I think this is a bug in the PowerSync Capacitor path on iOS.

Sync fails with:

Run: failed(message: "Error in reading buffer")

I traced line_binary payloads getting passed into control() in SqliteBucketStorage.ts#L366
which calls:

tx.executeRaw('SELECT powersync_control(?, ?)', [op, payload])

In this specific case the params look like:

["line_binary", Uint8Array(...)]

PowerSync side:

• line_binary command: BucketStorageAdapter.ts#L71
• powersync_control call: SqliteBucketStorage.ts#L368

Capacitor SQLite iOS side:

• custom buffer handling in run(...): CapacitorSQLite.swift#L888
• throws Error in reading buffer: CapacitorSQLite.swift#L898

I think the fix probably belongs in PowerSync, at the Capacitor/native boundary. Normalizing Uint8Array before passing it into SQLite on iOS fixes it locally.