllowAnonymous {
+				c.Next()
+				return
+			}
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error":   "unauthorized",
+				"message": "missing authorization header",
+			})
+			return
+		}
+
+		// Check Bearer prefix
+		parts := strings.SplitN(authHeader, " ", 2)
+		if len(parts) != 2 || strings.ToLower(parts[0]) != "bearer" {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error":   "unauthorized",
+				"message": "invalid authorization header format, expected: Bearer <token>",
+			})
+			return
+		}
+
+		token := parts[1]
+
+		// Validate access token
+		claims, err := config.JWTService.ValidateAccessToken(token)
+		if err != nil {
+			logger.Debug("Token validation failed",
+				zap.Error(err),
+				zap.String("path", path))
+
+			statusCode := http.StatusUnauthorized
+			message := "invalid token"
+
+			if err == jwt.ErrExpiredToken {
+				message = "token expired"
+			}
+
+			c.AbortWithStatusJSON(statusCode, gin.H{
+				"error":   "unauthorized",
+				"message": message,
+			})
+			return
+		}
+
+		// Store user info in context
+		userInfo := &UserInfo{
+			UserID:   claims.Subject,
+			Username: claims.Username,
+		}
+		c.Set(string(UserContextKey), userInfo)
+		c.Set(string(ClaimsContextKey), claims)
+
+		logger.Debug("Request authenticated",
+			zap.String("user_id", userInfo.UserID),
+			zap.String("username", userInfo.Username),
+			zap.String("path", path))
+
+		c.Next()
+	}
+}
+
+// GetUser extracts UserInfo from gin context
+func GetUser(c *gin.Context) *UserInfo {
+	if user, exists := c.Get(string(UserContextKey)); exists {
+		if userInfo, ok := user.(*UserInfo); ok {
+			return userInfo
+		}
+	}
+	return nil
+}
+
+// RequireUser is a middleware that ensures user is authenticated
+// Use this after BearerAuth with AllowAnonymous=true
+func RequireUser() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		user := GetUser(c)
+		if user == nil {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error":   "unauthorized",
+				"message": "authentication required",
+			})
+			return
+		}
+		c.Next()
+	}
+}
+
+// RequireOwnership is a middleware that ensures the authenticated user
+// matches the resource owner (identified by a path parameter)
+func RequireOwnership(paramName string) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		user := GetUser(c)
+		if user == nil {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{
+				"error":   "unauthorized",
+				"message": "authentication required",
+			})
+			return
+		}
+
+		resourceOwner := c.Param(paramName)
+		if resourceOwner != "" && resourceOwner != user.UserID && resourceOwner != user.Username {
+			c.AbortWithStatusJSON(http.StatusForbidden, gin.H{
+				"error":   "forbidden",
+				"message": "access denied to this resource",
+			})
+			return
+		}
+
+		c.Next()
+	}
+}
+
+// matchPath checks if a pattern matches a path
+// Supports wildcard suffix: "/auth/*" matches "/auth/login", "/auth/refresh"
+func matchPath(pattern, path string) bool {
+	// Exact match
+	if pattern == path {
+		return true
+	}
+
+	// Wildcard match
+	if strings.HasSuffix(pattern, "/*") {
+		prefix := strings.TrimSuffix(pattern, "/*")
+		return strings.HasPrefix(path, prefix+"/") || path == prefix
+	}
+
+	// Prefix match (for backward compatibility)
+	if strings.HasSuffix(pattern, "*") {
+		prefix := strings.TrimSuffix(pattern, "*")
+		return strings.HasPrefix(path, prefix)
+	}
+
+	return false
+}

backend/mpc-system/pkg/middleware/cors.go

@@ -0,0 +1,134 @@
+package middleware
+
+import (
+	"net/http"
+	"strconv"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+)
+
+// CORSConfig holds configuration for CORS middleware
+type CORSConfig struct {
+	// AllowOrigins is a list of origins that are allowed to access the resource
+	// Use "*" to allow all origins (not recommended for production)
+	AllowOrigins []string
+	// AllowMethods is a list of HTTP methods allowed for CORS requests
+	AllowMethods []string
+	// AllowHeaders is a list of headers that are allowed in CORS requests
+	AllowHeaders []string
+	// ExposeHeaders is a list of headers that the browser is allowed to access
+	ExposeHeaders []string
+	// AllowCredentials indicates whether credentials (cookies, auth headers) are allowed
+	AllowCredentials bool
+	// MaxAge is the maximum time (in seconds) that preflight results can be cached
+	MaxAge int
+}
+
+// DefaultCORSConfig returns a default CORS configuration
+func DefaultCORSConfig() CORSConfig {
+	return CORSConfig{
+		AllowOrigins: []string{},
+		AllowMethods: []string{"GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"},
+		AllowHeaders: []string{
+			"Origin",
+			"Content-Type",
+			"Accept",
+			"Authorization",
+			"X-Requested-With",
+			"X-Request-ID",
+		},
+		ExposeHeaders:    []string{"Content-Length", "X-Request-ID"},
+		AllowCredentials: true,
+		MaxAge:           86400, // 24 hours
+	}
+}
+
+// CORS creates a middleware that handles Cross-Origin Resource Sharing
+func CORS(config CORSConfig) gin.HandlerFunc {
+	// Precompute allowed origins map for fast lookup
+	allowedOrigins := make(map[string]bool)
+	allowAllOrigins := false
+	for _, origin := range config.AllowOrigins {
+		if origin == "*" {
+			allowAllOrigins = true
+			break
+		}
+		allowedOrigins[origin] = true
+	}
+
+	// Precompute header values
+	allowMethodsHeader := strings.Join(config.AllowMethods, ", ")
+	allowHeadersHeader := strings.Join(config.AllowHeaders, ", ")
+	exposeHeadersHeader := strings.Join(config.ExposeHeaders, ", ")
+	maxAgeHeader := strconv.Itoa(config.MaxAge)
+
+	return func(c *gin.Context) {
+		origin := c.GetHeader("Origin")
+
+		// If no origin header, this is not a CORS request
+		if origin == "" {
+			c.Next()
+			return
+		}
+
+		// Check if origin is allowed
+		var allowOrigin string
+		if allowAllOrigins {
+			allowOrigin = "*"
+		} else if allowedOrigins[origin] {
+			allowOrigin = origin
+		} else {
+			// Origin not allowed, but still process the request
+			// The browser will block the response based on missing headers
+			c.Next()
+			return
+		}
+
+		// Set CORS headers
+		c.Header("Access-Control-Allow-Origin", allowOrigin)
+
+		if config.AllowCredentials && !allowAllOrigins {
+			c.Header("Access-Control-Allow-Credentials", "true")
+		}
+
+		if exposeHeadersHeader != "" {
+			c.Header("Access-Control-Expose-Headers", exposeHeadersHeader)
+		}
+
+		// Handle preflight request
+		if c.Request.Method == http.MethodOptions {
+			c.Header("Access-Control-Allow-Methods", allowMethodsHeader)
+			c.Header("Access-Control-Allow-Headers", allowHeadersHeader)
+			c.Header("Access-Control-Max-Age", maxAgeHeader)
+			c.AbortWithStatus(http.StatusNoContent)
+			return
+		}
+
+		c.Next()
+	}
+}
+
+// AllowAllCORS is a permissive CORS middleware (for development only)
+// WARNING: Do not use in production
+func AllowAllCORS() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		origin := c.GetHeader("Origin")
+		if origin == "" {
+			origin = "*"
+		}
+
+		c.Header("Access-Control-Allow-Origin", origin)
+		c.Header("Access-Control-Allow-Methods", "GET, POST, PUT, PATCH, DELETE, OPTIONS")
+		c.Header("Access-Control-Allow-Headers", "Origin, Content-Type, Accept, Authorization, X-Requested-With")
+		c.Header("Access-Control-Allow-Credentials", "true")
+		c.Header("Access-Control-Max-Age", "86400")
+
+		if c.Request.Method == http.MethodOptions {
+			c.AbortWithStatus(http.StatusNoContent)
+			return
+		}
+
+		c.Next()
+	}
+}

backend/mpc-system/pkg/middleware/security.go

@@ -0,0 +1,90 @@
+package middleware
+
+import (
+	"github.com/gin-gonic/gin"
+)
+
+// SecurityConfig holds configuration for security headers middleware
+type SecurityConfig struct {
+	// EnableHSTS enables HTTP Strict Transport Security header
+	EnableHSTS bool
+	// HSTSMaxAge is the max-age value for HSTS in seconds (default: 31536000 = 1 year)
+	HSTSMaxAge int
+	// EnableNoSniff enables X-Content-Type-Options: nosniff
+	EnableNoSniff bool
+	// EnableXSSFilter enables X-XSS-Protection header
+	EnableXSSFilter bool
+	// EnableFrameDeny enables X-Frame-Options: DENY
+	EnableFrameDeny bool
+	// ContentSecurityPolicy sets the Content-Security-Policy header
+	ContentSecurityPolicy string
+	// ReferrerPolicy sets the Referrer-Policy header
+	ReferrerPolicy string
+}
+
+// DefaultSecurityConfig returns a secure default configuration
+func DefaultSecurityConfig() SecurityConfig {
+	return SecurityConfig{
+		EnableHSTS:            true,
+		HSTSMaxAge:            31536000, // 1 year
+		EnableNoSniff:         true,
+		EnableXSSFilter:       true,
+		EnableFrameDeny:       true,
+		ContentSecurityPolicy: "default-src 'self'",
+		ReferrerPolicy:        "strict-origin-when-cross-origin",
+	}
+}
+
+// SecurityHeaders creates a middleware that adds security headers to responses
+func SecurityHeaders(config SecurityConfig) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		// Prevent MIME type sniffing
+		if config.EnableNoSniff {
+			c.Header("X-Content-Type-Options", "nosniff")
+		}
+
+		// XSS protection (legacy, but still useful for older browsers)
+		if config.EnableXSSFilter {
+			c.Header("X-XSS-Protection", "1; mode=block")
+		}
+
+		// Prevent clickjacking
+		if config.EnableFrameDeny {
+			c.Header("X-Frame-Options", "DENY")
+		}
+
+		// HTTP Strict Transport Security
+		if config.EnableHSTS {
+			hstsValue := "max-age=31536000; includeSubDomains"
+			if config.HSTSMaxAge > 0 {
+				hstsValue = "max-age=" + string(rune(config.HSTSMaxAge)) + "; includeSubDomains"
+			}
+			c.Header("Strict-Transport-Security", hstsValue)
+		}
+
+		// Content Security Policy
+		if config.ContentSecurityPolicy != "" {
+			c.Header("Content-Security-Policy", config.ContentSecurityPolicy)
+		}
+
+		// Referrer Policy
+		if config.ReferrerPolicy != "" {
+			c.Header("Referrer-Policy", config.ReferrerPolicy)
+		}
+
+		// Permissions Policy (formerly Feature-Policy)
+		c.Header("Permissions-Policy", "geolocation=(), microphone=(), camera=()")
+
+		// Cache control for API responses
+		c.Header("Cache-Control", "no-store, no-cache, must-revalidate, proxy-revalidate")
+		c.Header("Pragma", "no-cache")
+		c.Header("Expires", "0")
+
+		c.Next()
+	}
+}
+
+// SecureHeaders is a convenience function that applies default security headers
+func SecureHeaders() gin.HandlerFunc {
+	return SecurityHeaders(DefaultSecurityConfig())
+}

backend/mpc-system/pkg/retry/retry.go

@@ -0,0 +1,136 @@
+package retry
+
+import (
+	"context"
+	"time"
+
+	"github.com/rwadurian/mpc-system/pkg/logger"
+	"go.uber.org/zap"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+// Config defines retry configuration
+type Config struct {
+	MaxAttempts     int           // Maximum number of retry attempts (default: 3)
+	InitialBackoff  time.Duration // Initial backoff duration (default: 100ms)
+	MaxBackoff      time.Duration // Maximum backoff duration (default: 5s)
+	BackoffMultiple float64       // Backoff multiplier (default: 2.0)
+}
+
+// DefaultConfig returns default retry configuration
+func DefaultConfig() Config {
+	return Config{
+		MaxAttempts:     3,
+		InitialBackoff:  100 * time.Millisecond,
+		MaxBackoff:      5 * time.Second,
+		BackoffMultiple: 2.0,
+	}
+}
+
+// Do executes a function with retry logic
+// Returns the result of the function or the last error after all retries are exhausted
+func Do[T any](ctx context.Context, cfg Config, operation string, fn func() (T, error)) (T, error) {
+	var result T
+	var lastErr error
+
+	backoff := cfg.InitialBackoff
+
+	for attempt := 1; attempt <= cfg.MaxAttempts; attempt++ {
+		result, lastErr = fn()
+		if lastErr == nil {
+			return result, nil
+		}
+
+		// Check if error is retryable
+		if !IsRetryable(lastErr) {
+			logger.Warn("Non-retryable error, not retrying",
+				zap.String("operation", operation),
+				zap.Int("attempt", attempt),
+				zap.Error(lastErr))
+			return result, lastErr
+		}
+
+		// Check if context is cancelled
+		if ctx.Err() != nil {
+			logger.Warn("Context cancelled, stopping retry",
+				zap.String("operation", operation),
+				zap.Int("attempt", attempt),
+				zap.Error(ctx.Err()))
+			return result, ctx.Err()
+		}
+
+		// Don't wait after the last attempt
+		if attempt < cfg.MaxAttempts {
+			logger.Warn("Operation failed, retrying",
+				zap.String("operation", operation),
+				zap.Int("attempt", attempt),
+				zap.Int("max_attempts", cfg.MaxAttempts),
+				zap.Duration("backoff", backoff),
+				zap.Error(lastErr))
+
+			select {
+			case <-ctx.Done():
+				return result, ctx.Err()
+			case <-time.After(backoff):
+			}
+
+			// Calculate next backoff
+			backoff = time.Duration(float64(backoff) * cfg.BackoffMultiple)
+			if backoff > cfg.MaxBackoff {
+				backoff = cfg.MaxBackoff
+			}
+		}
+	}
+
+	logger.Error("Operation failed after all retries",
+		zap.String("operation", operation),
+		zap.Int("attempts", cfg.MaxAttempts),
+		zap.Error(lastErr))
+
+	return result, lastErr
+}
+
+// DoVoid executes a function that returns only error with retry logic
+func DoVoid(ctx context.Context, cfg Config, operation string, fn func() error) error {
+	_, err := Do(ctx, cfg, operation, func() (struct{}, error) {
+		return struct{}{}, fn()
+	})
+	return err
+}
+
+// IsRetryable determines if an error is retryable
+func IsRetryable(err error) bool {
+	if err == nil {
+		return false
+	}
+
+	// Check gRPC status codes
+	st, ok := status.FromError(err)
+	if !ok {
+		// Not a gRPC error, assume retryable for network errors
+		return true
+	}
+
+	switch st.Code() {
+	case codes.Unavailable,
+		codes.ResourceExhausted,
+		codes.Aborted,
+		codes.Internal,
+		codes.Unknown,
+		codes.DeadlineExceeded:
+		return true
+	case codes.InvalidArgument,
+		codes.NotFound,
+		codes.AlreadyExists,
+		codes.PermissionDenied,
+		codes.FailedPrecondition,
+		codes.OutOfRange,
+		codes.Unimplemented,
+		codes.Canceled,
+		codes.Unauthenticated:
+		return false
+	default:
+		return false
+	}
+}

backend/mpc-system/services/account/adapters/input/http/account_handler.go

@@ -74,6 +74,7 @@ func (h *AccountHTTPHandler) RegisterRoutes(router *gin.RouterGroup) {
 	accounts := router.Group("/accounts")
 	{
 		accounts.POST("", h.CreateAccount)
+		accounts.POST("/from-keygen", h.CreateAccountFromKeygen)
 		accounts.GET("", h.ListAccounts)
 		accounts.GET("/:id", h.GetAccount)
 		accounts.PUT("/:id", h.UpdateAccount)
@@ -535,20 +536,15 @@ func (h *AccountHTTPHandler) CancelRecovery(c *gin.Context) {
 // ============================================
 
 // CreateKeygenSessionRequest represents the request for creating a keygen session
+// Coordinator will automatically select parties from registered pool
 type CreateKeygenSessionRequest struct {
-	ThresholdN   int                   `json:"threshold_n" binding:"required,min=2"`
+	ThresholdN      int  `json:"threshold_n" binding:"required,min=2"` // Total number of parties (e.g., 3)
-	ThresholdT   int                   `json:"threshold_t" binding:"required,min=1"`
+	ThresholdT      int  `json:"threshold_t" binding:"required,min=1"` // Threshold for signing (e.g., 2)
-	Participants []ParticipantRequest  `json:"participants" binding:"required,min=2"`
+	RequireDelegate bool `json:"require_delegate"`                     // If true, one party will be delegate (returns share to user)
-}
-
-// ParticipantRequest represents a participant in the request
-type ParticipantRequest struct {
-	PartyID    string `json:"party_id" binding:"required"`
-	DeviceType string `json:"device_type"`
-	DeviceID   string `json:"device_id"`
 }
 
 // CreateKeygenSession handles creating a new keygen session
+// Parties are automatically selected by Coordinator from registered pool
 func (h *AccountHTTPHandler) CreateKeygenSession(c *gin.Context) {
 	var req CreateKeygenSessionRequest
 	if err := c.ShouldBindJSON(&req); err != nil {
@@ -562,35 +558,33 @@ func (h *AccountHTTPHandler) CreateKeygenSession(c *gin.Context) {
 		return
 	}
 
-	if len(req.Participants) != req.ThresholdN {
+	// Call session coordinator via gRPC (no participants - coordinator selects automatically)
-		c.JSON(http.StatusBadRequest, gin.H{"error": "number of participants must equal threshold_n"})
-		return
-	}
-
-	// Convert participants to gRPC format
-	participants := make([]grpc.ParticipantInfo, len(req.Participants))
-	for i, p := range req.Participants {
-		participants[i] = grpc.ParticipantInfo{
-			PartyID:    p.PartyID,
-			DeviceType: p.DeviceType,
-			DeviceID:   p.DeviceID,
-		}
-	}
-
-	// Call session coordinator via gRPC
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()
 
-	logger.Info("Calling CreateKeygenSession via gRPC",
+	logger.Info("Calling CreateKeygenSession via gRPC (auto party selection)",
 		zap.Int("threshold_n", req.ThresholdN),
 		zap.Int("threshold_t", req.ThresholdT),
-		zap.Int("num_participants", len(participants)))
+		zap.Bool("require_delegate", req.RequireDelegate))
 
-	resp, err := h.sessionCoordinatorClient.CreateKeygenSession(
+	// Calculate party composition based on require_delegate
+	var persistentCount, delegateCount int
+	if req.RequireDelegate {
+		// One delegate party, rest are persistent
+		delegateCount = 1
+		persistentCount = req.ThresholdN - 1
+	} else {
+		// All persistent parties
+		persistentCount = req.ThresholdN
+		delegateCount = 0
+	}
+
+	resp, err := h.sessionCoordinatorClient.CreateKeygenSessionAuto(
 		ctx,
 		int32(req.ThresholdN),
 		int32(req.ThresholdT),
-		participants,
+		int32(persistentCount),
+		int32(delegateCount),
 		600, // 10 minutes expiry
 	)
 
@@ -602,26 +596,30 @@ func (h *AccountHTTPHandler) CreateKeygenSession(c *gin.Context) {
 
 	logger.Info("gRPC CreateKeygenSession succeeded",
 		zap.String("session_id", resp.SessionID),
-		zap.Int("num_join_tokens", len(resp.JoinTokens)))
+		zap.Int("num_parties", len(resp.SelectedParties)))
 
+	// Return response with selected parties info
 	c.JSON(http.StatusCreated, gin.H{
-		"session_id":  resp.SessionID,
+		"session_id":       resp.SessionID,
-		"session_type": "keygen",
+		"session_type":     "keygen",
-		"threshold_n": req.ThresholdN,
+		"threshold_n":      req.ThresholdN,
-		"threshold_t": req.ThresholdT,
+		"threshold_t":      req.ThresholdT,
-		"join_tokens": resp.JoinTokens,
+		"selected_parties": resp.SelectedParties,
-		"status":      "created",
+		"delegate_party":   resp.DelegateParty, // The party that will return share to user
+		"status":           "created",
 	})
 }
 
 // CreateSigningSessionRequest represents the request for creating a signing session
+// Coordinator will automatically select parties based on account's registered shares
 type CreateSigningSessionRequest struct {
-	AccountID    string               `json:"account_id" binding:"required"`
+	AccountID   string `json:"account_id" binding:"required"`    // Account to sign for
-	MessageHash  string               `json:"message_hash" binding:"required"`
+	MessageHash string `json:"message_hash" binding:"required"`  // SHA-256 hash to sign (hex encoded)
-	Participants []ParticipantRequest `json:"participants" binding:"required,min=2"`
+	UserShare   string `json:"user_share"`                       // Optional: user's encrypted share (hex) if delegate party is used
 }
 
 // CreateSigningSession handles creating a new signing session
+// Parties are automatically selected based on the account's registered shares
 func (h *AccountHTTPHandler) CreateSigningSession(c *gin.Context) {
 	var req CreateSigningSessionRequest
 	if err := c.ShouldBindJSON(&req); err != nil {
@@ -648,8 +646,8 @@ func (h *AccountHTTPHandler) CreateSigningSession(c *gin.Context) {
 		return
 	}
 
-	// Get account to verify it exists and get threshold info
+	// Get account to verify it exists and get share info
-	output, err := h.getAccountUC.Execute(c.Request.Context(), ports.GetAccountInput{
+	accountOutput, err := h.getAccountUC.Execute(c.Request.Context(), ports.GetAccountInput{
 		AccountID: &accountID,
 	})
 	if err != nil {
@@ -657,51 +655,59 @@ func (h *AccountHTTPHandler) CreateSigningSession(c *gin.Context) {
 		return
 	}
 
-	// Validate participant count against threshold
+	// Get the party IDs from account shares
-	if len(req.Participants) < output.Account.ThresholdT {
+	var partyIDs []string
-		c.JSON(http.StatusBadRequest, gin.H{
+	for _, share := range accountOutput.Shares {
-			"error": "insufficient participants",
+		if share.IsActive {
-			"required": output.Account.ThresholdT,
+			partyIDs = append(partyIDs, share.PartyID)
-			"provided": len(req.Participants),
+		}
-		})
-		return
 	}
 
-	// Convert participants to gRPC format
+	// Validate we have enough active shares
-	participants := make([]grpc.ParticipantInfo, len(req.Participants))
+	if len(partyIDs) < accountOutput.Account.ThresholdT {
-	for i, p := range req.Participants {
+		c.JSON(http.StatusBadRequest, gin.H{
-		participants[i] = grpc.ParticipantInfo{
+			"error":    "insufficient active shares for signing",
-			PartyID:    p.PartyID,
+			"required": accountOutput.Account.ThresholdT,
-			DeviceType: p.DeviceType,
+			"active":   len(partyIDs),
-			DeviceID:   p.DeviceID,
+		})
-		}
+		return
 	}
 
 	// Call session coordinator via gRPC
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()
 
-	resp, err := h.sessionCoordinatorClient.CreateSigningSession(
+	logger.Info("Calling CreateSigningSession via gRPC (auto party selection)",
+		zap.String("account_id", req.AccountID),
+		zap.Int("threshold_t", accountOutput.Account.ThresholdT),
+		zap.Int("available_parties", len(partyIDs)))
+
+	resp, err := h.sessionCoordinatorClient.CreateSigningSessionAuto(
 		ctx,
-		int32(output.Account.ThresholdT),
+		int32(accountOutput.Account.ThresholdT),
-		participants,
+		partyIDs,
 		messageHash,
 		600, // 10 minutes expiry
 	)
 
 	if err != nil {
+		logger.Error("gRPC CreateSigningSession failed", zap.Error(err))
 		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 		return
 	}
 
+	logger.Info("gRPC CreateSigningSession succeeded",
+		zap.String("session_id", resp.SessionID),
+		zap.Int("num_parties", len(resp.SelectedParties)))
+
 	c.JSON(http.StatusCreated, gin.H{
-		"session_id":   resp.SessionID,
+		"session_id":       resp.SessionID,
-		"session_type": "sign",
+		"session_type":     "sign",
-		"account_id":   req.AccountID,
+		"account_id":       req.AccountID,
-		"message_hash": req.MessageHash,
+		"message_hash":     req.MessageHash,
-		"threshold_t":  output.Account.ThresholdT,
+		"threshold_t":      accountOutput.Account.ThresholdT,
-		"join_tokens":  resp.JoinTokens,
+		"selected_parties": resp.SelectedParties,
-		"status":       "created",
+		"status":           "created",
 	})
 }
 
