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
index fe34a06..2aa9209 100644
--- a/packages/services/agent-service/src/infrastructure/stt/openai-stt.service.ts
+++ b/packages/services/agent-service/src/infrastructure/stt/openai-stt.service.ts
@@ -2,8 +2,8 @@
  * 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).
+ * Supports the self-signed proxy at 67.223.119.33:8443 by disabling TLS
+ * verification via https.request (Node 18 native fetch ignores https.Agent).
  */
 import { Injectable, Logger } from '@nestjs/common';
 import { ConfigService } from '@nestjs/config';
@@ -16,12 +16,12 @@ export class OpenAISttService {
   private readonly baseUrl: string;
 
   constructor(private readonly configService: ConfigService) {
-    this.apiKey = this.configService.get<string>('OPENAI_API_KEY', '');
     // Strip trailing slash and /v1 suffix — we always append /v1/...
-    this.baseUrl = this.configService.get<string>(
-      'OPENAI_BASE_URL',
-      'https://api.openai.com',
-    ).replace(/\/$/, '').replace(/\/v1$/, '');
+    this.baseUrl = this.configService
+      .get<string>('OPENAI_BASE_URL', 'https://api.openai.com')
+      .replace(/\/$/, '')
+      .replace(/\/v1$/, '');
+    this.apiKey = this.configService.get<string>('OPENAI_API_KEY', '');
   }
 
   /**
@@ -37,7 +37,9 @@ export class OpenAISttService {
     language = 'zh',
   ): Promise<string> {
     const url = `${this.baseUrl}/v1/audio/transcriptions`;
-    this.logger.log(`STT: transcribing ${filename} (${audioBuffer.length} bytes) → ${url}`);
+    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)}`;
@@ -66,27 +68,51 @@ export class OpenAISttService {
 
     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,
+    // Use https.request so rejectUnauthorized: false works for the self-signed
+    // proxy. Node 18 native fetch (undici) does NOT honour https.Agent.
+    const parsedUrl = new URL(url);
+    const result = await new Promise<{ text: string }>((resolve, reject) => {
+      const req = https.request(
+        {
+          hostname: parsedUrl.hostname,
+          port: parsedUrl.port || 443,
+          path: parsedUrl.pathname + parsedUrl.search,
+          method: 'POST',
+          headers: {
+            Authorization: `Bearer ${this.apiKey}`,
+            'Content-Type': `multipart/form-data; boundary=${boundary}`,
+            'Content-Length': body.length,
+          },
+          rejectUnauthorized: false,
+        },
+        (res) => {
+          const chunks: Buffer[] = [];
+          res.on('data', (chunk: Buffer) => chunks.push(chunk));
+          res.on('end', () => {
+            const text = Buffer.concat(chunks).toString('utf8');
+            if (res.statusCode && res.statusCode >= 400) {
+              reject(
+                new Error(
+                  `Whisper STT failed: HTTP ${res.statusCode} — ${text}`,
+                ),
+              );
+            } else {
+              try {
+                resolve(JSON.parse(text) as { text: string });
+              } catch {
+                reject(
+                  new Error(`Whisper STT: invalid JSON response: ${text}`),
+                );
+              }
+            }
+          });
+        },
+      );
+      req.on('error', reject);
+      req.write(body);
+      req.end();
     });
 
-    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 ?? '';
   }