fix: route Kimi coding fallback via Anthropic messages

agent/agent_init.py

@@ -307,10 +307,12 @@ def init_agent(
     elif agent.provider == "anthropic" or (provider_name is None and agent._base_url_hostname == "api.anthropic.com"):
         agent.api_mode = "anthropic_messages"
         agent.provider = "anthropic"
-    elif agent._base_url_lower.rstrip("/").endswith("/anthropic"):
+    elif agent._base_url_lower.rstrip("/").endswith("/anthropic") or (
+        agent._base_url_hostname == "api.kimi.com" and "/coding" in agent._base_url_lower
+    ):
         # Third-party Anthropic-compatible endpoints (e.g. MiniMax, DashScope)
-        # use a URL convention ending in /anthropic. Auto-detect these so the
-        # Anthropic Messages API adapter is used instead of chat completions.
+        # use a URL convention ending in /anthropic. Kimi Coding also speaks
+        # Anthropic Messages on /coding without using the /anthropic suffix.
         agent.api_mode = "anthropic_messages"
     elif agent.provider == "bedrock" or (
         agent._base_url_hostname.startswith("bedrock-runtime.")

agent/chat_completion_helpers.py

@@ -820,7 +820,9 @@ def try_activate_fallback(agent, reason: "FailoverReason | None" = None) -> bool
         _fb_is_azure = agent._is_azure_openai_url(fb_base_url)
         if fb_provider == "openai-codex":
             fb_api_mode = "codex_responses"
-        elif fb_provider == "anthropic" or fb_base_url.rstrip("/").lower().endswith("/anthropic"):
+        elif fb_provider == "anthropic" or fb_base_url.rstrip("/").lower().endswith("/anthropic") or (
+            base_url_hostname(fb_base_url) == "api.kimi.com" and "/coding" in fb_base_url.lower()
+        ):
             fb_api_mode = "anthropic_messages"
         elif _fb_is_azure:
             # Azure OpenAI serves gpt-5.x on /chat/completions — does NOT

tests/run_agent/test_run_agent.py

@@ -680,6 +680,24 @@ def test_anthropic_base_url_accepted(self):
             assert agent.api_mode == "anthropic_messages"
             mock_anthropic.Anthropic.assert_called_once()
 
+    def test_kimi_coding_base_url_uses_anthropic_messages_mode(self):
+        """Kimi Coding endpoints speak the Anthropic Messages wire format."""
+        with (
+            patch("run_agent.get_tool_definitions", return_value=[]),
+            patch("run_agent.check_toolset_requirements", return_value={}),
+            patch("agent.anthropic_adapter._anthropic_sdk") as mock_anthropic,
+        ):
+            agent = AIAgent(
+                api_key="sk-kimi-test",
+                base_url="https://api.kimi.com/coding/v1",
+                provider="kimi-coding",
+                quiet_mode=True,
+                skip_context_files=True,
+                skip_memory=True,
+            )
+            assert agent.api_mode == "anthropic_messages"
+            mock_anthropic.Anthropic.assert_called_once()
+
     def test_prompt_caching_claude_openrouter(self):
         """Claude model via OpenRouter should enable prompt caching."""
         with (
@@ -4501,6 +4519,36 @@ def test_fallback_to_anthropic_enables_prompt_caching(self, agent):
 
         assert agent._use_prompt_caching is True
 
+    def test_fallback_to_kimi_coding_sets_anthropic_messages_mode(self, agent):
+        agent._fallback_activated = False
+        agent._fallback_model = {
+            "provider": "kimi-coding",
+            "model": "kimi-k2.6",
+            "base_url": "https://api.kimi.com/coding/v1",
+        }
+        agent._fallback_chain = [agent._fallback_model]
+        agent._fallback_index = 0
+
+        mock_client = MagicMock()
+        mock_client.base_url = "https://api.kimi.com/coding"
+        mock_client.api_key = "sk-kimi-test"
+
+        with (
+            patch("agent.auxiliary_client.resolve_provider_client", return_value=(mock_client, None)),
+            patch("agent.anthropic_adapter.build_anthropic_client") as mock_build,
+            patch("agent.anthropic_adapter.resolve_anthropic_token", return_value=None),
+        ):
+            mock_build.return_value = MagicMock()
+            result = agent._try_activate_fallback()
+
+        assert result is True
+        assert agent.api_mode == "anthropic_messages"
+        assert agent.provider == "kimi-coding"
+        assert agent.model == "kimi-k2.6"
+        assert agent._anthropic_client is not None
+        assert agent.client is None
+        assert agent._client_kwargs == {}
+
     def test_fallback_to_openrouter_uses_openai_client(self, agent):
         agent._fallback_activated = False
         agent._fallback_model = {"provider": "openrouter", "model": "anthropic/claude-sonnet-4"}