PowerSync + TanStack DB Cross-Tab Bug Reproduction

This demonstrates data inconsistency issues when using TanStack DB's PowerSync collection across multiple browser tabs.

Observed Behavior

• Each tab only sees its own changes
• Cross-tab updates never appear in TanStack collections
• SQLite has all the data (verified via direct query)

To Reproduce

1. yarn dev
2. Open two tabs
3. Add an item in Tab A → Tab A sees it, Tab B doesn't
4. Add an item in Tab B → Tab B sees it, Tab A doesn't
5. Click "Query SQLite" in any tab → All items are there
6. Refresh any tab → All items appear (data was in SQLite all along)

Root Cause

TanStack DB uses TEMP triggers + BroadcastChannel table name mismatch

Each tab creates a randomly-named tracking table and TEMP trigger:

// @tanstack/powersync-db-collection/src/powersync.ts:275-280
const trackedTableName = `__${viewName}_tracking_${Math.floor(
  Math.random() * 0xffffffff
).toString(16).padStart(8, '0')}`;

The collection then listens for changes to this tracking table:

// Line ~360
onChangeWithCallback({ tables: [trackedTableName] })

But when PowerSync's BroadcastChannel notifies tabs of changes, it sends the actual table name (items), not the random tracking table names.

Source code: https://github.com/TanStack/db/blob/main/packages/powersync-db-collection/src/powersync.ts#L275-L280

Potential Fixes

1. Listen to BOTH the source table AND the tracking table for change notifications
2. Use a deterministic tracking table name so all tabs can share triggers
3. Add BroadcastChannel in TanStack DB to explicitly notify collections across tabs