Registry race: concurrent uploads of the same file need a regression test (F1) #191

Raised by the product owner on 4 Nov 2026 as "F1: registry race" in the code review feedback. Not reproduced in this session.

Label clash. Issue #178 is also labelled "F1" and is a different defect (distinct rows discarded as duplicates). Keep both; the labels are not interchangeable.

What the code shows (verified at c7bebd1)

• Migration alembic/versions/0002_registry_unique.py adds UNIQUE (file_hash) and UNIQUE (file_name) on csv_files. These constraints enforce the registry invariant at the database.
• The check-then-insert in the upload path is not verified as race-free by any test in this session.

Proposed

• Add a concurrency regression: two simultaneous uploads of the same file, and two uploads with the same name and different content.
• Assert one registry row, and an attributable rejection for the second request, with no partial state left behind.

Done when

• The concurrency test passes on the candidate build, with its run output (passed, failed, skipped) attached.
• The same test fails when the file_hash UNIQUE constraint is removed (mutation check).

Generated by Claude Code