liftoff - SKILL.md Agent Skill

name: liftoff description: Use when the user wants to build the planned tasks for a mission issue, or when /mission dispatches the build phase. Trigger on "liftoff " or "/liftoff". Thin wrapper around liftoff-workflow.js — Astronauts implement tasks in dependency rounds, Flight Controllers verify, commits land in the worktree. Requires a plan from /pre-launch.

Liftoff — Build

Run the liftoff workflow against the persisted flight plan.

Step 1: Locate the plan

ISSUE_NUM=…   # first non-flag argument; if omitted, infer from branch: claude/issue-<N>-*
STATE_DIR="${CLAUDE_PLUGIN_DATA}/mission-runs/issue-${ISSUE_NUM}"
[ -f "$STATE_DIR/plan.json" ] || { echo "No flight plan for issue #${ISSUE_NUM} — run /pre-launch ${ISSUE_NUM} first."; exit 1; }
PLAN=$(cat "$STATE_DIR/plan.json")
WORKTREE_PATH=$(echo "$PLAN" | jq -r '.worktree_path')
REPO=$(echo "$PLAN" | jq -r '.repo')

Step 2: Resolve models

Built-in defaults: director=fable, astronaut=sonnet, controller=sonnet, inspector=fable, capcom=sonnet, docking=sonnet, utility=haiku.

If .claude/mission.local.md exists at the repo root, Read it and take any entries under models: in its YAML frontmatter.
If the invocation included --models role=value,..., apply those entries on top.
Valid roles: director, astronaut, controller, inspector, capcom, docking, utility. Valid values: haiku, sonnet, opus, fable. Warn about and ignore any invalid entry — never abort over one.
Fable fallback. Fable is unavailable in some environments (e.g. headless or cron runs), where spawning an agent with it hard-errors. Before launching, for any role whose resolved value is fable, confirm Fable is among this session's available models. If you cannot confirm it, downgrade that role — director→opus, inspector→sonnet, every other role→sonnet — and tell the user which roles were downgraded. Never pass fable to an agent you cannot confirm supports it.

The merged result is MODELS, passed to the workflow as args.models.

Step 3: Enter the worktree

[ -d "$WORKTREE_PATH" ] || { echo "Worktree missing at $WORKTREE_PATH — re-run /pre-launch ${ISSUE_NUM}."; exit 1; }

Call EnterWorktree with path: $WORKTREE_PATH.

Step 4: Run the workflow

PRIOR=$(cat "$STATE_DIR/liftoff.runid" 2>/dev/null || echo "")

Call the Workflow tool with:

scriptPath: the literal string ${CLAUDE_PLUGIN_ROOT}/workflows/liftoff-workflow.js (expand the env var — do NOT use import() or cat)
resumeFromRunId: value of PRIOR if non-empty, otherwise omit the field entirely
args: { issue_number: <ISSUE_NUM>, repo: "<REPO>", plan: <plan.json object>, models: <MODELS>, plugin_root: "<value of $CLAUDE_PLUGIN_ROOT>" }

Save the returned runId:

echo "<runId>" > "$STATE_DIR/liftoff.runid"

If the workflow throws, present the error using the banner shape in references/halt-protocol.md — reason from the error message, where-we-are = "issue #N, liftoff", options: [1] fix the stated problem and re-run /liftoff <N> (resumes from the saved runId), [2] /pre-launch <N> --replan if the plan itself is wrong.

Step 5: Report

All tasks committed — liftoff complete for issue #<N>.
Next: /systems-check <N>  (or /mission <N> drives it automatically)