test(beyondleetcode): C43b multi-user fixture stops timing out on the shared database

[GauranshMathur]

Test-only fix for the "Operation has timed out" flake on the shared Multi-user test database (C43b). Only src/routes/users/multi-fixture.ts and playwright.config.ts change; no production code.

Root cause

Prisma's "Operation has timed out" (P1008) is SQLITE_BUSY. Two causes stack:

1. libSQL's busy timeout defaults to 0, and createDb does not set one, so a write that meets another process's lock fails at once.
2. Prisma's libSQL adapter opens transactions as deferred (read, then write). SQLite refuses a read-to-write upgrade at once, whatever the timeout, when another connection holds the write lock. A busy timeout alone does not fix this (reproduced: 3 processes x 40 ensureLearner calls still failed). Better Auth also swallows the error and throws "Failed to create user".

Fix

• multi-fixture.ts: the fixture opens its own client with a 10 s busy timeout, counts P1008 errors via a Prisma query extension, and retryWhenBusy re-runs ensureLearner / signIn (at most 4 attempts, jittered) only when a P1008 happened inside. Anything else (unique constraint, bad password) throws at once.
• playwright.config.ts: the 4174 test database is put in WAL mode (stored in the file). The server's own client (timeout 0, deferred transactions) was also failing sign-in in the e2e (P1008 in the server log), which the fixture cannot reach.

Results (flock .../BeyondLeetcode.worktrees/.playwright.lock bunx playwright test --project=e2e-multi, workers 4)

• Before WAL (fixture fix only): 6 of 10 runs passed; the 4 failures were all signin.multi.e2e.ts:353 where the server's own sign-in hit P1008.
• Final: 10 of 10 runs, 44 passed each; no P1008 in any log.
• Full bunx playwright test: 95 passed. biome check clean.

Follow-up (not done here, production code)

The app has the same exposure under concurrent writers: src/lib/server/db.ts could set a timeout and the adapter could begin transactions immediately. Worth a card.

Reviews

Self-review done. Codex second opinion skipped: test-only diff outside runner/learning/.github (board.md allows it). No security review for this card.

🤖 Generated with Claude Code