Ship Epic

/abc:ship-epic — Parallel multi-repo shipping coordinator

Drive a Linear parent issue with sub-issues to all-merged by firing one /loop 6m /abc:ship-issue <SUB-ID> per ready sub-issue, gating sub-issues with unmet blocked by relations, and aggregating status on the parent. Each worker (/abc:ship-issue) is independent — they run in parallel via their own cron entries, survive session close, and use Linear as the single source of truth.

This skill is the coordinator. It does NOT implement code, open PRs/MRs, or run tests directly — those are the workers' jobs.

See DESIGN.md for the architectural design rationale. This file is the operational procedure.

Hard rules

• Never spawn a worker for a sub-issue that has an unmet blocked by relation. Wait for the upstream to reach merged first.
• Never halt the epic just because one worker hits blocked-user. Other workers can continue; the blocked one waits for the human.
• Never modify worker state directly (no edits to <!-- ship-issue:* --> comments). Workers own their own state machines.
• Always self-cancel the epic's cron on terminal states (all merged, any failed). /abc:ship-issue self-cancels its own cron per its Phase 7; this skill mirrors that contract at the epic level.
• If the parent has no sub-issues → reject and point the user at /abc:ship-issue for single tickets.
• If the dependency graph has a cycle → Phase 5 § Dependency cycle (terminal): write <!-- ship-epic:event:cycle --> once (dedup against an identical prior marker), CronDelete the epic's own loop, and halt. Refuse to fire any workers.

Phase 0: Parse input and self-arm

Normalize the arg

Flag extraction (before shape detection): detect and strip a trailing --no-compact flag from $ARGUMENTS. When present, set no-compact mode for this invocation — the compact-on-merge prompt (Phase 4) is skipped, and the flag propagates to every worker fired in Phase 3. The flag stays in the raw arg string used for cron arming/matching, so the opt-out survives every subsequent wake. Contract and rationale live in ../_shared/compact-on-merge.md.

$ARGUMENTS is one of:

1. Linear issue URL (https://linear.app/<org>/issue/<id>) → strip prefix, extract TEAM-N (the parent ID).
2. Linear project URL (https://linear.app/<org>/project/<slug>/...) — project overview / issues / triage URLs that don't point at a parent issue → blocked-user with reason project-url-needs-parent-id. The block message lists the two supported shapes: bare parent ID (PROJ-100) and parent issue URL. Do not proceed to Phase 0.5 — no cron arming.
3. Bare ID (e.g. PROJ-100) → use as-is.
4. milestone:<uuid> (or a project URL with a #milestone-<uuid> fragment) → reject. The coordinator pattern needs a real parent issue for status aggregation — point the user at /abc:ship-issue milestone:<uuid> (the serial walker) instead. This mirrors how /abc:ship-epic-gh rejects milestone refs. blocked-user with reason milestone-needs-serial-walker; do not proceed to Phase 0.5 — no cron arming. (Whether a milestone-mode coordinator is worth building is an open question — see DESIGN.md § Open questions.)

For the rest of this doc, assume bare PARENT-ID unless noted.

Fetch parent + sub-issues

1. mcp__claude_ai_Linear__get_issue with id: PARENT-ID, includeRelations: true. Read description, labels, statusType.
2. Already-complete early exit. If the parent's statusType is completed (Done) on a fresh invocation → the epic is already complete. Print a one-line "epic already complete" summary and exit without arming a loop and without writing any comment (mirrors the /abc:ship-epic-gh closed-completed early exit). Do not proceed to Phase 0.5.
3. mcp__claude_ai_Linear__list_issues with parentId: PARENT-ID, no status filter (we want everything, including merged ones to derive merged state).

If the sub-issue list is empty → reject: "PARENT-ID has no sub-issues. Use /abc:ship-issue PARENT-ID for single-ticket shipping."

Self-arm the loop

Cron-entry match rule

Defined in ../_shared/cron-match.md; this skill is the ship-epic consumer (<boundary-class> = alphanumeric, -, ,; /loop interval 10m).

Arm check

• If a matching entry exists → no-op, proceed to Phase 1 (the common path on loop-triggered wakes).
• If no match → this is the first wake. Run the single-session constraint checks below before arming. If they pass, invoke Skill(skill: "loop", args: "10m <command-name> <raw-arg>") to arm the cron — substituting the captured <command-name>, not a hardcoded skill name. This is what makes the next wake's match check succeed against this cron entry. Then proceed to Phase 1 — the first wake also does the work of the first iteration.

