Recurring cron-tick loop that watches a single Slack thread for a literal
substring (for example WORKTREE APPROVED, MERGE APPROVED, DEPLOY APPROVED,
or a custom approval token) and executes a pre-known callback (delete
script, merge, deploy, etc.) on first match. Otherwise silent (one
heartbeat per cadence). Self-cancels on match or after a configurable
timeout. Sibling to the babysit-ao-pr-loop skill; that one is for
AO-worker PR babysits, while THIS one is for non-PR, no-AO-worker
approval-gate loops.
Bug-ref 2026-07-14, thread C0AJQ5M0A0Y/1784070882.257369. The disk-
pressure babysit 18bd680865d9 was a literal-token watch loop but auto-
loaded babysit-ao-pr-loop, which silently self-cancelled because there
was no PR and no AO worker to track. That false assurance (babysit
armed) is what this skill prevents.
Recurring cron-tick loop that watches a single Slack thread for a literal
substring (for example WORKTREE APPROVED, MERGE APPROVED, DEPLOY APPROVED,
or a custom approval token) and executes a pre-known callback (delete
script, merge, deploy, etc.) on first match. Otherwise silent (one
heartbeat per cadence). Self-cancels on match or after a configurable
timeout. Sibling to the babysit-ao-pr-loop skill; that one is for
AO-worker PR babysits, while THIS one is for non-PR, no-AO-worker
approval-gate loops.
Bug-ref 2026-07-14, thread C0AJQ5M0A0Y/1784070882.257369. The disk-
pressure babysit 18bd680865d9 was a literal-token watch loop but auto-
loaded babysit-ao-pr-loop, which silently self-cancelled because there
was no PR and no AO worker to track. That false assurance (babysit
armed) is what this skill prevents.
trigger
["watch this thread for WORKTREE APPROVED","watch for MERGE APPROVED in thread","literal token watch loop","approval-token gate cron","fire X when user types Y in this thread"]
changelog
["0.1.0 (2026-07-14): Initial authoring. Triggered by the 2026-07-14 babysit-ao-pr-loop v1.9.1 carve-out. Every prior literal-token watch loop was wired through babysit-ao-pr-loop, which assumes a PR + AO worker pair and exits immediately when neither exists. Drafted directly from the di[REDACTED_OPENAI_KEY] babysit prompt body (job 18bd680865d9), which is the reference implementation. Verified contract: tick equals conversations.replies substring scan + optional destructive callback + hermes cron remove on terminal state."]
slack-thread-token-watch
A scheduled cron job ticks every N minutes on a single Slack thread. Each tick scans the thread for a literal substring (the approval token). On first match, it executes a pre-known callback script (destructive or not) and self-cancels. Otherwise it stays silent (one optional heartbeat per cadence). The loop is finite and must terminate cleanly when the work is done, or after a configurable timeout.
When to load
A scheduled cron job is gating a destructive action behind a literal-substring approval from the human (for example, delete these worktrees when I type WORKTREE APPROVED, merge when I type MERGE APPROVED, deploy when I type DEPLOY APPROVED).
A user asks you to watch this thread for XYZ and run script.sh when it appears, gate the delete on my approval, stand by for APPROVE keyword, or approval-token cron.
You are inheriting an existing literal-token cron mid-life and need to keep its cadence without re-creating its contract.
Do NOT load babysit-ao-pr-loop for literal-token watch loops. That skill is for AO-worker PR babysits and silently self-cancels when no PR + worker pair exists (see bug-ref in babysit-ao-pr-loop v1.9.1 changelog). If --skill babysit-ao-pr-loop is the only --skill you reach for, you are in the wrong skill.
Do NOT load for one-shot approval flows (use the inline session directly), PR bring-to-green interactive loops (use drive-pr-to-green or finish-the-job), or any callback that is NOT a literal-substring scan of a known Slack thread.
The contract (each tick)
Each tick has exactly four phases. Do them in this order, every tick.
Phase 0 - Pre-flight (early-exit; run BEFORE composing any output)
Self-identity check. Run echo $CRON_JOB_ID and date -u +%FT%TZ. Confirm we know our own cron job id (required for Phase 0.5 self-cancel).
Did the callback already fire? Check the durable executed-flag (for example, /var/tmp/_executed):
Are the eligibility or candidate artifacts still valid? Run ls -la /path/to/eligibility.json and check path_whitelist_ok. If absent or invalid, post a one-liner warning and exit (do not delete anything).
If any of these short-circuit, do NOT post the heartbeat, do NOT run the callback. Exit cleanly.
Phase 1 - Scan the thread for the literal approval token
Use the Slack MCP tool when available, fall back to XOX-P curl:
Then scan the body of each message whose user is a real human (U-prefix, not a bot B-prefix) for the literal substring APPROVAL_TOKEN. Case-sensitive, exact substring. Never match a synonym or normalized form.
Critical pitfalls (see references/scan-pitfalls.md for full details):
Match on the text field, not attachments or block-kit element text fields. Those are post-render artifacts that can drift.
Skip the bot's own previous heartbeat rows (filter on bot_id is null OR empty).
Skip rows where the approval token appears in a fenced code block. The user was quoting it, not approving.
Treat a string match as a match only if the row was posted AFTER start_ts. Earlier messages in the thread are stale context, not approval.
