diff --git a/packages/services/agent-service/src/agent.module.ts b/packages/services/agent-service/src/agent.module.ts
index b93ef1e..2a53982 100644
--- a/packages/services/agent-service/src/agent.module.ts
+++ b/packages/services/agent-service/src/agent.module.ts
@@ -47,6 +47,7 @@ import { VoiceSessionController } from './interfaces/rest/controllers/voice-sess
 import { ConversationContextService } from './domain/services/conversation-context.service';
 import { VoiceSessionManager } from './domain/services/voice-session-manager.service';
 import { EventPublisherService } from './infrastructure/messaging/event-publisher.service';
+import { OpenAISttService } from './infrastructure/stt/openai-stt.service';
 
 @Module({
   imports: [
@@ -90,6 +91,7 @@ import { EventPublisherService } from './infrastructure/messaging/event-publishe
     AgentSkillService,
     HookScriptService,
     EventPublisherService,
+    OpenAISttService,
   ],
 })
 export class AgentModule {}
diff --git a/packages/services/agent-service/src/infrastructure/stt/openai-stt.service.ts b/packages/services/agent-service/src/infrastructure/stt/openai-stt.service.ts
new file mode 100644
index 0000000..5d7f8c7
--- /dev/null
+++ b/packages/services/agent-service/src/infrastructure/stt/openai-stt.service.ts
@@ -0,0 +1,92 @@
+/**
+ * OpenAISttService
+ *
+ * Calls the OpenAI Whisper transcriptions API to convert audio buffers to text.
+ * Supports the self-signed proxy at 67.223.119.33:8443 by disabling TLS verification
+ * when OPENAI_BASE_URL points to an https host (same pattern as voice-agent).
+ */
+import { Injectable, Logger } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import * as https from 'https';
+
+@Injectable()
+export class OpenAISttService {
+  private readonly logger = new Logger(OpenAISttService.name);
+  private readonly apiKey: string;
+  private readonly baseUrl: string;
+
+  constructor(private readonly configService: ConfigService) {
+    this.apiKey = this.configService.get<string>('OPENAI_API_KEY', '');
+    this.baseUrl = this.configService.get<string>(
+      'OPENAI_BASE_URL',
+      'https://api.openai.com',
+    ).replace(/\/$/, '');
+  }
+
+  /**
+   * Transcribe an audio buffer to text using OpenAI Whisper.
+   *
+   * @param audioBuffer  Raw audio bytes (any format Whisper accepts: m4a, webm, mp3, wav, etc.)
+   * @param filename     Original filename including extension — Whisper uses this to detect format
+   * @param language     BCP-47 language code hint (default: 'zh')
+   */
+  async transcribe(
+    audioBuffer: Buffer,
+    filename: string,
+    language = 'zh',
+  ): Promise<string> {
+    const url = `${this.baseUrl}/v1/audio/transcriptions`;
+    this.logger.log(`STT: transcribing ${filename} (${audioBuffer.length} bytes) → ${url}`);
+
+    // Build multipart/form-data manually to avoid external dependencies
+    const boundary = `----FormBoundary${Date.now().toString(16)}`;
+    const parts: Buffer[] = [];
+
+    const appendField = (name: string, value: string) => {
+      parts.push(
+        Buffer.from(
+          `--${boundary}\r\nContent-Disposition: form-data; name="${name}"\r\n\r\n${value}\r\n`,
+        ),
+      );
+    };
+
+    appendField('model', 'whisper-1');
+    appendField('language', language);
+    appendField('response_format', 'json');
+
+    // File field
+    parts.push(
+      Buffer.from(
+        `--${boundary}\r\nContent-Disposition: form-data; name="file"; filename="${filename}"\r\nContent-Type: application/octet-stream\r\n\r\n`,
+      ),
+    );
+    parts.push(audioBuffer);
+    parts.push(Buffer.from(`\r\n--${boundary}--\r\n`));
+
+    const body = Buffer.concat(parts);
+
+    // Use a custom https agent to allow self-signed certs (proxy at 67.223.119.33:8443)
+    const agent = new https.Agent({ rejectUnauthorized: false });
+
+    const response = await fetch(url, {
+      method: 'POST',
+      headers: {
+        Authorization: `Bearer ${this.apiKey}`,
+        'Content-Type': `multipart/form-data; boundary=${boundary}`,
+        'Content-Length': String(body.length),
+      },
+      body,
+      // @ts-ignore — undici (Node 18+ native fetch) accepts dispatcher via agent option
+      agent,
+    });
+
+    if (!response.ok) {
+      const errText = await response.text().catch(() => '');
+      throw new Error(`Whisper STT failed: HTTP ${response.status} — ${errText}`);
+    }
+
+    const result = (await response.json()) as { text: string };
+    this.logger.log(`STT result: "${result.text?.slice(0, 80)}"`);
+    return result.text ?? '';
+  }
+}
diff --git a/packages/services/agent-service/src/interfaces/rest/controllers/agent.controller.ts b/packages/services/agent-service/src/interfaces/rest/controllers/agent.controller.ts
index e6bf31f..7856c63 100644
--- a/packages/services/agent-service/src/interfaces/rest/controllers/agent.controller.ts
+++ b/packages/services/agent-service/src/interfaces/rest/controllers/agent.controller.ts
@@ -1,5 +1,8 @@
-import { Controller, Post, Body, Param, Delete, Get, NotFoundException, BadRequestException, ForbiddenException, Logger } from '@nestjs/common';
+import { Controller, Post, Body, Param, Delete, Get, NotFoundException, BadRequestException, ForbiddenException, Logger, UseInterceptors, UploadedFile } from '@nestjs/common';
+import { FileInterceptor } from '@nestjs/platform-express';
+import { memoryStorage } from 'multer';
 import { TenantId, EventPatterns } from '@it0/common';
+import { OpenAISttService } from '../../../infrastructure/stt/openai-stt.service';
 import { EngineRegistry } from '../../../infrastructure/engines/engine-registry';
 import { AgentStreamGateway } from '../../ws/agent-stream.gateway';
 import { SessionRepository } from '../../../infrastructure/repositories/session.repository';
@@ -30,6 +33,7 @@ export class AgentController {
     private readonly usageRecordRepository: UsageRecordRepository,
     private readonly contextService: ConversationContextService,
     private readonly eventPublisher: EventPublisherService,
+    private readonly sttService: OpenAISttService,
   ) {}
 
