[Divergence] JS Web SDK adds additionalInitializationFunctions for statically linked wa-sqlite extensions (powersync-js #1151) #704

What's changing: The @powersync/web database open options gain additionalInitializationFunctions, an optional array of exported function names that custom wa-sqlite builds with statically linked extensions can use to initialize those extensions. The names are forwarded to local connections and database workers, including read-only workers. powersync_init_static runs first, then each additional no-argument export, and every return code is checked before the database opens. A nonzero return code from the core or an extension, or a missing export, now rejects opening the database. The default makes no additional calls. The change is in a pending minor changeset for @powersync/web and has not been released yet.

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

For reviewer consideration — worth documenting

• Using SQLite Extensions (https://docs.powersync.com/client-sdks/advanced/sqlite-extensions), JavaScript "Web" section: says loading extensions with @powersync/web requires a custom wa-sqlite build, but does not mention how to initialize statically linked extensions. No page covers additionalInitializationFunctions yet.
• Open docs PR Document custom SQLite artifact pairs and connection probes #688 ("Document custom SQLite artifact pairs and connection probes") expands the same page and states it describes the custom-build integration independently of this option.

Source PR: powersync-ja/powersync-js#1151 — merged 2026-10-19

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