Configurable custom actions when a task is settled (e.g. clean build artifacts)

[phob]

Request

I'd like to configure custom actions that run automatically when a task/thread is settled in T3 Code.

My current workflow

1. T3 Code creates a new worktree for a task.
2. I work in that worktree, compile the code, and test the prepared build.
3. Once I'm satisfied and ready to merge, I use T3 Code's settling workflow to finish the task.
4. I manually trigger a cleanup action using a keyboard shortcut to remove the remaining build artifacts.

This last step is especially relevant for Rust projects, where build artifacts can take up several gigabytes per worktree. With multiple tasks, those leftovers quickly consume a lot of disk space.

Proposed behavior

Add an “on task settled” trigger for configurable custom actions. I could assign my existing cleanup action to that trigger and have it run automatically after the task is successfully settled, including when T3 Code settles it automatically, instead of remembering to press a shortcut every time.

Ideally, users could:

• Assign one or more custom actions to the task-settled event.
• Configure actions per project, since different projects need different cleanup commands.
• Run actions in the relevant task's worktree, with clear execution timing if settling also removes the worktree.
• See whether an action succeeded or failed.

For my use case, this could run cargo clean for a Rust project or the appropriate cleanup command for another build system. I want to keep builds available while working and testing, then clean up once the task is settled. Cleaning build artifacts should also be possible while retaining the worktree and conversation.

The trigger should represent the task/thread becoming settled, rather than an individual agent turn finishing. A configurable trigger would also support other post-task workflows beyond cleanup.

Related discussions

I searched existing issues and discussions and found related proposals, but none specifically covering assigning ordinary custom project actions to a task-settled trigger:

• Project actions: running state, stop, and auto-stop when a thread settles #11254 proposes stopping running project actions when a thread settles. This request is about starting a configured action at that point, such as a cleanup command.
• Workspace providers: pluggable create/remove commands (rift, CoW clones, Worktrunk), with support for non-git directories and cleanup on settle #11266 proposes configurable workspace creation/removal commands and removal on settle. This request can work with existing Git worktrees and does not require removing the workspace.
• [Feature]: Clean up worktrees for settled threads without deleting history #6856 and [Feature]: Add per-project retention limits for settled worktrees #6999 discuss removing settled worktrees or retaining a limited number. A comment on [Feature]: Clean up worktrees for settled threads without deleting history #6856 also suggests hooks before worktree deletion; the trigger requested here is settlement itself, even when the worktree is retained.

The smallest useful version would be a per-project option on a custom action to run when a task is settled, using the task's worktree as its working directory and exposing the execution result.