@@ -742,3 +748,112 @@ func (h *AccountHTTPHandler) GetSessionStatus(c *gin.Context) {
 
 	c.JSON(http.StatusOK, response)
 }
+
+// ============================================
+// Account Creation from Keygen (Internal API)
+// ============================================
+
+// CreateAccountFromKeygenRequest represents the request from Session Coordinator
+// after keygen completion
+type CreateAccountFromKeygenRequest struct {
+	PublicKey       string                     `json:"public_key" binding:"required"`
+	KeygenSessionID string                     `json:"keygen_session_id" binding:"required"`
+	ThresholdN      int                        `json:"threshold_n" binding:"required,min=2"`
+	ThresholdT      int                        `json:"threshold_t" binding:"required,min=1"`
+	Shares          []ShareInfoFromKeygenInput `json:"shares" binding:"required,min=1"`
+}
+
+// ShareInfoFromKeygenInput represents share info from keygen
+type ShareInfoFromKeygenInput struct {
+	PartyID    string `json:"party_id" binding:"required"`
+	PartyIndex int    `json:"party_index"`
+	ShareType  string `json:"share_type" binding:"required"` // "persistent" or "delegate"
+}
+
+// CreateAccountFromKeygen handles account creation after keygen completion
+// This is called by Session Coordinator when all parties complete keygen
+func (h *AccountHTTPHandler) CreateAccountFromKeygen(c *gin.Context) {
+	var req CreateAccountFromKeygenRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	// Validate threshold
+	if req.ThresholdT > req.ThresholdN {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "threshold_t cannot be greater than threshold_n"})
+		return
+	}
+
+	// Decode public key
+	publicKey, err := hex.DecodeString(req.PublicKey)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid public key format"})
+		return
+	}
+
+	// Parse keygen session ID
+	keygenSessionID, err := uuid.Parse(req.KeygenSessionID)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid keygen_session_id format"})
+		return
+	}
+
+	// Generate a unique username based on keygen session ID
+	// In production, you might want a different naming scheme
+	username := "wallet-" + req.KeygenSessionID[:8]
+
+	// Convert shares - map share type string to value_objects.ShareType
+	shares := make([]ports.ShareInput, len(req.Shares))
+	for i, s := range req.Shares {
+		var shareType value_objects.ShareType
+		switch s.ShareType {
+		case "persistent", "server":
+			shareType = value_objects.ShareTypeServer
+		case "delegate", "user_device":
+			shareType = value_objects.ShareTypeUserDevice
+		default:
+			shareType = value_objects.ShareTypeServer
+		}
+		shares[i] = ports.ShareInput{
+			ShareType:  shareType,
+			PartyID:    s.PartyID,
+			PartyIndex: s.PartyIndex,
+		}
+	}
+
+	logger.Info("Creating account from keygen",
+		zap.String("keygen_session_id", req.KeygenSessionID),
+		zap.String("username", username),
+		zap.Int("threshold_n", req.ThresholdN),
+		zap.Int("threshold_t", req.ThresholdT),
+		zap.Int("num_shares", len(shares)))
+
+	// Create account
+	output, err := h.createAccountUC.Execute(c.Request.Context(), ports.CreateAccountInput{
+		Username:        username,
+		PublicKey:       publicKey,
+		KeygenSessionID: keygenSessionID,
+		ThresholdN:      req.ThresholdN,
+		ThresholdT:      req.ThresholdT,
+		Shares:          shares,
+	})
+	if err != nil {
+		logger.Error("Failed to create account from keygen",
+			zap.String("keygen_session_id", req.KeygenSessionID),
+			zap.Error(err))
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+
+	logger.Info("Account created from keygen successfully",
+		zap.String("account_id", output.Account.ID.String()),
+		zap.String("username", output.Account.Username),
+		zap.String("keygen_session_id", req.KeygenSessionID))
+
+	c.JSON(http.StatusCreated, gin.H{
+		"account_id": output.Account.ID.String(),
+		"username":   output.Account.Username,
+		"public_key": hex.EncodeToString(output.Account.PublicKey),
+	})
+}

backend/mpc-system/services/account/adapters/output/grpc/session_coordinator_client.go

@@ -62,39 +62,34 @@ func NewSessionCoordinatorClient(address string) (*SessionCoordinatorClient, err
 	}, nil
 }
 
-// CreateKeygenSession creates a new keygen session
+// CreateKeygenSessionAuto creates a new keygen session with automatic party selection
-func (c *SessionCoordinatorClient) CreateKeygenSession(
+// Coordinator will select parties from registered pool based on composition requirements
+func (c *SessionCoordinatorClient) CreateKeygenSessionAuto(
 	ctx context.Context,
 	thresholdN int32,
 	thresholdT int32,
-	participants []ParticipantInfo,
+	persistentCount int32,
+	delegateCount int32,
 	expiresInSeconds int64,
-) (*CreateSessionResponse, error) {
+) (*CreateSessionAutoResponse, error) {
-	pbParticipants := make([]*coordinatorpb.ParticipantInfo, len(participants))
-	for i, p := range participants {
-		pbParticipants[i] = &coordinatorpb.ParticipantInfo{
-			PartyId: p.PartyID,
-			DeviceInfo: &coordinatorpb.DeviceInfo{
-				DeviceType: p.DeviceType,
-				DeviceId:   p.DeviceID,
-				Platform:   p.Platform,
-				AppVersion: p.AppVersion,
-			},
-		}
-	}
-
 	req := &coordinatorpb.CreateSessionRequest{
 		SessionType:      "keygen",
 		ThresholdN:       thresholdN,
 		ThresholdT:       thresholdT,
-		Participants:     pbParticipants,
+		Participants:     nil, // No participants - coordinator selects automatically
 		ExpiresInSeconds: expiresInSeconds,
+		PartyComposition: &coordinatorpb.PartyComposition{
+			PersistentCount: persistentCount,
+			DelegateCount:   delegateCount,
+		},
 	}
 
-	logger.Info("Sending CreateSession gRPC request",
+	logger.Info("Sending CreateSession gRPC request (auto party selection)",
 		zap.String("session_type", "keygen"),
 		zap.Int32("threshold_n", thresholdN),
-		zap.Int32("threshold_t", thresholdT))
+		zap.Int32("threshold_t", thresholdT),
+		zap.Int32("persistent_count", persistentCount),
+		zap.Int32("delegate_count", delegateCount))
 
 	resp, err := c.client.CreateSession(ctx, req)
 	if err != nil {
@@ -102,56 +97,81 @@ func (c *SessionCoordinatorClient) CreateKeygenSession(
 		return nil, fmt.Errorf("failed to create keygen session: %w", err)
 	}
 
+	// Extract selected parties and delegate party from response
+	var selectedParties []string
+	var delegateParty string
+	for partyID := range resp.JoinTokens {
+		selectedParties = append(selectedParties, partyID)
+	}
+	if resp.DelegatePartyId != "" {
+		delegateParty = resp.DelegatePartyId
+	}
+
 	logger.Info("CreateSession gRPC call succeeded",
 		zap.String("session_id", resp.SessionId),
-		zap.Int("num_join_tokens", len(resp.JoinTokens)))
+		zap.Int("num_parties", len(selectedParties)),
+		zap.String("delegate_party", delegateParty))
 
-	return &CreateSessionResponse{
+	return &CreateSessionAutoResponse{
-		SessionID:  resp.SessionId,
+		SessionID:       resp.SessionId,
-		JoinTokens: resp.JoinTokens,
+		SelectedParties: selectedParties,
-		ExpiresAt:  resp.ExpiresAt,
+		DelegateParty:   delegateParty,
+		JoinTokens:      resp.JoinTokens,
+		ExpiresAt:       resp.ExpiresAt,
 	}, nil
 }
 
-// CreateSigningSession creates a new signing session
+// CreateSigningSessionAuto creates a new signing session with automatic party selection
-func (c *SessionCoordinatorClient) CreateSigningSession(
+// Coordinator will select parties from the provided party IDs (from account shares)
+func (c *SessionCoordinatorClient) CreateSigningSessionAuto(
 	ctx context.Context,
 	thresholdT int32,
-	participants []ParticipantInfo,
+	partyIDs []string,
 	messageHash []byte,
 	expiresInSeconds int64,
-) (*CreateSessionResponse, error) {
+) (*CreateSessionAutoResponse, error) {
-	pbParticipants := make([]*coordinatorpb.ParticipantInfo, len(participants))
+	// Convert party IDs to participant info (minimal info, coordinator will fill in details)
-	for i, p := range participants {
+	pbParticipants := make([]*coordinatorpb.ParticipantInfo, len(partyIDs))
+	for i, partyID := range partyIDs {
 		pbParticipants[i] = &coordinatorpb.ParticipantInfo{
-			PartyId: p.PartyID,
+			PartyId: partyID,
-			DeviceInfo: &coordinatorpb.DeviceInfo{
-				DeviceType: p.DeviceType,
-				DeviceId:   p.DeviceID,
-				Platform:   p.Platform,
-				AppVersion: p.AppVersion,
-			},
 		}
 	}
 
 	req := &coordinatorpb.CreateSessionRequest{
 		SessionType:      "sign",
-		ThresholdN:       int32(len(participants)),
+		ThresholdN:       int32(len(partyIDs)),
 		ThresholdT:       thresholdT,
 		Participants:     pbParticipants,
 		MessageHash:      messageHash,
 		ExpiresInSeconds: expiresInSeconds,
 	}
 
+	logger.Info("Sending CreateSigningSession gRPC request",
+		zap.Int32("threshold_t", thresholdT),
+		zap.Int("num_parties", len(partyIDs)))
+
 	resp, err := c.client.CreateSession(ctx, req)
 	if err != nil {
+		logger.Error("CreateSigningSession gRPC call failed", zap.Error(err))
 		return nil, fmt.Errorf("failed to create signing session: %w", err)
 	}
 
-	return &CreateSessionResponse{
+	// Extract selected parties from response
-		SessionID:  resp.SessionId,
+	var selectedParties []string
-		JoinTokens: resp.JoinTokens,
+	for partyID := range resp.JoinTokens {
-		ExpiresAt:  resp.ExpiresAt,
+		selectedParties = append(selectedParties, partyID)
+	}
+
+	logger.Info("CreateSigningSession gRPC call succeeded",
+		zap.String("session_id", resp.SessionId),
+		zap.Int("num_parties", len(selectedParties)))
+
+	return &CreateSessionAutoResponse{
+		SessionID:       resp.SessionId,
+		SelectedParties: selectedParties,
+		JoinTokens:      resp.JoinTokens,
+		ExpiresAt:       resp.ExpiresAt,
 	}, nil
 }
 
@@ -202,6 +222,15 @@ type CreateSessionResponse struct {
 	ExpiresAt  int64
 }
 
+// CreateSessionAutoResponse contains the created session info with auto-selected parties
+type CreateSessionAutoResponse struct {
+	SessionID       string
+	SelectedParties []string
+	DelegateParty   string
+	JoinTokens      map[string]string
+	ExpiresAt       int64
+}
+
 // SessionStatusResponse contains session status information
 type SessionStatusResponse struct {
 	Status           string

backend/mpc-system/services/account/adapters/output/memory/cache_adapter.go

@@ -0,0 +1,135 @@
+package memory
+
+import (
+	"context"
+	"encoding/json"
+	"sync"
+	"time"
+
+	"github.com/rwadurian/mpc-system/services/account/application/ports"
+)
+
+// cacheEntry holds a cached value with its expiration time
+type cacheEntry struct {
+	value     []byte
+	expiresAt time.Time
+}
+
+// CacheAdapter implements CacheService using in-memory storage
+type CacheAdapter struct {
+	mu    sync.RWMutex
+	store map[string]cacheEntry
+}
+
+// NewCacheAdapter creates a new in-memory CacheAdapter
+func NewCacheAdapter() ports.CacheService {
+	adapter := &CacheAdapter{
+		store: make(map[string]cacheEntry),
+	}
+	// Start cleanup goroutine
+	go adapter.cleanupLoop()
+	return adapter
+}
+
+// cleanupLoop periodically removes expired entries
+func (c *CacheAdapter) cleanupLoop() {
+	ticker := time.NewTicker(1 * time.Minute)
+	defer ticker.Stop()
+
+	for range ticker.C {
+		c.cleanup()
+	}
+}
+
+// cleanup removes expired entries
+func (c *CacheAdapter) cleanup() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	now := time.Now()
+	for key, entry := range c.store {
+		if !entry.expiresAt.IsZero() && now.After(entry.expiresAt) {
+			delete(c.store, key)
+		}
+	}
+}
+
+// Set sets a value in the cache
+func (c *CacheAdapter) Set(ctx context.Context, key string, value interface{}, ttlSeconds int) error {
+	data, err := json.Marshal(value)
+	if err != nil {
+		return err
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	entry := cacheEntry{
+		value: data,
+	}
+	if ttlSeconds > 0 {
+		entry.expiresAt = time.Now().Add(time.Duration(ttlSeconds) * time.Second)
+	}
+
+	c.store[key] = entry
+	return nil
+}
+
+// Get gets a value from the cache
+func (c *CacheAdapter) Get(ctx context.Context, key string) (interface{}, error) {
+	c.mu.RLock()
+	entry, exists := c.store[key]
+	c.mu.RUnlock()
+
+	if !exists {
+		return nil, nil
+	}
+
+	// Check expiration
+	if !entry.expiresAt.IsZero() && time.Now().After(entry.expiresAt) {
+		c.mu.Lock()
+		delete(c.store, key)
+		c.mu.Unlock()
+		return nil, nil
+	}
+
+	var value interface{}
+	if err := json.Unmarshal(entry.value, &value); err != nil {
+		return nil, err
+	}
+
+	return value, nil
+}
+
+// Delete deletes a value from the cache
+func (c *CacheAdapter) Delete(ctx context.Context, key string) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	delete(c.store, key)
+	return nil
+}
+
+// Exists checks if a key exists in the cache
+func (c *CacheAdapter) Exists(ctx context.Context, key string) (bool, error) {
+	c.mu.RLock()
+	entry, exists := c.store[key]
+	c.mu.RUnlock()
+
+	if !exists {
+		return false, nil
+	}
+
+	// Check expiration
+	if !entry.expiresAt.IsZero() && time.Now().After(entry.expiresAt) {
+		c.mu.Lock()
+		delete(c.store, key)
+		c.mu.Unlock()
+		return false, nil
+	}
+
+	return true, nil
+}
+
+// Ensure interface compliance
+var _ ports.CacheService = (*CacheAdapter)(nil)

backend/mpc-system/services/account/adapters/output/memory/event_publisher.go

@@ -0,0 +1,34 @@
+package memory
+
+import (
+	"context"
+
+	"github.com/rwadurian/mpc-system/pkg/logger"
+	"github.com/rwadurian/mpc-system/services/account/application/ports"
+	"go.uber.org/zap"
+)
+
+// EventPublisherAdapter implements EventPublisher using in-memory logging
+// Events are logged but not distributed (suitable for single-instance deployment)
+type EventPublisherAdapter struct{}
+
+// NewEventPublisherAdapter creates a new in-memory event publisher
+func NewEventPublisherAdapter() ports.EventPublisher {
+	return &EventPublisherAdapter{}
+}
+
+// Publish logs the event (no actual distribution in single-instance mode)
+func (p *EventPublisherAdapter) Publish(ctx context.Context, event ports.AccountEvent) error {
+	logger.Info("Account event published",
+		zap.String("type", string(event.Type)),
+		zap.String("account_id", event.AccountID))
+	return nil
+}
+
+// Close is a no-op for in-memory publisher
+func (p *EventPublisherAdapter) Close() error {
+	return nil
+}
+
+// Ensure interface compliance
+var _ ports.EventPublisher = (*EventPublisherAdapter)(nil)

backend/mpc-system/services/account/cmd/server/main.go

@@ -8,23 +8,22 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"strings"
 	"syscall"
 	"time"
 
 	"github.com/gin-gonic/gin"
 	_ "github.com/lib/pq"
-	amqp "github.com/rabbitmq/amqp091-go"
-	"github.com/redis/go-redis/v9"
 
 	"github.com/rwadurian/mpc-system/pkg/config"
 	"github.com/rwadurian/mpc-system/pkg/jwt"
 	"github.com/rwadurian/mpc-system/pkg/logger"
+	"github.com/rwadurian/mpc-system/pkg/middleware"
 	httphandler "github.com/rwadurian/mpc-system/services/account/adapters/input/http"
 	grpcadapter "github.com/rwadurian/mpc-system/services/account/adapters/output/grpc"
 	jwtadapter "github.com/rwadurian/mpc-system/services/account/adapters/output/jwt"
+	"github.com/rwadurian/mpc-system/services/account/adapters/output/memory"
 	"github.com/rwadurian/mpc-system/services/account/adapters/output/postgres"
-	"github.com/rwadurian/mpc-system/services/account/adapters/output/rabbitmq"
-	redisadapter "github.com/rwadurian/mpc-system/services/account/adapters/output/redis"
 	"github.com/rwadurian/mpc-system/services/account/application/use_cases"
 	"github.com/rwadurian/mpc-system/services/account/domain/services"
 	"go.uber.org/zap"
@@ -63,19 +62,11 @@ func main() {
 	}
 	defer db.Close()
 
-	// Initialize Redis connection
-	redisClient := initRedis(cfg.Redis)
-	defer redisClient.Close()
-
-	// Initialize RabbitMQ connection
-	rabbitConn, err := initRabbitMQ(cfg.RabbitMQ)
-	if err != nil {
-		logger.Fatal("Failed to connect to RabbitMQ", zap.Error(err))
-	}
-	defer rabbitConn.Close()
-
 	// Initialize gRPC client for session coordinator
-	sessionCoordinatorAddr := "mpc-session-coordinator:50051"
+	sessionCoordinatorAddr := os.Getenv("MPC_COORDINATOR_URL")
+	if sessionCoordinatorAddr == "" {
+		sessionCoordinatorAddr = "mpc-session-coordinator:50051"
+	}
 	sessionCoordinatorClient, err := grpcadapter.NewSessionCoordinatorClient(sessionCoordinatorAddr)
 	if err != nil {
 		logger.Fatal("Failed to connect to session coordinator", zap.Error(err))
@@ -87,14 +78,9 @@ func main() {
 	shareRepo := postgres.NewAccountSharePostgresRepo(db)
 	recoveryRepo := postgres.NewRecoverySessionPostgresRepo(db)
 
-	// Initialize adapters
+	// Initialize adapters (using in-memory implementations)
-	eventPublisher, err := rabbitmq.NewEventPublisherAdapter(rabbitConn)
+	eventPublisher := memory.NewEventPublisherAdapter()
-	if err != nil {
+	cacheAdapter := memory.NewCacheAdapter()
-		logger.Fatal("Failed to create event publisher", zap.Error(err))
-	}
-	defer eventPublisher.Close()
-
-	cacheAdapter := redisadapter.NewCacheAdapter(redisClient)
 
 	// Initialize JWT service
 	jwtService := jwt.NewJWTService(
@@ -132,6 +118,7 @@ func main() {
 	go func() {
 		if err := startHTTPServer(
 			cfg,
+			jwtService,
 			createAccountUC,
 			getAccountUC,
 			updateAccountUC,
@@ -229,140 +216,9 @@ func initDatabase(cfg config.DatabaseConfig) (*sql.DB, error) {
 	return nil, fmt.Errorf("failed to connect to database after %d retries: %w", maxRetries, err)
 }
 
-func initRedis(cfg config.RedisConfig) *redis.Client {
-	const maxRetries = 10
-	const retryDelay = 2 * time.Second
-
-	client := redis.NewClient(&redis.Options{
-		Addr:     cfg.Addr(),
-		Password: cfg.Password,
-		DB:       cfg.DB,
-	})
-
-	// Test connection with retry
-	ctx := context.Background()
-	for i := 0; i < maxRetries; i++ {
-		if err := client.Ping(ctx).Err(); err != nil {
-			logger.Warn("Redis connection failed, retrying...",
-				zap.Int("attempt", i+1),
-				zap.Int("max_retries", maxRetries),
-				zap.Error(err))
-			time.Sleep(retryDelay * time.Duration(i+1))
-			continue
-		}
-		logger.Info("Connected to Redis")
-		return client
-	}
-
-	logger.Warn("Redis connection failed after retries, continuing without cache")
-	return client
-}
-
-func initRabbitMQ(cfg config.RabbitMQConfig) (*amqp.Connection, error) {
-	const maxRetries = 10
-	const retryDelay = 2 * time.Second
-
-	var conn *amqp.Connection
-	var err error
-
-	for i := 0; i < maxRetries; i++ {
-		// Attempt to dial RabbitMQ
-		conn, err = amqp.Dial(cfg.URL())
-		if err != nil {
-			logger.Warn("Failed to dial RabbitMQ, retrying...",
-				zap.Int("attempt", i+1),
-				zap.Int("max_retries", maxRetries),
-				zap.String("url", maskPassword(cfg.URL())),
-				zap.Error(err))
-			time.Sleep(retryDelay * time.Duration(i+1))
-			continue
-		}
-
-		// Verify connection is actually usable by opening a channel
-		ch, err := conn.Channel()
-		if err != nil {
-			logger.Warn("RabbitMQ connection established but channel creation failed, retrying...",
-				zap.Int("attempt", i+1),
-				zap.Int("max_retries", maxRetries),
-				zap.Error(err))
-			conn.Close()
-			time.Sleep(retryDelay * time.Duration(i+1))
-			continue
-		}
-
-		// Test the channel with a simple operation (declare a test exchange)
-		err = ch.ExchangeDeclare(
-			"mpc.health.check", // name
-			"fanout",           // type
-			false,              // durable
-			true,               // auto-deleted
-			false,              // internal
-			false,              // no-wait
-			nil,                // arguments
-		)
-		if err != nil {
-			logger.Warn("RabbitMQ channel created but exchange declaration failed, retrying...",
-				zap.Int("attempt", i+1),
-				zap.Int("max_retries", maxRetries),
-				zap.Error(err))
-			ch.Close()
-			conn.Close()
-			time.Sleep(retryDelay * time.Duration(i+1))
-			continue
-		}
-
-		// Clean up test exchange
-		ch.ExchangeDelete("mpc.health.check", false, false)
-		ch.Close()
-
-		// Setup connection close notification
-		closeChan := make(chan *amqp.Error, 1)
-		conn.NotifyClose(closeChan)
-		go func() {
-			err := <-closeChan
-			if err != nil {
-				logger.Error("RabbitMQ connection closed unexpectedly", zap.Error(err))
-			}
-		}()
-
-		logger.Info("Connected to RabbitMQ and verified connectivity",
-			zap.Int("attempt", i+1))
-		return conn, nil
-	}
-
-	return nil, fmt.Errorf("failed to connect to RabbitMQ after %d retries: %w", maxRetries, err)
-}
-
-// maskPassword masks the password in the RabbitMQ URL for logging
-func maskPassword(url string) string {
-	// Simple masking: amqp://user:password@host:port -> amqp://user:****@host:port
-	start := 0
-	for i := 0; i < len(url); i++ {
-		if url[i] == ':' && i > 0 && url[i-1] != '/' {
-			start = i + 1
-			break
-		}
-	}
-	if start == 0 {
-		return url
-	}
-
-	end := start
-	for i := start; i < len(url); i++ {
-		if url[i] == '@' {
-			end = i
-			break
-		}
-	}
-	if end == start {
-		return url
-	}
-
-	return url[:start] + "****" + url[end:]
-}
-
 func startHTTPServer(
 	cfg *config.Config,
+	jwtService *jwt.JWTService,
 	createAccountUC *use_cases.CreateAccountUseCase,
 	getAccountUC *use_cases.GetAccountUseCase,
 	updateAccountUC *use_cases.UpdateAccountUseCase,
@@ -387,6 +243,29 @@ func startHTTPServer(
 	router.Use(gin.Recovery())
 	router.Use(gin.Logger())
 
+	// Apply security headers middleware
+	router.Use(middleware.SecureHeaders())
+
+	// Apply CORS middleware
+	// Parse allowed origins from environment or use defaults
+	allowedOrigins := []string{}
+	if origins := os.Getenv("CORS_ALLOWED_ORIGINS"); origins != "" {
+		allowedOrigins = strings.Split(origins, ",")
+	}
+	if cfg.Server.Environment != "production" {
+		// Allow all origins in development
+		router.Use(middleware.AllowAllCORS())
+	} else if len(allowedOrigins) > 0 {
+		router.Use(middleware.CORS(middleware.CORSConfig{
+			AllowOrigins:     allowedOrigins,
+			AllowMethods:     []string{"GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"},
+			AllowHeaders:     []string{"Origin", "Content-Type", "Accept", "Authorization", "X-Requested-With"},
+			ExposeHeaders:    []string{"Content-Length", "X-Request-ID"},
+			AllowCredentials: true,
+			MaxAge:           86400,
+		}))
+	}
+
 	// Create HTTP handler with session coordinator client
 	httpHandler := httphandler.NewAccountHTTPHandler(
 		createAccountUC,
@@ -405,7 +284,7 @@ func startHTTPServer(
 		sessionCoordinatorClient,
 	)
 
-	// Health check
+	// Health check (public)
 	router.GET("/health", func(c *gin.Context) {
 		c.JSON(http.StatusOK, gin.H{
 			"status":  "healthy",
@@ -413,10 +292,26 @@ func startHTTPServer(
 		})
 	})
 
-	// Register API routes
+	// Configure authentication middleware
+	// Skip paths that don't require authentication
+	authConfig := middleware.AuthConfig{
+		JWTService: jwtService,
+		SkipPaths: []string{
+			"/health",
+			"/api/v1/auth/*",           // Auth endpoints (login, refresh, challenge)
+			"/api/v1/accounts/from-keygen", // Internal API from coordinator
+		},
+		AllowAnonymous: false,
+	}
+
+	// API routes with authentication
 	api := router.Group("/api/v1")
+	api.Use(middleware.BearerAuth(authConfig))
 	httpHandler.RegisterRoutes(api)
 
-	logger.Info("Starting HTTP server", zap.Int("port", cfg.Server.HTTPPort))
+	logger.Info("Starting HTTP server",
+		zap.Int("port", cfg.Server.HTTPPort),
+		zap.String("environment", cfg.Server.Environment),
+		zap.Bool("cors_enabled", len(allowedOrigins) > 0 || cfg.Server.Environment != "production"))
 	return router.Run(fmt.Sprintf(":%d", cfg.Server.HTTPPort))
 }

backend/mpc-system/services/message-router/adapters/input/grpc/message_grpc_handler.go

@@ -2,35 +2,44 @@ package grpc
 
 import (
 	"context"
+	"time"
 
 	pb "github.com/rwadurian/mpc-system/api/grpc/router/v1"
 	"github.com/rwadurian/mpc-system/pkg/logger"
-	"github.com/rwadurian/mpc-system/services/message-router/adapters/output/rabbitmq"
 	"github.com/rwadurian/mpc-system/services/message-router/application/use_cases"
 	"github.com/rwadurian/mpc-system/services/message-router/domain"
 	"github.com/rwadurian/mpc-system/services/message-router/domain/entities"
+	"github.com/rwadurian/mpc-system/services/message-router/domain/repositories"
 	"go.uber.org/zap"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 )
 
+// MessageBroker defines the interface for message subscription
+type MessageBroker interface {
+	SubscribeToPartyMessages(ctx context.Context, partyID string) (<-chan *entities.MessageDTO, error)
+	SubscribeToSessionMessages(ctx context.Context, sessionID string, partyID string) (<-chan *entities.MessageDTO, error)
+}
+
 // MessageRouterServer implements the gRPC MessageRouter service
 type MessageRouterServer struct {
 	pb.UnimplementedMessageRouterServer
 	routeMessageUC       *use_cases.RouteMessageUseCase
 	getPendingMessagesUC *use_cases.GetPendingMessagesUseCase
-	messageBroker        *rabbitmq.MessageBrokerAdapter
+	messageBroker        MessageBroker
 	partyRegistry        *domain.PartyRegistry
 	eventBroadcaster     *domain.SessionEventBroadcaster
+	messageRepo          repositories.MessageRepository
 }
 