Single-session constraint (first wake only)

The coordinator is single-session: exactly one coordinator loop per parent. On the first wake (no matching cron yet — about to arm), before arming:

• Live sibling coordinator. If a recent <!-- ship-epic:status --> comment exists on the parent that THIS session did not write, suspect a live sibling coordinator already running in another session → blocked-user with reason possible-duplicate-coordinator. Do not arm a second loop.
• Parent already serial-walked. If CronList shows a serial-walker entry for this same parent — a worker cron of the form ship-issue <PARENT-ID> (the namespace-aware worker cron-match rule below applied to the parent's own ID, i.e. someone ran /abc:ship-issue <parent> to walk the sub-issues serially) → refuse to start with reason parent-already-serial-walked. Coordinating in parallel while the parent is being walked serially would double-fire workers.

(On non-first wakes a matching coordinator cron exists, so these checks are skipped — they guard the initial arm only.)

10-minute cadence is intentional (longer than the 6-minute worker cadence): the coordinator only needs to react when a worker reaches merged (unblocks downstream) or terminal (failed/blocked-user). Both events surface in Linear within seconds; 10-minute lag is acceptable.

Derived worker command (defined once — referenced by Phase 2 in-flight match AND Phase 3 fire string)

Do not hardcode /abc:. Derive the worker command from the captured coordinator <command-name> so a coordinator invoked top-level fires a top-level worker, and a plugin-namespaced coordinator fires a same-namespace worker:

<worker-command> = the captured <command-name> with its trailing skill name ship-epic swapped to ship-issue, preserving any namespace prefix verbatim. So /abc:ship-epic → /abc:ship-issue, and a top-level /ship-epic → /ship-issue.

Worker cron-match rule (the single match key)

The Phase 3 fire string and the Phase 2 in-flight match key MUST be the same string — they are defined here once and referenced from both. Firing /loop 6m <worker-command> <SUB-ID> while classifying in-flight against a different substring (e.g. the hardcoded /ship-issue <SUB-ID>) is exactly the bug this fixes: the namespaced fire string /abc:ship-issue <SUB-ID> never matches a bare /ship-issue <SUB-ID> grep, so the coordinator never recognizes its own running workers and re-fires duplicates.

A CronList entry is the worker for sub-issue <SUB-ID> when its command string matches the namespace-aware regex (same shape as the epic's own cron-match rule, with the Linear-ID boundary class):

(?:^|[^A-Za-z0-9])(?:[A-Za-z][A-Za-z0-9_-]*:)?ship-issue <SUB-ID>(?![A-Za-z0-9_,-])

The optional <plugin>: prefix capture matches whatever namespace the worker was fired under (it is the same namespace as <worker-command>); the trailing negative-lookahead is the Linear-ID boundary class (no //# exclusions — the GitHub sibling needs those, Linear doesn't). This is the same string as the Phase 3 fire string's command portion — define it once here, reference it by name from both Phase 2 (in-flight) and Phase 5 (kill targeting).

Phase 1: Build the dependency graph

For each sub-issue:

1. Read its blocks and blocked by relations from the relations field on the get_issue response.
2. Filter relations: only keep edges where BOTH endpoints are in our sub-issue set. External blockers (e.g. a sub-issue blocked by a ticket outside this epic) surface as the external-blocker state for that sub-issue (Phase 2), recorded only in the epic's <!-- ship-epic:status --> comment — never as a comment on the sub-issue itself.
3. Build adjacency lists: blocksMap[id]: Set<id>, blockedByMap[id]: Set<id>.

Detect cycles via DFS. On cycle → go to Phase 5 § Dependency cycle (terminal) — refuse to fire any workers. Phase 5 owns the marker-dedup + CronDelete + halt; do not write the marker or fire workers here.

Phase 2: Classify each sub-issue

First match wins (no need to re-read CronList per sub-issue — pull it once at the top of the phase):

Re-fire on human reply (how a blocked sub-issue resumes). No worker ever writes an event:resumed marker — there is no such marker. A blocked-user sub-issue resumes by the coordinator re-firing its worker. The rule: take the sub-issue's latest <!-- ship-issue:event:blocked --> marker. If a human (non-skill) comment or a <!-- ship-issue:verify:passed --> marker postdates it (later timestamp), the human has answered the block → treat the sub-issue as re-fireable: it classifies ready (if its blockers are satisfied and no worker cron is in-flight) and Phase 3 fires a fresh worker, which is what resumes it. If nothing postdates the blocked marker, the sub-issue is still blocked-user and waits.

