parallel-pr-scope-overlap-tiebreaker-delta-checklisted

Before applying a handoff prompt's tiebreaker default ("merge the first-mover", "the clean-against-main one", "the one with reviewer APPROVE") to pick a winner between two parallel PRs that implemented the SAME scope, run `gh pr diff` on BOTH and audit for substantive deltas. Use when: (1) a session prompt or handoff doc surfaces a parallel-PR collision and recommends a tiebreaker, (2) two PRs targeting the same issue / same fix area are open simultaneously authored by different sessions, (3) the prompt's recommended winner is the older / cleaner / single-reviewer one — exactly the conditions under which "first-mover" rules can ship the inferior implementation, (4) you're tempted to skip the delta-check because the diffs "are probably substantively equivalent" or the prompt already analyzed them. Symptom of having skipped this check: weeks later a follow-up PR re-implements a correctness improvement that was already in the loser's diff. Sister to `synthetic-id-collision-rebase` (same-id register collisions; m
wan-huiyan/agent-traffic-control · ★ 2 · AI & Automation · score 79

Install: claude install-skill wan-huiyan/agent-traffic-control

# Pre-Tiebreaker Delta Check on Scope-Overlapping Parallel PRs ## Problem Two parallel sessions independently opened PRs targeting the same issue (same fix scope, same files, same goal). A session-handoff prompt later asks a third session to pick a winner. The prompt's recommended tiebreaker is some combination of: - "Merge the first-mover" (older PR by createdAt) - "Merge the one that's clean against main" (mergeable: CLEAN, no rebase needed) - "Merge the one with reviewer APPROVE" (assumed implies higher quality) - "Merge the one with wider scope" (e.g., bundles verification + handoff doc) These rules are about **merge mechanics**, not implementation quality. They can — and do — ship the inferior PR while the better implementation gets closed. ## Trigger Conditions ALL of the following must hold: 1. Two parallel PRs are open simultaneously, targeting overlapping scope (same issue number cited as `Closes #N`; same files touched; same fix intent). 2. A session-handoff prompt explicitly suggests a tiebreaker default ("merge #X because it's first-mover", "clean against main", "wider scope"), or you're operating from such instructions in auto-mode. 3. The two PRs were authored by different sessions (different worktrees, different branches, different timestamps, different commit authors or different `co-authored-by` chains). 4. You haven't yet run `gh pr diff <A>` and `gh pr diff <B>` side-by-side to compare implementations. If those conditions hold a