 // NewMessageRouterServer creates a new gRPC server
 func NewMessageRouterServer(
 	routeMessageUC *use_cases.RouteMessageUseCase,
 	getPendingMessagesUC *use_cases.GetPendingMessagesUseCase,
-	messageBroker *rabbitmq.MessageBrokerAdapter,
+	messageBroker MessageBroker,
 	partyRegistry *domain.PartyRegistry,
 	eventBroadcaster *domain.SessionEventBroadcaster,
+	messageRepo repositories.MessageRepository,
 ) *MessageRouterServer {
 	return &MessageRouterServer{
 		routeMessageUC:       routeMessageUC,
@@ -38,6 +47,7 @@ func NewMessageRouterServer(
 		messageBroker:        messageBroker,
 		partyRegistry:        partyRegistry,
 		eventBroadcaster:     eventBroadcaster,
+		messageRepo:          messageRepo,
 	}
 }
 
@@ -152,13 +162,30 @@ func (s *MessageRouterServer) RegisterParty(
 		return nil, status.Error(codes.InvalidArgument, "party_id is required")
 	}
 
-	// Register party
+	// Convert notification channel if provided
-	party := s.partyRegistry.Register(req.PartyId, req.PartyRole, req.Version)
+	var notification *domain.NotificationChannel
+	if req.Notification != nil {
+		notification = &domain.NotificationChannel{
+			Email:     req.Notification.Email,
+			Phone:     req.Notification.Phone,
+			PushToken: req.Notification.PushToken,
+		}
+	}
+
+	// Register party with notification channel
+	party := s.partyRegistry.RegisterWithNotification(req.PartyId, req.PartyRole, req.Version, notification)
+
+	mode := "real-time"
+	if party.IsOfflineMode() {
+		mode = "offline"
+	}
 
 	logger.Info("Party registered",
 		zap.String("party_id", req.PartyId),
 		zap.String("role", req.PartyRole),
-		zap.String("version", req.Version))
+		zap.String("version", req.Version),
+		zap.String("mode", mode),
+		zap.Bool("has_notification", notification != nil && notification.HasAnyChannel()))
 
 	return &pb.RegisterPartyResponse{
 		Success:      true,
@@ -167,6 +194,92 @@ func (s *MessageRouterServer) RegisterParty(
 	}, nil
 }
 
+// Heartbeat handles party heartbeat to keep the connection alive
+func (s *MessageRouterServer) Heartbeat(
+	ctx context.Context,
+	req *pb.HeartbeatRequest,
+) (*pb.HeartbeatResponse, error) {
+	if req.PartyId == "" {
+		return nil, status.Error(codes.InvalidArgument, "party_id is required")
+	}
+
+	// Update heartbeat
+	if !s.partyRegistry.Heartbeat(req.PartyId) {
+		return nil, status.Error(codes.NotFound, "party not registered")
+	}
+
+	// Count pending messages for this party
+	pendingMessages := int32(0)
+	if s.messageRepo != nil {
+		count, err := s.messageRepo.CountPendingByParty(ctx, req.PartyId)
+		if err != nil {
+			logger.Warn("Failed to count pending messages",
+				zap.String("party_id", req.PartyId),
+				zap.Error(err))
+		} else {
+			pendingMessages = int32(count)
+		}
+	}
+
+	return &pb.HeartbeatResponse{
+		Success:         true,
+		ServerTimestamp: time.Now().UnixMilli(),
+		PendingMessages: pendingMessages,
+	}, nil
+}
+
+// AcknowledgeMessage acknowledges receipt of a message
+func (s *MessageRouterServer) AcknowledgeMessage(
+	ctx context.Context,
+	req *pb.AcknowledgeMessageRequest,
+) (*pb.AcknowledgeMessageResponse, error) {
+	if req.MessageId == "" {
+		return nil, status.Error(codes.InvalidArgument, "message_id is required")
+	}
+	if req.PartyId == "" {
+		return nil, status.Error(codes.InvalidArgument, "party_id is required")
+	}
+
+	// TODO: Store acknowledgment in database for message tracking
+	// For now, just log and return success
+	logger.Debug("Message acknowledged",
+		zap.String("message_id", req.MessageId),
+		zap.String("party_id", req.PartyId),
+		zap.String("session_id", req.SessionId),
+		zap.Bool("success", req.Success))
+
+	if !req.Success {
+		logger.Warn("Message processing failed",
+			zap.String("message_id", req.MessageId),
+			zap.String("party_id", req.PartyId),
+			zap.String("error", req.ErrorMessage))
+	}
+
+	return &pb.AcknowledgeMessageResponse{
+		Success: true,
+		Message: "Acknowledgment received",
+	}, nil
+}
+
+// GetMessageStatus returns the delivery status of a message
+func (s *MessageRouterServer) GetMessageStatus(
+	ctx context.Context,
+	req *pb.GetMessageStatusRequest,
+) (*pb.GetMessageStatusResponse, error) {
+	if req.MessageId == "" {
+		return nil, status.Error(codes.InvalidArgument, "message_id is required")
+	}
+
+	// TODO: Implement actual message status tracking in database
+	// For now, return a placeholder response
+	return &pb.GetMessageStatusResponse{
+		MessageId:       req.MessageId,
+		SessionId:       req.SessionId,
+		Deliveries:      []*pb.MessageDeliveryStatus{},
+		AllAcknowledged: false,
+	}, nil
+}
+
 // SubscribeSessionEvents subscribes to session lifecycle events (streaming)
 func (s *MessageRouterServer) SubscribeSessionEvents(
 	req *pb.SubscribeSessionEventsRequest,
@@ -277,19 +390,34 @@ func (s *MessageRouterServer) GetRegisteredParties(
 	// Convert to protobuf format
 	protoParties := make([]*pb.RegisteredParty, 0, len(parties))
 	for _, party := range parties {
-		// For now, consider all registered parties as online
+		// Filter by online status if requested
-		// TODO: Track actual online status via heartbeats
+		if req.OnlyOnline && !party.Online {
-		protoParties = append(protoParties, &pb.RegisteredParty{
+			continue
+		}
+
+		protoParty := &pb.RegisteredParty{
 			PartyId:      party.PartyID,
 			Role:         party.Role,
-			Online:       true, // Assume online if registered
+			Online:       party.Online,
 			RegisteredAt: party.RegisteredAt.UnixMilli(),
 			LastSeenAt:   party.LastSeen.UnixMilli(),
-		})
+		}
+
+		// Include notification channel if present
+		if party.Notification != nil && party.Notification.HasAnyChannel() {
+			protoParty.Notification = &pb.NotificationChannel{
+				Email:     party.Notification.Email,
+				Phone:     party.Notification.Phone,
+				PushToken: party.Notification.PushToken,
+			}
+		}
+
+		protoParties = append(protoParties, protoParty)
 	}
 
 	logger.Debug("GetRegisteredParties called",
 		zap.String("role_filter", req.RoleFilter),
+		zap.Bool("only_online", req.OnlyOnline),
 		zap.Int("party_count", len(protoParties)))
 
 	return &pb.GetRegisteredPartiesResponse{

backend/mpc-system/services/message-router/adapters/output/memory/message_broker.go

@@ -0,0 +1,209 @@
+package memory
+
+import (
+	"context"
+	"sync"
+
+	"github.com/rwadurian/mpc-system/pkg/logger"
+	"github.com/rwadurian/mpc-system/services/message-router/application/use_cases"
+	"github.com/rwadurian/mpc-system/services/message-router/domain/entities"
+	"go.uber.org/zap"
+)
+
+// MessageBrokerAdapter implements MessageBroker using in-memory channels
+type MessageBrokerAdapter struct {
+	mu sync.RWMutex
+	// partyChannels maps partyID to their message channel
+	partyChannels map[string]chan *entities.MessageDTO
+	// sessionChannels maps sessionID:partyID to their broadcast channel
+	sessionChannels map[string]chan *entities.MessageDTO
+}
+
+// NewMessageBrokerAdapter creates a new in-memory message broker
+func NewMessageBrokerAdapter() *MessageBrokerAdapter {
+	return &MessageBrokerAdapter{
+		partyChannels:   make(map[string]chan *entities.MessageDTO),
+		sessionChannels: make(map[string]chan *entities.MessageDTO),
+	}
+}
+
+// PublishToParty publishes a message to a specific party
+func (a *MessageBrokerAdapter) PublishToParty(ctx context.Context, partyID string, message *entities.MessageDTO) error {
+	a.mu.RLock()
+	ch, exists := a.partyChannels[partyID]
+	a.mu.RUnlock()
+
+	if !exists {
+		logger.Debug("party channel not found, message will be available via polling",
+			zap.String("party_id", partyID))
+		return nil
+	}
+
+	select {
+	case ch <- message:
+		logger.Debug("published message to party",
+			zap.String("party_id", partyID),
+			zap.String("message_id", message.ID))
+	case <-ctx.Done():
+		return ctx.Err()
+	default:
+		// Channel full, message will be available via polling
+		logger.Warn("party channel full, message available via polling",
+			zap.String("party_id", partyID))
+	}
+
+	return nil
+}
+
+// PublishToSession publishes a message to all parties in a session (except sender)
+func (a *MessageBrokerAdapter) PublishToSession(
+	ctx context.Context,
+	sessionID string,
+	excludeParty string,
+	message *entities.MessageDTO,
+) error {
+	a.mu.RLock()
+	defer a.mu.RUnlock()
+
+	prefix := sessionID + ":"
+	for key, ch := range a.sessionChannels {
+		if len(key) > len(prefix) && key[:len(prefix)] == prefix {
+			partyID := key[len(prefix):]
+			if partyID == excludeParty {
+				continue
+			}
+
+			select {
+			case ch <- message:
+				logger.Debug("broadcast message to party",
+					zap.String("session_id", sessionID),
+					zap.String("party_id", partyID))
+			case <-ctx.Done():
+				return ctx.Err()
+			default:
+				// Channel full
+				logger.Warn("session channel full for party",
+					zap.String("party_id", partyID))
+			}
+		}
+	}
+
+	return nil
+}
+
+// SubscribeToPartyMessages subscribes to messages for a specific party
+func (a *MessageBrokerAdapter) SubscribeToPartyMessages(
+	ctx context.Context,
+	partyID string,
+) (<-chan *entities.MessageDTO, error) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	// Create channel if not exists
+	if _, exists := a.partyChannels[partyID]; !exists {
+		a.partyChannels[partyID] = make(chan *entities.MessageDTO, 100)
+	}
+
+	ch := a.partyChannels[partyID]
+
+	// Return a read-only channel
+	out := make(chan *entities.MessageDTO, 100)
+	go func() {
+		defer close(out)
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case msg, ok := <-ch:
+				if !ok {
+					return
+				}
+				select {
+				case out <- msg:
+				case <-ctx.Done():
+					return
+				}
+			}
+		}
+	}()
+
+	return out, nil
+}
+
+// SubscribeToSessionMessages subscribes to all messages in a session
+func (a *MessageBrokerAdapter) SubscribeToSessionMessages(
+	ctx context.Context,
+	sessionID string,
+	partyID string,
+) (<-chan *entities.MessageDTO, error) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	key := sessionID + ":" + partyID
+
+	// Create channel if not exists
+	if _, exists := a.sessionChannels[key]; !exists {
+		a.sessionChannels[key] = make(chan *entities.MessageDTO, 100)
+	}
+
+	ch := a.sessionChannels[key]
+
+	// Return a read-only channel
+	out := make(chan *entities.MessageDTO, 100)
+	go func() {
+		defer close(out)
+		for {
+			select {
+			case <-ctx.Done():
+				// Cleanup on context done
+				a.mu.Lock()
+				delete(a.sessionChannels, key)
+				a.mu.Unlock()
+				return
+			case msg, ok := <-ch:
+				if !ok {
+					return
+				}
+				select {
+				case out <- msg:
+				case <-ctx.Done():
+					return
+				}
+			}
+		}
+	}()
+
+	return out, nil
+}
+
+// UnsubscribeParty removes a party's channel
+func (a *MessageBrokerAdapter) UnsubscribeParty(partyID string) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	if ch, exists := a.partyChannels[partyID]; exists {
+		close(ch)
+		delete(a.partyChannels, partyID)
+	}
+}
+
+// Close closes all channels
+func (a *MessageBrokerAdapter) Close() error {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	for _, ch := range a.partyChannels {
+		close(ch)
+	}
+	for _, ch := range a.sessionChannels {
+		close(ch)
+	}
+
+	a.partyChannels = make(map[string]chan *entities.MessageDTO)
+	a.sessionChannels = make(map[string]chan *entities.MessageDTO)
+
+	return nil
+}
+
+// Ensure interface compliance
+var _ use_cases.MessageBroker = (*MessageBrokerAdapter)(nil)

backend/mpc-system/services/message-router/adapters/output/postgres/message_repo.go

@@ -94,6 +94,22 @@ func (r *MessagePostgresRepo) GetPendingMessages(
 	return r.scanMessages(rows)
 }
 
+// CountPendingByParty counts all pending messages for a party across all sessions
+func (r *MessagePostgresRepo) CountPendingByParty(ctx context.Context, partyID string) (int64, error) {
+	var count int64
+	err := r.db.QueryRowContext(ctx, `
+		SELECT COUNT(*)
+		FROM mpc_messages
+		WHERE delivered_at IS NULL
+		  AND from_party != $1
+		  AND (to_parties IS NULL OR cardinality(to_parties) = 0 OR $1 = ANY(to_parties))
+	`, partyID).Scan(&count)
+	if err != nil {
+		return 0, err
+	}
+	return count, nil
+}
+
 // GetMessagesByRound retrieves messages for a specific round
 func (r *MessagePostgresRepo) GetMessagesByRound(
 	ctx context.Context,

backend/mpc-system/services/message-router/cmd/server/main.go

@@ -14,7 +14,6 @@ import (
 
 	"github.com/gin-gonic/gin"
 	_ "github.com/lib/pq"
-	amqp "github.com/rabbitmq/amqp091-go"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/reflection"
 
@@ -22,8 +21,8 @@ import (
 	"github.com/rwadurian/mpc-system/pkg/config"
 	"github.com/rwadurian/mpc-system/pkg/logger"
 	grpcadapter "github.com/rwadurian/mpc-system/services/message-router/adapters/input/grpc"
+	"github.com/rwadurian/mpc-system/services/message-router/adapters/output/memory"
 	"github.com/rwadurian/mpc-system/services/message-router/adapters/output/postgres"
-	"github.com/rwadurian/mpc-system/services/message-router/adapters/output/rabbitmq"
 	"github.com/rwadurian/mpc-system/services/message-router/application/use_cases"
 	"github.com/rwadurian/mpc-system/services/message-router/domain"
 	"go.uber.org/zap"
@@ -63,19 +62,11 @@ func main() {
 	}
 	defer db.Close()
 
-	// Initialize RabbitMQ connection
-	rabbitConn, err := initRabbitMQ(cfg.RabbitMQ)
-	if err != nil {
-		logger.Fatal("Failed to connect to RabbitMQ", zap.Error(err))
-	}
-	defer rabbitConn.Close()
-
 	// Initialize repositories and adapters
 	messageRepo := postgres.NewMessagePostgresRepo(db)
-	messageBroker, err := rabbitmq.NewMessageBrokerAdapter(rabbitConn)
+
-	if err != nil {
+	// Initialize in-memory message broker (replaces RabbitMQ)
-		logger.Fatal("Failed to create message broker", zap.Error(err))
+	messageBroker := memory.NewMessageBrokerAdapter()
-	}
 	defer messageBroker.Close()
 
 	// Initialize party registry and event broadcaster for party-driven architecture
@@ -89,6 +80,9 @@ func main() {
 	// Start message cleanup background job
 	go runMessageCleanup(messageRepo)
 
+	// Start stale party detection background job
+	go runStalePartyDetection(partyRegistry)
+
 	// Create shutdown context
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
@@ -98,7 +92,7 @@ func main() {
 
 	// Start gRPC server
 	go func() {
-		if err := startGRPCServer(cfg, routeMessageUC, getPendingMessagesUC, messageBroker, partyRegistry, eventBroadcaster); err != nil {
+		if err := startGRPCServer(cfg, routeMessageUC, getPendingMessagesUC, messageBroker, partyRegistry, eventBroadcaster, messageRepo); err != nil {
 			errChan <- fmt.Errorf("gRPC server error: %w", err)
 		}
 	}()
@@ -187,116 +181,14 @@ func initDatabase(cfg config.DatabaseConfig) (*sql.DB, error) {
 	return nil, fmt.Errorf("failed to connect to database after %d retries: %w", maxRetries, err)
 }
 
-func initRabbitMQ(cfg config.RabbitMQConfig) (*amqp.Connection, error) {
-	const maxRetries = 10
-	const retryDelay = 2 * time.Second
-
-	var conn *amqp.Connection
-	var err error
-
-	for i := 0; i < maxRetries; i++ {
-		// Attempt to dial RabbitMQ
-		conn, err = amqp.Dial(cfg.URL())
-		if err != nil {
-			logger.Warn("Failed to dial RabbitMQ, retrying...",
-				zap.Int("attempt", i+1),
-				zap.Int("max_retries", maxRetries),
-				zap.String("url", maskPassword(cfg.URL())),
-				zap.Error(err))
-			time.Sleep(retryDelay * time.Duration(i+1))
-			continue
-		}
-
-		// Verify connection is actually usable by opening a channel
-		ch, err := conn.Channel()
-		if err != nil {
-			logger.Warn("RabbitMQ connection established but channel creation failed, retrying...",
-				zap.Int("attempt", i+1),
-				zap.Int("max_retries", maxRetries),
-				zap.Error(err))
-			conn.Close()
-			time.Sleep(retryDelay * time.Duration(i+1))
-			continue
-		}
-
-		// Test the channel with a simple operation (declare a test exchange)
-		err = ch.ExchangeDeclare(
-			"mpc.health.check", // name
-			"fanout",           // type
-			false,              // durable
-			true,               // auto-deleted
-			false,              // internal
-			false,              // no-wait
-			nil,                // arguments
-		)
-		if err != nil {
-			logger.Warn("RabbitMQ channel created but exchange declaration failed, retrying...",
-				zap.Int("attempt", i+1),
-				zap.Int("max_retries", maxRetries),
-				zap.Error(err))
-			ch.Close()
-			conn.Close()
-			time.Sleep(retryDelay * time.Duration(i+1))
-			continue
-		}
-
-		// Clean up test exchange
-		ch.ExchangeDelete("mpc.health.check", false, false)
-		ch.Close()
-
-		// Setup connection close notification
-		closeChan := make(chan *amqp.Error, 1)
-		conn.NotifyClose(closeChan)
-		go func() {
-			err := <-closeChan
-			if err != nil {
-				logger.Error("RabbitMQ connection closed unexpectedly", zap.Error(err))
-			}
-		}()
-
-		logger.Info("Connected to RabbitMQ and verified connectivity",
-			zap.Int("attempt", i+1))
-		return conn, nil
-	}
-
-	return nil, fmt.Errorf("failed to connect to RabbitMQ after %d retries: %w", maxRetries, err)
-}
-
-// maskPassword masks the password in the RabbitMQ URL for logging
-func maskPassword(url string) string {
-	// Simple masking: amqp://user:password@host:port -> amqp://user:****@host:port
-	start := 0
-	for i := 0; i < len(url); i++ {
-		if url[i] == ':' && i > 0 && url[i-1] != '/' {
-			start = i + 1
-			break
-		}
-	}
-	if start == 0 {
-		return url
-	}
-
-	end := start
-	for i := start; i < len(url); i++ {
-		if url[i] == '@' {
-			end = i
-			break
-		}
-	}
-	if end == start {
-		return url
-	}
-
-	return url[:start] + "****" + url[end:]
-}
-
 func startGRPCServer(
 	cfg *config.Config,
 	routeMessageUC *use_cases.RouteMessageUseCase,
 	getPendingMessagesUC *use_cases.GetPendingMessagesUseCase,
-	messageBroker *rabbitmq.MessageBrokerAdapter,
+	messageBroker *memory.MessageBrokerAdapter,
 	partyRegistry *domain.PartyRegistry,
 	eventBroadcaster *domain.SessionEventBroadcaster,
+	messageRepo *postgres.MessagePostgresRepo,
 ) error {
 	listener, err := net.Listen("tcp", fmt.Sprintf(":%d", cfg.Server.GRPCPort))
 	if err != nil {
@@ -312,6 +204,7 @@ func startGRPCServer(
 		messageBroker,
 		partyRegistry,
 		eventBroadcaster,
+		messageRepo,
 	)
 	pb.RegisterMessageRouterServer(grpcServer, messageRouterServer)
 
@@ -422,3 +315,32 @@ func runMessageCleanup(messageRepo *postgres.MessagePostgresRepo) {
 		}
 	}
 }
+
+// runStalePartyDetection periodically checks for stale parties and marks them as offline
+// Parties that haven't sent a heartbeat within the timeout are considered offline
+func runStalePartyDetection(partyRegistry *domain.PartyRegistry) {
+	// Check every 30 seconds for stale parties
+	ticker := time.NewTicker(30 * time.Second)
+	defer ticker.Stop()
+
+	// Parties are considered stale if no heartbeat for 2 minutes
+	staleTimeout := 2 * time.Minute
+
+	logger.Info("Started stale party detection",
+		zap.Duration("check_interval", 30*time.Second),
+		zap.Duration("stale_timeout", staleTimeout))
+
+	for range ticker.C {
+		staleParties := partyRegistry.MarkStalePartiesOffline(staleTimeout)
+
+		if len(staleParties) > 0 {
+			for _, party := range staleParties {
+				logger.Warn("Party marked as offline (no heartbeat)",
+					zap.String("party_id", party.PartyID),
+					zap.String("role", party.Role),
+					zap.Time("last_seen", party.LastSeen),
+					zap.Bool("has_notification", party.IsOfflineMode()))
+			}
+		}
+	}
+}

backend/mpc-system/services/message-router/domain/party_registry.go

@@ -5,6 +5,18 @@ import (
 	"time"
 )
 
+// NotificationChannel represents notification channels for offline parties
+type NotificationChannel struct {
+	Email     string
+	Phone     string
+	PushToken string
+}
+
+// HasAnyChannel returns true if any notification channel is configured
+func (nc *NotificationChannel) HasAnyChannel() bool {
+	return nc != nil && (nc.Email != "" || nc.Phone != "" || nc.PushToken != "")
+}
+
 // RegisteredParty represents a party registered with the router
 type RegisteredParty struct {
 	PartyID      string
@@ -12,6 +24,13 @@ type RegisteredParty struct {
 	Version      string
 	RegisteredAt time.Time
 	LastSeen     time.Time
+	Online       bool                 // Whether the party is currently connected
+	Notification *NotificationChannel // Optional notification channels for offline mode
+}
+
+// IsOfflineMode returns true if the party operates in offline mode (has notification channels)
+func (p *RegisteredParty) IsOfflineMode() bool {
+	return p.Notification != nil && p.Notification.HasAnyChannel()
 }
 
 // PartyRegistry manages registered parties
@@ -29,6 +48,11 @@ func NewPartyRegistry() *PartyRegistry {
 
 // Register registers a party
 func (r *PartyRegistry) Register(partyID, role, version string) *RegisteredParty {
+	return r.RegisterWithNotification(partyID, role, version, nil)
+}
+
+// RegisterWithNotification registers a party with optional notification channels
+func (r *PartyRegistry) RegisterWithNotification(partyID, role, version string, notification *NotificationChannel) *RegisteredParty {
 	r.mu.Lock()
 	defer r.mu.Unlock()
 
@@ -39,6 +63,8 @@ func (r *PartyRegistry) Register(partyID, role, version string) *RegisteredParty
 		Version:      version,
 		RegisteredAt: now,
 		LastSeen:     now,
+		Online:       true,
+		Notification: notification,
 	}
 
 	r.parties[partyID] = party
@@ -105,3 +131,87 @@ func (r *PartyRegistry) Count() int {
 
 	return len(r.parties)
 }
+
+// SetOnline sets the online status of a party
+func (r *PartyRegistry) SetOnline(partyID string, online bool) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	if party, exists := r.parties[partyID]; exists {
+		party.Online = online
+		if online {
+			party.LastSeen = time.Now()
+		}
+	}
+}
+
+// IsOnline checks if a party is currently online
+func (r *PartyRegistry) IsOnline(partyID string) bool {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	if party, exists := r.parties[partyID]; exists {
+		return party.Online
+	}
+	return false
+}
+
+// GetOnlineParties returns all online parties
+func (r *PartyRegistry) GetOnlineParties() []*RegisteredParty {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	parties := make([]*RegisteredParty, 0)
+	for _, party := range r.parties {
+		if party.Online {
+			parties = append(parties, party)
+		}
+	}
+	return parties
+}
+
+// GetOfflineParties returns all parties that are offline (have notification channels but not connected)
+func (r *PartyRegistry) GetOfflineParties() []*RegisteredParty {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	parties := make([]*RegisteredParty, 0)
+	for _, party := range r.parties {
+		if !party.Online && party.IsOfflineMode() {
+			parties = append(parties, party)
+		}
+	}
+	return parties
+}
+
+// MarkStalePartiesOffline marks parties as offline if they haven't sent a heartbeat within the timeout
+// Returns the list of parties that were marked offline
+func (r *PartyRegistry) MarkStalePartiesOffline(timeout time.Duration) []*RegisteredParty {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	now := time.Now()
+	staleParties := make([]*RegisteredParty, 0)
+
+	for _, party := range r.parties {
+		if party.Online && now.Sub(party.LastSeen) > timeout {
+			party.Online = false
+			staleParties = append(staleParties, party)
+		}
+	}
+
+	return staleParties
+}
+
+// Heartbeat updates the last seen timestamp and marks the party as online
+func (r *PartyRegistry) Heartbeat(partyID string) bool {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	if party, exists := r.parties[partyID]; exists {
+		party.LastSeen = time.Now()
+		party.Online = true
+		return true
+	}
+	return false
+}

backend/mpc-system/services/message-router/domain/repositories/message_repository.go

@@ -19,6 +19,9 @@ type MessageRepository interface {
 	// GetPendingMessages retrieves pending messages for a party
 	GetPendingMessages(ctx context.Context, sessionID uuid.UUID, partyID string, afterTime time.Time) ([]*entities.MPCMessage, error)
 
+	// CountPendingByParty counts all pending messages for a party across all sessions
+	CountPendingByParty(ctx context.Context, partyID string) (int64, error)
+
 	// GetMessagesByRound retrieves messages for a specific round
 	GetMessagesByRound(ctx context.Context, sessionID uuid.UUID, roundNumber int) ([]*entities.MPCMessage, error)
 

backend/mpc-system/services/server-party-api/cmd/server/main.go

@@ -17,12 +17,15 @@ import (
 	"github.com/rwadurian/mpc-system/pkg/config"
 	"github.com/rwadurian/mpc-system/pkg/crypto"
 	"github.com/rwadurian/mpc-system/pkg/logger"
-	"github.com/rwadurian/mpc-system/pkg/tss"
 	grpcclient "github.com/rwadurian/mpc-system/services/server-party/adapters/output/grpc"
 	"github.com/rwadurian/mpc-system/services/server-party/application/use_cases"
+	"github.com/rwadurian/mpc-system/services/server-party/infrastructure/cache"
 	"go.uber.org/zap"
 )
 
