feat: update default ASR vendor selection based on client area; enhance documentation and tests

Author: seymourtang

docs/concepts/agent.md

@@ -46,7 +46,7 @@ agent = Agent(client=client).with_llm(
 | `rtc` | `RtcConfig` | No | RTC media encryption |
 | `filler_words` | `FillerWordsConfig` | No | Filler words while waiting for LLM |
 
-When `client` is provided, `Agent(client=...)` returns `CNAgent` for `Area.CN` and `GlobalAgent` for global areas.
+When `client` is provided, `Agent(client=...)` returns `CNAgent` for `Area.CN` and `GlobalAgent` for global areas. If `with_stt()` is omitted, the bound client also determines the default ASR vendor: `Fengming` for `Area.CN`, otherwise `Ares`.
 
 ## Builder Methods
 

docs/concepts/vendors.md

@@ -103,7 +103,7 @@ tts = ElevenLabsTTS(
 
 Used with `agent.with_stt()`.
 
-Use `turn_detection.language` for Agora interaction language; it defaults to `en-US`. STT vendor `language` options are serialized under `asr.params` using each provider's own format. Ares does not take a provider language option; AgentKit uses `turn_detection.language` for REST `asr.language`.
+Use `turn_detection.language` for Agora interaction language; it defaults to `en-US`. STT vendor `language` options are serialized under `asr.params` using each provider's own format. If `with_stt()` is omitted, AgentKit defaults to `AresSTT` for global clients and `FengmingSTT` for `Area.CN` clients. Ares does not take a provider language option; AgentKit uses `turn_detection.language` for REST `asr.language`.
 
 | Class | Provider | Required Parameters |
 |---|---|---|

docs/guides/regional-routing.md

@@ -36,6 +36,7 @@ client = Agora(
 ## Recommended vendors by area
 
 Bind `client` into `Agent(client=client, ...)` and construct vendors directly with SDK classes. The bound client selects `CNAgent` or `GlobalAgent` for IDE hints based on `area`, but does not restrict which vendor classes you can configure.
+If you omit `with_stt()`, AgentKit uses `FengmingSTT` by default for `Area.CN` clients and `AresSTT` for global clients.
 
 | Client area | STT classes | LLM classes | TTS classes | Avatar classes |
 |---|---|---|---|---|
@@ -125,6 +126,7 @@ agent = Agent(client=client, turn_detection={"language": "zh-CN"})
 ```
 
 `Agent(client=...)` returns `CNAgent` for `Area.CN` and `GlobalAgent` for global areas. A bound `client` is required. The SDK does not reject mismatched vendor classes at build time or session start.
+The same bound client also controls the default ASR vendor when `with_stt()` is omitted.
 
 ## How the domain pool works
 

docs/reference/agent.md

@@ -9,6 +9,7 @@ description: Full API reference for the Python Agent builder class.
 **Import:** `from agora_agent import Agent, CNAgent, GlobalAgent`
 
 Bind the client on every `Agent` builder via `Agent(client=client, ...)`, then pass vendor classes directly. The bound client sets the API routing region and provides area-specific IDE hints via `CNAgent` / `GlobalAgent`:
+it also selects the default ASR vendor when `with_stt()` is omitted (`Fengming` for `Area.CN`, otherwise `Ares`).
 
 > **`client` is required.** `create_session()` and `create_async_session()` raise `ValueError` if no client was bound on the agent.
 

docs/reference/vendors.md

@@ -412,7 +412,7 @@ The SDK also includes named helpers for the remaining Agora-supported LLM provid
 
 ## STT Vendors
 
-Use `turn_detection.language` for Agora interaction language; it defaults to `en-US`. Provider-specific language values remain under `asr.params` and may use a different format. AgentKit populates REST `asr.language` from `turn_detection.language`.
+Use `turn_detection.language` for Agora interaction language; it defaults to `en-US`. Provider-specific language values remain under `asr.params` and may use a different format. If `with_stt()` is omitted, AgentKit defaults to `AresSTT` for global clients and `FengmingSTT` for `Area.CN` clients. AgentKit populates REST `asr.language` from `turn_detection.language`.
 
 ### `SpeechmaticsSTT`
 

src/agora_agent/agentkit/agent.py

@@ -1078,7 +1078,8 @@ def _resolve_llm_config(self) -> typing.Dict[str, typing.Any]:
     def _resolve_asr_config(self, turn_detection_config: TurnDetectionInput) -> typing.Dict[str, typing.Any]:
         asr_config = dict(self._stt or {})
         if not asr_config:
-            asr_config["vendor"] = "ares"
+            area_scope = getattr(self._client, "area_scope", None)
+            asr_config["vendor"] = "fengming" if area_scope == "cn" else "ares"
         asr_config["language"] = self._field_value(turn_detection_config, "language")
         return asr_config
 

tests/custom/test_regional_vendors.py

@@ -66,6 +66,26 @@ def test_agent_constructor_auto_selects_area_aware_subclass() -> None:
     assert global_agent.__class__.__name__ == "GlobalAgent"
 
 
+def test_default_asr_vendor_is_area_aware_when_with_stt_is_omitted() -> None:
+    cn_properties = Agent(client=_client(Area.CN)).to_properties(
+        channel="room",
+        agent_uid="1",
+        remote_uids=["100"],
+        token="rtc-token",
+    )
+    global_properties = Agent(client=_client(Area.US)).to_properties(
+        channel="room",
+        agent_uid="1",
+        remote_uids=["100"],
+        token="rtc-token",
+    )
+
+    assert cn_properties.asr is not None
+    assert cn_properties.asr.vendor == "fengming"
+    assert global_properties.asr is not None
+    assert global_properties.asr.vendor == "ares"
+
+
 def test_cn_client_allows_global_only_vendor() -> None:
     client = _client(Area.CN)
     agent = Agent(client=client).with_stt(

tests/custom/test_stt_language.py

@@ -2,6 +2,7 @@
 
 from agora_agent import (
     Agent,
+    Area,
     AmazonSTT,
     AssemblyAISTT,
     DeepgramSTT,
@@ -85,6 +86,18 @@ def test_default_turn_detection_language_is_sent_without_stt() -> None:
     assert props["turn_detection"] == {"language": "en-US"}
 
 
+def test_default_stt_vendor_depends_on_client_area_when_stt_is_omitted() -> None:
+    global_props = properties(base_agent())
+    cn_props = properties(
+        Agent(test_client(area=Area.CN))
+        .with_llm(OpenAI(api_key="llm-key", model="gpt-4o-mini", base_url="https://api.openai.com/v1/chat/completions"))
+        .with_tts(ElevenLabsTTS(key="tts-key", voice_id="voice", model_id="eleven_flash_v2_5", base_url="wss://api.elevenlabs.io/v1"))
+    )
+
+    assert global_props["asr"] == {"vendor": "ares", "language": "en-US"}
+    assert cn_props["asr"] == {"vendor": "fengming", "language": "en-US"}
+
+
 def test_stt_vendor_params_match_documented_shapes() -> None:
     deepgram_managed = DeepgramSTT(model="nova-3", language="en-US").to_config()
     assert "language" not in deepgram_managed