fix: prune stale tool results during session repair

Author: he-yufeng

src/strands/session/repository_session_manager.py

@@ -282,13 +282,34 @@ def _fix_broken_tool_use(self, messages: list[Message]) -> list[Message]:
                     ]
 
                     # Check if there are more messages after the current toolUse message
-                    tool_result_ids = [
-                        content["toolResult"]["toolUseId"]
-                        for content in messages[index + 1]["content"]
-                        if "toolResult" in content
-                    ]
+                    next_message_content = messages[index + 1]["content"]
+                    seen_tool_result_ids: set[str] = set()
+                    cleaned_next_message_content = []
+                    removed_orphaned_tool_results = False
+                    for content in next_message_content:
+                        if "toolResult" not in content:
+                            cleaned_next_message_content.append(content)
+                            continue
+
+                        tool_result_id = content["toolResult"]["toolUseId"]
+                        if tool_result_id in tool_use_ids and tool_result_id not in seen_tool_result_ids:
+                            seen_tool_result_ids.add(tool_result_id)
+                            cleaned_next_message_content.append(content)
+                        else:
+                            removed_orphaned_tool_results = True
 
-                    missing_tool_use_ids = list(set(tool_use_ids) - set(tool_result_ids))
+                    if removed_orphaned_tool_results:
+                        logger.warning(
+                            "Session message history has orphaned or duplicate toolResult blocks. "
+                            "Removing them to keep toolUse/toolResult pairs valid."
+                        )
+                        messages[index + 1]["content"] = cleaned_next_message_content
+
+                    tool_result_ids = list(seen_tool_result_ids)
+
+                    missing_tool_use_ids = [
+                        tool_use_id for tool_use_id in tool_use_ids if tool_use_id not in tool_result_ids
+                    ]
                     # If there are missing tool use ids, that means the messages history is broken
                     if missing_tool_use_ids:
                         logger.warning(

tests/strands/session/test_repository_session_manager.py

@@ -370,6 +370,35 @@ def test_fix_broken_tool_use_extends_partial_tool_results(existing_session_manag
     assert missing_result["toolResult"]["content"][0]["text"] == "Tool was interrupted."
 
 
+def test_fix_broken_tool_use_prunes_extra_tool_results(session_manager):
+    """Test fixing a user message with extra toolResults before adding missing ones."""
+    messages = [
+        {
+            "role": "assistant",
+            "content": [
+                {"toolUse": {"toolUseId": "complete-123", "name": "test_tool", "input": {"input": "test1"}}},
+                {"toolUse": {"toolUseId": "missing-456", "name": "test_tool", "input": {"input": "test2"}}},
+            ],
+        },
+        {
+            "role": "user",
+            "content": [
+                {"toolResult": {"toolUseId": "complete-123", "status": "success", "content": [{"text": "result"}]}},
+                {"toolResult": {"toolUseId": "complete-123", "status": "success", "content": [{"text": "dup"}]}},
+                {"toolResult": {"toolUseId": "stale-999", "status": "success", "content": [{"text": "stale"}]}},
+            ],
+        },
+    ]
+
+    fixed_messages = session_manager._fix_broken_tool_use(messages)
+
+    tool_results = [content["toolResult"] for content in fixed_messages[1]["content"] if "toolResult" in content]
+    assert [tool_result["toolUseId"] for tool_result in tool_results] == ["complete-123", "missing-456"]
+    missing_result = next(tool_result for tool_result in tool_results if tool_result["toolUseId"] == "missing-456")
+    assert missing_result["status"] == "error"
+    assert missing_result["content"][0]["text"] == "Tool was interrupted."
+
+
 def test_fix_broken_tool_use_handles_multiple_orphaned_tools(existing_session_manager):
     """Test fixing multiple orphaned toolUse messages."""