+// Global share cache for delegate parties
+var globalShareCache *cache.ShareCache
+
 func main() {
 	// Parse flags
 	configPath := flag.String("config", "", "Path to config file")
@@ -45,10 +48,14 @@ func main() {
 	}
 	defer logger.Sync()
 
-	logger.Info("Starting Server Party API Service",
+	logger.Info("Starting Server Party API Service (Delegate Mode)",
 		zap.String("environment", cfg.Server.Environment),
 		zap.Int("http_port", cfg.Server.HTTPPort))
 
+	// Initialize share cache for delegate parties (15 minute TTL)
+	globalShareCache = cache.NewShareCache(15 * time.Minute)
+	logger.Info("Share cache initialized", zap.Duration("ttl", 15*time.Minute))
+
 	// Initialize crypto service with master key from environment
 	masterKeyHex := os.Getenv("MPC_CRYPTO_MASTER_KEY")
 	if masterKeyHex == "" {
@@ -96,14 +103,16 @@ func main() {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	// Get party ID from environment (or generate one)
+	// Get party ID from environment (or use default)
 	partyID := os.Getenv("PARTY_ID")
 	if partyID == "" {
 		partyID = "server-party-api"
 	}
 
+	// Force PARTY_ROLE to delegate for this service
+	os.Setenv("PARTY_ROLE", "delegate")
+
 	// Register this party as a delegate party with Message Router
-	// This allows Session Coordinator to discover this party for session creation
 	logger.Info("Registering party with Message Router",
 		zap.String("party_id", partyID),
 		zap.String("role", "delegate"))
@@ -116,10 +125,25 @@ func main() {
 		zap.String("party_id", partyID),
 		zap.String("role", "delegate"))
 
+	// Initialize use cases with nil keyShareRepo (delegate doesn't use DB)
+	// The use cases check PARTY_ROLE env var to determine behavior
+	participateKeygenUC := use_cases.NewParticipateKeygenUseCase(
+		nil, // No database storage for delegate
+		sessionClient,
+		messageRouter,
+		cryptoService,
+	)
+	participateSigningUC := use_cases.NewParticipateSigningUseCase(
+		nil, // No database storage for delegate
+		sessionClient,
+		messageRouter,
+		cryptoService,
+	)
+
 	// Start HTTP server
 	errChan := make(chan error, 1)
 	go func() {
-		if err := startHTTPServer(cfg, sessionClient, messageRouter, cryptoService, apiKey); err != nil {
+		if err := startHTTPServer(cfg, participateKeygenUC, participateSigningUC, cryptoService, apiKey); err != nil {
 			errChan <- fmt.Errorf("HTTP server error: %w", err)
 		}
 	}()
@@ -147,8 +171,8 @@ func main() {
 
 func startHTTPServer(
 	cfg *config.Config,
-	sessionClient use_cases.SessionCoordinatorClient,
+	participateKeygenUC *use_cases.ParticipateKeygenUseCase,
-	messageRouter use_cases.MessageRouterClient,
+	participateSigningUC *use_cases.ParticipateSigningUseCase,
 	cryptoService *crypto.CryptoService,
 	apiKey string,
 ) error {
@@ -165,6 +189,7 @@ func startHTTPServer(
 		c.JSON(http.StatusOK, gin.H{
 			"status":  "healthy",
 			"service": "server-party-api",
+			"role":    "delegate",
 		})
 	})
 
@@ -175,15 +200,12 @@ func startHTTPServer(
 	}
 
 	{
-		// Generate user share - synchronous endpoint that returns the share
+		// Keygen participation - same as server-party but returns share
-		// This is the main endpoint for mpc-service to call
+		api.POST("/keygen/participate", func(c *gin.Context) {
-		api.POST("/keygen/generate-user-share", func(c *gin.Context) {
 			var req struct {
 				SessionID string `json:"session_id" binding:"required"`
 				PartyID   string `json:"party_id" binding:"required"`
 				JoinToken string `json:"join_token" binding:"required"`
-				// Optional: encryption key for the share (provided by user)
-				UserPublicKey string `json:"user_public_key"`
 			}
 
 			if err := c.ShouldBindJSON(&req); err != nil {
@@ -197,26 +219,23 @@ func startHTTPServer(
 				return
 			}
 
-			logger.Info("Generating user share",
+			logger.Info("Starting keygen participation (delegate)",
 				zap.String("session_id", req.SessionID),
 				zap.String("party_id", req.PartyID))
 
-			// Execute keygen synchronously and return the share
+			// Execute keygen synchronously for delegate party
 			ctx, cancel := context.WithTimeout(c.Request.Context(), 10*time.Minute)
 			defer cancel()
 
-			result, err := generateUserShare(
+			input := use_cases.ParticipateKeygenInput{
-				ctx,
+				SessionID: sessionID,
-				sessionClient,
+				PartyID:   req.PartyID,
-				messageRouter,
+				JoinToken: req.JoinToken,
-				cryptoService,
+			}
-				sessionID,
+
-				req.PartyID,
+			output, err := participateKeygenUC.Execute(ctx, input)
-				req.JoinToken,
-				req.UserPublicKey,
-			)
 			if err != nil {
-				logger.Error("Failed to generate user share",
+				logger.Error("Keygen participation failed",
 					zap.String("session_id", req.SessionID),
 					zap.String("party_id", req.PartyID),
 					zap.Error(err))
@@ -229,28 +248,41 @@ func startHTTPServer(
 				return
 			}
 
-			logger.Info("User share generated successfully",
+			logger.Info("Keygen participation completed (delegate)",
 				zap.String("session_id", req.SessionID),
-				zap.String("party_id", req.PartyID))
+				zap.String("party_id", req.PartyID),
+				zap.Bool("success", output.Success))
 
+			// For delegate party, ShareForUser contains the encrypted share
+			if len(output.ShareForUser) == 0 {
+				c.JSON(http.StatusInternalServerError, gin.H{
+					"error": "share not generated for delegate party",
+				})
+				return
+			}
+
+			// Store in cache for retrieval (optional, for async pattern)
+			globalShareCache.Store(sessionID, req.PartyID, output.ShareForUser, output.PublicKey)
+
+			// Return share directly
 			c.JSON(http.StatusOK, gin.H{
 				"success":     true,
 				"session_id":  req.SessionID,
 				"party_id":    req.PartyID,
-				"party_index": result.PartyIndex,
+				"party_index": output.KeyShare.PartyIndex,
-				"share_data":  result.ShareData,
+				"share_data":  hex.EncodeToString(output.ShareForUser),
-				"public_key":  result.PublicKey,
+				"public_key":  hex.EncodeToString(output.PublicKey),
 			})
 		})
 
-		// Sign with user share - synchronous endpoint
+		// Signing with user-provided share
-		api.POST("/sign/with-user-share", func(c *gin.Context) {
+		api.POST("/sign/participate", func(c *gin.Context) {
 			var req struct {
 				SessionID   string `json:"session_id" binding:"required"`
 				PartyID     string `json:"party_id" binding:"required"`
 				JoinToken   string `json:"join_token" binding:"required"`
-				ShareData   string `json:"share_data" binding:"required"`
+				ShareData   string `json:"share_data" binding:"required"` // User's encrypted share
-				MessageHash string `json:"message_hash" binding:"required"`
+				MessageHash string `json:"message_hash"`
 			}
 
 			if err := c.ShouldBindJSON(&req); err != nil {
@@ -270,32 +302,34 @@ func startHTTPServer(
 				return
 			}
 
-			messageHash, err := hex.DecodeString(req.MessageHash)
+			var messageHash []byte
-			if err != nil {
+			if req.MessageHash != "" {
-				c.JSON(http.StatusBadRequest, gin.H{"error": "invalid message_hash format (expected hex)"})
+				messageHash, err = hex.DecodeString(req.MessageHash)
-				return
+				if err != nil {
+					c.JSON(http.StatusBadRequest, gin.H{"error": "invalid message_hash format (expected hex)"})
+					return
+				}
 			}
 
-			logger.Info("Signing with user share",
+			logger.Info("Starting signing participation (delegate)",
 				zap.String("session_id", req.SessionID),
 				zap.String("party_id", req.PartyID))
 
+			// Execute signing synchronously
 			ctx, cancel := context.WithTimeout(c.Request.Context(), 5*time.Minute)
 			defer cancel()
 
-			result, err := signWithUserShare(
+			input := use_cases.ParticipateSigningInput{
-				ctx,
+				SessionID:     sessionID,
-				sessionClient,
+				PartyID:       req.PartyID,
-				messageRouter,
+				JoinToken:     req.JoinToken,
-				cryptoService,
+				MessageHash:   messageHash,
-				sessionID,
+				UserShareData: shareData, // Pass user's share
-				req.PartyID,
+			}
-				req.JoinToken,
+
-				shareData,
+			output, err := participateSigningUC.Execute(ctx, input)
-				messageHash,
-			)
 			if err != nil {
-				logger.Error("Failed to sign with user share",
+				logger.Error("Signing participation failed",
 					zap.String("session_id", req.SessionID),
 					zap.String("party_id", req.PartyID),
 					zap.Error(err))
@@ -308,18 +342,62 @@ func startHTTPServer(
 				return
 			}
 
-			logger.Info("Signing completed successfully",
+			logger.Info("Signing participation completed (delegate)",
 				zap.String("session_id", req.SessionID),
-				zap.String("party_id", req.PartyID))
+				zap.String("party_id", req.PartyID),
+				zap.Bool("success", output.Success))
+
+			// Return signature
+			var rHex, sHex string
+			if output.R != nil {
+				rHex = hex.EncodeToString(output.R.Bytes())
+			}
+			if output.S != nil {
+				sHex = hex.EncodeToString(output.S.Bytes())
+			}
 
 			c.JSON(http.StatusOK, gin.H{
 				"success":    true,
 				"session_id": req.SessionID,
 				"party_id":   req.PartyID,
-				"signature":  result.Signature,
+				"signature":  hex.EncodeToString(output.Signature),
-				"r":          result.R,
+				"r":          rHex,
-				"s":          result.S,
+				"s":          sHex,
-				"v":          result.V,
+			})
+		})
+
+		// Get user share from cache (for async keygen pattern)
+		api.GET("/sessions/:session_id/user-share", func(c *gin.Context) {
+			sessionIDStr := c.Param("session_id")
+
+			sessionID, err := uuid.Parse(sessionIDStr)
+			if err != nil {
+				c.JSON(http.StatusBadRequest, gin.H{
+					"error": "invalid session_id format",
+				})
+				return
+			}
+
+			// Retrieve and delete share from cache (one-time retrieval)
+			entry, exists := globalShareCache.GetAndDelete(sessionID)
+			if !exists {
+				c.JSON(http.StatusNotFound, gin.H{
+					"error": "Share not found or already retrieved",
+					"note":  "Shares can only be retrieved once and expire after 15 minutes",
+				})
+				return
+			}
+
+			logger.Info("User share retrieved successfully",
+				zap.String("session_id", sessionIDStr),
+				zap.String("party_id", entry.PartyID))
+
+			c.JSON(http.StatusOK, gin.H{
+				"session_id": sessionIDStr,
+				"party_id":   entry.PartyID,
+				"share":      hex.EncodeToString(entry.Share),
+				"public_key": hex.EncodeToString(entry.PublicKey),
+				"note":       "This share has been deleted from memory and cannot be retrieved again",
 			})
 		})
 	}
@@ -342,373 +420,3 @@ func apiKeyAuth(expectedKey string) gin.HandlerFunc {
 		c.Next()
 	}
 }
-
-// UserShareResult contains the result of user share generation
-type UserShareResult struct {
-	PartyIndex int
-	ShareData  string // hex encoded
-	PublicKey  string // hex encoded
-}
-
-// generateUserShare generates a share for the user without storing it
-func generateUserShare(
-	ctx context.Context,
-	sessionClient use_cases.SessionCoordinatorClient,
-	messageRouter use_cases.MessageRouterClient,
-	cryptoService *crypto.CryptoService,
-	sessionID uuid.UUID,
-	partyID string,
-	joinToken string,
-	userPublicKey string,
-) (*UserShareResult, error) {
-	// 1. Join session via coordinator
-	sessionInfo, err := sessionClient.JoinSession(ctx, sessionID, partyID, joinToken)
-	if err != nil {
-		return nil, fmt.Errorf("failed to join session: %w", err)
-	}
-
-	if sessionInfo.SessionType != "keygen" {
-		return nil, fmt.Errorf("invalid session type: expected keygen, got %s", sessionInfo.SessionType)
-	}
-
-	// 2. Find self in participants and build party index map
-	var selfIndex int
-	partyIndexMap := make(map[string]int)
-	for _, p := range sessionInfo.Participants {
-		partyIndexMap[p.PartyID] = p.PartyIndex
-		if p.PartyID == partyID {
-			selfIndex = p.PartyIndex
-		}
-	}
-
-	// 3. Subscribe to messages
-	msgChan, err := messageRouter.SubscribeMessages(ctx, sessionID, partyID)
-	if err != nil {
-		return nil, fmt.Errorf("failed to subscribe to messages: %w", err)
-	}
-
-	// 4. Run TSS Keygen protocol
-	saveData, publicKey, err := runKeygenProtocol(
-		ctx,
-		sessionID,
-		partyID,
-		selfIndex,
-		sessionInfo.Participants,
-		sessionInfo.ThresholdN,
-		sessionInfo.ThresholdT,
-		msgChan,
-		partyIndexMap,
-		messageRouter,
-	)
-	if err != nil {
-		return nil, fmt.Errorf("keygen protocol failed: %w", err)
-	}
-
-	// 5. Encrypt share (optionally with user's public key if provided)
-	var encryptedShare []byte
-	if userPublicKey != "" {
-		// TODO: Encrypt with user's public key for end-to-end encryption
-		encryptedShare, err = cryptoService.EncryptShare(saveData, partyID)
-	} else {
-		encryptedShare, err = cryptoService.EncryptShare(saveData, partyID)
-	}
-	if err != nil {
-		return nil, fmt.Errorf("failed to encrypt share: %w", err)
-	}
-
-	// 6. Report completion to coordinator
-	if err := sessionClient.ReportCompletion(ctx, sessionID, partyID, publicKey); err != nil {
-		logger.Error("failed to report completion", zap.Error(err))
-		// Don't fail - share is generated
-	}
-
-	return &UserShareResult{
-		PartyIndex: selfIndex,
-		ShareData:  hex.EncodeToString(encryptedShare),
-		PublicKey:  hex.EncodeToString(publicKey),
-	}, nil
-}
-
-// SigningResult contains the result of signing
-type SigningResult struct {
-	Signature string
-	R         string
-	S         string
-	V         int
-}
-
-// signWithUserShare signs using the user's share
-func signWithUserShare(
-	ctx context.Context,
-	sessionClient use_cases.SessionCoordinatorClient,
-	messageRouter use_cases.MessageRouterClient,
-	cryptoService *crypto.CryptoService,
-	sessionID uuid.UUID,
-	partyID string,
-	joinToken string,
-	shareData []byte,
-	messageHash []byte,
-) (*SigningResult, error) {
-	// 1. Join session via coordinator
-	sessionInfo, err := sessionClient.JoinSession(ctx, sessionID, partyID, joinToken)
-	if err != nil {
-		return nil, fmt.Errorf("failed to join session: %w", err)
-	}
-
-	if sessionInfo.SessionType != "sign" {
-		return nil, fmt.Errorf("invalid session type: expected sign, got %s", sessionInfo.SessionType)
-	}
-
-	// 2. Decrypt share
-	decryptedShare, err := cryptoService.DecryptShare(shareData, partyID)
-	if err != nil {
-		return nil, fmt.Errorf("failed to decrypt share: %w", err)
-	}
-
-	// 3. Find self in participants
-	var selfIndex int
-	partyIndexMap := make(map[string]int)
-	for _, p := range sessionInfo.Participants {
-		partyIndexMap[p.PartyID] = p.PartyIndex
-		if p.PartyID == partyID {
-			selfIndex = p.PartyIndex
-		}
-	}
-
-	// 4. Subscribe to messages
-	msgChan, err := messageRouter.SubscribeMessages(ctx, sessionID, partyID)
-	if err != nil {
-		return nil, fmt.Errorf("failed to subscribe to messages: %w", err)
-	}
-
-	// 5. Run TSS Signing protocol
-	signature, r, s, v, err := runSigningProtocol(
-		ctx,
-		sessionID,
-		partyID,
-		selfIndex,
-		sessionInfo.Participants,
-		sessionInfo.ThresholdN,
-		sessionInfo.ThresholdT,
-		msgChan,
-		partyIndexMap,
-		messageRouter,
-		decryptedShare,
-		messageHash,
-	)
-	if err != nil {
-		return nil, fmt.Errorf("signing protocol failed: %w", err)
-	}
-
-	// 6. Report completion to coordinator
-	if err := sessionClient.ReportCompletion(ctx, sessionID, partyID, signature); err != nil {
-		logger.Error("failed to report completion", zap.Error(err))
-	}
-
-	return &SigningResult{
-		Signature: hex.EncodeToString(signature),
-		R:         hex.EncodeToString(r),
-		S:         hex.EncodeToString(s),
-		V:         v,
-	}, nil
-}
-
-// runKeygenProtocol runs the TSS keygen protocol
-func runKeygenProtocol(
-	ctx context.Context,
-	sessionID uuid.UUID,
-	partyID string,
-	selfIndex int,
-	participants []use_cases.ParticipantInfo,
-	n, t int,
-	msgChan <-chan *use_cases.MPCMessage,
-	partyIndexMap map[string]int,
-	messageRouter use_cases.MessageRouterClient,
-) ([]byte, []byte, error) {
-	logger.Info("Running keygen protocol",
-		zap.String("session_id", sessionID.String()),
-		zap.String("party_id", partyID),
-		zap.Int("self_index", selfIndex),
-		zap.Int("n", n),
-		zap.Int("t", t))
-
-	// Create message handler adapter
-	msgHandler := &messageHandler{
-		sessionID:     sessionID,
-		partyID:       partyID,
-		messageRouter: messageRouter,
-		msgChan:       make(chan *tss.ReceivedMessage, 100),
-		partyIndexMap: partyIndexMap,
-	}
-
-	// Start message conversion goroutine
-	go msgHandler.convertMessages(ctx, msgChan)
-
-	// Create keygen config
-	config := tss.KeygenConfig{
-		Threshold:    t,
-		TotalParties: n,
-		Timeout:      10 * time.Minute,
-	}
-
-	// Create party list
-	allParties := make([]tss.KeygenParty, len(participants))
-	for i, p := range participants {
-		allParties[i] = tss.KeygenParty{
-			PartyID:    p.PartyID,
-			PartyIndex: p.PartyIndex,
-		}
-	}
-
-	selfParty := tss.KeygenParty{
-		PartyID:    partyID,
-		PartyIndex: selfIndex,
-	}
-
-	// Create keygen session
-	session, err := tss.NewKeygenSession(config, selfParty, allParties, msgHandler)
-	if err != nil {
-		return nil, nil, err
-	}
-
-	// Run keygen
-	result, err := session.Start(ctx)
-	if err != nil {
-		return nil, nil, err
-	}
-
-	logger.Info("Keygen completed successfully",
-		zap.String("session_id", sessionID.String()),
-		zap.String("party_id", partyID))
-
-	return result.LocalPartySaveData, result.PublicKeyBytes, nil
-}
-
-// runSigningProtocol runs the TSS signing protocol
-func runSigningProtocol(
-	ctx context.Context,
-	sessionID uuid.UUID,
-	partyID string,
-	selfIndex int,
-	participants []use_cases.ParticipantInfo,
-	n, t int,
-	msgChan <-chan *use_cases.MPCMessage,
-	partyIndexMap map[string]int,
-	messageRouter use_cases.MessageRouterClient,
-	shareData []byte,
-	messageHash []byte,
-) ([]byte, []byte, []byte, int, error) {
-	logger.Info("Running signing protocol",
-		zap.String("session_id", sessionID.String()),
-		zap.String("party_id", partyID),
-		zap.Int("self_index", selfIndex))
-
-	// Create message handler adapter
-	msgHandler := &messageHandler{
-		sessionID:     sessionID,
-		partyID:       partyID,
-		messageRouter: messageRouter,
-		msgChan:       make(chan *tss.ReceivedMessage, 100),
-		partyIndexMap: partyIndexMap,
-	}
-
-	// Start message conversion goroutine
-	go msgHandler.convertMessages(ctx, msgChan)
-
-	// Create signing config
-	config := tss.SigningConfig{
-		Threshold:    t,
-		TotalSigners: n,
-		Timeout:      5 * time.Minute,
-	}
-
-	// Create party list
-	allParties := make([]tss.SigningParty, len(participants))
-	for i, p := range participants {
-		allParties[i] = tss.SigningParty{
-			PartyID:    p.PartyID,
-			PartyIndex: p.PartyIndex,
-		}
-	}
-
-	selfParty := tss.SigningParty{
-		PartyID:    partyID,
-		PartyIndex: selfIndex,
-	}
-
-	// Create signing session
-	session, err := tss.NewSigningSession(config, selfParty, allParties, shareData, messageHash, msgHandler)
-	if err != nil {
-		return nil, nil, nil, 0, err
-	}
-
-	// Run signing
-	result, err := session.Start(ctx)
-	if err != nil {
-		return nil, nil, nil, 0, err
-	}
-
-	logger.Info("Signing completed successfully",
-		zap.String("session_id", sessionID.String()),
-		zap.String("party_id", partyID))
-
-	// Convert big.Int to []byte
-	var rBytes, sBytes []byte
-	if result.R != nil {
-		rBytes = result.R.Bytes()
-	}
-	if result.S != nil {
-		sBytes = result.S.Bytes()
-	}
-
-	return result.Signature, rBytes, sBytes, result.RecoveryID, nil
-}
-
-// messageHandler adapts MPCMessage channel to tss.MessageHandler
-type messageHandler struct {
-	sessionID     uuid.UUID
-	partyID       string
-	messageRouter use_cases.MessageRouterClient
-	msgChan       chan *tss.ReceivedMessage
-	partyIndexMap map[string]int
-}
-
-func (h *messageHandler) SendMessage(ctx context.Context, isBroadcast bool, toParties []string, msgBytes []byte) error {
-	return h.messageRouter.RouteMessage(ctx, h.sessionID, h.partyID, toParties, 0, msgBytes)
-}
-
-func (h *messageHandler) ReceiveMessages() <-chan *tss.ReceivedMessage {
-	return h.msgChan
-}
-
-func (h *messageHandler) convertMessages(ctx context.Context, inChan <-chan *use_cases.MPCMessage) {
-	for {
-		select {
-		case <-ctx.Done():
-			close(h.msgChan)
-			return
-		case msg, ok := <-inChan:
-			if !ok {
-				close(h.msgChan)
-				return
-			}
-
-			fromIndex, exists := h.partyIndexMap[msg.FromParty]
-			if !exists {
-				continue
-			}
-
-			tssMsg := &tss.ReceivedMessage{
-				FromPartyIndex: fromIndex,
-				IsBroadcast:    msg.IsBroadcast,
-				MsgBytes:       msg.Payload,
-			}
-
-			select {
-			case h.msgChan <- tssMsg:
-			case <-ctx.Done():
-				return
-			}
-		}
-	}
-}

backend/mpc-system/services/server-party/adapters/output/grpc/message_router_client.go

@@ -8,49 +8,70 @@ import (
 
 	"github.com/google/uuid"
 	router "github.com/rwadurian/mpc-system/api/grpc/router/v1"
+	"github.com/rwadurian/mpc-system/pkg/grpcutil"
 	"github.com/rwadurian/mpc-system/pkg/logger"
+	"github.com/rwadurian/mpc-system/pkg/retry"
 	"github.com/rwadurian/mpc-system/services/server-party/application/use_cases"
 	"go.uber.org/zap"
 	"google.golang.org/grpc"
-	"google.golang.org/grpc/credentials/insecure"
 )
 
 // MessageRouterClient implements use_cases.MessageRouterClient
 type MessageRouterClient struct {
-	conn    *grpc.ClientConn
+	resilientConn *grpcutil.ResilientConn
-	address string
+	address       string
-	mu      sync.Mutex
+	mu            sync.Mutex
+	retryCfg      retry.Config
 }
 
-// NewMessageRouterClient creates a new message router gRPC client
+// NewMessageRouterClient creates a new message router gRPC client with auto-reconnection
 func NewMessageRouterClient(address string) (*MessageRouterClient, error) {
-	conn, err := grpc.Dial(
+	config := grpcutil.DefaultClientConfig(address)
-		address,
+	resilientConn, err := grpcutil.NewResilientConn(config)
-		grpc.WithTransportCredentials(insecure.NewCredentials()),
-		grpc.WithBlock(),
-		grpc.WithTimeout(10*time.Second),
-	)
 	if err != nil {
 		return nil, err
 	}
 
-	logger.Info("Connected to Message Router", zap.String("address", address))
+	logger.Info("Connected to Message Router with keepalive",
+		zap.String("address", address),
+		zap.Duration("keepalive_time", config.KeepaliveTime),
+		zap.Bool("auto_reconnect", config.EnableReconnect))
 
 	return &MessageRouterClient{
-		conn:    conn,
+		resilientConn: resilientConn,
-		address: address,
+		address:       address,
+		retryCfg:      retry.DefaultConfig(),
 	}, nil
 }
 
+// getConn returns the current gRPC connection
+func (c *MessageRouterClient) getConn() *grpc.ClientConn {
+	return c.resilientConn.GetConn()
+}
+
 // Close closes the gRPC connection
 func (c *MessageRouterClient) Close() error {
-	if c.conn != nil {
+	if c.resilientConn != nil {
-		return c.conn.Close()
+		return c.resilientConn.Close()
 	}
 	return nil
 }
 
+// IsConnected returns true if the connection is ready
+func (c *MessageRouterClient) IsConnected() bool {
+	return c.resilientConn != nil && c.resilientConn.IsConnected()
+}
+
+// WaitForReady waits for the connection to be ready
+func (c *MessageRouterClient) WaitForReady(ctx context.Context) bool {
+	if c.resilientConn == nil {
+		return false
+	}
+	return c.resilientConn.WaitForReady(ctx)
+}
+
 // RouteMessage sends an MPC protocol message to other parties
+// Includes automatic retry with exponential backoff for transient failures
 func (c *MessageRouterClient) RouteMessage(
 	ctx context.Context,
 	sessionID uuid.UUID,
@@ -68,29 +89,27 @@ func (c *MessageRouterClient) RouteMessage(
 		Payload:     payload,
 	}
 
