## Summary
- apply Fusion's existing stale-base reconciliation to freshly
reacquired and pooled execution worktrees
- advance retained task branches to the current local integration commit
after dependencies land
- keep planning and Worktrunk behavior unchanged while preserving
dirty/conflict fail-closed handling
## Problem
A dependent task can be planned before its dependency lands. If the
dependency merges and its branch is deleted, a later execution retry may
recreate the dependent worktree from its already-existing task branch.
That branch can still point at the pre-dependency commit.
Fusion already refreshes reused execution worktrees, but fresh
acquisition returned without calling the same reconciliation primitive.
The dependent task therefore executed without the landed dependency
output even though Fusion marked the dependency complete.
## Fix
When `refreshStaleBase` is enabled, run `refreshReusedWorktreeBase`
after a native fresh or pooled worktree is acquired and before cleanup,
init, or session execution. Track the actual backend used by injected
and fallback creators so a native fallback still refreshes while
Worktrunk-managed paths remain excluded. The existing primitive:
- resolves the current local integration branch without requiring a
remote
- resets branches with no task-owned commits
- rebases branches with task-owned commits
- blocks dirty or conflicting worktrees
- persists the integration commit as `baseCommitSha`
If refresh blocks a pooled checkout, clear the task's durable binding
before releasing the checkout for reuse.
Planning callers do not enable `refreshStaleBase`, so planning worktrees
remain unchanged.
## Verification
- `pnpm --filter @fusion/engine exec vitest run
src/__tests__/worktree-base-refresh.test.ts
src/__tests__/worktree-acquisition.test.ts --silent=passed-only
--reporter=dot` — 34 passed
- `pnpm --filter @fusion/engine typecheck`
- `pnpm --filter @fusion/engine build`
- `pnpm test:gate:static`
- `pnpm check:changesets`
- `git diff --check`
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Bug Fixes**
* Improved worktree acquisition by refreshing stale branches against the
current integration branch.
* Added refresh support for recreated, pooled, and native fallback
worktrees.
* Prevented task execution when refresh fails and safely released
affected pooled worktrees.
* Avoided unnecessary refreshes for newly created Worktrunk worktrees.
* **Tests**
* Added coverage for stale-base refresh behavior across supported
acquisition scenarios.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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