Fix tournament bracket corruption after started mutations

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Bug and impact

• Editing a completed earlier category knockout match could reset its direct child but leave deeper completed matches (for example the final/champion) intact with stale winners, corrupting persisted bracket results.
• Several destructive roster/group write paths still allowed changes after tournament start: single guest deletion, new team creation, group rebalance, and team group changes. These could desync teams, entries, classification matches, standings, and fixtures mid-event.

Root cause

• recomputeCategoryBracketAfterWinnerChange built the completed-match winner map once, so downstream matches continued to trust winners from matches that were being reset in the same operation.
• Recent started guards were applied to sibling endpoints but not to all write paths that mutate teams/entries/group assignments.

Fix

• Recompute category bracket invalidation to a fixed point, excluding already-invalidated matches from winner/loser maps before applying resets and slot updates.
• Block post-start group rebalance/team creation/team group changes/single guest deletion with the existing tournament-started invariant, plus a defensive match-lock check in rebalance.
• Add regression tests for transitive bracket reset and rebalance start guard.

Validation

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

  

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Project	Deployment	Actions	Updated (UTC)
matchpoint	Ready	Preview, Comment	May 24, 2026 10:41am