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fix(engine): harden worktree-pool branch creation and auto-reanchor foreign-only contamination

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WorktreePool.prepareForTask now rejects empty/"HEAD" base values and verifies
that the worktree's HEAD actually landed at the resolved base SHA after
`git checkout --detach`. This closes the FN-5432 / FN-5255 contamination
pattern where a recycled worktree branched from a stale HEAD (reflog:
"branch: Created from HEAD") and pinned the new task's tip to the previous
occupant's commit.

SelfHealingManager.tryReanchorForeignOnlyContamination is invoked from both
PR-conflict and self-owned-branch-conflict catch sites before the
unrecoverable-pause path. When the conflicted branch carries only foreign
commits (no own work), the branch is reset to base via the existing
recoverForeignOnlyContamination flow instead of being escalated for human
adjudication.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
gsxdsm
2026-05-22 04:13:15 -07:00
parent 3a0d179ba2
commit 2d661df870
3 changed files with 101 additions and 0 deletions
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"@runfusion/fusion": patch
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fix(engine): prevent worktree-pool branch creation from inheriting a previous occupant's tip, and auto-reanchor branches that already inherited foreign commits.
- `WorktreePool.prepareForTask` now rejects empty/`HEAD` base values and verifies post-detach HEAD matches the resolved base SHA before creating the branch. This closes the FN-5432 / FN-5255 contamination pattern where recycled worktrees branched from a stale HEAD (reflog: `branch: Created from HEAD`) and pinned the new task's tip to the previous task's commit.
- `SelfHealingManager` now attempts a foreign-only contamination reanchor before pausing a task with `branch-conflict-unrecoverable`. When the task's branch carries only foreign commits (no own work), the branch is reset back to its base via the existing `recoverForeignOnlyContamination` path instead of stranding the task for human adjudication.