[BUG] Strands Swallows Tool Call Errors

[mattdai01]

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

1.33

Python Version

3.12

Operating System

macOS/AL2023

Installation Method

pip

Steps to Reproduce

The exception flow is:

1. Tool raises → _stream() catches it at ~line 259
2. _stream() builds error_result = {"status": "error", ...} and yields ToolResultEvent
3. _stream_with_trace() receives the ToolResultEvent and calls end_tool_call_span(span, result) — without the error param
4. In tracer.py, end_tool_call_span() falls into the else branch → span.set_status(StatusCode.OK)

The exception object is lost before end_tool_call_span is ever called.

gen_ai.tool.status: "error" attribute IS correctly set — but the span StatusCode remains OK.

Expected Behavior

Tool spans should have StatusCode.ERROR when result["status"] == "error".

This is critical because Langfuse relies on this error code to raise alarms/statistics on failed tool calls. Without this, it is difficult to see which tools failed.

Actual Behavior

When a tool raises, Strands catches it and produces this ToolResult dict:
1{
2 "toolUseId": "",
3 "status": "error", # ← error IS here
4 "content": [{"text": "Error: ValueError - some message"}] # ← message too
5}This is wrapped in a ToolResultEvent and yielded. The original exception object is gone — only the dict survives.
So for the GitHub issue's Actual Behavior section:The tool span always gets StatusCode.OK. The error is recorded — but only as a string in result["content"][0]["text"] and gen_ai.tool.status: "error" attribute. The Python exception object is dropped, so end_tool_call_span never sees it and always calls span.set_status(StatusCode.OK).

Additional Context

No response

Possible Solution

No response

Related Issues

No response