[Feature]: Run a project action before worktree removal (runOnWorktreeRemove), for resources outside the worktree

[mateosayas]

Before submitting

• I searched existing issues and did not find an open issue covering this exact behavior.
• I am describing a concrete problem or use case, not just a vague idea.

Area

apps/server

Problem or use case

runOnWorktreeCreate can start resources that live outside the worktree, for example a per-worktree Postgres container (docker compose -p <slug> up). There is no matching hook for removal.

When a thread is deleted in the UI, T3 Code removes the worktree directory, but the container and its volume stay. They accumulate until Docker consumes most of the machine's RAM and disk.

The teardown needs state that lives in the worktree (in our case a .dev/workspace.env holding the compose project name). Once the directory is gone, that state is gone too, so a cleanup after the fact cannot work reliably.

Proposed solution

Add an optional project action flag, runOnWorktreeRemove, that:

• runs in the worktree before git worktree remove
• receives T3CODE_WORKTREE_PATH / T3CODE_PROJECT_ROOT, like the create action
• applies to every removal path: manual thread delete, archive/settle cleanup, and the Storage cleanup rules

Smallest useful scope

Run the flagged action before git worktree remove on manual thread delete. The other removal paths can follow.

Alternatives considered

• A teardown script that runs our teardown and then removes the worktree: works, but the UI delete and archive buttons skip it.
• Cleanup after removal: the state the teardown needs is gone with the worktree directory.

Examples or references

• Project scripts: add worktree deletion lifecycle hooks #425 and feat(worktrees): run actions before removal #9337 both implemented this. feat(worktrees): run actions before removal #9337 was closed so V2 can land first; this Discussion records the request so it can be part of the V2 design.
• Related: Configurable custom actions when a task is settled (e.g. clean build artifacts) #12522, Workspace providers: pluggable create/remove commands (rift, CoW clones, Worktrunk), with support for non-git directories and cleanup on settle #11266, [Feature]: Clean up worktrees for settled threads without deleting history #6856.

Contribution

• I would be open to helping implement this.