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Stage 12 failure records keep only the exception class name

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@anth-volk is already working on this.

Since Oct 13, 2026.

  • #791 by @anth-volk — open

Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
25/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Stale
Tech stack
python
Domain
backend

Research direction

Start in the Stage 12 coordinator, worker and result-comparison handlers, where error_summary is set from type(error).__name__ and RuntimeError("Stage 12 report coordination failed") is raised. Check where a worker's saved cause is overwritten by the wait error. Pull request #791 is already open against this issue, so review it before starting. Done means the record keeps a redacted cause (type, stage, role, message) without secrets or input values, a worker-saved cause survives, and the exceptions returned to Modal are unchanged.

Written by the indexing model from the issue text.

Description

Problem

Stage 12 failure records don't say what went wrong. The coordinator, worker and result-comparison handlers store only type(error).__name__ in error_summary. They then raise RuntimeError("Stage 12 report coordination failed").

From 6 to 13 October 2026, 47 of the 153 production Stage 12 failures were recorded only as that generic coordination failure. Finding their causes meant replaying saved artifacts and reading retained Modal results. The causes turned out to be:

  • 42 a UK aggregate validation defect (#786)
  • 2 invalid reform parameter paths
  • 1 non-finite reform income
  • 1 congressional-district sample below the aggregation minimum
  • 1 database session limit

The coordinator can also overwrite a cause that a failed worker had already saved, replacing it with the class name of the wait error.

Expected

  • A failure record stores a bounded, redacted cause: the exception type, the failing or last finished stage, the simulation role, and the message.
  • Credentials, connection strings, tokens, signed URLs, validation input values and SQL parameters are never stored.
  • A cause saved by a worker is kept, not overwritten.
  • The exceptions returned to Modal are unchanged.
Dominant language
Python
Stars
1
Forks
1
Avg merge
1d 4h
Merged PRs (30d)
27

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