Flaky integration test: blob.test.mjs 'Per-device-type LMDB database sharding' — schema missing from describe_all (shard 3/6) #1557

Symptom

integrationTests/apiTests/blob.test.mjs → "Per-device-type LMDB database sharding" fails intermittently in CI on Integration Tests shard 3/6, and passes on re-run with no code change. Two occurrences on the same PR (#1106) on 2026-07-01/02 alone — a PR whose diff is a pure formatter + test files that never touch blob/sharding code:

• Run 28542021803, Node v22: AssertionError: doorlock schema missing (in all three device-type schemas are visible in describe_all), then cascading SQL queries target each device database independently: expected 200 "OK", got 404 "Not Found", with HdbError: Table 'doorlock.DoorlockBlob' does not exist in the Harper log. Passed on re-run.
• Run 28558632042, Node v22 (re-run): same shape, different fixture — AssertionError: sensor schema missing, then the same 200→404 cascade. Passed on re-run.

Both times the same shard passed simultaneously on Bun, Node v24, Node v26, and Windows — the failure is timing-dependent, not version-deterministic (observed twice on v22, but the mechanism looks like scheduling luck rather than a v22 behavior).

Shape of the race

The failing assertion is schema visibility: a device-type schema (doorlock, sensor — varies per occurrence) created during setup is missing from a subsequent describe_all, and SQL against that device database then 404s. The suite itself times out around ~30s (Per-device-type LMDB database sharding (29992ms / 35174ms)). This smells like create-schema/table completing on one worker thread before the metadata is visible to the thread serving the next request — same eventual-consistency family as #1497 (async ITC not awaited) and adjacent to #687 (create_table returns success before table is available). Possibly a condition-wait issue per the AGENTS.md guidance (prefer waitFor(condition) over fixed sleeps).

Context

• The tests were added by Expand blob tests: multi-path blobPaths striping, per-device-type DB sharding #1195 ("Expand blob tests: multi-path blobPaths striping, per-device-type DB sharding", closed).
• Filed after the flake burned two re-run cycles on PR feat(models): add openaiStream() OpenAI-compatible SSE formatter #1106 in a single day; it's currently the most frequent CI red we're hitting on unrelated PRs.

Acceptance

• Root-cause the visibility race (or confirm it's a fixture-setup race) and fix, OR make the test's setup wait on actual schema visibility (waitFor-style condition on describe_all contents) rather than assuming synchronous visibility.
• No recurrence across ~20 consecutive shard-3 CI runs.

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