sync-wasm connect() fails with 'unexpected path .db-log: files must be created in advance for OPFS IO'

TL;DR: if @tursodatabase/sync-wasm connect() rejects with unexpected path fresh-[id].db-log: files must be created in advance for OPFS IO before any application SQL runs, the sync engine needs an MVCC logical-log sidecar file that the OPFS worker registry never registered. Use 0.8.0-pre.9 or newer, where PR #8524 registers the MVCC log path before connecting. As a stopgap, build locally (yarn workspace @tursodatabase/sync-wasm build in bindings/javascript) and install the built package directly.

Internal error: unexpected path fresh-[id].db-log: files must be created in advance for OPFS IO

Steps

1. Upgrade:

npm install @tursodatabase/sync-wasm@^0.8.0-pre.9

Expected: the installed build includes PR #8524.

2. Re-run connect() against the hosted database.

   Expected: the connection proceeds to sync. Success check: application SQL runs without the db-log error.

When to use this

• sync-wasm 0.7.2 through 0.8.0-pre.7, hosted Turso database negotiating MVCC sync.
• The error names a .db-log path.

When NOT to use this

• Non-MVCC sync setups; the sidecar requirement is MVCC-specific.
• Local-only databases; OPFS registration is about the sync path.

Compatibility

• @tursodatabase/sync-wasm 0.8.0-pre.9+. The maintainer re-tagged main to push it to npm after the pre.8 release job failed.

Variant phrasings

• "sync-wasm connect db-log OPFS"
• "turso sync-wasm MVCC unexpected path"

Root cause

The JavaScript OPFS worker registry registered the main db, -wal, -wal-revert, -info, and -changes paths but not the MVCC log sidecar, so the sync engine's first access to it was rejected.

Edge cases

• The local-build stopgap works but you lose npm updates; prefer the fixed release.

Source: https://github.com/tursodatabase/turso/issues/8516