-	resp := &router.RouteMessageResponse{}
+	return retry.DoVoid(ctx, c.retryCfg, "RouteMessage", func() error {
-	err := c.conn.Invoke(ctx, "/mpc.router.v1.MessageRouter/RouteMessage", req, resp)
+		resp := &router.RouteMessageResponse{}
-	if err != nil {
+		err := c.getConn().Invoke(ctx, "/mpc.router.v1.MessageRouter/RouteMessage", req, resp)
-		logger.Error("Failed to route message",
+		if err != nil {
-			zap.Error(err),
+			return err
+		}
+
+		if !resp.Success {
+			logger.Error("Message routing failed",
+				zap.String("session_id", sessionID.String()))
+			return use_cases.ErrKeygenFailed
+		}
+
+		logger.Debug("Message routed successfully",
 			zap.String("session_id", sessionID.String()),
-			zap.String("from", fromParty))
+			zap.String("from", fromParty),
-		return err
+			zap.Int("to_count", len(toParties)),
-	}
+			zap.Int("round", roundNumber))
 
-	if !resp.Success {
+		return nil
-		logger.Error("Message routing failed",
+	})
-			zap.String("session_id", sessionID.String()))
-		return use_cases.ErrKeygenFailed
-	}
-
-	logger.Debug("Message routed successfully",
-		zap.String("session_id", sessionID.String()),
-		zap.String("from", fromParty),
-		zap.Int("to_count", len(toParties)),
-		zap.Int("round", roundNumber))
-
-	return nil
 }
 
 // SubscribeMessages subscribes to MPC messages for a party
@@ -145,6 +164,8 @@ func (c *MessageRouterClient) SubscribeMessages(
 
 				// Convert to use_cases.MPCMessage
 				mpcMsg := &use_cases.MPCMessage{
+					MessageID:   msg.MessageId,
+					SessionID:   msg.SessionId,
 					FromParty:   msg.FromParty,
 					IsBroadcast: msg.IsBroadcast,
 					RoundNumber: int(msg.RoundNumber),
@@ -154,8 +175,24 @@ func (c *MessageRouterClient) SubscribeMessages(
 				select {
 				case msgChan <- mpcMsg:
 					logger.Debug("Received MPC message",
+						zap.String("message_id", msg.MessageId),
 						zap.String("from", msg.FromParty),
 						zap.Int("round", int(msg.RoundNumber)))
+
+					// Send acknowledgment for the received message
+					go func(messageID, sessionIDStr, pID string) {
+						ackCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+						defer cancel()
+						sid, _ := uuid.Parse(sessionIDStr)
+						if err := c.AcknowledgeMessage(ackCtx, messageID, sid, pID, true, ""); err != nil {
+							logger.Warn("Failed to acknowledge message",
+								zap.String("message_id", messageID),
+								zap.Error(err))
+						} else {
+							logger.Debug("Message acknowledged",
+								zap.String("message_id", messageID))
+						}
+					}(msg.MessageId, msg.SessionId, partyID)
 				case <-ctx.Done():
 					return
 				}
@@ -180,7 +217,7 @@ func (c *MessageRouterClient) createSubscribeStream(
 		ServerStreams: true,
 	}
 
-	stream, err := c.conn.NewStream(ctx, streamDesc, "/mpc.router.v1.MessageRouter/SubscribeMessages")
+	stream, err := c.getConn().NewStream(ctx, streamDesc, "/mpc.router.v1.MessageRouter/SubscribeMessages")
 	if err != nil {
 		return nil, err
 	}
@@ -197,6 +234,7 @@ func (c *MessageRouterClient) createSubscribeStream(
 }
 
 // GetPendingMessages gets pending messages (polling alternative)
+// Includes automatic retry with exponential backoff for transient failures
 func (c *MessageRouterClient) GetPendingMessages(
 	ctx context.Context,
 	sessionID uuid.UUID,
@@ -209,31 +247,81 @@ func (c *MessageRouterClient) GetPendingMessages(
 		AfterTimestamp: afterTimestamp,
 	}
 
-	resp := &router.GetPendingMessagesResponse{}
+	return retry.Do(ctx, c.retryCfg, "GetPendingMessages", func() ([]*use_cases.MPCMessage, error) {
-	err := c.conn.Invoke(ctx, "/mpc.router.v1.MessageRouter/GetPendingMessages", req, resp)
+		resp := &router.GetPendingMessagesResponse{}
-	if err != nil {
+		err := c.getConn().Invoke(ctx, "/mpc.router.v1.MessageRouter/GetPendingMessages", req, resp)
-		return nil, err
+		if err != nil {
-	}
+			return nil, err
-
-	messages := make([]*use_cases.MPCMessage, len(resp.Messages))
-	for i, msg := range resp.Messages {
-		messages[i] = &use_cases.MPCMessage{
-			FromParty:   msg.FromParty,
-			IsBroadcast: msg.IsBroadcast,
-			RoundNumber: int(msg.RoundNumber),
-			Payload:     msg.Payload,
 		}
-	}
 
-	return messages, nil
+		messages := make([]*use_cases.MPCMessage, len(resp.Messages))
+		for i, msg := range resp.Messages {
+			messages[i] = &use_cases.MPCMessage{
+				MessageID:   msg.MessageId,
+				SessionID:   msg.SessionId,
+				FromParty:   msg.FromParty,
+				IsBroadcast: msg.IsBroadcast,
+				RoundNumber: int(msg.RoundNumber),
+				Payload:     msg.Payload,
+			}
+
+			// Send acknowledgment for each received message
+			go func(messageID, sessionIDStr, pID string) {
+				ackCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+				defer cancel()
+				sid, _ := uuid.Parse(sessionIDStr)
+				if err := c.AcknowledgeMessage(ackCtx, messageID, sid, pID, true, ""); err != nil {
+					logger.Warn("Failed to acknowledge pending message",
+						zap.String("message_id", messageID),
+						zap.Error(err))
+				}
+			}(msg.MessageId, msg.SessionId, partyID)
+		}
+
+		return messages, nil
+	})
+}
+
+// NotificationConfig represents notification channel configuration for a party
+// If any notification channel is set, party operates in OFFLINE mode (24h async)
+// If no notification channels are set, party operates in REAL-TIME mode (Message Router push)
+type NotificationConfig struct {
+	Email     string // Optional: email address for session invitations
+	Phone     string // Optional: phone number for SMS notifications
+	PushToken string // Optional: push notification token (FCM/APNs)
+}
+
+// HasAnyChannel returns true if any notification channel is configured
+func (nc *NotificationConfig) HasAnyChannel() bool {
+	return nc != nil && (nc.Email != "" || nc.Phone != "" || nc.PushToken != "")
 }
 
 // RegisterParty registers this party with the message router
+// This should be called on startup and whenever party configuration changes
 func (c *MessageRouterClient) RegisterParty(
 	ctx context.Context,
 	partyID string,
 	partyRole string,
 	version string,
+) error {
+	return c.RegisterPartyWithNotification(ctx, partyID, partyRole, version, nil)
+}
+
+// RegisterPartyWithNotification registers party with optional notification channels
+// If notification channels are provided, party operates in offline mode (24h async)
+// If no notification channels, party operates in real-time mode (Message Router push)
+// Includes automatic retry with exponential backoff for transient failures
+//
+// This method should be called:
+// 1. On startup to register the party
+// 2. When notification channels are updated (e.g., user binds email/phone)
+// 3. When party configuration changes
+func (c *MessageRouterClient) RegisterPartyWithNotification(
+	ctx context.Context,
+	partyID string,
+	partyRole string,
+	version string,
+	notification *NotificationConfig,
 ) error {
 	req := &router.RegisterPartyRequest{
 		PartyId:   partyID,
@@ -241,21 +329,58 @@ func (c *MessageRouterClient) RegisterParty(
 		Version:   version,
 	}
 
-	resp := &router.RegisterPartyResponse{}
+	// Set notification channel if configured (enables offline mode)
-	err := c.conn.Invoke(ctx, "/mpc.router.v1.MessageRouter/RegisterParty", req, resp)
+	if notification != nil && notification.HasAnyChannel() {
-	if err != nil {
+		req.Notification = &router.NotificationChannel{
-		logger.Error("Failed to register party",
+			Email:     notification.Email,
-			zap.Error(err),
+			Phone:     notification.Phone,
-			zap.String("party_id", partyID))
+			PushToken: notification.PushToken,
-		return err
+		}
 	}
 
-	logger.Info("Party registered successfully",
+	// Log registration mode
-		zap.String("party_id", partyID),
+	mode := "real-time"
-		zap.String("role", partyRole),
+	if notification != nil && notification.HasAnyChannel() {
-		zap.Bool("success", resp.Success))
+		mode = "offline"
+	}
 
-	return nil
+	return retry.DoVoid(ctx, c.retryCfg, "RegisterParty", func() error {
+		resp := &router.RegisterPartyResponse{}
+		err := c.getConn().Invoke(ctx, "/mpc.router.v1.MessageRouter/RegisterParty", req, resp)
+		if err != nil {
+			return err
+		}
+
+		logger.Info("Party registered successfully",
+			zap.String("party_id", partyID),
+			zap.String("role", partyRole),
+			zap.String("mode", mode),
+			zap.Bool("has_email", notification != nil && notification.Email != ""),
+			zap.Bool("has_phone", notification != nil && notification.Phone != ""),
+			zap.Bool("has_push", notification != nil && notification.PushToken != ""),
+			zap.Bool("success", resp.Success))
+
+		return nil
+	})
+}
+
+// UpdateNotificationChannels re-registers party with new notification channels
+// Call this when party's notification configuration changes
+// TODO: Implement when notification management is needed
+func (c *MessageRouterClient) UpdateNotificationChannels(
+	ctx context.Context,
+	partyID string,
+	partyRole string,
+	version string,
+	notification *NotificationConfig,
+) error {
+	logger.Info("Updating party notification channels",
+		zap.String("party_id", partyID),
+		zap.Bool("has_email", notification != nil && notification.Email != ""),
+		zap.Bool("has_phone", notification != nil && notification.Phone != ""),
+		zap.Bool("has_push", notification != nil && notification.PushToken != ""))
+
+	return c.RegisterPartyWithNotification(ctx, partyID, partyRole, version, notification)
 }
 
 // SubscribeSessionEvents subscribes to session lifecycle events
@@ -330,7 +455,7 @@ func (c *MessageRouterClient) createSessionEventStream(
 		ServerStreams: true,
 	}
 
-	stream, err := c.conn.NewStream(ctx, streamDesc, "/mpc.router.v1.MessageRouter/SubscribeSessionEvents")
+	stream, err := c.getConn().NewStream(ctx, streamDesc, "/mpc.router.v1.MessageRouter/SubscribeSessionEvents")
 	if err != nil {
 		return nil, err
 	}
@@ -345,3 +470,132 @@ func (c *MessageRouterClient) createSessionEventStream(
 
 	return stream, nil
 }
+
+// AcknowledgeMessage acknowledges receipt and processing of a message
+// This should be called after successfully processing an MPC message
+// Includes automatic retry with exponential backoff
+func (c *MessageRouterClient) AcknowledgeMessage(
+	ctx context.Context,
+	messageID string,
+	sessionID uuid.UUID,
+	partyID string,
+	success bool,
+	errorMessage string,
+) error {
+	req := &router.AcknowledgeMessageRequest{
+		MessageId:    messageID,
+		PartyId:      partyID,
+		SessionId:    sessionID.String(),
+		Success:      success,
+		ErrorMessage: errorMessage,
+	}
+
+	return retry.DoVoid(ctx, c.retryCfg, "AcknowledgeMessage", func() error {
+		resp := &router.AcknowledgeMessageResponse{}
+		err := c.getConn().Invoke(ctx, "/mpc.router.v1.MessageRouter/AcknowledgeMessage", req, resp)
+		if err != nil {
+			return err
+		}
+
+		if !resp.Success {
+			logger.Warn("Message acknowledgment failed",
+				zap.String("message_id", messageID),
+				zap.String("response", resp.Message))
+		}
+
+		return nil
+	})
+}
+
+// GetMessageStatus gets the delivery status of a message
+// Includes automatic retry with exponential backoff
+func (c *MessageRouterClient) GetMessageStatus(
+	ctx context.Context,
+	messageID string,
+	sessionID uuid.UUID,
+) (*router.GetMessageStatusResponse, error) {
+	req := &router.GetMessageStatusRequest{
+		MessageId: messageID,
+		SessionId: sessionID.String(),
+	}
+
+	return retry.Do(ctx, c.retryCfg, "GetMessageStatus", func() (*router.GetMessageStatusResponse, error) {
+		resp := &router.GetMessageStatusResponse{}
+		err := c.getConn().Invoke(ctx, "/mpc.router.v1.MessageRouter/GetMessageStatus", req, resp)
+		if err != nil {
+			return nil, err
+		}
+		return resp, nil
+	})
+}
+
+// Heartbeat sends a heartbeat to keep the party connection alive
+// Returns the number of pending messages for this party
+// Includes automatic retry with exponential backoff
+func (c *MessageRouterClient) Heartbeat(
+	ctx context.Context,
+	partyID string,
+) (int32, error) {
+	req := &router.HeartbeatRequest{
+		PartyId:   partyID,
+		Timestamp: time.Now().UnixMilli(),
+	}
+
+	return retry.Do(ctx, c.retryCfg, "Heartbeat", func() (int32, error) {
+		resp := &router.HeartbeatResponse{}
+		err := c.getConn().Invoke(ctx, "/mpc.router.v1.MessageRouter/Heartbeat", req, resp)
+		if err != nil {
+			return 0, err
+		}
+
+		if resp.PendingMessages > 0 {
+			logger.Debug("Heartbeat response",
+				zap.String("party_id", partyID),
+				zap.Int32("pending_messages", resp.PendingMessages))
+		}
+
+		return resp.PendingMessages, nil
+	})
+}
+
+// StartHeartbeat starts a background goroutine that sends heartbeats periodically
+// Returns a cancel function to stop the heartbeat
+func (c *MessageRouterClient) StartHeartbeat(
+	ctx context.Context,
+	partyID string,
+	interval time.Duration,
+	onPendingMessages func(count int32),
+) context.CancelFunc {
+	heartbeatCtx, cancel := context.WithCancel(ctx)
+
+	go func() {
+		ticker := time.NewTicker(interval)
+		defer ticker.Stop()
+
+		for {
+			select {
+			case <-heartbeatCtx.Done():
+				logger.Info("Heartbeat stopped", zap.String("party_id", partyID))
+				return
+			case <-ticker.C:
+				pendingCount, err := c.Heartbeat(heartbeatCtx, partyID)
+				if err != nil {
+					logger.Warn("Heartbeat failed",
+						zap.String("party_id", partyID),
+						zap.Error(err))
+					continue
+				}
+
+				if onPendingMessages != nil && pendingCount > 0 {
+					onPendingMessages(pendingCount)
+				}
+			}
+		}
+	}()
+
+	logger.Info("Heartbeat started",
+		zap.String("party_id", partyID),
+		zap.Duration("interval", interval))
+
+	return cancel
+}

backend/mpc-system/services/server-party/adapters/output/grpc/session_coordinator_client.go

@@ -2,52 +2,72 @@ package grpc
 
 import (
 	"context"
-	"time"
 
 	"github.com/google/uuid"
 	coordinator "github.com/rwadurian/mpc-system/api/grpc/coordinator/v1"
+	"github.com/rwadurian/mpc-system/pkg/grpcutil"
 	"github.com/rwadurian/mpc-system/pkg/logger"
+	"github.com/rwadurian/mpc-system/pkg/retry"
 	"github.com/rwadurian/mpc-system/services/server-party/application/use_cases"
 	"go.uber.org/zap"
 	"google.golang.org/grpc"
-	"google.golang.org/grpc/credentials/insecure"
 )
 
 // SessionCoordinatorClient implements use_cases.SessionCoordinatorClient
 type SessionCoordinatorClient struct {
-	conn    *grpc.ClientConn
+	resilientConn *grpcutil.ResilientConn
-	address string
+	address       string
+	retryCfg      retry.Config
 }
 
-// NewSessionCoordinatorClient creates a new session coordinator gRPC client
+// NewSessionCoordinatorClient creates a new session coordinator gRPC client with auto-reconnection
 func NewSessionCoordinatorClient(address string) (*SessionCoordinatorClient, error) {
-	conn, err := grpc.Dial(
+	config := grpcutil.DefaultClientConfig(address)
-		address,
+	resilientConn, err := grpcutil.NewResilientConn(config)
-		grpc.WithTransportCredentials(insecure.NewCredentials()),
-		grpc.WithBlock(),
-		grpc.WithTimeout(10*time.Second),
-	)
 	if err != nil {
 		return nil, err
 	}
 
-	logger.Info("Connected to Session Coordinator", zap.String("address", address))
+	logger.Info("Connected to Session Coordinator with keepalive",
+		zap.String("address", address),
+		zap.Duration("keepalive_time", config.KeepaliveTime),
+		zap.Bool("auto_reconnect", config.EnableReconnect))
 
 	return &SessionCoordinatorClient{
-		conn:    conn,
+		resilientConn: resilientConn,
-		address: address,
+		address:       address,
+		retryCfg:      retry.DefaultConfig(),
 	}, nil
 }
 
+// getConn returns the current gRPC connection
+func (c *SessionCoordinatorClient) getConn() *grpc.ClientConn {
+	return c.resilientConn.GetConn()
+}
+
 // Close closes the gRPC connection
 func (c *SessionCoordinatorClient) Close() error {
-	if c.conn != nil {
+	if c.resilientConn != nil {
-		return c.conn.Close()
+		return c.resilientConn.Close()
 	}
 	return nil
 }
 
+// IsConnected returns true if the connection is ready
+func (c *SessionCoordinatorClient) IsConnected() bool {
+	return c.resilientConn != nil && c.resilientConn.IsConnected()
+}
+
+// WaitForReady waits for the connection to be ready
+func (c *SessionCoordinatorClient) WaitForReady(ctx context.Context) bool {
+	if c.resilientConn == nil {
+		return false
+	}
+	return c.resilientConn.WaitForReady(ctx)
+}
+
 // JoinSession joins an MPC session
+// Includes automatic retry with exponential backoff for transient failures
 func (c *SessionCoordinatorClient) JoinSession(
 	ctx context.Context,
 	sessionID uuid.UUID,
@@ -66,53 +86,55 @@ func (c *SessionCoordinatorClient) JoinSession(
 		},
 	}
 
-	// Make the gRPC call using the raw connection
+	return retry.Do(ctx, c.retryCfg, "JoinSession", func() (*use_cases.SessionInfo, error) {
-	resp := &coordinator.JoinSessionResponse{}
+		// Make the gRPC call using the raw connection
-	err := c.conn.Invoke(ctx, "/mpc.coordinator.v1.SessionCoordinator/JoinSession", req, resp)
+		resp := &coordinator.JoinSessionResponse{}
-	if err != nil {
+		err := c.getConn().Invoke(ctx, "/mpc.coordinator.v1.SessionCoordinator/JoinSession", req, resp)
-		logger.Error("Failed to join session", zap.Error(err))
+		if err != nil {
-		return nil, err
+			return nil, err
-	}
-
-	if !resp.Success {
-		logger.Error("Join session failed", zap.String("session_id", sessionID.String()))
-		return nil, use_cases.ErrInvalidSession
-	}
-
-	// Convert response to SessionInfo
-	// Note: OtherParties should include ALL participants (including self) from coordinator
-	participants := make([]use_cases.ParticipantInfo, len(resp.OtherParties))
-	for i, p := range resp.OtherParties {
-		// Debug: Log what we received from gRPC
-		logger.Info("gRPC client - received party_index from protobuf response",
-			zap.String("party_id", p.PartyId),
-			zap.Int32("proto_party_index", p.PartyIndex),
-			zap.Int("converted_party_index", int(p.PartyIndex)))
-
-		participants[i] = use_cases.ParticipantInfo{
-			PartyID:    p.PartyId,
-			PartyIndex: int(p.PartyIndex),
 		}
-	}
 
-	sessionInfo := &use_cases.SessionInfo{
+		if !resp.Success {
-		SessionID:    sessionID,
+			logger.Error("Join session failed", zap.String("session_id", sessionID.String()))
-		SessionType:  resp.SessionInfo.SessionType,
+			return nil, use_cases.ErrInvalidSession
-		ThresholdN:   int(resp.SessionInfo.ThresholdN),
+		}
-		ThresholdT:   int(resp.SessionInfo.ThresholdT),
-		MessageHash:  resp.SessionInfo.MessageHash,
-		Participants: participants,
-	}
 
-	logger.Info("Joined session successfully",
+		// Convert response to SessionInfo
-		zap.String("session_id", sessionID.String()),
+		// Note: OtherParties should include ALL participants (including self) from coordinator
-		zap.String("party_id", partyID),
+		participants := make([]use_cases.ParticipantInfo, len(resp.OtherParties))
-		zap.String("session_type", sessionInfo.SessionType))
+		for i, p := range resp.OtherParties {
+			// Debug: Log what we received from gRPC
+			logger.Debug("gRPC client - received party_index from protobuf response",
+				zap.String("party_id", p.PartyId),
+				zap.Int32("proto_party_index", p.PartyIndex),
+				zap.Int("converted_party_index", int(p.PartyIndex)))
 
-	return sessionInfo, nil
+			participants[i] = use_cases.ParticipantInfo{
+				PartyID:    p.PartyId,
+				PartyIndex: int(p.PartyIndex),
+			}
+		}
+
+		sessionInfo := &use_cases.SessionInfo{
+			SessionID:    sessionID,
+			SessionType:  resp.SessionInfo.SessionType,
+			ThresholdN:   int(resp.SessionInfo.ThresholdN),
+			ThresholdT:   int(resp.SessionInfo.ThresholdT),
+			MessageHash:  resp.SessionInfo.MessageHash,
+			Participants: participants,
+		}
+
+		logger.Info("Joined session successfully",
+			zap.String("session_id", sessionID.String()),
+			zap.String("party_id", partyID),
+			zap.String("session_type", sessionInfo.SessionType))
+
+		return sessionInfo, nil
+	})
 }
 
 // ReportCompletion reports that a party has completed the MPC protocol
+// Includes automatic retry with exponential backoff for transient failures
 func (c *SessionCoordinatorClient) ReportCompletion(
 	ctx context.Context,
 	sessionID uuid.UUID,
@@ -125,22 +147,24 @@ func (c *SessionCoordinatorClient) ReportCompletion(
 		PublicKey: resultData, // For keygen, this is public key; for signing, this is signature
 	}
 
-	resp := &coordinator.ReportCompletionResponse{}
+	return retry.DoVoid(ctx, c.retryCfg, "ReportCompletion", func() error {
-	err := c.conn.Invoke(ctx, "/mpc.coordinator.v1.SessionCoordinator/ReportCompletion", req, resp)
+		resp := &coordinator.ReportCompletionResponse{}
-	if err != nil {
+		err := c.getConn().Invoke(ctx, "/mpc.coordinator.v1.SessionCoordinator/ReportCompletion", req, resp)
-		logger.Error("Failed to report completion", zap.Error(err))
+		if err != nil {
-		return err
+			return err
-	}
+		}
 
-	logger.Info("Reported completion",
+		logger.Info("Reported completion",
-		zap.String("session_id", sessionID.String()),
+			zap.String("session_id", sessionID.String()),
-		zap.String("party_id", partyID),
+			zap.String("party_id", partyID),
-		zap.Bool("all_completed", resp.AllCompleted))
+			zap.Bool("all_completed", resp.AllCompleted))
 
-	return nil
+		return nil
+	})
 }
 
 // MarkPartyReady marks the party as ready to start the protocol
+// Includes automatic retry with exponential backoff for transient failures
 func (c *SessionCoordinatorClient) MarkPartyReady(
 	ctx context.Context,
 	sessionID uuid.UUID,
@@ -151,22 +175,24 @@ func (c *SessionCoordinatorClient) MarkPartyReady(
 		PartyId:   partyID,
 	}
 
-	resp := &coordinator.MarkPartyReadyResponse{}
+	return retry.Do(ctx, c.retryCfg, "MarkPartyReady", func() (bool, error) {
-	err := c.conn.Invoke(ctx, "/mpc.coordinator.v1.SessionCoordinator/MarkPartyReady", req, resp)
+		resp := &coordinator.MarkPartyReadyResponse{}
-	if err != nil {
+		err := c.getConn().Invoke(ctx, "/mpc.coordinator.v1.SessionCoordinator/MarkPartyReady", req, resp)
-		logger.Error("Failed to mark party ready", zap.Error(err))
+		if err != nil {
-		return false, err
+			return false, err
-	}
+		}
 
-	logger.Info("Marked party ready",
+		logger.Info("Marked party ready",
-		zap.String("session_id", sessionID.String()),
+			zap.String("session_id", sessionID.String()),
-		zap.String("party_id", partyID),
+			zap.String("party_id", partyID),
-		zap.Bool("all_ready", resp.AllReady))
+			zap.Bool("all_ready", resp.AllReady))
 
-	return resp.AllReady, nil
+		return resp.AllReady, nil
+	})
 }
 
 // GetSessionStatus gets the current session status
+// Includes automatic retry with exponential backoff for transient failures
 func (c *SessionCoordinatorClient) GetSessionStatus(
 	ctx context.Context,
 	sessionID uuid.UUID,
@@ -175,13 +201,15 @@ func (c *SessionCoordinatorClient) GetSessionStatus(
 		SessionId: sessionID.String(),
 	}
 
-	resp := &coordinator.GetSessionStatusResponse{}
+	return retry.Do(ctx, c.retryCfg, "GetSessionStatus", func() (string, error) {
-	err := c.conn.Invoke(ctx, "/mpc.coordinator.v1.SessionCoordinator/GetSessionStatus", req, resp)
+		resp := &coordinator.GetSessionStatusResponse{}
-	if err != nil {
+		err := c.getConn().Invoke(ctx, "/mpc.coordinator.v1.SessionCoordinator/GetSessionStatus", req, resp)
-		return "", err
+		if err != nil {
-	}
+			return "", err
+		}
 
-	return resp.Status, nil
+		return resp.Status, nil
+	})
 }
 
 // findPartyIndex finds the party index from the list of parties

backend/mpc-system/services/server-party/application/use_cases/participate_keygen.go