   @Post('tasks')
@@ -399,6 +403,111 @@ export class AgentController {
     }
   }
 
+  /**
+   * Voice message endpoint — WhatsApp-style push-to-talk.
+   *
+   * Accepts a recorded audio file, transcribes it via Whisper, then:
+   *   • If the session has a running task → hard-interrupt it and inject the transcript
+   *   • Otherwise → start a fresh task with the transcript
+   *
+   * This naturally solves the speaker-diarization problem: whoever presses
+   * record owns the message.  It also doubles as an async voice interrupt:
+   * the user can send audio commands into any active agent workflow.
+   *
+   * POST /api/v1/agent/sessions/:sessionId/voice-message
+   * Content-Type: multipart/form-data
+   * Fields: audio (file), language? (string, default 'zh')
+   *
+   * Response: { sessionId, taskId, transcript }
+   */
+  @Post('sessions/:sessionId/voice-message')
+  @UseInterceptors(FileInterceptor('audio', { storage: memoryStorage() }))
+  async sendVoiceMessage(
+    @TenantId() tenantId: string,
+    @Param('sessionId') sessionId: string,
+    @UploadedFile() file: { buffer: Buffer; originalname: string; mimetype: string } | undefined,
+    @Body('language') language?: string,
+  ) {
+    if (!file?.buffer?.length) {
+      throw new BadRequestException('audio file is required');
+    }
+
+    const session = await this.sessionRepository.findById(sessionId);
+    if (!session || session.tenantId !== tenantId) {
+      throw new NotFoundException(`Session ${sessionId} not found`);
+    }
+
+    // STT: transcribe audio → text
+    const transcript = await this.sttService.transcribe(
+      file.buffer,
+      file.originalname || 'audio.m4a',
+      language ?? 'zh',
+    );
+
+    if (!transcript?.trim()) {
+      throw new BadRequestException('Could not transcribe audio — empty result');
+    }
+
+    const engine = this.engineRegistry.switchEngine(session.engineType as AgentEngineType);
+
+    // Hard-interrupt any running task so the voice command takes effect immediately
+    const runningTask = await this.taskRepository.findRunningBySessionId(sessionId);
+    if (runningTask) {
+      this.logger.log(`[VoiceMsg ${sessionId}] Interrupting running task ${runningTask.id}`);
+      this.captureSdkSessionId(engine, session, runningTask.id);
+      await engine.cancelTask(session.id).catch(() => {});
+      runningTask.status = TaskStatus.CANCELLED;
+      runningTask.completedAt = new Date();
+      await this.taskRepository.save(runningTask);
+      await this.awaitTaskCleanup(runningTask.id);
+      this.gateway.emitStreamEvent(session.id, {
+        type: 'cancelled',
+        message: 'Interrupted by voice message',
+        code: 'VOICE_INJECT',
+      });
+    }
+
+    // Save user message and build context
+    await this.contextService.saveUserMessage(session.id, transcript);
+    const conversationHistory = await this.contextService.loadContext(session.id, 20);
+    const historyForEngine = conversationHistory.slice(0, -1);
+
+    const isSdkEngine = engine.engineType === AgentEngineType.CLAUDE_AGENT_SDK;
+    const resumeSessionId = isSdkEngine
+      ? (session.metadata as any)?.sdkSessionId as string | undefined
+      : undefined;
+
+    // Create task record
+    const task = new AgentTask();
+    task.id = crypto.randomUUID();
+    task.tenantId = tenantId;
+    task.sessionId = session.id;
+    task.prompt = transcript;
+    task.status = TaskStatus.RUNNING;
+    task.startedAt = new Date();
+    task.createdAt = new Date();
+    await this.taskRepository.save(task);
+
+    session.status = 'active';
+    session.updatedAt = new Date();
+    await this.sessionRepository.save(session);
+
+    // Notify WS subscribers of the new task
+    this.gateway.emitStreamEvent(session.id, { type: 'task_info', taskId: task.id });
+
+    // Fire-and-forget stream
+    this.runTaskStream(engine, session, task, {
+      prompt: transcript,
+      systemPrompt: session.systemPrompt || '',
+      allowedTools: [],
+      maxTurns: 10,
+      conversationHistory: historyForEngine.length > 0 ? historyForEngine : undefined,
+      resumeSessionId,
+    });
+
+    return { sessionId: session.id, taskId: task.id, transcript };
+  }
+
   @Get('engines')
   async listEngines() {
     const engines = this.engineRegistry.listAvailable();