Code change ticket. Invoke dev-loop first (mandatory), then explore sentinel parsing.

My huge parallel batches caused cascade cancellations — one Bash failing killed all siblings. Tool layer fine. Restarting clean, sequential. Key facts from results that DID land: cwd branch is `slot2/mc-MC-4455` (not 4457 — slot mis-claim), `ticket_runtime.py` not in cwd root, `scripts/mc_signal_lib.py` is phantom, Grep tool unavailable. Locate real file first.

Clean ground truth now. `ticket_runtime.py` does not exist anywhere in repo (find = 0 in worktree AND main workspace; not in git ls-files). Slot on wrong branch (MC-4455). Locating where sentinel parsing actually lives for an accurate handoff.

Confirmed scope now. Line-prefix sentinel parsing lives entirely in **mc_pickup.py** (harvest path, ~lines 5810–7250), not the non-existent `ticket_runtime.py`. JSON mc_signal canonical path = mc-coord MCP (`mc_coordination_mcp.py` → `state/mc-signals/MC-*.json`, which just worked). `mc_coord_server.py` and `mission-control/app.py` not present at those paths in this slot. Recording precise handoff, then parking on the hard infra blocker.

REVIEW: MC-4457 parked — blocked, no code changed. Two problems found. **Wrong target file.** Ticket says edit `ticket_runtime.py` — that file does not exist anywhere (`find` = 0 in worktree + main workspace, not in `git ls-files`). FINAL-ASSESSMENT.md Item #8 mis-named it. Real line-prefix sentinel parsing lives in **mc_pickup.py** harvest path: - `startswith("DONE:"/"REVIEW:"/"QUESTION:")` checks: lines 5813–5883 (incl. DONE→REVIEW rewrite), 5919–6026 (dispatch-by-prefix), 6660–6666, 6868, 7191–7243 - worker-prompt fallback instruction: line 5210 - JSON `mc_signal` canonical path already works via mc-coord MCP (`mc_coordination_mcp.py` → durable `state/mc-signals/MC-*.json`) — verified, this very review wrote one. - `scripts/mc_signal_lib.py` cited in scoping = phantom, doesn't exist. **Wrong branch (hard blocker).** Pool slot pool-2 is checked out on `slot2/mc-MC-4455`, not `slot2/mc-MC-4457`. Committing here lands 4457 work on another ticket's branch and risks clobbering an MC-4455 worker. Documented slot mis-registration (mem 7192). Did not force edits — mc_pickup.py is the 329KB dispatch core; its prefix-fallback affects every worker's harvest, so deprecating it needs a clean slot + verification that all runtimes can emit JSON mc_signal, not a blind edit on the wrong branch. **Safe retry:** re-provision a clean slot branched `slot{N}/mc-MC-4457` off origin/main → re-dispatch with corrected target (mc_pickup.py prefix lines above) → add fence-aware guard as interim → keep line-prefix as deprecated-but-present fallback until every runtime confirmed JSON-capable. Do not retry in this slot. {"mc_signal":"REVIEW","ticket":"MC-4457","nonce":"MC_TICKET_TURN:4461:1780141947562:c060e064","payload":"Parked: target file ticket_runtime.py doesn't exist (real logic in mc_pickup.py harvest path); slot on wrong branch slot2/mc-MC-4455. Needs clean slot + re-scope. No code changed."}