Root cause: addParticipant appended participant to participants[] without
checking id uniqueness. Two participants with same id in array. On
togglePause resume, turnOrderIds rebuilt via sort → dup id appears twice.
nextTurn then stuck repeating that id (rotation breaks).
This was the enabling step for BUG-1's full corruption (audit chain):
pause blocks advance → totalTurns frozen → addParticipant re-adds
same r${totalTurns} id → resume dup → nextTurn stuck.
Fix: throw on duplicate id in addParticipant. Caller must use fresh id
(crypto.randomUUID in App, replay already does).
Evidence:
- Test: 'addParticipant rejects duplicate id' (was test.skip, now live).
- Pre-fix: 1 RED (Received function did not throw).
- Post-fix: 50 green (shared), 23 green (server), 62 green (FE).
- Reachability in normal app: low (App uses crypto.randomUUID) but no
guard existed before. Defensive + unblocks BUG-1 isolation.
No other behavior changed.
david raistrick
d35a730e12