[BUG] AgentCoreCodeInterpreter's _create_tool_result stringifies binary content, breaking readFiles for binary files #370
Description
Checks
- I have updated to the lastest minor and patch version of Strands
- I have checked the documentation and this is not expected behavior
- I have searched ./issues and there are no duplicates of my issue
Strands Version
0.2.19
Tools Package Version
0.2.19
Tools used
AgentCoreCodeInterpreter
Python Version
3.11.9
Operating System
Amazon Linux 2
Installation Method
other
Steps to Reproduce
- Execute code in sandbox that generates a PNG (e.g., matplotlib chart)
- Call
readFilesto retrieve it - Binary data is corrupted
Expected Behavior
readFiles returns binary content (bytes) that can be used to recreate files locally (e.g., PNG images generated by matplotlib).
Actual Behavior
Binary content is wrapped in str(), returning a string like "b'\x89PNG\r\n...'" instead of actual bytes.
Additional Context
When reading binary files (e.g., PNG images) via readFiles, the _create_tool_result method wraps content in str(), destroying binary data.
Discovered while trying to generate matplotlib charts in the sandbox and retrieve the PNG files.
Location
src/strands_tools/code_interpreter/agent_core_code_interpreter.py, line ~495
Current behavior
return {
"status": "success" if not is_error else "error",
"content": [{"text": str(result.get("content"))}], # Destroys binary
}Binary content becomes a string like "b'\\x89PNG\\r\\n...'" instead of actual bytes.
Possible Solution
Patched the issue with:
def _create_tool_result(self, response: Dict[str, Any]) -> Dict[str, Any]:
"""Create tool result from response without stringifying resource content."""
if "stream" in response:
event_stream = response["stream"]
for event in event_stream:
if "result" in event:
result = event["result"]
content = result.get("content")
is_error = response.get("isError", False)
# Preserve content structure instead of stringifying
if isinstance(content, list):
return {
"status": "success" if not is_error else "error",
"content": content,
}
# Fall back to text wrapping for non-list content
return {
"status": "success" if not is_error else "error",
"content": [{"text": str(content)}],
}
return {
"status": "error",
"content": [{"text": f"Failed to create tool result: {response}"}],
}
return responseThis worked for my use case.
Related Issues
No response