Read-failure rule. Mirror the worker's rule (/abc:ship-issue Phase 3): if any read this phase fails (non-zero exit, timeout, an MCP error, pagination the coordinator can't reconcile), skip classifying that sub-issue this wake — do not fall through to a wrong state (e.g. treating an unread list_comments as "no blocked marker"). The sub-issue keeps its prior surfaced state until a clean read. If the parent itself is unreadable on consecutive wakes → CronDelete the epic's loop and halt (Phase 5 § Parent unreadable).

Re-derive fresh on every wake — nothing is persisted locally.

Phase 3: Fire workers for ready sub-issues

For each sub-issue in ready state, fire the derived <worker-command> (Phase 0.5 § Derived worker command — never the hardcoded /abc: literal):

Skill(skill: "loop", args: "6m <worker-command> <SUB-ID>")

The <worker-command> <SUB-ID> portion is the same string the Phase 2 in-flight worker cron-match rule keys on — that is what lets the next wake recognize this worker as in-flight instead of re-firing it. (e.g. coordinator /abc:ship-epic → <worker-command> is /abc:ship-issue.)

In no-compact mode, append the flag so workers inherit the opt-out: Skill(skill: "loop", args: "6m <worker-command> <SUB-ID> --no-compact") (see ../_shared/compact-on-merge.md § --no-compact).

This kicks off the worker's first wake and arms its own cron. The coordinator does NOT wait — it returns and the worker runs independently on its own loop.

Do not fire workers for sub-issues already in-flight (the worker's own Phase 0.5 cron-match would no-op anyway, but skip explicitly for clarity and to avoid any potential race).

If multiple sub-issues are ready in the same wake, fire all of them — the workers run in parallel on independent cron entries.

Phase 4: Aggregate status

Linear comment on the parent

Append (not edit) a single <!-- ship-epic:status --> comment on the parent with the current snapshot:

<!-- ship-epic:status -->
Wake: 2026-05-17T18:30:00Z  (4 of 6 merged)

| State | Sub-issue | Latest |
|---|---|---|
| merged | PROJ-101 | <PR URL> |
| merged | PROJ-102 | <PR URL> |
| in-flight | PROJ-103 | pr-open, <PR URL> |
| ready | PROJ-104 | → firing worker this wake |
| waiting | PROJ-105 | blocked by PROJ-104 |
| blocked-user | PROJ-106 | awaiting-manual-verification |

Terminal block (Phase 8-style output)

/abc:ship-epic wake <ts>
Parent: PROJ-100  "Add WidgetRow to dashboard"  (4 of 6 merged)

[merged]         PROJ-101  <PR URL>
[merged]         PROJ-102  <PR URL>
[in-flight]      PROJ-103  pr-open <PR URL>
[ready→firing]   PROJ-104
[waiting]        PROJ-105  blocked by PROJ-104
[blocked-user]   PROJ-106  awaiting-manual-verification

Next wake: /loop 10m /abc:ship-epic PROJ-100

Keep terminal output short on no-op wakes (no state changes since last wake) — just one line: no-op wake — 4 of 6 merged, 1 in-flight, 1 blocked-user.

Compact-on-merge (end of wake)

When this wake observed one or more sub-issues newly reach merged — derived statelessly by comparing against the most recent prior <!-- ship-epic:status --> comment (a child is newly merged when a prior status comment exists and didn't list it as merged) — print, after the terminal block, as the last output of the wake:

🗜 <n> child(ren) merged this wake. Run /compact now to free context before the next coordinator wake.

First-wake baseline guard: when no prior <!-- ship-epic:status --> comment exists — the first coordinator wake, including resuming an epic whose sub-issues already merged before the coordinator ever ran — treat the current merged set as the baseline, not as newly merged: this wake's status comment establishes the snapshot and no prompt is printed.

Skip in no-compact mode, on wakes with no newly-merged children, and on terminal wakes (all merged → the epic is closing and the loop is ending anyway). At most once per wake regardless of how many children merged. Full rules: ../_shared/compact-on-merge.md.

