On a user's first login the authed shell fires several API calls at once;
each ran the JIT-provision path and raced to INSERT the same new user row,
tripping the partial unique index on auth_subject. The losing requests
500'd and the post-login SSR errored out. Use INSERT ... ON CONFLICT
(auth_subject) DO UPDATE ... RETURNING so concurrent callers converge on
the row the winner created. Regenerated the .sqlx offline query cache.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
