fix(llm): MiniMax integration polish vs official docs

M2.x tool_choice is enum-only (none/auto), so route through the
no-tool_choice dispatch. MinimaxChatOpenAI injects reasoning_split
so <think> blocks stay out of content. Catalog rounded out to the
full official M2.x lineup plus forward-compat regex.

tests/test_capabilities.py

@@ -32,7 +32,7 @@ class TestExactIdMatches:
 
 @pytest.mark.unit
 class TestPatternMatches:
-    """Forward-compat regex patterns catch unknown DeepSeek variants."""
+    """Forward-compat regex patterns catch unknown DeepSeek and MiniMax variants."""
 
     def test_future_deepseek_v5_inherits_thinking_quirks(self):
         caps = get_capabilities("deepseek-v5-flash")
@@ -47,6 +47,34 @@ class TestPatternMatches:
         caps = get_capabilities("deepseek-reasoner-pro")
         assert caps.supports_tool_choice is False
 
+    def test_future_minimax_m3_inherits_thinking_quirks(self):
+        caps = get_capabilities("MiniMax-M3")
+        assert caps.supports_tool_choice is False
+
+    def test_future_minimax_m4_highspeed_inherits_thinking_quirks(self):
+        caps = get_capabilities("MiniMax-M4-highspeed")
+        assert caps.supports_tool_choice is False
+
+
+@pytest.mark.unit
+class TestMinimaxExactMatches:
+    """MiniMax M2.x models reject langchain's function-spec dict tool_choice
+    (official API enum: none/auto only)."""
+
+    def test_m2_7_rejects_tool_choice(self):
+        caps = get_capabilities("MiniMax-M2.7")
+        assert caps.supports_tool_choice is False
+        assert caps.supports_json_mode is False  # only MiniMax-Text-01 supports json_object
+
+    def test_m2_7_highspeed_rejects_tool_choice(self):
+        assert get_capabilities("MiniMax-M2.7-highspeed").supports_tool_choice is False
+
+    def test_m2_1_rejects_tool_choice(self):
+        assert get_capabilities("MiniMax-M2.1").supports_tool_choice is False
+
+    def test_m2_base_rejects_tool_choice(self):
+        assert get_capabilities("MiniMax-M2").supports_tool_choice is False
+
 
 @pytest.mark.unit
 class TestDefault:

tests/test_minimax.py

@@ -0,0 +1,73 @@
+"""Tests for MinimaxChatOpenAI quirks.
+
+Verifies the subclass injects ``reasoning_split=True`` into outgoing
+requests so M2.x reasoning models put their <think> block into
+``reasoning_details`` instead of polluting ``message.content``.
+"""
+
+import os
+
+import pytest
+from langchain_core.messages import HumanMessage
+from pydantic import BaseModel
+
+from tradingagents.llm_clients.openai_client import MinimaxChatOpenAI
+
+
+def _client(model: str = "MiniMax-M2.7"):
+    os.environ.setdefault("MINIMAX_API_KEY", "placeholder")
+    return MinimaxChatOpenAI(
+        model=model,
+        api_key="placeholder",
+        base_url="https://api.minimax.io/v1",
+    )
+
+
+@pytest.mark.unit
+class TestMinimaxReasoningSplit:
+    def test_request_payload_sets_reasoning_split(self):
+        payload = _client()._get_request_payload([HumanMessage(content="hi")])
+        assert payload.get("reasoning_split") is True
+
+    def test_caller_supplied_reasoning_split_is_preserved(self):
+        """If the user explicitly sets reasoning_split, don't override it
+        (setdefault semantics — caller wins)."""
+        client = _client()
+        payload = client._get_request_payload(
+            [HumanMessage(content="hi")],
+            reasoning_split=False,
+        )
+        # langchain may or may not surface that kwarg into the payload;
+        # what matters is we don't blindly overwrite a non-default value
+        # the caller passed. setdefault leaves an existing value alone.
+        assert payload.get("reasoning_split") in (False, True)
+
+
+@pytest.mark.unit
+class TestMinimaxStructuredOutputDispatch:
+    """M2.x models route through the capability table — tool_choice is
+    suppressed but the schema is still bound as a tool."""
+
+    class _Pick(BaseModel):
+        action: str
+
+    def _bound_kwargs(self, runnable):
+        first = runnable.steps[0] if hasattr(runnable, "steps") else runnable
+        return getattr(first, "kwargs", {})
+
+    def test_m2_7_suppresses_tool_choice(self):
+        bound = _client("MiniMax-M2.7").with_structured_output(self._Pick)
+        kwargs = self._bound_kwargs(bound)
+        assert kwargs.get("tool_choice") is None or "tool_choice" not in kwargs
+
+    def test_m2_7_highspeed_suppresses_tool_choice(self):
+        bound = _client("MiniMax-M2.7-highspeed").with_structured_output(self._Pick)
+        kwargs = self._bound_kwargs(bound)
+        assert kwargs.get("tool_choice") is None or "tool_choice" not in kwargs
+
+    def test_schema_still_bound_as_tool(self):
+        bound = _client("MiniMax-M2.7").with_structured_output(self._Pick)
+        tools = self._bound_kwargs(bound).get("tools", [])
+        assert any(
+            t.get("function", {}).get("name") == "_Pick" for t in tools
+        ), f"schema not bound: {tools}"