@@ -67,6 +67,8 @@ type ParticipantInfo struct {
 
 // MPCMessage represents an MPC message from the router
 type MPCMessage struct {
+	MessageID   string // Unique message ID for acknowledgment
+	SessionID   string // Session ID for acknowledgment
 	FromParty   string
 	IsBroadcast bool
 	RoundNumber int

backend/mpc-system/services/server-party/application/use_cases/participate_signing.go

@@ -10,6 +10,7 @@ import (
 	"github.com/rwadurian/mpc-system/pkg/crypto"
 	"github.com/rwadurian/mpc-system/pkg/logger"
 	"github.com/rwadurian/mpc-system/pkg/tss"
+	"github.com/rwadurian/mpc-system/services/server-party/domain/entities"
 	"github.com/rwadurian/mpc-system/services/server-party/domain/repositories"
 	"go.uber.org/zap"
 )
@@ -27,6 +28,8 @@ type ParticipateSigningInput struct {
 	PartyID     string
 	JoinToken   string
 	MessageHash []byte
+	// For delegate parties: encrypted share provided by user (not loaded from DB)
+	UserShareData []byte
 }
 
 // ParticipateSigningOutput contains output from signing participation
@@ -75,19 +78,37 @@ func (uc *ParticipateSigningUseCase) Execute(
 		return nil, ErrInvalidSignSession
 	}
 
-	// 2. Load key share for this party
+	// 2. Get share data - either from user input (delegate) or from database (persistent)
-	keyShares, err := uc.keyShareRepo.ListByParty(ctx, input.PartyID)
+	var shareData []byte
-	if err != nil || len(keyShares) == 0 {
+	var keyShareForUpdate *entities.PartyKeyShare
-		return nil, ErrKeyShareNotFound
-	}
 
-	// Use the most recent key share (in production, would match by public key or session reference)
+	if len(input.UserShareData) > 0 {
-	keyShare := keyShares[len(keyShares)-1]
+		// Delegate party: use share provided by user
+		shareData, err = uc.cryptoService.DecryptShare(input.UserShareData, input.PartyID)
+		if err != nil {
+			return nil, err
+		}
+		logger.Info("Using user-provided share (delegate party)",
+			zap.String("party_id", input.PartyID),
+			zap.String("session_id", input.SessionID.String()))
+	} else {
+		// Persistent party: load from database
+		keyShares, err := uc.keyShareRepo.ListByParty(ctx, input.PartyID)
+		if err != nil || len(keyShares) == 0 {
+			return nil, ErrKeyShareNotFound
+		}
 
-	// 3. Decrypt share data
+		// Use the most recent key share (in production, would match by public key or session reference)
-	shareData, err := uc.cryptoService.DecryptShare(keyShare.ShareData, input.PartyID)
+		keyShareForUpdate = keyShares[len(keyShares)-1]
-	if err != nil {
+
-		return nil, err
+		// Decrypt share data
+		shareData, err = uc.cryptoService.DecryptShare(keyShareForUpdate.ShareData, input.PartyID)
+		if err != nil {
+			return nil, err
+		}
+		logger.Info("Using database share (persistent party)",
+			zap.String("party_id", input.PartyID),
+			zap.String("session_id", input.SessionID.String()))
 	}
 
 	// 4. Find self in participants and build party index map
@@ -129,10 +150,12 @@ func (uc *ParticipateSigningUseCase) Execute(
 		return nil, err
 	}
 
-	// 7. Update key share last used
+	// 7. Update key share last used (only for persistent parties)
-	keyShare.MarkUsed()
+	if keyShareForUpdate != nil {
-	if err := uc.keyShareRepo.Update(ctx, keyShare); err != nil {
+		keyShareForUpdate.MarkUsed()
-		logger.Warn("failed to update key share last used", zap.Error(err))
+		if err := uc.keyShareRepo.Update(ctx, keyShareForUpdate); err != nil {
+			logger.Warn("failed to update key share last used", zap.Error(err))
+		}
 	}
 
 	// 8. Report completion to coordinator

backend/mpc-system/services/server-party/cmd/server/main.go

@@ -16,6 +16,7 @@ import (
 	"github.com/google/uuid"
 	_ "github.com/lib/pq"
 
+	router "github.com/rwadurian/mpc-system/api/grpc/router/v1"
 	"github.com/rwadurian/mpc-system/pkg/config"
 	"github.com/rwadurian/mpc-system/pkg/crypto"
 	"github.com/rwadurian/mpc-system/pkg/logger"
@@ -139,33 +140,64 @@ func main() {
 		partyRole = "persistent"
 	}
 
+	// Get optional notification channels from environment
+	// If notification channels are set, party operates in OFFLINE mode (24h async)
+	// If no notification channels, party operates in REAL-TIME mode (Message Router push)
+	var notificationConfig *grpcclient.NotificationConfig
+	partyEmail := os.Getenv("PARTY_NOTIFICATION_EMAIL")
+	partyPhone := os.Getenv("PARTY_NOTIFICATION_PHONE")
+	partyPushToken := os.Getenv("PARTY_NOTIFICATION_PUSH_TOKEN")
+
+	if partyEmail != "" || partyPhone != "" || partyPushToken != "" {
+		notificationConfig = &grpcclient.NotificationConfig{
+			Email:     partyEmail,
+			Phone:     partyPhone,
+			PushToken: partyPushToken,
+		}
+		logger.Info("Party configured for OFFLINE mode (notification channels set)",
+			zap.Bool("has_email", partyEmail != ""),
+			zap.Bool("has_phone", partyPhone != ""),
+			zap.Bool("has_push", partyPushToken != ""))
+	} else {
+		logger.Info("Party configured for REAL-TIME mode (no notification channels)")
+	}
+
 	// Register this party with Message Router
+	// This should be called again whenever party configuration changes
 	logger.Info("Registering party with Message Router",
 		zap.String("party_id", partyID),
 		zap.String("role", partyRole))
 
-	if err := messageRouter.RegisterParty(ctx, partyID, partyRole, "1.0.0"); err != nil {
+	if err := messageRouter.RegisterPartyWithNotification(ctx, partyID, partyRole, "1.0.0", notificationConfig); err != nil {
 		logger.Fatal("Failed to register party", zap.Error(err))
 	}
 
+	// Start heartbeat to keep party registered and detect pending messages
+	// Heartbeat interval: 30 seconds, callback for pending messages notification
+	heartbeatCancel := messageRouter.StartHeartbeat(ctx, partyID, 30*time.Second, func(pendingCount int32) {
+		if pendingCount > 0 {
+			logger.Info("Pending messages detected via heartbeat",
+				zap.String("party_id", partyID),
+				zap.Int32("pending_count", pendingCount))
+		}
+	})
+	defer heartbeatCancel()
+	logger.Info("Heartbeat started", zap.String("party_id", partyID), zap.Duration("interval", 30*time.Second))
+
 	// Subscribe to session events and handle them automatically
-	// Note: This will work after protobuf regeneration
 	logger.Info("Subscribing to session events", zap.String("party_id", partyID))
 
-	// TODO: Uncomment after protobuf regeneration
+	eventHandler := createSessionEventHandler(
-	/*
+		ctx,
-		eventHandler := createSessionEventHandler(
+		partyID,
-			ctx,
+		participateKeygenUC,
-			partyID,
+		participateSigningUC,
-			participateKeygenUC,
+		sessionClient,
-			participateSigningUC,
+	)
-			sessionClient,
-		)
 
-		if err := messageRouter.SubscribeSessionEvents(ctx, partyID, eventHandler); err != nil {
+	if err := messageRouter.SubscribeSessionEvents(ctx, partyID, eventHandler); err != nil {
-			logger.Fatal("Failed to subscribe to session events", zap.Error(err))
+		logger.Fatal("Failed to subscribe to session events", zap.Error(err))
-		}
+	}
-	*/
 
 	logger.Info("Party-driven architecture initialized successfully",
 		zap.String("party_id", partyID),
@@ -496,120 +528,107 @@ func startHTTPServer(
 	return router.Run(fmt.Sprintf(":%d", cfg.Server.HTTPPort))
 }
 
-// createSessionEventHandler creates a handler for session events
+// createSessionEventHandler creates a handler for session events (party-driven architecture)
-// This implements the party-driven architecture where parties automatically
+// Parties automatically respond to session creation events by joining keygen or signing sessions
-// respond to session creation events
-//
-// TODO: After protobuf regeneration, uncomment this function and update the import
-// to include: router "github.com/rwadurian/mpc-system/api/grpc/router/v1"
 func createSessionEventHandler(
 	ctx context.Context,
 	partyID string,
 	participateKeygenUC *use_cases.ParticipateKeygenUseCase,
 	participateSigningUC *use_cases.ParticipateSigningUseCase,
 	sessionClient *grpcclient.SessionCoordinatorClient,
-) func(event interface{}) {
+) func(*router.SessionEvent) {
-	return func(eventInterface interface{}) {
+	return func(event *router.SessionEvent) {
-		// After protobuf regeneration, uncomment and use this implementation:
+		// Check if this party is selected for the session
-		/*
+		isSelected := false
-			event, ok := eventInterface.(*router.SessionEvent)
+		for _, selectedParty := range event.SelectedParties {
-			if !ok {
+			if selectedParty == partyID {
-				logger.Error("Invalid event type")
+				isSelected = true
-				return
+				break
 			}
+		}
 
-			// Check if this party is selected for the session
+		if !isSelected {
-			isSelected := false
+			logger.Debug("Party not selected for this session",
-			for _, selectedParty := range event.SelectedParties {
-				if selectedParty == partyID {
-					isSelected = true
-					break
-				}
-			}
-
-			if !isSelected {
-				logger.Debug("Party not selected for this session",
-					zap.String("session_id", event.SessionId),
-					zap.String("party_id", partyID))
-				return
-			}
-
-			// Get join token for this party
-			joinToken, exists := event.JoinTokens[partyID]
-			if !exists {
-				logger.Error("No join token found for party",
-					zap.String("session_id", event.SessionId),
-					zap.String("party_id", partyID))
-				return
-			}
-
-			logger.Info("Party selected for session, auto-participating",
 				zap.String("session_id", event.SessionId),
-				zap.String("party_id", partyID),
+				zap.String("party_id", partyID))
-				zap.String("event_type", event.EventType))
+			return
+		}
 
-			// Parse session ID
+		// Get join token for this party
-			sessionID, err := uuid.Parse(event.SessionId)
+		joinToken, exists := event.JoinTokens[partyID]
-			if err != nil {
+		if !exists {
-				logger.Error("Invalid session ID", zap.Error(err))
+			logger.Error("No join token found for party",
-				return
+				zap.String("session_id", event.SessionId),
-			}
+				zap.String("party_id", partyID))
+			return
+		}
 
-			// Automatically participate based on session type
+		logger.Info("Party selected for session, auto-participating",
-			go func() {
+			zap.String("session_id", event.SessionId),
-				ctx := context.Background()
+			zap.String("party_id", partyID),
+			zap.String("event_type", event.EventType))
 
-				// Determine session type from event
+		// Parse session ID
-				if event.EventType == "session_created" {
+		sessionID, err := uuid.Parse(event.SessionId)
-					// Check if it's keygen or sign based on message_hash
+		if err != nil {
-					if len(event.MessageHash) == 0 {
+			logger.Error("Invalid session ID", zap.Error(err))
-						// Keygen session
+			return
-						logger.Info("Auto-participating in keygen session",
+		}
-							zap.String("session_id", event.SessionId),
-							zap.String("party_id", partyID))
 
-						input := use_cases.ParticipateKeygenInput{
+		// Automatically participate based on session type
-							SessionID: sessionID,
+		go func() {
-							PartyID:   partyID,
+			ctx := context.Background()
-							JoinToken: joinToken,
-						}
 
-						result, err := participateKeygenUC.Execute(ctx, input)
+			// Determine session type from event
-						if err != nil {
+			if event.EventType == "session_created" {
-							logger.Error("Keygen participation failed",
+				// Check if it's keygen or sign based on message_hash
-								zap.Error(err),
+				if len(event.MessageHash) == 0 {
-								zap.String("session_id", event.SessionId))
+					// Keygen session
-						} else {
+					logger.Info("Auto-participating in keygen session",
-							logger.Info("Keygen participation completed",
+						zap.String("session_id", event.SessionId),
-								zap.String("session_id", event.SessionId),
+						zap.String("party_id", partyID))
-								zap.String("public_key", result.PublicKeyHex))
+
-						}
+					input := use_cases.ParticipateKeygenInput{
+						SessionID: sessionID,
+						PartyID:   partyID,
+						JoinToken: joinToken,
+					}
+
+					result, err := participateKeygenUC.Execute(ctx, input)
+					if err != nil {
+						logger.Error("Keygen participation failed",
+							zap.Error(err),
+							zap.String("session_id", event.SessionId))
 					} else {
-						// Sign session
+						logger.Info("Keygen participation completed",
-						logger.Info("Auto-participating in sign session",
 							zap.String("session_id", event.SessionId),
-							zap.String("party_id", partyID))
+							zap.String("public_key", hex.EncodeToString(result.PublicKey)))
+					}
+				} else {
+					// Sign session
+					logger.Info("Auto-participating in sign session",
+						zap.String("session_id", event.SessionId),
+						zap.String("party_id", partyID))
 
-						input := use_cases.ParticipateSigningInput{
+					input := use_cases.ParticipateSigningInput{
-							SessionID:   sessionID,
+						SessionID:   sessionID,
-							PartyID:     partyID,
+						PartyID:     partyID,
-							JoinToken:   joinToken,
+						JoinToken:   joinToken,
-							MessageHash: event.MessageHash,
+						MessageHash: event.MessageHash,
-						}
+					}
 
-						result, err := participateSigningUC.Execute(ctx, input)
+					result, err := participateSigningUC.Execute(ctx, input)
-						if err != nil {
+					if err != nil {
-							logger.Error("Signing participation failed",
+						logger.Error("Signing participation failed",
-								zap.Error(err),
+							zap.Error(err),
-								zap.String("session_id", event.SessionId))
+							zap.String("session_id", event.SessionId))
-						} else {
+					} else {
-							logger.Info("Signing participation completed",
+						logger.Info("Signing participation completed",
-								zap.String("session_id", event.SessionId),
+							zap.String("session_id", event.SessionId),
-								zap.String("signature", result.SignatureHex))
+							zap.String("signature", hex.EncodeToString(result.Signature)))
-						}
 					}
 				}
-			}()
+			}
-		*/
+		}()
 	}
 }

backend/mpc-system/services/session-coordinator/adapters/output/grpc/message_router_client.go

@@ -2,51 +2,60 @@ package grpc
 
 import (
 	"context"
-	"time"
 
 	"github.com/google/uuid"
 	router "github.com/rwadurian/mpc-system/api/grpc/router/v1"
+	"github.com/rwadurian/mpc-system/pkg/grpcutil"
 	"github.com/rwadurian/mpc-system/pkg/logger"
+	"github.com/rwadurian/mpc-system/pkg/retry"
 	"go.uber.org/zap"
-	"google.golang.org/grpc"
-	"google.golang.org/grpc/credentials/insecure"
 )
 
 // MessageRouterClient wraps gRPC client for Message Router service
 type MessageRouterClient struct {
-	conn   *grpc.ClientConn
+	resilientConn *grpcutil.ResilientConn
-	client router.MessageRouterClient
+	retryCfg      retry.Config
 }
 
-// NewMessageRouterClient creates a new Message Router gRPC client
+// NewMessageRouterClient creates a new Message Router gRPC client with auto-reconnection
 func NewMessageRouterClient(address string) (*MessageRouterClient, error) {
-	conn, err := grpc.Dial(
+	config := grpcutil.DefaultClientConfig(address)
-		address,
+	resilientConn, err := grpcutil.NewResilientConn(config)
-		grpc.WithTransportCredentials(insecure.NewCredentials()),
-		grpc.WithBlock(),
-		grpc.WithTimeout(10*time.Second),
-	)
 	if err != nil {
 		return nil, err
 	}
 
-	logger.Info("Connected to Message Router", zap.String("address", address))
+	logger.Info("Connected to Message Router with keepalive",
+		zap.String("address", address),
+		zap.Duration("keepalive_time", config.KeepaliveTime),
+		zap.Bool("auto_reconnect", config.EnableReconnect))
 
 	return &MessageRouterClient{
-		conn:   conn,
+		resilientConn: resilientConn,
-		client: router.NewMessageRouterClient(conn),
+		retryCfg:      retry.DefaultConfig(),
 	}, nil
 }
 
+// getClient returns a new MessageRouterClient using the current connection
+func (c *MessageRouterClient) getClient() router.MessageRouterClient {
+	return router.NewMessageRouterClient(c.resilientConn.GetConn())
+}
+
 // Close closes the gRPC connection
 func (c *MessageRouterClient) Close() error {
-	if c.conn != nil {
+	if c.resilientConn != nil {
-		return c.conn.Close()
+		return c.resilientConn.Close()
 	}
 	return nil
 }
 
+// IsConnected returns true if the connection is ready
+func (c *MessageRouterClient) IsConnected() bool {
+	return c.resilientConn != nil && c.resilientConn.IsConnected()
+}
+
 // PublishSessionEvent publishes a session event to all subscribed parties
+// Includes automatic retry with exponential backoff for transient failures
 func (c *MessageRouterClient) PublishSessionEvent(
 	ctx context.Context,
 	event *router.SessionEvent,
@@ -60,24 +69,23 @@ func (c *MessageRouterClient) PublishSessionEvent(
 		Event: event,
 	}
 
-	resp, err := c.client.PublishSessionEvent(ctx, req)
+	return retry.DoVoid(ctx, c.retryCfg, "PublishSessionEvent", func() error {
-	if err != nil {
+		resp, err := c.getClient().PublishSessionEvent(ctx, req)
-		logger.Error("Failed to publish session event",
+		if err != nil {
-			zap.Error(err),
+			return err
+		}
+
+		logger.Info("Session event published successfully",
 			zap.String("event_type", event.EventType),
-			zap.String("session_id", event.SessionId))
+			zap.String("session_id", event.SessionId),
-		return err
+			zap.Int32("subscriber_count", resp.SubscriberCount))
-	}
 
-	logger.Info("Session event published successfully",
+		return nil
-		zap.String("event_type", event.EventType),
+	})
-		zap.String("session_id", event.SessionId),
-		zap.Int32("subscriber_count", resp.SubscriberCount))
-
-	return nil
 }
 
 // GetRegisteredParties retrieves registered parties from Message Router
+// Includes automatic retry with exponential backoff for transient failures
 func (c *MessageRouterClient) GetRegisteredParties(
 	ctx context.Context,
 	roleFilter string,
@@ -87,19 +95,18 @@ func (c *MessageRouterClient) GetRegisteredParties(
 		OnlyOnline: true,
 	}
 
-	resp, err := c.client.GetRegisteredParties(ctx, req)
+	return retry.Do(ctx, c.retryCfg, "GetRegisteredParties", func() ([]*router.RegisteredParty, error) {
-	if err != nil {
+		resp, err := c.getClient().GetRegisteredParties(ctx, req)
-		logger.Error("Failed to get registered parties",
+		if err != nil {
-			zap.Error(err),
+			return nil, err
-			zap.String("role_filter", roleFilter))
+		}
-		return nil, err
-	}
 
-	logger.Debug("Retrieved registered parties from Message Router",
+		logger.Debug("Retrieved registered parties from Message Router",
-		zap.String("role_filter", roleFilter),
+			zap.String("role_filter", roleFilter),
-		zap.Int32("count", resp.TotalCount))
+			zap.Int32("count", resp.TotalCount))
 
-	return resp.Parties, nil
+		return resp.Parties, nil
+	})
 }
 
 // PublishSessionCreated publishes a session_created event

backend/mpc-system/services/session-coordinator/adapters/output/http/account_service_client.go

@@ -0,0 +1,127 @@
+package http
+
+import (
+	"bytes"
+	"context"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+
+	"github.com/rwadurian/mpc-system/pkg/logger"
+	"github.com/rwadurian/mpc-system/services/session-coordinator/application/ports/output"
+	"go.uber.org/zap"
+)
+
+// AccountServiceClient implements AccountServicePort using HTTP
+type AccountServiceClient struct {
+	baseURL    string
+	httpClient *http.Client
+}
+
+// NewAccountServiceClient creates a new Account Service HTTP client
+func NewAccountServiceClient(baseURL string) *AccountServiceClient {
+	return &AccountServiceClient{
+		baseURL: baseURL,
+		httpClient: &http.Client{
+			Timeout: 30 * time.Second,
+		},
+	}
+}
+
+// createAccountRequest represents the request body for account creation
+type createAccountRequest struct {
+	PublicKey       string              `json:"public_key"`
+	KeygenSessionID string              `json:"keygen_session_id"`
+	ThresholdN      int                 `json:"threshold_n"`
+	ThresholdT      int                 `json:"threshold_t"`
+	Shares          []shareInfoRequest  `json:"shares"`
+}
+
+type shareInfoRequest struct {
+	PartyID    string `json:"party_id"`
+	PartyIndex int    `json:"party_index"`
+	ShareType  string `json:"share_type"`
+}
+
+// createAccountResponse represents the response from account creation
+type createAccountResponse struct {
+	AccountID string `json:"account_id"`
+	Username  string `json:"username"`
+	PublicKey string `json:"public_key"`
+}
+
+// CreateAccountFromKeygen creates an account record after successful keygen
+func (c *AccountServiceClient) CreateAccountFromKeygen(
+	ctx context.Context,
+	input output.CreateAccountInput,
+) (*output.CreateAccountOutput, error) {
+	// Build request
+	shares := make([]shareInfoRequest, len(input.Shares))
+	for i, s := range input.Shares {
+		shares[i] = shareInfoRequest{
+			PartyID:    s.PartyID,
+			PartyIndex: s.PartyIndex,
+			ShareType:  s.ShareType,
+		}
+	}
+
+	reqBody := createAccountRequest{
+		PublicKey:       hex.EncodeToString(input.PublicKey),
+		KeygenSessionID: input.KeygenSessionID,
+		ThresholdN:      input.ThresholdN,
+		ThresholdT:      input.ThresholdT,
+		Shares:          shares,
+	}
+
+	jsonBody, err := json.Marshal(reqBody)
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal request: %w", err)
+	}
+
+	// Make HTTP request
+	url := fmt.Sprintf("%s/api/v1/accounts/from-keygen", c.baseURL)
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(jsonBody))
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+
+	logger.Info("Calling Account Service to create account from keygen",
+		zap.String("url", url),
+		zap.String("keygen_session_id", input.KeygenSessionID))
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("failed to call account service: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusOK {
+		logger.Error("Account Service returned error",
+			zap.Int("status_code", resp.StatusCode),
+			zap.String("body", string(body)))
+		return nil, fmt.Errorf("account service error: status=%d, body=%s", resp.StatusCode, string(body))
+	}
+
+	var result createAccountResponse
+	if err := json.Unmarshal(body, &result); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal response: %w", err)
+	}
+
+	logger.Info("Account created successfully from keygen",
+		zap.String("account_id", result.AccountID),
+		zap.String("keygen_session_id", input.KeygenSessionID))
+
+	return &output.CreateAccountOutput{
+		AccountID: result.AccountID,
+		Success:   true,
+	}, nil
+}

backend/mpc-system/services/session-coordinator/adapters/output/memory/event_publisher_adapter.go

@@ -0,0 +1,49 @@
+package memory
+
+import (
+	"context"
+
+	"github.com/rwadurian/mpc-system/pkg/logger"
+	"github.com/rwadurian/mpc-system/services/session-coordinator/application/ports/output"
+	"go.uber.org/zap"
+)
+
+// EventPublisherAdapter implements MessageBrokerPort using in-memory logging
+// Events are logged but not distributed (suitable for single-instance deployment)
+type EventPublisherAdapter struct{}
+
+// NewEventPublisherAdapter creates a new in-memory event publisher
+func NewEventPublisherAdapter() output.MessageBrokerPort {
+	return &EventPublisherAdapter{}
+}
+
+// PublishEvent logs the event
+func (p *EventPublisherAdapter) PublishEvent(ctx context.Context, topic string, event interface{}) error {
+	logger.Info("Session event published",
+		zap.String("topic", topic),
+		zap.Any("event", event))
+	return nil
+}
+
+// PublishMessage logs the message
+func (p *EventPublisherAdapter) PublishMessage(ctx context.Context, partyID string, message interface{}) error {
+	logger.Debug("Message published to party",
+		zap.String("party_id", partyID))
+	return nil
+}
+
+// Subscribe returns a nil channel (no actual subscription in single-instance mode)
+func (p *EventPublisherAdapter) Subscribe(ctx context.Context, topic string) (<-chan []byte, error) {
+	// Return a closed channel since we don't have actual pub/sub
+	ch := make(chan []byte)
+	close(ch)
+	return ch, nil
+}
+
+// Close is a no-op for in-memory publisher
+func (p *EventPublisherAdapter) Close() error {
+	return nil
+}
+
+// Ensure interface compliance
+var _ output.MessageBrokerPort = (*EventPublisherAdapter)(nil)

backend/mpc-system/services/session-coordinator/adapters/output/notification/notification_stub.go

