AgentFixboard
OpenLast checked LangGraph#tool-calls#error-messages

interrupt() inside a tool is reported as a tool-error on the tools stream

A tool that calls interrupt() emits a tools stream event {'event': 'tool-error', 'tool_call_id': 'tc1', 'message': "(Interrupt(value='ok?', id='...'),)"} instead of pausing only on __interrupt__. The structured Interrupt id and value are flattened to str(error).

From GitHub

langchain-ai/langgraph

Issue

Difficulty
Easy
Time
~5 min
Steps
2
Fixed in
—
Last checked

Not fixed upstream yet: the issue is open. Source: issue open. Last checked 2026-10-20.

Symptom

A tool that calls interrupt() emits a tools stream event {'event': 'tool-error', 'tool_call_id': 'tc1', 'message': "(Interrupt(value='ok?', id='...'),)"} instead of pausing only on __interrupt__. The structured Interrupt id and value are flattened to str(error).

Evidence what you'll see

  • The report's print for stream_mode=["tools"] is {'event': 'tool-started', ...} then that tool-error payload. The expected tools stream is only tool-started.
  • The handler is StreamToolCallHandler._error in libs/langgraph/langgraph/pregel/_tools.py, which sends "event": "tool-error" and "message": str(error) for every exception.
  • Reproduced on main and on langgraph 1.2.6, Python 3.12.

Why it happens

GraphInterrupt is a GraphBubbleUp control-flow pause, not a tool failure. _runner, _executor, and _retry already skip GraphBubbleUp. The tools stream handler does not, so a pause is labeled tool-error and the Interrupt objects are lost.

Affected versions

langgraph 1.2.6 and main, Python 3.12. The linked issue does not name an operating system.

Fix steps

0 of 2 done

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How to check it worked

  • A tool that return interrupt(question) emits tool-started on the tools stream and no tool-error, and graph.get_state(config).interrupts still has the Interrupt id and value.

If it still fails

  • Pull requests 8219 and 8282 skip tool-error when isinstance(error, GraphBubbleUp) and were closed without merge.
  • The linked issue does not name a release that keeps the Interrupt payload on the tools stream.

Sources and credit

Summarized in our own words from these public reports. Credit goes to their authors.

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