Adds a layered recovery cascade to the merger's pre-rebase stage so tasks
no longer get stuck in in-review when their declared dependency was
squash-merged to main and left orphan raw commits in the dependent's
history. Also prevents the orphan situation at the source for new tasks.
Why:
- 13 tasks were stuck in in-review for hours, all hitting the same
pre-merge rebase abort because they shared 6 raw commits inherited
from FN-2729's branch (declared baseBranch). FN-2729 was then
squash-merged to main, turning those raw commits into orphans whose
content is in main but in a different commit shape, conflicting with
later-merged tasks. The merger's `smart-prefer-main` strategy
correctly refused -X ours (which would silently re-introduce main's
deletions), but the only escape hatch was a 30-min cooldown loop
that retried the same impossible rebase forever.
Recovery cascade (merger.ts pre-rebase stage):
- Layer 1: surgical `git rebase --onto <main> <dep-tip> <branch>` when
task.baseBranch is set. Resolves the dep tip from the live branch ref
or recorded baseCommitSha; peels off the dep's inherited commits
cleanly. Captures the squash-merge-of-dep case end-to-end.
- Layer 2: generic patch-id duplicate-content stripping. Walks the last
500 main commits, computes patch-ids, then drops branch commits whose
patch-id matches and cherry-picks the remainder onto main. Captures
manual cherry-picks, double-merges, and any other duplicate-content
variant Layer 1 doesn't see. Restores the branch's pre-mutation SHA
on partial-failure so worst case leaves the worktree no worse than
before the recovery attempt.
- Layer 3: AI arbitration fall-through. If Layers 1+2 fail, log the
situation and proceed to the existing 3-attempt AI merge cascade
instead of throwing. The deterministic post-merge verification
(test + build) gates whatever the AI produces — that gate is what
enforces prefer-main's safety contract under fall-through (no silent
re-introduction of main's deletions).
- Critical: the unsafe `-X ours` Attempt 3 is suppressed under
fall-through. AI Attempts 1+2 are the only paths that can complete
the merge; if both fail and verification rejects them, the task
bounces back to in-progress via the existing engine path rather than
silently merging.
Prevention (executor.ts worktree creation):
- When a task declares a non-main `baseBranch`, branch the worktree
off main (origin/<defaultBranch> when worktreeRebaseBeforeMerge is
enabled and a remote is resolvable; otherwise local rootDir HEAD)
and `git merge --squash` the dep's content as a single import commit.
The dependent branch then carries main's history + 1 commit instead
of inheriting the dep's raw commits, so a future squash-merge of the
dep produces patch-id-matching content that rebases cleanly.
- Honors settings: respects `worktreeRebaseBeforeMerge`,
`worktreeRebaseRemote`, and falls back to local HEAD when no remote
is resolvable. Fully fail-soft: any squash-import error falls back to
the legacy fork-from-dep behavior so worktree creation still works
for setups where the squash flow can't run.
Engine-side last-retry fix (project-engine.ts):
- Changed conflict-retry condition from `currentRetries < MAX` to
`currentRetries + 1 < MAX` so the bounce-to-in-progress code fires
in the same engine tick as the failing attempt, rather than relying
on a setTimeout-scheduled Nth attempt that dies on engine restart.
Without this, a dev-time engine restart between the 3rd and 4th
retry left the task with mergeRetries=MAX and only the 30-min
cooldown sweep could try again.
Tests:
- New "Layer 1 recovery" test asserts the surgical --onto rebase fires
when baseBranch is set and primary rebase aborts, and that Layer 3
fall-through is NOT triggered when Layer 1 succeeds.
- Updated the "no silent fall-through to -X ours" test to cover the
new fall-through path: even after Layers 1+2 fail and the merge
cascade proceeds, -X ours must not run, and the task log must record
both the Layer 3 fall-through entry and the Attempt 3 suppression.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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