fix(provider): preserve Bedrock tool config for history

Co-authored-by: Cursor <cursoragent@cursor.com>

nanobot/providers/bedrock_provider.py

@@ -18,6 +18,7 @@ _IMAGE_DATA_URL = re.compile(r"^data:image/([a-zA-Z0-9.+-]+);base64,(.*)$", re.D
 _TEXT_BLOCK_TYPES = {"text", "input_text", "output_text"}
 _TEMPERATURE_UNSUPPORTED_MODEL_TOKENS = ("claude-opus-4-7",)
 _ADAPTIVE_THINKING_ONLY_MODEL_TOKENS = ("claude-opus-4-7",)
+_NOOP_TOOL_NAME = "nanobot_noop"
 
 
 def _deep_merge(base: dict[str, Any], override: dict[str, Any]) -> dict[str, Any]:
@@ -325,6 +326,27 @@ class BedrockProvider(LLMProvider):
             result.append({"toolSpec": spec})
         return result or None
 
+    @staticmethod
+    def _contains_tool_blocks(messages: list[dict[str, Any]]) -> bool:
+        for msg in messages:
+            content = msg.get("content")
+            if not isinstance(content, list):
+                continue
+            for block in content:
+                if isinstance(block, dict) and ("toolUse" in block or "toolResult" in block):
+                    return True
+        return False
+
+    @staticmethod
+    def _noop_tool() -> dict[str, Any]:
+        return {
+            "toolSpec": {
+                "name": _NOOP_TOOL_NAME,
+                "description": "Internal placeholder for Bedrock tool history validation.",
+                "inputSchema": {"json": {"type": "object", "properties": {}}},
+            }
+        }
+
     @staticmethod
     def _convert_tool_choice(
         tool_choice: str | dict[str, Any] | None,
@@ -389,11 +411,16 @@ class BedrockProvider(LLMProvider):
             kwargs["additionalModelRequestFields"] = additional
 
         bedrock_tools = self._convert_tools(tools)
+        tool_config: dict[str, Any] | None = None
         if bedrock_tools:
-            tool_config: dict[str, Any] = {"tools": bedrock_tools}
+            tool_config = {"tools": bedrock_tools}
             choice = self._convert_tool_choice(tool_choice)
             if choice:
                 tool_config["toolChoice"] = choice
+        elif self._contains_tool_blocks(bedrock_messages):
+            tool_config = {"tools": [self._noop_tool()]}
+
+        if tool_config:
             kwargs["toolConfig"] = tool_config
 
         return kwargs

tests/providers/test_bedrock_provider.py

@@ -106,6 +106,7 @@ def test_generic_bedrock_model_keeps_temperature_and_skips_anthropic_thinking()
     assert kwargs["modelId"] == "amazon.nova-lite-v1:0"
     assert kwargs["inferenceConfig"] == {"maxTokens": 1024, "temperature": 0.3}
     assert "additionalModelRequestFields" not in kwargs
+    assert "toolConfig" not in kwargs
 
 
 def test_build_kwargs_converts_messages_tools_and_tool_results() -> None:
@@ -160,6 +161,39 @@ def test_build_kwargs_converts_messages_tools_and_tool_results() -> None:
     assert kwargs["toolConfig"]["toolChoice"] == {"any": {}}
 
 
+def test_build_kwargs_keeps_tool_config_for_historical_tool_blocks_without_tools() -> None:
+    provider = BedrockProvider(region="us-east-1", client=FakeClient())
+    messages = [
+        {"role": "user", "content": "read x"},
+        {
+            "role": "assistant",
+            "content": "",
+            "tool_calls": [{
+                "id": "toolu_1",
+                "type": "function",
+                "function": {"name": "read_file", "arguments": '{"path": "x"}'},
+            }],
+        },
+        {"role": "tool", "tool_call_id": "toolu_1", "name": "read_file", "content": "ok"},
+        {"role": "user", "content": "continue"},
+    ]
+
+    kwargs = provider._build_kwargs(
+        messages=messages,
+        tools=[],
+        model="bedrock/anthropic.claude-opus-4-7",
+        max_tokens=1024,
+        temperature=0.7,
+        reasoning_effort=None,
+        tool_choice=None,
+    )
+
+    assert any("toolUse" in block for msg in kwargs["messages"] for block in msg["content"])
+    assert any("toolResult" in block for msg in kwargs["messages"] for block in msg["content"])
+    assert kwargs["toolConfig"]["tools"][0]["toolSpec"]["name"] == "nanobot_noop"
+    assert "toolChoice" not in kwargs["toolConfig"]
+
+
 def test_parse_response_maps_text_tools_reasoning_usage_and_stop_reason() -> None:
     response = {
         "output": {