@@ -0,0 +1,115 @@
+package notification
+
+import (
+	"context"
+
+	"github.com/rwadurian/mpc-system/pkg/logger"
+	"github.com/rwadurian/mpc-system/services/session-coordinator/application/ports/output"
+	"go.uber.org/zap"
+)
+
+// StubNotificationService is a placeholder implementation of NotificationServicePort
+// It logs notification requests but does not actually send them
+//
+// TODO: Implement real notification adapters:
+// - EmailNotificationAdapter: Uses SMTP or email service (SendGrid, SES, etc.)
+// - SMSNotificationAdapter: Uses SMS gateway (Twilio, etc.)
+// - PushNotificationAdapter: Uses FCM/APNs for mobile push notifications
+type StubNotificationService struct{}
+
+// NewStubNotificationService creates a new stub notification service
+func NewStubNotificationService() *StubNotificationService {
+	return &StubNotificationService{}
+}
+
+// SendSessionInvitation logs the invitation but does not send it
+// TODO: Implement actual notification sending
+func (s *StubNotificationService) SendSessionInvitation(
+	ctx context.Context,
+	input output.SessionInvitationInput,
+) error {
+	logger.Info("[TODO] Would send session invitation notification",
+		zap.String("party_id", input.PartyID),
+		zap.String("session_id", input.SessionID),
+		zap.String("session_type", input.SessionType),
+		zap.String("email", maskEmail(input.Email)),
+		zap.String("phone", maskPhone(input.Phone)),
+		zap.Bool("has_push_token", input.PushToken != ""),
+		zap.Int64("expires_at", input.ExpiresAt))
+
+	// TODO: Implement actual notification sending:
+	// 1. If email is set, send email with session details and join link
+	// 2. If phone is set, send SMS with short message and link
+	// 3. If push_token is set, send push notification
+
+	return nil
+}
+
+// SendSessionReminder logs the reminder but does not send it
+// TODO: Implement actual notification sending
+func (s *StubNotificationService) SendSessionReminder(
+	ctx context.Context,
+	input output.SessionReminderInput,
+) error {
+	logger.Info("[TODO] Would send session reminder notification",
+		zap.String("party_id", input.PartyID),
+		zap.String("session_id", input.SessionID),
+		zap.String("time_remaining", input.TimeRemaining),
+		zap.Int("reminder_count", input.ReminderCount))
+
+	return nil
+}
+
+// SendSessionExpiredNotification logs the expiration but does not send it
+// TODO: Implement actual notification sending
+func (s *StubNotificationService) SendSessionExpiredNotification(
+	ctx context.Context,
+	input output.SessionExpiredInput,
+) error {
+	logger.Info("[TODO] Would send session expired notification",
+		zap.String("party_id", input.PartyID),
+		zap.String("session_id", input.SessionID),
+		zap.Int64("expired_at", input.ExpiredAt))
+
+	return nil
+}
+
+// maskEmail masks an email address for logging (e.g., "j***@example.com")
+func maskEmail(email string) string {
+	if email == "" {
+		return ""
+	}
+	if len(email) < 3 {
+		return "***"
+	}
+	// Find @ position
+	atPos := -1
+	for i, c := range email {
+		if c == '@' {
+			atPos = i
+			break
+		}
+	}
+	if atPos <= 0 {
+		return "***"
+	}
+	return email[:1] + "***" + email[atPos:]
+}
+
+// maskPhone masks a phone number for logging (e.g., "+1***1234")
+func maskPhone(phone string) string {
+	if phone == "" {
+		return ""
+	}
+	if len(phone) < 4 {
+		return "***"
+	}
+	// Keep first 2 and last 4 characters
+	if len(phone) <= 6 {
+		return phone[:1] + "***" + phone[len(phone)-2:]
+	}
+	return phone[:2] + "***" + phone[len(phone)-4:]
+}
+
+// Ensure StubNotificationService implements NotificationServicePort
+var _ output.NotificationServicePort = (*StubNotificationService)(nil)

backend/mpc-system/services/session-coordinator/adapters/output/postgres/session_postgres_repo.go

@@ -149,6 +149,7 @@ func (r *SessionPostgresRepo) FindByUUID(ctx context.Context, id uuid.UUID) (*en
 		session.Status,
 		session.MessageHash,
 		session.PublicKey,
+		"", // delegatePartyID - not stored in DB yet, will be empty for old sessions
 		session.CreatedBy,
 		session.CreatedAt,
 		session.UpdatedAt,
@@ -189,6 +190,23 @@ func (r *SessionPostgresRepo) FindExpired(ctx context.Context) ([]*entities.MPCS
 	return r.scanSessions(ctx, rows)
 }
 
+// FindActive retrieves all active sessions (created or in_progress)
+func (r *SessionPostgresRepo) FindActive(ctx context.Context) ([]*entities.MPCSession, error) {
+	rows, err := r.db.QueryContext(ctx, `
+		SELECT id, session_type, threshold_n, threshold_t, status,
+			   message_hash, public_key, created_by, created_at, updated_at, expires_at, completed_at
+		FROM mpc_sessions
+		WHERE status IN ('created', 'in_progress')
+		ORDER BY created_at ASC
+	`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	return r.scanSessions(ctx, rows)
+}
+
 // FindByCreator retrieves sessions created by a user
 func (r *SessionPostgresRepo) FindByCreator(ctx context.Context, creatorID string) ([]*entities.MPCSession, error) {
 	rows, err := r.db.QueryContext(ctx, `
@@ -400,6 +418,7 @@ func (r *SessionPostgresRepo) scanSessions(ctx context.Context, rows *sql.Rows)
 			s.Status,
 			s.MessageHash,
 			s.PublicKey,
+			"", // delegatePartyID - not stored in DB yet
 			s.CreatedBy,
 			s.CreatedAt,
 			s.UpdatedAt,

backend/mpc-system/services/session-coordinator/adapters/output/redis/session_cache_adapter.go

@@ -265,6 +265,7 @@ func cacheEntryToSession(entry sessionCacheEntry) (*entities.MPCSession, error)
 		entry.Status,
 		entry.MessageHash,
 		entry.PublicKey,
+		"", // delegatePartyID - not cached
 		entry.CreatedBy,
 		time.UnixMilli(entry.CreatedAt),
 		time.UnixMilli(entry.UpdatedAt),

backend/mpc-system/services/session-coordinator/application/ports/output/account_service_port.go

@@ -0,0 +1,32 @@
+package output
+
+import "context"
+
+// ShareInfo contains information about a key share for account creation
+type ShareInfo struct {
+	PartyID    string
+	PartyIndex int
+	ShareType  string // "persistent" or "delegate"
+}
+
+// CreateAccountInput contains input for creating an account after keygen
+type CreateAccountInput struct {
+	KeygenSessionID string
+	PublicKey       []byte
+	ThresholdN      int
+	ThresholdT      int
+	Shares          []ShareInfo
+	DelegatePartyID string // The delegate party ID if any (for user share retrieval)
+}
+
+// CreateAccountOutput contains output from account creation
+type CreateAccountOutput struct {
+	AccountID string
+	Success   bool
+}
+
+// AccountServicePort defines the interface for account service integration
+type AccountServicePort interface {
+	// CreateAccountFromKeygen creates an account record after successful keygen
+	CreateAccountFromKeygen(ctx context.Context, input CreateAccountInput) (*CreateAccountOutput, error)
+}

backend/mpc-system/services/session-coordinator/application/ports/output/message_broker_port.go

@@ -21,16 +21,17 @@ type MessageBrokerPort interface {
 
 // Event types
 const (
-	TopicSessionCreated      = "mpc.session.created"
+	TopicSessionCreated       = "mpc.session.created"
-	TopicSessionStarted      = "mpc.session.started"
+	TopicSessionStarted       = "mpc.session.started"
-	TopicSessionCompleted    = "mpc.session.completed"
+	TopicSessionCompleted     = "mpc.session.completed"
-	TopicSessionFailed       = "mpc.session.failed"
+	TopicSessionFailed        = "mpc.session.failed"
-	TopicSessionExpired      = "mpc.session.expired"
+	TopicSessionExpired       = "mpc.session.expired"
-	TopicParticipantJoined   = "mpc.participant.joined"
+	TopicParticipantJoined    = "mpc.participant.joined"
-	TopicParticipantReady    = "mpc.participant.ready"
+	TopicParticipantReady     = "mpc.participant.ready"
 	TopicParticipantCompleted = "mpc.participant.completed"
-	TopicParticipantFailed   = "mpc.participant.failed"
+	TopicParticipantFailed    = "mpc.participant.failed"
-	TopicMPCMessage          = "mpc.message"
+	TopicParticipantTimedOut  = "mpc.participant.timed_out"
+	TopicMPCMessage           = "mpc.message"
 )
 
 // SessionCreatedEvent is published when a session is created
@@ -100,6 +101,14 @@ type ParticipantFailedEvent struct {
 	FailedAt  int64  `json:"failed_at"`
 }
 
+// ParticipantTimedOutEvent is published when a participant times out due to inactivity
+type ParticipantTimedOutEvent struct {
+	SessionID         string `json:"session_id"`
+	PartyID           string `json:"party_id"`
+	InactivitySeconds int64  `json:"inactivity_seconds"`
+	TimedOutAt        int64  `json:"timed_out_at"`
+}
+
 // MPCMessageEvent is published when an MPC message is routed
 type MPCMessageEvent struct {
 	MessageID   string   `json:"message_id"`

backend/mpc-system/services/session-coordinator/application/ports/output/notification_service_port.go

@@ -0,0 +1,86 @@
+package output
+
+import "context"
+
+// NotificationServicePort defines the interface for sending notifications to parties
+// This is used for parties operating in OFFLINE mode (with notification channels configured)
+//
+// Parties without notification channels operate in REAL-TIME mode:
+//   - Session events are pushed via Message Router
+//   - Parties must be connected to receive events immediately
+//
+// Parties with notification channels operate in OFFLINE mode:
+//   - Session invitations are sent via email/SMS/push notifications
+//   - Parties have 24 hours to complete their participation
+//   - Parties poll for pending sessions when they come online
+//
+// TODO: Implement notification service adapters (email, SMS, push)
+type NotificationServicePort interface {
+	// SendSessionInvitation sends a session invitation notification to a party
+	// This is called when a party with notification channels is selected for a session
+	SendSessionInvitation(ctx context.Context, input SessionInvitationInput) error
+
+	// SendSessionReminder sends a reminder for a pending session
+	// Called periodically for sessions approaching expiration
+	SendSessionReminder(ctx context.Context, input SessionReminderInput) error
+
+	// SendSessionExpiredNotification notifies a party that a session has expired
+	SendSessionExpiredNotification(ctx context.Context, input SessionExpiredInput) error
+}
+
+// SessionInvitationInput contains data for sending a session invitation
+type SessionInvitationInput struct {
+	// Party identification
+	PartyID string
+
+	// Notification channels (at least one should be set)
+	Email     string
+	Phone     string
+	PushToken string
+
+	// Session details
+	SessionID   string
+	SessionType string // "keygen" or "sign"
+	JoinToken   string
+	ExpiresAt   int64 // Unix timestamp milliseconds
+
+	// Optional context
+	InitiatorID  string // Who initiated the session
+	MessageToSign string // For sign sessions, human-readable description
+}
+
+// SessionReminderInput contains data for sending a session reminder
+type SessionReminderInput struct {
+	PartyID   string
+	Email     string
+	Phone     string
+	PushToken string
+
+	SessionID   string
+	SessionType string
+	JoinToken   string
+	ExpiresAt   int64
+
+	// Reminder specific
+	TimeRemaining string // e.g., "2 hours", "30 minutes"
+	ReminderCount int    // How many reminders have been sent
+}
+
+// SessionExpiredInput contains data for sending session expiration notification
+type SessionExpiredInput struct {
+	PartyID   string
+	Email     string
+	Phone     string
+	PushToken string
+
+	SessionID   string
+	SessionType string
+	ExpiredAt   int64
+}
+
+// NotificationResult represents the result of a notification attempt
+type NotificationResult struct {
+	Success bool
+	Channel string // Which channel was used: "email", "sms", "push"
+	Error   string // Error message if failed
+}

backend/mpc-system/services/session-coordinator/application/ports/output/party_pool_port.go

@@ -14,13 +14,43 @@ const (
 	PartyRoleTemporary PartyRole = "temporary"
 )
 
+// NotificationChannel represents notification channels for a party
+// If a party has any notification channel set, it operates in OFFLINE mode (24h async completion)
+// If no notification channels are set, it operates in REAL-TIME mode (Message Router push)
+type NotificationChannel struct {
+	Email     string // Optional: email address for session invitations
+	Phone     string // Optional: phone number for SMS notifications
+	PushToken string // Optional: push notification token (FCM/APNs)
+}
+
+// HasAnyChannel returns true if any notification channel is configured
+func (nc *NotificationChannel) HasAnyChannel() bool {
+	return nc != nil && (nc.Email != "" || nc.Phone != "" || nc.PushToken != "")
+}
+
+// IsRealTimeMode returns true if party operates in real-time mode (no notification channels)
+func (nc *NotificationChannel) IsRealTimeMode() bool {
+	return !nc.HasAnyChannel()
+}
+
 // PartyEndpoint represents a party from the pool
 // Note: Address is removed - parties connect to Message Router themselves
 // Session Coordinator only needs PartyID for message routing
 type PartyEndpoint struct {
-	PartyID string
+	PartyID      string
-	Ready   bool
+	Ready        bool
-	Role    PartyRole // Role of the party (persistent, delegate, temporary)
+	Role         PartyRole            // Role of the party (persistent, delegate, temporary)
+	Notification *NotificationChannel // Optional: notification channels for offline mode
+}
+
+// IsRealTimeMode returns true if party operates in real-time mode
+func (p *PartyEndpoint) IsRealTimeMode() bool {
+	return p.Notification == nil || p.Notification.IsRealTimeMode()
+}
+
+// IsOfflineMode returns true if party operates in offline mode (has notification channels)
+func (p *PartyEndpoint) IsOfflineMode() bool {
+	return !p.IsRealTimeMode()
 }
 
 // PartySelectionFilter defines filtering criteria for party selection

backend/mpc-system/services/session-coordinator/application/use_cases/check_party_timeouts.go

@@ -0,0 +1,126 @@
+package use_cases
+
+import (
+	"context"
+	"time"
+
+	"github.com/rwadurian/mpc-system/pkg/logger"
+	"github.com/rwadurian/mpc-system/services/session-coordinator/application/ports/output"
+	"github.com/rwadurian/mpc-system/services/session-coordinator/domain/repositories"
+	"go.uber.org/zap"
+)
+
+// CheckPartyTimeoutsUseCase handles checking for timed-out parties in active sessions
+type CheckPartyTimeoutsUseCase struct {
+	sessionRepo      repositories.SessionRepository
+	eventPublisher   output.MessageBrokerPort
+	inactivityTimeout time.Duration
+}
+
+// CheckPartyTimeoutsResult contains the result of the timeout check
+type CheckPartyTimeoutsResult struct {
+	SessionsChecked    int
+	PartiesTimedOut    int
+	SessionsFailedDueToTimeout int
+}
+
+// NewCheckPartyTimeoutsUseCase creates a new check party timeouts use case
+func NewCheckPartyTimeoutsUseCase(
+	sessionRepo repositories.SessionRepository,
+	eventPublisher output.MessageBrokerPort,
+	inactivityTimeout time.Duration,
+) *CheckPartyTimeoutsUseCase {
+	// Default to 2 minutes if not specified
+	if inactivityTimeout <= 0 {
+		inactivityTimeout = 2 * time.Minute
+	}
+	return &CheckPartyTimeoutsUseCase{
+		sessionRepo:       sessionRepo,
+		eventPublisher:    eventPublisher,
+		inactivityTimeout: inactivityTimeout,
+	}
+}
+
+// Execute checks all active sessions for timed-out parties
+func (uc *CheckPartyTimeoutsUseCase) Execute(ctx context.Context) (*CheckPartyTimeoutsResult, error) {
+	result := &CheckPartyTimeoutsResult{}
+
+	// 1. Find all active sessions
+	sessions, err := uc.sessionRepo.FindActive(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	result.SessionsChecked = len(sessions)
+
+	for _, session := range sessions {
+		// 2. Check for timed-out parties
+		timedOutParties := session.MarkTimedOutPartiesAsFailed(uc.inactivityTimeout)
+
+		if len(timedOutParties) == 0 {
+			continue
+		}
+
+		result.PartiesTimedOut += len(timedOutParties)
+
+		// 3. Publish timeout events for each timed-out party
+		for _, party := range timedOutParties {
+			event := output.ParticipantTimedOutEvent{
+				SessionID:         session.ID.String(),
+				PartyID:           party.PartyID.String(),
+				InactivitySeconds: int64(party.TimeSinceLastActivity().Seconds()),
+				TimedOutAt:        time.Now().UnixMilli(),
+			}
+			if err := uc.eventPublisher.PublishEvent(ctx, output.TopicParticipantTimedOut, event); err != nil {
+				logger.Error("failed to publish participant timeout event",
+					zap.String("session_id", session.ID.String()),
+					zap.String("party_id", party.PartyID.String()),
+					zap.Error(err))
+			}
+
+			logger.Warn("Party timed out due to inactivity",
+				zap.String("session_id", session.ID.String()),
+				zap.String("party_id", party.PartyID.String()),
+				zap.Duration("inactivity", party.TimeSinceLastActivity()),
+				zap.Duration("timeout_threshold", uc.inactivityTimeout))
+		}
+
+		// 4. If any party timed out in an in_progress session, fail the entire session
+		// MPC requires all parties to participate; if one fails, the session fails
+		if session.Status.IsActive() && len(timedOutParties) > 0 {
+			if err := session.Fail(); err != nil {
+				logger.Error("failed to mark session as failed after party timeout",
+					zap.String("session_id", session.ID.String()),
+					zap.Error(err))
+			} else {
+				result.SessionsFailedDueToTimeout++
+
+				// Publish session failed event
+				failedEvent := output.SessionFailedEvent{
+					SessionID: session.ID.String(),
+					Reason:    "party timed out due to inactivity",
+					FailedAt:  time.Now().UnixMilli(),
+				}
+				if err := uc.eventPublisher.PublishEvent(ctx, output.TopicSessionFailed, failedEvent); err != nil {
+					logger.Error("failed to publish session failed event",
+						zap.String("session_id", session.ID.String()),
+						zap.Error(err))
+				}
+			}
+		}
+
+		// 5. Save updated session
+		if err := uc.sessionRepo.Update(ctx, session); err != nil {
+			logger.Error("failed to update session after party timeout",
+				zap.String("session_id", session.ID.String()),
+				zap.Error(err))
+		}
+	}
+
+	return result, nil
+}
+
+// GetInactivityTimeout returns the configured inactivity timeout
+func (uc *CheckPartyTimeoutsUseCase) GetInactivityTimeout() time.Duration {
+	return uc.inactivityTimeout
+}

backend/mpc-system/services/session-coordinator/application/use_cases/create_session.go

@@ -38,6 +38,7 @@ type CreateSessionUseCase struct {
 	eventPublisher      output.MessageBrokerPort
 	partyPool           output.PartyPoolPort
 	messageRouterClient MessageRouterClient
+	notificationService output.NotificationServicePort // TODO: Wire up notification service
 	coordinatorSvc      *services.SessionCoordinatorService
 }
 
@@ -55,6 +56,28 @@ func NewCreateSessionUseCase(
 		eventPublisher:      eventPublisher,
 		partyPool:           partyPool,
 		messageRouterClient: messageRouterClient,
+		notificationService: nil, // TODO: Inject notification service
+		coordinatorSvc:      services.NewSessionCoordinatorService(),
+	}
+}
+
+// NewCreateSessionUseCaseWithNotification creates a new create session use case with notification support
+// TODO: Use this constructor when notification service is implemented
+func NewCreateSessionUseCaseWithNotification(
+	sessionRepo repositories.SessionRepository,
+	tokenGen jwt.TokenGenerator,
+	eventPublisher output.MessageBrokerPort,
+	partyPool output.PartyPoolPort,
+	messageRouterClient MessageRouterClient,
+	notificationService output.NotificationServicePort,
+) *CreateSessionUseCase {
+	return &CreateSessionUseCase{
+		sessionRepo:         sessionRepo,
+		tokenGen:            tokenGen,
+		eventPublisher:      eventPublisher,
+		partyPool:           partyPool,
+		messageRouterClient: messageRouterClient,
+		notificationService: notificationService,
 		coordinatorSvc:      services.NewSessionCoordinatorService(),
 	}
 }
@@ -145,6 +168,10 @@ func (uc *CreateSessionUseCase) Execute(
 				}
 				tokens["*"] = universalToken
 			} else {
+				// Track parties by mode for notification/push routing
+				var realTimeParties []output.PartyEndpoint
+				var offlineParties []output.PartyEndpoint
+
 				// Add selected parties as participants
 				for i, party := range selectedParties {
 					partyID, err := value_objects.NewPartyID(party.PartyID)
@@ -162,17 +189,40 @@ func (uc *CreateSessionUseCase) Execute(
 						return nil, err
 					}
 
+					// Track delegate party for user share retrieval
+					if party.Role == output.PartyRoleDelegate {
+						session.DelegatePartyID = party.PartyID
+					}
+
 					// Generate join token for this party
 					token, err := uc.tokenGen.GenerateJoinToken(session.ID.UUID(), party.PartyID, expiresIn)
 					if err != nil {
 						return nil, err
 					}
 					tokens[party.PartyID] = token
+
+					// Categorize party by mode based on notification channel presence
+					// Real-time mode: No notification channel - use Message Router push
+					// Offline mode: Has notification channel - send notification, 24h to complete
+					if party.IsRealTimeMode() {
+						realTimeParties = append(realTimeParties, party)
+					} else {
+						offlineParties = append(offlineParties, party)
+					}
 				}
 
-				logger.Info("selected parties from K8s pool",
+				logger.Info("selected parties from pool",
 					zap.String("session_id", session.ID.String()),
-					zap.Int("party_count", len(selectedParties)))
+					zap.Int("party_count", len(selectedParties)),
+					zap.Int("realtime_parties", len(realTimeParties)),
+					zap.Int("offline_parties", len(offlineParties)),
+					zap.String("delegate_party", session.DelegatePartyID))
+
+				// TODO: Send notifications to offline parties
+				// Offline parties have notification channels and can complete within 24 hours
+				if len(offlineParties) > 0 && uc.notificationService != nil {
+					uc.sendNotificationsToOfflineParties(ctx, session, offlineParties, tokens)
+				}
 			}
 		} else {
 			// No party pool configured - fallback to dynamic join
@@ -337,3 +387,57 @@ func extractPartyIDs(participants []input.ParticipantInfo) []string {
 	}
 	return ids
 }
+
+// sendNotificationsToOfflineParties sends session invitation notifications to offline parties
+// Offline parties have notification channels configured and can complete within 24 hours
+// TODO: Implement actual notification sending when NotificationService is ready
+func (uc *CreateSessionUseCase) sendNotificationsToOfflineParties(
+	ctx context.Context,
+	session *entities.MPCSession,
+	offlineParties []output.PartyEndpoint,
+	tokens map[string]string,
+) {
+	for _, party := range offlineParties {
+		joinToken, exists := tokens[party.PartyID]
+		if !exists {
+			logger.Warn("no join token found for offline party",
+				zap.String("session_id", session.ID.String()),
+				zap.String("party_id", party.PartyID))
+			continue
+		}
+
+		// Build notification input
+		notificationInput := output.SessionInvitationInput{
+			PartyID:     party.PartyID,
+			SessionID:   session.ID.String(),
+			SessionType: string(session.SessionType),
+			JoinToken:   joinToken,
+			ExpiresAt:   session.ExpiresAt.UnixMilli(),
+			InitiatorID: session.CreatedBy,
+		}
+
+		// Add notification channels from party
+		if party.Notification != nil {
+			notificationInput.Email = party.Notification.Email
+			notificationInput.Phone = party.Notification.Phone
+			notificationInput.PushToken = party.Notification.PushToken
+		}
+
+		// Send notification (async to not block session creation)
+		go func(input output.SessionInvitationInput) {
+			if err := uc.notificationService.SendSessionInvitation(ctx, input); err != nil {
+				logger.Error("failed to send session invitation notification",
+					zap.String("session_id", input.SessionID),
+					zap.String("party_id", input.PartyID),
+					zap.Error(err))
+			} else {
+				logger.Info("session invitation notification sent",
+					zap.String("session_id", input.SessionID),
+					zap.String("party_id", input.PartyID),
+					zap.Bool("has_email", input.Email != ""),
+					zap.Bool("has_phone", input.Phone != ""),
+					zap.Bool("has_push", input.PushToken != ""))
+			}
+		}(notificationInput)
+	}
+}

backend/mpc-system/services/session-coordinator/application/use_cases/join_session.go

@@ -117,6 +117,14 @@ func (uc *JoinSessionUseCase) Execute(
 		return nil, err
 	}
 
+	// 6.1 Update party activity timestamp for timeout tracking
+	if err := session.UpdatePartyActivity(partyID); err != nil {
+		logger.Warn("failed to update party activity",
+			zap.String("session_id", session.ID.String()),
+			zap.String("party_id", inputData.PartyID),
+			zap.Error(err))
+	}
+
 	// 7. Check if session should start (all participants joined)
 	if uc.coordinatorSvc.ShouldStartSession(session) {
 		if err := session.Start(); err != nil {

backend/mpc-system/services/session-coordinator/application/use_cases/report_completion.go

@@ -7,6 +7,7 @@ import (
 	"github.com/rwadurian/mpc-system/pkg/logger"
 	"github.com/rwadurian/mpc-system/services/session-coordinator/application/ports/input"
 	"github.com/rwadurian/mpc-system/services/session-coordinator/application/ports/output"
+	"github.com/rwadurian/mpc-system/services/session-coordinator/domain/entities"
 	"github.com/rwadurian/mpc-system/services/session-coordinator/domain/repositories"
 	"github.com/rwadurian/mpc-system/services/session-coordinator/domain/services"
 	"github.com/rwadurian/mpc-system/services/session-coordinator/domain/value_objects"
@@ -17,6 +18,7 @@ import (
 type ReportCompletionUseCase struct {
 	sessionRepo    repositories.SessionRepository
 	eventPublisher output.MessageBrokerPort
+	accountService output.AccountServicePort
 	coordinatorSvc *services.SessionCoordinatorService
 }
 
@@ -24,10 +26,12 @@ type ReportCompletionUseCase struct {
 func NewReportCompletionUseCase(
 	sessionRepo repositories.SessionRepository,
 	eventPublisher output.MessageBrokerPort,
+	accountService output.AccountServicePort,
 ) *ReportCompletionUseCase {
 	return &ReportCompletionUseCase{
 		sessionRepo:    sessionRepo,
 		eventPublisher: eventPublisher,
+		accountService: accountService,
 		coordinatorSvc: services.NewSessionCoordinatorService(),
 	}
 }
@@ -54,6 +58,14 @@ func (uc *ReportCompletionUseCase) Execute(
 		return nil, err
 	}
 
+	// 3.1 Update party activity timestamp (party is still active)
+	if err := session.UpdatePartyActivity(partyID); err != nil {
+		logger.Warn("failed to update party activity",
+			zap.String("session_id", session.ID.String()),
+			zap.String("party_id", inputData.PartyID),
+			zap.Error(err))
+	}
+
 	// 4. Update participant's public key if provided
 	participant, err := session.GetParticipant(partyID)
 	if err != nil {
@@ -82,6 +94,11 @@ func (uc *ReportCompletionUseCase) Execute(
 				zap.String("session_id", session.ID.String()),
 				zap.Error(err))
 		}
+
+		// For keygen sessions, automatically create account record
+		if session.SessionType == entities.SessionTypeKeygen && uc.accountService != nil {
+			uc.createAccountFromKeygen(ctx, session)
+		}
 	}
 
