Fix post-start tournament corruption paths

[cursor]

Bug and impact

• Post-start deleteGuestPlayer could dissolve a team that already had classification/category matches, leaving persisted matches pointing at a deleted team.
• Post-start group rebalancing and direct groupIndex PATCHes could rewrite team group placement without regenerating classification fixtures, desynchronizing standings/fixtures from persisted matches.
• Correcting a completed knockout winner could reset an intermediate match while later matches still consumed that intermediate match's stale winner.

Root cause

• UI-level locks were not mirrored by server guards for single guest deletion, rebalance, or team group changes.
• Bracket recompute built winner/loser maps from the pre-reset match snapshot and did not cascade invalidation to descendants of reset matches.

Fix

• Block single guest deletion and team group changes after tournament start.
• Make group rebalancing reject started tournaments and any tournament with in-progress/completed matches.
• Cascade knockout recompute resets so descendants of reset matches clear dependent slots instead of using stale winners.
• Added focused regression tests for rebalance guards and knockout cascade behavior.

Validation

• npm test -- --run tests/criticalTournamentMutations.test.ts
• npm test
• npm run typecheck
• npm run lint (passes with existing warnings)

  

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Project	Deployment	Actions	Updated (UTC)
matchpoint	Ready	Preview, Comment	May 29, 2026 10:44am