fix(chat): route OAuth backend through native provider

deeptutor/core/agentic/client.py

@@ -50,14 +50,21 @@ def build_openai_client(config: LLMClientConfig) -> Any:
     if spec and spec.backend == "anthropic":
         from deeptutor.services.llm.provider_core import AnthropicProvider
 
-        provider = AnthropicProvider(
+        anthropic_provider = AnthropicProvider(
             api_key=config.api_key,
             api_base=config.base_url or spec.default_api_base or None,
             default_model=config.model or "claude-sonnet-4-20250514",
             extra_headers=config.extra_headers,
             supports_prompt_caching=spec.supports_prompt_caching,
         )
-        return _AnthropicOpenAIAdapter(provider)
+        return _AnthropicOpenAIAdapter(anthropic_provider)
+    if spec and spec.backend == "openai_codex":
+        from deeptutor.services.llm.provider_core import OpenAICodexProvider
+
+        oauth_provider = OpenAICodexProvider(
+            default_model=config.model or "openai-codex/gpt-5.1-codex",
+        )
+        return _AnthropicOpenAIAdapter(oauth_provider)
 
     http_client = None
     if load_system_settings()["disable_ssl_verify"]:

tests/core/test_agentic_client_provider_kwargs.py

@@ -115,6 +115,31 @@ def __init__(self, **kwargs):
     assert captured["extra_headers"] == {"X-Test": "1"}
 
 
+def test_build_openai_client_routes_oauth_backend_through_adapter(monkeypatch) -> None:
+    captured = {}
+
+    class FakeProvider:
+        def __init__(self, **kwargs):
+            captured.update(kwargs)
+
+    monkeypatch.setattr(
+        "deeptutor.services.llm.provider_core.OpenAICodexProvider",
+        FakeProvider,
+    )
+
+    client = build_openai_client(
+        LLMClientConfig(
+            binding="openai_codex",
+            model="openai-codex/gpt-5.5",
+            api_key="unused",
+            base_url="https://chatgpt.com/backend-api",
+        )
+    )
+
+    assert isinstance(client, _AnthropicOpenAIAdapter)
+    assert captured["default_model"] == "openai-codex/gpt-5.5"
+
+
 def test_anthropic_backend_can_use_native_tool_calling() -> None:
     assert can_use_native_tool_calling(binding="custom_anthropic", model="claude-test") is True
     assert can_use_native_tool_calling(binding="minimax_anthropic", model="MiniMax-M2") is True