fix: normalize non-scalar prediction; harden predictions insert

tests/unit/test_harness_inference.py

@@ -559,6 +559,65 @@ class TestPredictionAlwaysWritten:
         assert rows[0]["prediction"] is None
 
 
+def _make_nonscalar_llm_response() -> LLMResponse:
+    """构造 submit_answer 提交非标量 answer（list）的 LLMResponse。"""
+    content = json.dumps(
+        {
+            "reflect": {"observation": "找到答案"},
+            "plan": {"next_step": "提交"},
+            "action": {
+                "tool": "submit_answer",
+                "args": {
+                    "answer": ["B"],
+                    "evidence": "证据文本",
+                    "reasoning": "推理过程",
+                },
+            },
+        }
+    )
+    return LLMResponse(
+        content=content,
+        thinking="思考过程",
+        model="test-model",
+        provider="test",
+        prompt_tokens=100,
+        completion_tokens=50,
+        latency_ms=200,
+        ttft_ms=30.0,
+        max_inter_token_ms=5.0,
+        cache_hit=False,
+        call_id="test-call-nonscalar",
+    )
+
+
+class TestNonScalarPrediction:
+    """非标量 prediction 归一化 + 落库加固测试。"""
+
+    @pytest.mark.asyncio
+    async def test_nonscalar_prediction_does_not_crash(self, harness_log: HarnessLog) -> None:
+        """submit_answer 返回 {'answer': ['B']} 时归一化落库，不抛 sqlite 绑定异常。"""
+        llm = AsyncMock()
+        llm.chat.return_value = _make_nonscalar_llm_response()
+
+        result = await run_inference(
+            [_make_question(answer="B")],
+            llm=llm,
+            tool_dispatch_fn=_stub_tool_dispatch,
+            prompt_builder=_stub_prompt_builder,
+            log=harness_log,
+            run_id="run-nonscalar",
+            concurrency=1,
+            max_steps=10,
+            skill_mode="auto",
+        )
+
+        assert result.total == 1
+        rows = harness_log.query("SELECT * FROM predictions WHERE run_id = ?", ("test-run",))
+        assert len(rows) == 1
+        # prediction 被 JSON 序列化为字符串，不再是 Python list
+        assert rows[0]["prediction"] == '["B"]'
+
+
 class TestPluginsFactory:
     """plugins_factory 调用测试。"""