diff --git a/app/agent/llm/capability.py b/app/agent/llm/capability.py
index d4953942..a406df73 100644
--- a/app/agent/llm/capability.py
+++ b/app/agent/llm/capability.py
@@ -146,6 +146,8 @@ class OpenAIChatAudioProvider(AudioCapabilityProvider):
         ".opus": "audio/ogg",
         ".wav": "audio/wav",
     }
+    TRANSCODED_STT_SUFFIX = ".wav"
+    TRANSCODED_STT_SAMPLE_RATE = "16000"
 
     def _build_client(self, api_key: str, base_url: Optional[str]):
         from openai import OpenAI
@@ -229,6 +231,76 @@ class OpenAIChatAudioProvider(AudioCapabilityProvider):
             "format": self._guess_audio_format(filename),
         }
 
+    def _normalize_audio_for_transcription(
+        self, content: bytes, filename: str
+    ) -> Optional[tuple[bytes, str]]:
+        """
+        将转写输入归一化为 Chat Audio provider 明确支持的格式。
+
+        :param content: 原始音频字节
+        :param filename: 原始音频文件名
+        :return: 成功时返回可提交的音频字节和文件名，失败时返回 None
+        """
+        suffix = Path(filename or "").suffix.lower()
+        if suffix in self.SUPPORTED_AUDIO_MIME_TYPES:
+            return content, filename
+        return self._convert_audio_for_transcription(content=content, filename=filename)
+
+    def _convert_audio_for_transcription(
+        self, content: bytes, filename: str
+    ) -> Optional[tuple[bytes, str]]:
+        """
+        将 AMR 等第三方 STT 不支持的输入转为 WAV。
+
+        :param content: 原始音频字节
+        :param filename: 原始音频文件名
+        :return: 成功时返回 WAV 字节和文件名，失败时返回 None
+        """
+        if not shutil.which("ffmpeg"):
+            logger.warning(
+                "%s STT 不支持当前音频格式且 ffmpeg 不可用，无法转码: filename=%s",
+                self.DISPLAY_NAME,
+                filename,
+            )
+            return None
+
+        suffix = Path(filename or "").suffix.lower() or ".audio"
+        voice_dir = settings.TEMP_PATH / "voice"
+        voice_dir.mkdir(parents=True, exist_ok=True)
+        input_path = voice_dir / f"{uuid4().hex}{suffix}"
+        output_path = input_path.with_suffix(self.TRANSCODED_STT_SUFFIX)
+        try:
+            input_path.write_bytes(content)
+            cmd = [
+                "ffmpeg",
+                "-y",
+                "-i",
+                str(input_path),
+                "-ar",
+                self.TRANSCODED_STT_SAMPLE_RATE,
+                "-ac",
+                "1",
+                "-f",
+                "wav",
+                str(output_path),
+            ]
+            result = subprocess.run(cmd, capture_output=True, text=True, check=False)
+            if result.returncode != 0 or not output_path.exists():
+                logger.warning(
+                    "%s STT 音频转 WAV 失败: returncode=%s, stderr=%s",
+                    self.DISPLAY_NAME,
+                    result.returncode,
+                    (result.stderr or "").strip()[:500],
+                )
+                return None
+            return output_path.read_bytes(), f"{input_path.stem}{self.TRANSCODED_STT_SUFFIX}"
+        finally:
+            for temp_path in (input_path, output_path):
+                try:
+                    temp_path.unlink(missing_ok=True)
+                except OSError as err:
+                    logger.debug(f"清理 STT 临时音频失败: path={temp_path}, error={err}")
+
     @staticmethod
     def _extract_message_text(message) -> Optional[str]:
         """兼容音频理解响应可能放在 content 或 reasoning_content 的情况。"""
@@ -310,6 +382,12 @@ class OpenAIChatAudioProvider(AudioCapabilityProvider):
             if not api_key:
                 raise ValueError("音频输入 provider 未配置 API Key")
             client = self._build_client(api_key=api_key, base_url=base_url)
+            normalized_audio = self._normalize_audio_for_transcription(
+                content=content, filename=filename
+            )
+            if not normalized_audio:
+                return None
+            content, filename = normalized_audio
             language = (settings.AUDIO_INPUT_LANGUAGE or "").strip()
             prompt = "请将这段音频完整转写为文字，只输出转写结果，不要添加解释。"
             if language:
diff --git a/tests/test_agent_llm_capability.py b/tests/test_agent_llm_capability.py
index 0fcf9ee0..6b58e4a1 100644
--- a/tests/test_agent_llm_capability.py
+++ b/tests/test_agent_llm_capability.py
@@ -232,6 +232,38 @@ class AgentCapabilityManagerTest(unittest.TestCase):
         )
         self.assertIn("只输出转写结果", content[1]["text"])
 
+    def test_mimo_stt_transcodes_amr_before_payload(self):
+        """校验 MiMo 音频输入会先将企业微信 AMR 转为受支持的 WAV。"""
+        provider = MiMoAudioProvider()
+        fake_client = Mock()
+        fake_client.chat.completions.create.return_value = SimpleNamespace(
+            choices=[SimpleNamespace(message=SimpleNamespace(content="你好"))]
+        )
+
+        with patch.object(provider, "_build_client", return_value=fake_client), patch.object(
+            provider,
+            "_convert_audio_for_transcription",
+            return_value=(b"wav-bytes", "input.wav"),
+        ) as convert_audio, patch.object(settings, "AUDIO_INPUT_MODEL", "mimo-v2.5"), patch.object(
+            settings, "AUDIO_INPUT_LANGUAGE", "zh"
+        ), patch.object(
+            settings, "AUDIO_INPUT_API_KEY", "sk-test"
+        ), patch.object(
+            settings, "AUDIO_INPUT_BASE_URL", "https://api.xiaomimimo.com/v1"
+        ):
+            result = provider.transcribe_audio(b"amr-bytes", filename="input.amr")
+
+        self.assertEqual(result, "你好")
+        convert_audio.assert_called_once_with(
+            content=b"amr-bytes", filename="input.amr"
+        )
+        request = fake_client.chat.completions.create.call_args.kwargs
+        content = request["messages"][0]["content"]
+        self.assertEqual(
+            content[0]["input_audio"]["data"],
+            f"data:audio/wav;base64,{b64encode(b'wav-bytes').decode('utf-8')}",
+        )
+
     def test_minimax_stt_normalizes_openai_default_model(self):
         """校验 MiniMax 音频输入会把 OpenAI 默认模型兜底为 MiniMax 模型。"""
         provider = MiniMaxAudioProvider()