Echo DeepSeek thinking reasoning_content on the next turn.

HubAudio U11/U12/U38 400'd after a thinking-only review turn because
the retry dropped reasoning_content. Native client now appends that
field and continues; hierarchical sheet ingest stays in 2.60.10.

tests/test_deepseek_provider.py

@@ -182,31 +182,36 @@ def test_forced_tool_choice_disables_thinking():
     assert captured["tool_choice"]["function"]["name"] == "save_resolved_specs"
 
 
-def test_thinking_only_retries_with_thinking_disabled():
+def test_thinking_only_echoes_reasoning_content_on_follow_up():
+    """Live U11/U12/U38: thinking-only then retry without reasoning_content → 400."""
     calls: list[dict] = []
 
     class FakeCompletions:
         async def create(self, **kwargs):
             calls.append({
                 "thinking": kwargs["extra_body"]["thinking"]["type"],
+                "messages": kwargs["messages"],
             })
             usage = SimpleNamespace(
                 prompt_tokens=10, completion_tokens=5,
                 prompt_cache_hit_tokens=0, prompt_tokens_details=None,
             )
-            if kwargs["extra_body"]["thinking"]["type"] == "enabled":
+            if kwargs["extra_body"]["thinking"]["type"] == "enabled" and len(calls) == 1:
                 msg = SimpleNamespace(
                     content=None,
                     reasoning_content="pondering the schematic",
                     tool_calls=None,
+                    model_extra=None,
                 )
                 return SimpleNamespace(
                     choices=[SimpleNamespace(message=msg, finish_reason="stop")],
                     usage=usage,
                 )
-            fn = SimpleNamespace(name="get_pintable", arguments='{"ref":"U19"}')
+            fn = SimpleNamespace(name="get_pintable", arguments='{"ref":"U11"}')
             tc = SimpleNamespace(id="c1", function=fn)
-            msg = SimpleNamespace(content=None, reasoning_content=None, tool_calls=[tc])
+            msg = SimpleNamespace(
+                content=None, reasoning_content=None, tool_calls=[tc], model_extra=None,
+            )
             return SimpleNamespace(
                 choices=[SimpleNamespace(message=msg, finish_reason="tool_calls")],
                 usage=usage,
@@ -222,14 +227,14 @@ def test_thinking_only_retries_with_thinking_disabled():
 
     session = DeepSeekSession(
         client=FakeClient(),
-        model="deepseek-v4-pro",
+        model="deepseek-flash",
         system="sys",
         max_tokens=256,
         thinking=True,
         reasoning_effort="medium",
     )
     completion = asyncio.run(session.complete(
-        messages=[Message("user", [TextBlock("review U19")])],
+        messages=[Message("user", [TextBlock("review U11")])],
         tools=[ToolSchema(
             name="get_pintable", description="x",
             input_schema={"type": "object"},
@@ -238,10 +243,40 @@ def test_thinking_only_retries_with_thinking_disabled():
     ))
     assert len(calls) == 2
     assert calls[0]["thinking"] == "enabled"
-    assert calls[1]["thinking"] == "disabled"
+    assert calls[1]["thinking"] == "enabled"
+    asst = [m for m in calls[1]["messages"] if m.get("role") == "assistant"]
+    assert asst
+    assert asst[0]["reasoning_content"] == "pondering the schematic"
+    assert asst[0]["content"] == ""
     assert completion.tool_calls[0].name == "get_pintable"
 
 
+def test_completion_from_openai_reads_model_extra_reasoning():
+    fn = SimpleNamespace(name="get_pintable", arguments='{"ref":"U11"}')
+    tc = SimpleNamespace(id="c1", function=fn)
+    msg = SimpleNamespace(
+        content=None,
+        reasoning_content=None,
+        tool_calls=[tc],
+        model_extra={"reasoning_content": "need pin table"},
+    )
+    usage = SimpleNamespace(
+        prompt_tokens=10, completion_tokens=5,
+        prompt_cache_hit_tokens=0, prompt_tokens_details=None,
+    )
+    resp = SimpleNamespace(
+        choices=[SimpleNamespace(message=msg, finish_reason="tool_calls")],
+        usage=usage,
+    )
+    completion = completion_from_openai(resp)
+    assert completion.raw_assistant_blocks[0].reasoning_content == "need pin table"
+    out = messages_to_openai(
+        [Message("assistant", list(completion.raw_assistant_blocks))],
+        vision=False,
+    )
+    assert out[0]["reasoning_content"] == "need pin table"
+
+
 def test_tool_schema_and_choice():
     schema = ToolSchema(
         name="save_pintable",