Phase 5: Terminal states

All sub-issues merged

1. Transition parent to Done via save_issue.
2. Write <!-- ship-epic:event:complete --> comment: ✅ Epic complete: <N> sub-issues merged.
3. Cancel the epic's /loop via CronDelete (use the same match rule as Phase 0).
4. Worker loops should already have self-cancelled per /abc:ship-issue Phase 7 — if any remain in CronList, leave them; they'll wake, derive merged, and self-cancel.

Any sub-issue failed

A sub-issue counts as failed for the all-stop only when it carries the worker's <!-- ship-issue:event:failed --> marker. A sub-issue that is canceled without that marker is a human cancellation, not a worker failure — classify it dropped (human-canceled) (Phase 2), surface it, and do not halt.

1. Write <!-- ship-epic:event:failed --> on the parent: ❌ Epic halted: <SUB-ID> failed (<reason>). Other sub-issues left in their current state.
2. CronDelete the epic's /loop.
3. Also CronDelete all in-flight worker /loops for this epic's sub-issues — they shouldn't keep grinding after the epic is halted. Identify each worker cron via the Worker cron-match rule (Phase 0.5) per sub-issue ID — not a loose substring. After killing a sub-issue's worker cron, append an informational comment to that sub-issue that does NOT contain any <!-- ship-issue:* --> marker (so it isn't mistaken for a worker-authored event): Epic halted upstream; this sub-issue's worker loop was cancelled. Re-run to resume. (use the derived <worker-command>).
4. Halt.

Open question: should we let other workers finish even if one failed? v1 halts because cross-repo failures usually mean the design has a problem. If this is wrong in practice, flip to "let others continue, just block fan-out."

Dependency cycle (terminal)

Reached from Phase 1 when DFS detects a cycle:

1. Write <!-- ship-epic:event:cycle --> on the parent listing the cycle members in order — once: if an identical <!-- ship-epic:event:cycle --> marker comment already exists (same cycle membership), do not repost (dedup against the prior marker).
2. CronDelete the epic's /loop.
3. Halt. No workers were fired (Phase 1 refuses to proceed on a cycle).

Parent unreadable (terminal)

Reached from Phase 2's read-failure rule when the parent is unreadable on consecutive wakes:

1. CronDelete the epic's /loop.
2. Halt — print the read error. The parent is the aggregation target; with it unreadable the coordinator can't classify anything. A single transient read failure does not trigger this — only consecutive-wake failure.

Any sub-issue blocked-user or external-blocker

Do not halt. Leave the epic loop running — other workers may still be making progress. Surface in the terminal block and Linear status comment, but the loop continues.

User @-mentions Claude on the parent

Treat as a direct interrupt — read the comment, decide whether to halt or adjust. If unclear, write a blocked-user comment with reason user-mention-ambiguous:<parent-comment-id>, CronDelete the epic's /loop (this halt self-cancels like every other terminal path), and halt.

Phase 6: Stop

The epic's /loop self-cancels on every terminal-state phase via CronDelete. The user should not have to run /loop cancel manually.

If CronDelete fails (entry already gone, job-ID not found), print a note and continue. The Linear comment is authoritative.

Notes on edge cases

• Sub-issue added to the parent mid-flight: next wake re-fetches the sub-issue list. New sub-issues with repo: labels become ready (if no blocked by) or waiting (if blocked). Fired automatically.
• Sub-issue removed from the parent mid-flight: if it's in-flight, leave its worker running — the worker is on its own contract. Just drop it from the epic's status aggregation.
• blocked by edge added mid-flight to an in-flight sub-issue: the worker keeps running. The edge takes effect for state classification only — if the worker reaches a terminal state and a new sub-issue depends on it, the dependency is honored from then on.
• Multiple /abc:ship-epic invocations on the same parent: cron-match deduplicates (idempotent self-arm). Second invocation in the same session no-ops. A second invocation in a different session is caught by the Phase 0.5 § Single-session constraint first-wake checks (possible-duplicate-coordinator if a foreign <!-- ship-epic:status --> comment exists; parent-already-serial-walked if a ship-issue <PARENT-ID> walker cron is live) — the coordinator is single-session per parent.
• Worker death (machine reboot, manual /loop cancel): next wake sees the worker as no longer in-flight but Linear state not terminal — re-classifies as ready (if blocks satisfied) and fires a new worker. Re-arming is idempotent at the worker level.