Phase 2 - Run the callback (only if match + flag not set)
The callback is whatever was pre-defined in the cron prompt. Common shapes:
Destructive delete with whitelist:
python3 << 'PY'import json, os, subprocess
d = json.load(open('/tmp/eligibility.json'))
WHITELIST_PREFIXES = ('$HOME/projects/', '$HOME/.lvl-lanes/', ...)
freed_mb = 0; deleted = 0for r in d:
p = r['path']
if r.get('locked') or r.get('age_days', 0) < 14: continueifnot p.startswith(WHITELIST_PREFIXES): continueifnot os.path.exists(p): continue
subprocess.run(['rm', '-rf', p], check=False)
freed_mb += r['size_mb']; deleted += 1print(f'deleted={deleted} freed_mb={freed_mb:.2f}')
PY
:red_circle: [thread-token-watch] APPROVAL_TOKEN received but callback failed - <error>. Loop NOT self-cancelled; investigate.
Do NOT self-cancel on failure; operator must inspect.
On age-out (no match, TIMEOUT_TICKS reached):
:hourglass_flowing_sand: [thread-token-watch] aged out after <N> ticks without APPROVAL_TOKEN. Self-cancelling.
On heartbeat-only (no match, under TIMEOUT_TICKS):
If the last heartbeat was under 6 hours ago: emit [SILENT] (cron playbook contract).
Otherwise post a one-liner: :yellow_circle: [thread-token-watch] still holding gate; df G/G (%); proposal age h. Type APPROVAL_TOKEN to fire the action.
Explicit "do NOT post multi-option menus" guardrail.
Explicit "do NOT spawn new cron jobs from inside this babysit" guardrail.
Do NOT pass --skill babysit-ao-pr-loop. That is the wrong skill for this task and the babysit will silently self-cancel on first tick (see bug-ref in v1.9.1 changelog).
Guardrails (NEVER VIOLATE)
NEVER fire the callback without exact substring match (case-sensitive) on a row whose user is a real human (U-prefix, bot_id null).
NEVER delete a row outside the path whitelist, with locked=true, or with age_days under FLOOR_DAYS.
NEVER rm -rf without trying trash first (Finder recoverable).
NEVER post a multi-option menu (A/B/C/D forks).
NEVER spawn new cron jobs from inside this cron (avoid recursive-cron leak).
NEVER pre-load babysit-ao-pr-loop. That is the wrong skill.
Pre-send gate: every Slack message must avoid MEDIA:/path text tokens (use the 3-stage files.completeUploadExternal API for any binary evidence; see evidence-attach-to-slack skill).
Termination rules
The loop terminates when ANY of these are true:
Approval token matched and callback completed successfully.
Approval token matched but callback failed (operator must inspect; do NOT auto-cancel).
Loop aged out (TICK greater than TIMEOUT_TICKS).
Cron schedule itself has been disabled (hermes cron edit --repeat 0 or hermes cron remove).
Operator manually runs hermes cron remove.
On termination: self-cancel via hermes cron remove "$CRON_JOB_ID" and post the appropriate terminal status message.
Anti-patterns (do NOT do)
Auto-loading babysit-ao-pr-loop because the prompt mentions watch, babysit, or tick. That skill assumes a PR + AO worker pair and exits after one tick when neither exists. The false assurance (watch loop armed) is the failure mode this skill exists to prevent.
Posting the callback result on every tick after the work is done. One tick owns the close; later ticks own silence.
Posting to Slack when nothing changed and the playbook says [SILENT]. Noise is worse than silence; the human inbox is the precious resource.
Re-implementing the path whitelist inline as a bash regex. Use Python startswith() on each whitelist tuple; bash globbing silently misses edge cases.
Treating bot_id non-null rows as approval. Bot rows are heartbeat artifacts, not human input.
Using mcp__slack__conversations_add_message for thread replies without first checking the channel scope (fails with not_in_channel for some channels; fall back to XOX-P curl per SOUL.md slack-cross-workspace-fallback-xoxp).
Calling hermes cron remove from inside a Phase 1 scan (race with self). Always Phase 3.
Tool usage notes
Use terminal for curl, python3, and hermes cron. Fan-out parallel where possible.
Use mcp__slack__conversations_replies for the canonical scan (preferred over curl; gets paginated thread properly).
Fall back to XOX-P curl chat.postMessage when the MCP bot returns not_in_channel or missing_scope (per SOUL.md slack-cross-workspace-fallback-xoxp).
Use hermes cron list for the self-cancel CLI + audit recipe.
Use python3 -c "import json; ..." for eligibility filtering. Never inline shell JSON parsing on multi-line fields (it breaks on body field LF bytes; see babysit-ao-pr-loop v1.6.0 changelog).
Verification
Before posting the first tick of a new loop, confirm:
The cron is correctly delivering to the channel + thread configured by the operator.
The literal approval token is exactly the substring the operator will type (case-sensitive; no leading/trailing whitespace in the prompt's match string).
The callback shell/Python block is syntactically valid (bash -n or python3 -c dry-run).
The path whitelist is correct; verify each prefix exists and is owned by the operator.
The executed-flag path is in a writable location (for example, /var/tmp/_executed, NOT inside ~/.hermes/).
The TIMEOUT_TICKS ceiling is reasonable (for example, 48 for a 30-min cadence = 24 h; 200 for 30-min = 100 h).
references/prompt-template.md - drop-in prompt body template with all required fields (literal token, callback, path whitelist, executed-flag, TIMEOUT_TICKS, guardrails).
references/bug-ref-2026-07-14.md - full transcript of the di[REDACTED_OPENAI_KEY] babysit 18bd680865d9 failure mode and the cron-output dump that diagnosed it.
