[Divergence] New storage.chunk_compaction_concurrency config option for storage version 4 compaction (powersync-service #793)

[benitav]

What's changing: Chunk-merge compaction on storage version 4 can now run concurrently across buckets instead of one at a time. A new storage.chunk_compaction_concurrency config option controls the shared worker limit, defaulting to 4 when object storage is enabled and 2 otherwise. Full compactions remain sequential.

High priority — existing docs are now inaccurate or incomplete
None identified.

For reviewer consideration — worth documenting

• Self-Hosted Instance Configuration (https://docs.powersync.com/configuration/powersync-service/self-hosted-instances), storage configuration reference: no entry exists yet for chunk_compaction_concurrency, which would sit alongside the existing max_pool_size and default_storage_version fields.

Source PR: powersync-ja/powersync-service#793 — merged 2026-09-10.

Filed automatically by Claude Code (claude-sonnet-5). A human must verify the scope, prepare the docs PR, and publish it only once this update has been released.