/abc:scaffold-sub-issues — Convert PLAN(s) to Linear sub-issues

Take one or more PLAN-*.md files, parse their sub-tasks, propose a Linear parent issue (or add to an existing one) with sub-issues + dependency edges + repo: labels + an optional ## Validation gate, then create them after the user confirms.

The output of this skill is a parent issue ID you can paste straight into /abc:ship-epic (parallel multi-repo) or /abc:ship-issue (serial single-repo loop).

Hard rules

• Never create Linear issues without an explicit confirmation gate. Issue creation is write-heavy and visible to teammates; the user must see the full proposed structure before any save_issue call.
• Never create new Linear labels silently. If a sub-task references repo:<name> that doesn't exist as a label, surface it and ask whether to create the label or rename the sub-task.
• Never invent sub-tasks not present in the plan. Parse what's there. If the plan is missing acceptance criteria or a repo, ask the user — don't fabricate.
• Sub-issues must be created sequentially, not in parallel. Linear's createdAt is the fallback sort key when blocks/blocked by aren't read by the consumer (e.g. /abc:ship-issue walks createdAt ascending). Parallel save_issue calls can collide at sub-second precision and scramble walk order.
• When multiple plan files are provided, reconcile conflicts before building the tree. Never silently pick one plan's version over another — surface contradictions via AskUserQuestion.
• The parent issue's description is the full plan markdown (concatenated if multiple), not a summary. Reviewers should be able to read the parent and understand the full context.

Workflow

Phase 0: Parse arguments + locate plans

$ARGUMENTS has three shapes — detect in order, first match wins:

1. Empty → auto-detect mode. Look for PLAN-*.md in cwd (newest by mtime wins), fall back to ~/.claude/plans/PLAN-*.md (newest wins). If multiple candidates, ask the user to pick via AskUserQuestion. If none, abort with: "No PLAN-*.md found. Run /abc:plan first."
2. First token fully matches `^[A-Z]+-\d+$` (e.g. PROJ-45) and is not an existing file → existing-parent mode. Treat the first token as the parent Linear issue ID. Remaining tokens are plan file paths (all required, all must exist). This skill will add sub-issues to that parent instead of creating a new one. (The full-token anchor + file-existence precedence stop a path that happens to start with capital letters from being misread as a Linear ID — if the token names a file on disk, it's a plan path, shape 3.)
3. Otherwise → all tokens are plan file paths (one or more). Resolve relative to cwd or as absolute paths. This is new-parent mode with explicit input.

Read all selected plan files in full. Concatenate them in the order provided (Phase 1.5 handles conflicts).

Phase 1: Parse the plan structure

Parse each plan per the canonical grammar in ../plan/plan-format.md — the strict/loose formats, the sub-task block fields, the (none)/(empty)/omitted relations sentinel, and the validation-gate resolution order are all defined there (single-sourced so this skill and scaffold-sub-issues-gh can't drift). If neither format matches, halt with the message that doc specifies.

Linear-specific deltas (everything else follows plan-format.md verbatim):

• The per-sub-task validation: bullet (or a sub-task-level ## Validation) becomes that child's manual-validation gate — the post-merge blocked-verify halt for /abc:ship-issue. A top-level ## Validation section is unattached; Phase 4 asks which sub-issue inherits it.
• repo:<name> maps to a Linear repo:<name> label (Linear has a single workspace, so the cross-owner repo:<owner>/<name> form has no meaning here — treat the whole token as the label name).

Phase 1.5: Reconcile multiple plans (only if 2+ plans given)

Scan the parsed plans for conflicting decisions:

• Same ST-N ID with different content.
• Same repo:<name> with different scope.
• Headings appearing in multiple plans with materially different prose (e.g. one plan says "experiment-gated", another says "unconditional").

For each conflict:

• AskUserQuestion with both options side-by-side. Tag the option from the newer plan (by file mtime) as (Recommended).
• Bake the user's choice into the canonical structure used by Phase 2 onward.

If no conflicts detected, fall through silently.

Phase 2: Resolve Linear context

Two branches depending on mode:

Existing-parent mode (parent ID was passed in Phase 0):

1. mcp__claude_ai_Linear__get_issue id=<parent-id> includeRelations: true. Capture team, project, existing labels.
2. Use the parent's team + project as defaults for all new sub-issues.

New-parent mode (no parent ID):

1. Linear team — mcp__claude_ai_Linear__list_teams. If multiple, ask the user. Cache the choice.
2. Project (optional) — mcp__claude_ai_Linear__list_projects with the team filter. If the plan title hints at a project (matches a project name), pre-select it. Otherwise leave blank and ask.

In both modes:

1. `repo:` labels — mcp__claude_ai_Linear__list_issue_labels team=<team>. Match each sub-task's repo:<name> to an existing label. Track missing labels for Phase 4 approval — do not create here.

Phase 2.5: cwd subdirectory advisory (soft warning)

For each unique repo:<name> referenced in the parsed structure, check whether <cwd>/<name>/ exists (ls in cwd). If missing, note it for the Phase 7 advisory — don't halt. The user might invoke /abc:ship-issue from a different cwd than where they're running this skill.

