The claim verb both claims and starts the task — there is no separate `start` call. For developers, `i_will_work_on` also creates the `feature/{team}/{task-hierarchy}` branch and **adds a dedicated per-task worktree** at `{clone_root}/.worktrees/{task-id-first-8}/`, checking out the branch there. Your container is started with that worktree as its cwd, and the clone root's HEAD is never moved by the claim — so a second claim (or a coordinator PM's many parallel roots) never overwrites your first task's uncommitted work. See `docs/rag/architecture/workspaces.md` for the worktree model.
Exactly one active WorkSession exists per task at a time (enforced in the service layer and by a DB unique index). A re-claim — pool release, reaper unclaim, escalation redirect — supersedes any prior agent's stale active session for that task and re-points the worktree at the new claim.
1. Check you have capacity (developers / QA / documenters work one task at a time; **PM coordinators are exempt** — a Main / Cell PM may hold many roots at once, gated only by sequence dependencies)
- **One at a time (workers only)**: Developers, QA, and documenters can't hold multiple in-progress tasks at once. A **blocked** task still counts as active — a blocked dev cannot `claim` a second task; unblock or `unclaim` first. **PM coordinators are exempt** — a Main / Cell PM plans and delegates many roots in parallel, so it may hold several at once; only a real upstream **sequence dependency** (an unfinished task it depends on) holds one of its roots back.
`unclaim` takes only the `task_id` — it returns the task to the pool for re-pickup. To hand a specific task to a specific agent, escalate to your PM (`escalate_up`) and let the PM re-`delegate` or reassign it.