 	// 6. Save updated session
@@ -107,3 +124,42 @@ func (uc *ReportCompletionUseCase) Execute(
 		AllCompleted: allCompleted,
 	}, nil
 }
+
+// createAccountFromKeygen creates an account record after successful keygen
+func (uc *ReportCompletionUseCase) createAccountFromKeygen(ctx context.Context, session *entities.MPCSession) {
+	// Build share info from participants
+	shares := make([]output.ShareInfo, 0, len(session.Participants))
+	for _, p := range session.Participants {
+		shareType := "persistent"
+		if p.PartyID.String() == session.DelegatePartyID {
+			shareType = "delegate"
+		}
+		shares = append(shares, output.ShareInfo{
+			PartyID:    p.PartyID.String(),
+			PartyIndex: p.PartyIndex,
+			ShareType:  shareType,
+		})
+	}
+
+	// Call account service to create account
+	accountInput := output.CreateAccountInput{
+		KeygenSessionID: session.ID.String(),
+		PublicKey:       session.PublicKey,
+		ThresholdN:      session.Threshold.N(),
+		ThresholdT:      session.Threshold.T(),
+		Shares:          shares,
+		DelegatePartyID: session.DelegatePartyID,
+	}
+
+	result, err := uc.accountService.CreateAccountFromKeygen(ctx, accountInput)
+	if err != nil {
+		logger.Error("failed to create account from keygen",
+			zap.String("session_id", session.ID.String()),
+			zap.Error(err))
+		return
+	}
+
+	logger.Info("account created from keygen",
+		zap.String("session_id", session.ID.String()),
+		zap.String("account_id", result.AccountID))
+}

backend/mpc-system/services/session-coordinator/application/use_cases/route_message.go

@@ -78,6 +78,21 @@ func (uc *RouteMessageUseCase) Execute(
 		return err
 	}
 
+	// 4.1 Update sender's activity timestamp (they're actively participating)
+	if err := session.UpdatePartyActivity(fromPartyID); err != nil {
+		logger.Warn("failed to update sender activity",
+			zap.String("session_id", session.ID.String()),
+			zap.String("party_id", input.FromParty),
+			zap.Error(err))
+	}
+
+	// 4.2 Save updated activity timestamp
+	if err := uc.sessionRepo.Update(ctx, session); err != nil {
+		logger.Warn("failed to persist activity update",
+			zap.String("session_id", session.ID.String()),
+			zap.Error(err))
+	}
+
 	// 5. Create message entity
 	msg := entities.NewSessionMessage(
 		session.ID,

backend/mpc-system/services/session-coordinator/cmd/server/main.go

@@ -9,13 +9,12 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
+	"strings"
 	"syscall"
 	"time"
 
 	"github.com/gin-gonic/gin"
 	_ "github.com/lib/pq"
-	amqp "github.com/rabbitmq/amqp091-go"
-	"github.com/redis/go-redis/v9"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/reflection"
 
@@ -23,12 +22,14 @@ import (
 	"github.com/rwadurian/mpc-system/pkg/config"
 	"github.com/rwadurian/mpc-system/pkg/jwt"
 	"github.com/rwadurian/mpc-system/pkg/logger"
+	"github.com/rwadurian/mpc-system/pkg/middleware"
 	grpcadapter "github.com/rwadurian/mpc-system/services/session-coordinator/adapters/input/grpc"
 	httphandler "github.com/rwadurian/mpc-system/services/session-coordinator/adapters/input/http"
 	grpcclient "github.com/rwadurian/mpc-system/services/session-coordinator/adapters/output/grpc"
+	httpclient "github.com/rwadurian/mpc-system/services/session-coordinator/adapters/output/http"
+	"github.com/rwadurian/mpc-system/services/session-coordinator/adapters/output/memory"
+	"github.com/rwadurian/mpc-system/services/session-coordinator/adapters/output/notification"
 	"github.com/rwadurian/mpc-system/services/session-coordinator/adapters/output/postgres"
-	"github.com/rwadurian/mpc-system/services/session-coordinator/adapters/output/rabbitmq"
-	redisadapter "github.com/rwadurian/mpc-system/services/session-coordinator/adapters/output/redis"
 	"github.com/rwadurian/mpc-system/services/session-coordinator/application/use_cases"
 	"github.com/rwadurian/mpc-system/services/session-coordinator/domain/repositories"
 	"github.com/rwadurian/mpc-system/services/session-coordinator/infrastructure/discovery"
@@ -69,25 +70,12 @@ func main() {
 	}
 	defer db.Close()
 
-	// Initialize Redis connection
-	redisClient := initRedis(cfg.Redis)
-	defer redisClient.Close()
-
-	// Initialize RabbitMQ connection
-	rabbitConn, err := initRabbitMQ(cfg.RabbitMQ)
-	if err != nil {
-		logger.Fatal("Failed to connect to RabbitMQ", zap.Error(err))
-	}
-	defer rabbitConn.Close()
-
 	// Initialize repositories and adapters
 	sessionRepo := postgres.NewSessionPostgresRepo(db)
 	messageRepo := postgres.NewMessagePostgresRepo(db)
-	sessionCache := redisadapter.NewSessionCacheAdapter(redisClient)
+
-	eventPublisher, err := rabbitmq.NewEventPublisherAdapter(rabbitConn)
+	// Initialize in-memory event publisher (replaces RabbitMQ)
-	if err != nil {
+	eventPublisher := memory.NewEventPublisherAdapter()
-		logger.Fatal("Failed to create event publisher", zap.Error(err))
-	}
 	defer eventPublisher.Close()
 
 	// Initialize JWT service
@@ -114,17 +102,34 @@ func main() {
 	partyPool := discovery.NewMessageRouterPartyDiscovery(messageRouterClient, logger.Log)
 	logger.Info("Party discovery initialized using Message Router")
 
+	// Initialize Account Service HTTP client
+	accountServiceAddr := os.Getenv("ACCOUNT_SERVICE_ADDR")
+	if accountServiceAddr == "" {
+		accountServiceAddr = "http://localhost:8081" // Default for local development
+	}
+	accountServiceClient := httpclient.NewAccountServiceClient(accountServiceAddr)
+	logger.Info("Account Service client initialized", zap.String("address", accountServiceAddr))
+
+	// Initialize Notification Service (stub implementation - logs but doesn't send)
+	// Replace with real implementation (email/SMS/push) when notification providers are configured
+	notificationService := notification.NewStubNotificationService()
+	logger.Info("Notification Service initialized (stub mode - logging only)")
+
 	// Initialize use cases
-	createSessionUC := use_cases.NewCreateSessionUseCase(sessionRepo, jwtService, eventPublisher, partyPool, messageRouterClient)
+	createSessionUC := use_cases.NewCreateSessionUseCaseWithNotification(sessionRepo, jwtService, eventPublisher, partyPool, messageRouterClient, notificationService)
 	joinSessionUC := use_cases.NewJoinSessionUseCase(sessionRepo, jwtService, eventPublisher)
 	getSessionStatusUC := use_cases.NewGetSessionStatusUseCase(sessionRepo)
-	reportCompletionUC := use_cases.NewReportCompletionUseCase(sessionRepo, eventPublisher)
+	reportCompletionUC := use_cases.NewReportCompletionUseCase(sessionRepo, eventPublisher, accountServiceClient)
 	closeSessionUC := use_cases.NewCloseSessionUseCase(sessionRepo, messageRepo, eventPublisher)
 	expireSessionsUC := use_cases.NewExpireSessionsUseCase(sessionRepo, eventPublisher)
+	checkPartyTimeoutsUC := use_cases.NewCheckPartyTimeoutsUseCase(sessionRepo, eventPublisher, 2*time.Minute)
 
 	// Start session expiration background job
 	go runSessionExpiration(expireSessionsUC)
 
+	// Start party timeout checking background job
+	go runPartyTimeoutCheck(checkPartyTimeoutsUC)
+
 	// Create shutdown context
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
@@ -151,6 +156,7 @@ func main() {
 	go func() {
 		if err := startHTTPServer(
 			cfg,
+			jwtService,
 			createSessionUC,
 			joinSessionUC,
 			getSessionStatusUC,
@@ -182,7 +188,6 @@ func main() {
 	logger.Info("Shutdown complete")
 
 	_ = ctx
-	_ = sessionCache
 }
 
 func initDatabase(cfg config.DatabaseConfig) (*sql.DB, error) {
@@ -225,138 +230,6 @@ func initDatabase(cfg config.DatabaseConfig) (*sql.DB, error) {
 	return nil, fmt.Errorf("failed to connect to database after %d retries: %w", maxRetries, err)
 }
 
-func initRedis(cfg config.RedisConfig) *redis.Client {
-	const maxRetries = 10
-	const retryDelay = 2 * time.Second
-
-	client := redis.NewClient(&redis.Options{
-		Addr:     cfg.Addr(),
-		Password: cfg.Password,
-		DB:       cfg.DB,
-	})
-
-	// Test connection with retry
-	ctx := context.Background()
-	for i := 0; i < maxRetries; i++ {
-		if err := client.Ping(ctx).Err(); err != nil {
-			logger.Warn("Redis connection failed, retrying...",
-				zap.Int("attempt", i+1),
-				zap.Int("max_retries", maxRetries),
-				zap.Error(err))
-			time.Sleep(retryDelay * time.Duration(i+1))
-			continue
-		}
-		logger.Info("Connected to Redis")
-		return client
-	}
-
-	logger.Warn("Redis connection failed after retries, continuing without cache")
-	return client
-}
-
-func initRabbitMQ(cfg config.RabbitMQConfig) (*amqp.Connection, error) {
-	const maxRetries = 10
-	const retryDelay = 2 * time.Second
-
-	var conn *amqp.Connection
-	var err error
-
-	for i := 0; i < maxRetries; i++ {
-		// Attempt to dial RabbitMQ
-		conn, err = amqp.Dial(cfg.URL())
-		if err != nil {
-			logger.Warn("Failed to dial RabbitMQ, retrying...",
-				zap.Int("attempt", i+1),
-				zap.Int("max_retries", maxRetries),
-				zap.String("url", maskPassword(cfg.URL())),
-				zap.Error(err))
-			time.Sleep(retryDelay * time.Duration(i+1))
-			continue
-		}
-
-		// Verify connection is actually usable by opening a channel
-		ch, err := conn.Channel()
-		if err != nil {
-			logger.Warn("RabbitMQ connection established but channel creation failed, retrying...",
-				zap.Int("attempt", i+1),
-				zap.Int("max_retries", maxRetries),
-				zap.Error(err))
-			conn.Close()
-			time.Sleep(retryDelay * time.Duration(i+1))
-			continue
-		}
-
-		// Test the channel with a simple operation (declare a test exchange)
-		err = ch.ExchangeDeclare(
-			"mpc.health.check", // name
-			"fanout",           // type
-			false,              // durable
-			true,               // auto-deleted
-			false,              // internal
-			false,              // no-wait
-			nil,                // arguments
-		)
-		if err != nil {
-			logger.Warn("RabbitMQ channel created but exchange declaration failed, retrying...",
-				zap.Int("attempt", i+1),
-				zap.Int("max_retries", maxRetries),
-				zap.Error(err))
-			ch.Close()
-			conn.Close()
-			time.Sleep(retryDelay * time.Duration(i+1))
-			continue
-		}
-
-		// Clean up test exchange
-		ch.ExchangeDelete("mpc.health.check", false, false)
-		ch.Close()
-
-		// Setup connection close notification
-		closeChan := make(chan *amqp.Error, 1)
-		conn.NotifyClose(closeChan)
-		go func() {
-			err := <-closeChan
-			if err != nil {
-				logger.Error("RabbitMQ connection closed unexpectedly", zap.Error(err))
-			}
-		}()
-
-		logger.Info("Connected to RabbitMQ and verified connectivity",
-			zap.Int("attempt", i+1))
-		return conn, nil
-	}
-
-	return nil, fmt.Errorf("failed to connect to RabbitMQ after %d retries: %w", maxRetries, err)
-}
-
-// maskPassword masks the password in the RabbitMQ URL for logging
-func maskPassword(url string) string {
-	// Simple masking: amqp://user:password@host:port -> amqp://user:****@host:port
-	start := 0
-	for i := 0; i < len(url); i++ {
-		if url[i] == ':' && i > 0 && url[i-1] != '/' {
-			start = i + 1
-			break
-		}
-	}
-	if start == 0 {
-		return url
-	}
-
-	end := start
-	for i := start; i < len(url); i++ {
-		if url[i] == '@' {
-			end = i
-			break
-		}
-	}
-	if end == start {
-		return url
-	}
-
-	return url[:start] + "****" + url[end:]
-}
-
 func startGRPCServer(
 	cfg *config.Config,
 	createSessionUC *use_cases.CreateSessionUseCase,
@@ -393,6 +266,7 @@ func startGRPCServer(
 
 func startHTTPServer(
 	cfg *config.Config,
+	jwtService *jwt.JWTService,
 	createSessionUC *use_cases.CreateSessionUseCase,
 	joinSessionUC *use_cases.JoinSessionUseCase,
 	getSessionStatusUC *use_cases.GetSessionStatusUseCase,
@@ -409,6 +283,27 @@ func startHTTPServer(
 	router.Use(gin.Recovery())
 	router.Use(gin.Logger())
 
+	// Apply security headers middleware
+	router.Use(middleware.SecureHeaders())
+
+	// Apply CORS middleware
+	allowedOrigins := []string{}
+	if origins := os.Getenv("CORS_ALLOWED_ORIGINS"); origins != "" {
+		allowedOrigins = strings.Split(origins, ",")
+	}
+	if cfg.Server.Environment != "production" {
+		router.Use(middleware.AllowAllCORS())
+	} else if len(allowedOrigins) > 0 {
+		router.Use(middleware.CORS(middleware.CORSConfig{
+			AllowOrigins:     allowedOrigins,
+			AllowMethods:     []string{"GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"},
+			AllowHeaders:     []string{"Origin", "Content-Type", "Accept", "Authorization", "X-Requested-With"},
+			ExposeHeaders:    []string{"Content-Length", "X-Request-ID"},
+			AllowCredentials: true,
+			MaxAge:           86400,
+		}))
+	}
+
 	// Create HTTP handler
 	httpHandler := httphandler.NewSessionHTTPHandler(
 		createSessionUC,
@@ -419,7 +314,7 @@ func startHTTPServer(
 		sessionRepo,
 	)
 
-	// Health check
+	// Health check (public)
 	router.GET("/health", func(c *gin.Context) {
 		c.JSON(http.StatusOK, gin.H{
 			"status":  "healthy",
@@ -427,11 +322,25 @@ func startHTTPServer(
 		})
 	})
 
-	// Register API routes
+	// Configure authentication middleware
+	// Session Coordinator HTTP API requires authentication
+	// Note: gRPC endpoints have separate authentication (service-to-service)
+	authConfig := middleware.AuthConfig{
+		JWTService: jwtService,
+		SkipPaths: []string{
+			"/health",
+		},
+		AllowAnonymous: false,
+	}
+
+	// API routes with authentication
 	api := router.Group("/api/v1")
+	api.Use(middleware.BearerAuth(authConfig))
 	httpHandler.RegisterRoutes(api)
 
-	logger.Info("Starting HTTP server", zap.Int("port", cfg.Server.HTTPPort))
+	logger.Info("Starting HTTP server",
+		zap.Int("port", cfg.Server.HTTPPort),
+		zap.String("environment", cfg.Server.Environment))
 	return router.Run(fmt.Sprintf(":%d", cfg.Server.HTTPPort))
 }
 
@@ -451,3 +360,28 @@ func runSessionExpiration(expireSessionsUC *use_cases.ExpireSessionsUseCase) {
 		}
 	}
 }
+
+func runPartyTimeoutCheck(checkPartyTimeoutsUC *use_cases.CheckPartyTimeoutsUseCase) {
+	// Check for party timeouts every 30 seconds
+	ticker := time.NewTicker(30 * time.Second)
+	defer ticker.Stop()
+
+	logger.Info("Party timeout checker started",
+		zap.Duration("check_interval", 30*time.Second),
+		zap.Duration("inactivity_timeout", checkPartyTimeoutsUC.GetInactivityTimeout()))
+
+	for range ticker.C {
+		ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+		result, err := checkPartyTimeoutsUC.Execute(ctx)
+		cancel()
+
+		if err != nil {
+			logger.Error("Failed to check party timeouts", zap.Error(err))
+		} else if result.PartiesTimedOut > 0 {
+			logger.Warn("Detected timed-out parties",
+				zap.Int("sessions_checked", result.SessionsChecked),
+				zap.Int("parties_timed_out", result.PartiesTimedOut),
+				zap.Int("sessions_failed", result.SessionsFailedDueToTimeout))
+		}
+	}
+}

backend/mpc-system/services/session-coordinator/domain/entities/mpc_session.go

@@ -9,13 +9,14 @@ import (
 )
 
 var (
-	ErrSessionNotFound        = errors.New("session not found")
+	ErrSessionNotFound         = errors.New("session not found")
-	ErrSessionFull            = errors.New("session is full")
+	ErrSessionFull             = errors.New("session is full")
-	ErrSessionExpired         = errors.New("session expired")
+	ErrSessionExpired          = errors.New("session expired")
-	ErrSessionNotInProgress   = errors.New("session not in progress")
+	ErrSessionNotInProgress    = errors.New("session not in progress")
-	ErrParticipantNotFound    = errors.New("participant not found")
+	ErrParticipantNotFound     = errors.New("participant not found")
-	ErrInvalidSessionType     = errors.New("invalid session type")
+	ErrInvalidSessionType      = errors.New("invalid session type")
 	ErrInvalidStatusTransition = errors.New("invalid status transition")
+	ErrParticipantTimedOut     = errors.New("participant timed out")
 )
 
 // SessionType represents the type of MPC session
@@ -34,18 +35,19 @@ func (t SessionType) IsValid() bool {
 // MPCSession represents an MPC session
 // Coordinator only manages session metadata, does not participate in MPC computation
 type MPCSession struct {
-	ID           value_objects.SessionID
+	ID              value_objects.SessionID
-	SessionType  SessionType
+	SessionType     SessionType
-	Threshold    value_objects.Threshold
+	Threshold       value_objects.Threshold
-	Participants []*Participant
+	Participants    []*Participant
-	Status       value_objects.SessionStatus
+	Status          value_objects.SessionStatus
-	MessageHash  []byte // Used for Sign sessions
+	MessageHash     []byte // Used for Sign sessions
-	PublicKey    []byte // Group public key after Keygen completion
+	PublicKey       []byte // Group public key after Keygen completion
-	CreatedBy    string
+	DelegatePartyID string // The delegate party ID (returns share to user instead of storing)
-	CreatedAt    time.Time
+	CreatedBy       string
-	UpdatedAt    time.Time
+	CreatedAt       time.Time
-	ExpiresAt    time.Time
+	UpdatedAt       time.Time
-	CompletedAt  *time.Time
+	ExpiresAt       time.Time
+	CompletedAt     *time.Time
 }
 
 // NewMPCSession creates a new MPC session
@@ -282,6 +284,50 @@ func (s *MPCSession) GetOtherParties(excludePartyID value_objects.PartyID) []*Pa
 	return others
 }
 
+// UpdatePartyActivity updates the activity timestamp for a party
+func (s *MPCSession) UpdatePartyActivity(partyID value_objects.PartyID) error {
+	for _, p := range s.Participants {
+		if p.PartyID.Equals(partyID) {
+			p.UpdateActivity()
+			s.UpdatedAt = time.Now().UTC()
+			return nil
+		}
+	}
+	return ErrParticipantNotFound
+}
+
+// GetTimedOutParties returns participants that have exceeded the inactivity timeout
+// Only checks active participants (joined or ready, not yet completed/failed)
+func (s *MPCSession) GetTimedOutParties(timeout time.Duration) []*Participant {
+	timedOut := make([]*Participant, 0)
+	for _, p := range s.Participants {
+		// Only check active participants
+		if p.IsJoined() && !p.IsCompleted() && !p.IsFailed() {
+			if p.IsTimedOut(timeout) {
+				timedOut = append(timedOut, p)
+			}
+		}
+	}
+	return timedOut
+}
+
+// HasTimedOutParties checks if any active participant has timed out
+func (s *MPCSession) HasTimedOutParties(timeout time.Duration) bool {
+	return len(s.GetTimedOutParties(timeout)) > 0
+}
+
+// MarkTimedOutPartiesAsFailed marks all timed-out parties as failed
+func (s *MPCSession) MarkTimedOutPartiesAsFailed(timeout time.Duration) []*Participant {
+	timedOut := s.GetTimedOutParties(timeout)
+	for _, p := range timedOut {
+		p.MarkFailed()
+	}
+	if len(timedOut) > 0 {
+		s.UpdatedAt = time.Now().UTC()
+	}
+	return timedOut
+}
+
 // ToDTO converts to a DTO for API responses
 func (s *MPCSession) ToDTO() SessionDTO {
 	participants := make([]ParticipantDTO, len(s.Participants))
@@ -333,6 +379,7 @@ func ReconstructSession(
 	thresholdT, thresholdN int,
 	status string,
 	messageHash, publicKey []byte,
+	delegatePartyID string,
 	createdBy string,
 	createdAt, updatedAt, expiresAt time.Time,
 	completedAt *time.Time,
@@ -349,17 +396,18 @@ func ReconstructSession(
 	}
 
 	return &MPCSession{
-		ID:           value_objects.SessionIDFromUUID(id),
+		ID:              value_objects.SessionIDFromUUID(id),
-		SessionType:  SessionType(sessionType),
+		SessionType:    SessionType(sessionType),
-		Threshold:    threshold,
+		Threshold:      threshold,
-		Participants: participants,
+		Participants:   participants,
-		Status:       sessionStatus,
+		Status:         sessionStatus,
-		MessageHash:  messageHash,
+		MessageHash:    messageHash,
-		PublicKey:    publicKey,
+		PublicKey:      publicKey,
-		CreatedBy:    createdBy,
+		DelegatePartyID: delegatePartyID,
-		CreatedAt:    createdAt,
+		CreatedBy:      createdBy,
-		UpdatedAt:    updatedAt,
+		CreatedAt:      createdAt,
-		ExpiresAt:    expiresAt,
+		UpdatedAt:      updatedAt,
-		CompletedAt:  completedAt,
+		ExpiresAt:      expiresAt,
+		CompletedAt:    completedAt,
 	}, nil
 }

backend/mpc-system/services/session-coordinator/domain/entities/participant.go

@@ -15,13 +15,14 @@ var (
 
 // Participant represents a party in an MPC session
 type Participant struct {
-	PartyID     value_objects.PartyID
+	PartyID        value_objects.PartyID
-	PartyIndex  int
+	PartyIndex     int
-	Status      value_objects.ParticipantStatus
+	Status         value_objects.ParticipantStatus
-	DeviceInfo  DeviceInfo
+	DeviceInfo     DeviceInfo
-	PublicKey   []byte // Party's identity public key (for authentication)
+	PublicKey      []byte     // Party's identity public key (for authentication)
-	JoinedAt    time.Time
+	JoinedAt       time.Time
-	CompletedAt *time.Time
+	CompletedAt    *time.Time
+	LastActivityAt time.Time  // Last activity timestamp for timeout detection
 }
 
 // NewParticipant creates a new participant
@@ -107,3 +108,27 @@ func (p *Participant) IsFailed() bool {
 func (p *Participant) SetPublicKey(publicKey []byte) {
 	p.PublicKey = publicKey
 }
+
+// UpdateActivity updates the last activity timestamp
+func (p *Participant) UpdateActivity() {
+	p.LastActivityAt = time.Now().UTC()
+}
+
+// IsTimedOut checks if the participant has exceeded the inactivity timeout
+func (p *Participant) IsTimedOut(timeout time.Duration) bool {
+	// If LastActivityAt is zero, use JoinedAt as reference
+	refTime := p.LastActivityAt
+	if refTime.IsZero() {
+		refTime = p.JoinedAt
+	}
+	return time.Since(refTime) > timeout
+}
+
+// TimeSinceLastActivity returns the duration since the last activity
+func (p *Participant) TimeSinceLastActivity() time.Duration {
+	refTime := p.LastActivityAt
+	if refTime.IsZero() {
+		refTime = p.JoinedAt
+	}
+	return time.Since(refTime)
+}

backend/mpc-system/services/session-coordinator/domain/repositories/session_repository.go

@@ -26,6 +26,9 @@ type SessionRepository interface {
 	// FindExpired retrieves all expired sessions
 	FindExpired(ctx context.Context) ([]*entities.MPCSession, error)
 
+	// FindActive retrieves all active sessions (created or in_progress)
+	FindActive(ctx context.Context) ([]*entities.MPCSession, error)
+
 	// FindByCreator retrieves sessions created by a user
 	FindByCreator(ctx context.Context, creatorID string) ([]*entities.MPCSession, error)
 

backend/mpc-system/services/session-coordinator/infrastructure/discovery/message_router_discovery.go

@@ -39,11 +39,24 @@ func (d *MessageRouterPartyDiscovery) GetAvailableParties() []output.PartyEndpoi
 
 	endpoints := make([]output.PartyEndpoint, 0, len(parties))
 	for _, party := range parties {
-		endpoints = append(endpoints, output.PartyEndpoint{
+		endpoint := output.PartyEndpoint{
 			PartyID: party.PartyId,
 			Ready:   party.Online,
 			Role:    output.PartyRole(party.Role),
-		})
+		}
+
+		// Parse notification channel from party registration
+		// If notification channel is present, party operates in offline mode
+		// If not present, party operates in real-time mode (Message Router push)
+		if party.Notification != nil {
+			endpoint.Notification = &output.NotificationChannel{
+				Email:     party.Notification.Email,
+				Phone:     party.Notification.Phone,
+				PushToken: party.Notification.PushToken,
+			}
+		}
+
+		endpoints = append(endpoints, endpoint)
 	}
 
 	return endpoints
@@ -65,11 +78,24 @@ func (d *MessageRouterPartyDiscovery) GetAvailablePartiesByRole(role output.Part
 
 	endpoints := make([]output.PartyEndpoint, 0, len(parties))
 	for _, party := range parties {
-		endpoints = append(endpoints, output.PartyEndpoint{
+		endpoint := output.PartyEndpoint{
 			PartyID: party.PartyId,
 			Ready:   party.Online,
 			Role:    output.PartyRole(party.Role),
-		})
+		}
+
+		// Parse notification channel from party registration
+		// If notification channel is present, party operates in offline mode
+		// If not present, party operates in real-time mode (Message Router push)
+		if party.Notification != nil {
+			endpoint.Notification = &output.NotificationChannel{
+				Email:     party.Notification.Email,
+				Phone:     party.Notification.Phone,
+				PushToken: party.Notification.PushToken,
+			}
+		}
+
+		endpoints = append(endpoints, endpoint)
 	}
 
 	return endpoints