Phase 3: Build the proposed issue tree

Compose the structure in memory:

Parent:
  team: <resolved team>
  project: <resolved or null>
  title: <plan title>           # new-parent mode only; existing-parent skips this
  description: <full plan markdown, concatenated if multiple>
  labels: [<deduped union of all sub-task repo labels>]

Sub-issues (in plan order):
  ST-1 (or Sub-issue 1):
    title: <ST-1 title>
    description: |
      ## Scope
      <scope text>
      ## Acceptance criteria
      - <bullets>
      [optional ## Validation block, only on the chosen gate sub-issue]
    parent: <parent ID, set on creation>
    labels: [repo:<name>]
    relations:
      blocks: [<ST-IDs>]
      blocked by: [<ST-IDs>]
  ST-2: …

Existing-parent mode collision check. Also call mcp__claude_ai_Linear__list_issues parentId=<parent-id> limit=50. If the parent already has sub-issues:

• AskUserQuestion: "Parent <parent-id> already has N sub-issues. Halt (default), Append more (warning: createdAt order will be sandwiched after the existing ones), or Show me the existing ones before deciding?"
• On Halt → exit cleanly, no writes.
• On Append → proceed with Phase 4 but warn in the preview.

Phase 4: Show the user the proposed structure

Print a readable preview:

/abc:scaffold-sub-issues — proposed Linear structure

Mode: new-parent | existing-parent (<PARENT-ID>) | existing-parent (append)
Parent: <Title>
  Team: <Team>
  Project: <Project or "none">
  Labels: repo:web-frontend, repo:analytics-tools
  Description: <2000-char preview>

Sub-issues:

  [ST-1] Add WidgetRow component to web frontend
    Labels: repo:web-frontend
    Blocks: ST-3
    Blocked by: (none)

  [ST-2] Publish shared WidgetRow types in analytics-tools
    Labels: repo:analytics-tools
    Blocks: (none)
    Blocked by: (none)

  [ST-3] Wire WidgetRow into dashboard page  ← carries ## Validation gate
    Labels: repo:web-frontend
    Blocks: (none)
    Blocked by: ST-1

Dependency graph:
  ST-2 → (independent)
  ST-1 → ST-3

Missing labels to create: repo:web-frontend  (will prompt)
cwd advisory: <cwd>/analytics-tools/ not found  (you'll need to invoke /abc:ship-issue from a cwd containing this subdir)

Then ask via AskUserQuestion:

1. Confirm structure:

• Create everything as shown (Recommended)
• Edit before creating — user replies with adjustments
• Create just the parent, skip sub-issues — for when sub-task scoping isn't ready (new-parent mode only)
• Cancel

1. Validation gate (only if no ## Validation was attached in Phase 1, or there's a top-level Validation section that needs an owner):

• "Which sub-issue should carry the ## Validation section to trigger /abc:ship-issue's blocked-verify flow?" Default: last UI-touching sub-issue if detectable, else "none".

1. Missing labels (only if Phase 2 found any):

• "These repo: labels don't exist yet: <list>. Create them, or rename the sub-tasks?"

If "Edit before creating" — wait for user input, re-render the preview, re-ask.

Phase 5: Create labels, parent (if needed), then sub-issues sequentially

1. Missing labels first. For each approved missing label, call mcp__claude_ai_Linear__create_issue_label with teamId=<team-id>. Capture each new label ID.
2. Parent (new-parent mode only). Call mcp__claude_ai_Linear__save_issue with team, project, title, description (full plan markdown), labels. Capture the new parent ID.
3. Sub-issues, sequentially. For each sub-task in plan order:

• Build the description: include ## Scope, ## Acceptance criteria, plus the ## Validation block on the chosen gate sub-issue.
• Call mcp__claude_ai_Linear__save_issue with parentId, team, project (if any), title, description, labels.
• Wait for the response before issuing the next call. Do not parallelize. Linear's createdAt ordering is the fallback walk order for /abc:ship-issue; parallel creates collide at sub-second precision and scramble order.
• Capture each returned sub-issue ID into an ST-N → ID map.

1. Relations pass. After all sub-issues exist, wire blocks / blocked by relations in a second pass. For each sub-issue with blocks: [ST-X, ST-Y], call mcp__claude_ai_Linear__save_issue id=<sub-issue-id> blocks: [<X-id>, <Y-id>]. Same for blocked by via blockedBy:. (These fields are append-only per the save_issue schema — safe to call after creation.)

Phase 6: Self-check

1. mcp__claude_ai_Linear__list_issues parentId=<parent-id> orderBy=createdAt limit=50. Don't assume a sort direction — the MCP's orderBy direction isn't contractually guaranteed. Sort the returned issues by their createdAt field explicitly (ascending) client-side before comparing, rather than relying on the response order or reversing it blindly.
2. Verify count matches (expected = plan sub-tasks created in this run; in append mode, expected = original count + new count).
3. Verify IDs match the ST-N → ID map from Phase 5.
4. Verify createdAt timestamps are strictly increasing among newly created sub-issues. If any two share the same second → log a warning (consumer might still walk in unspecified order); the user can manually reorder by editing in Linear or by re-running with a comma-separated list to /abc:ship-issue.

Phase 7: Print the handoff

✓ Created parent: <PARENT-ID> "<Title>"             # new-parent mode
✓ Added 5 sub-issues to <PARENT-ID> "<Title>"       # existing-parent mode
✓ Wired 2 dependency links
✓ Created 1 new repo: label

Sub-issues (createdAt order — what /abc:ship-issue will walk):
  1. <SUB-ID-1> <repo:foo>  <URL>
  2. <SUB-ID-2> <repo:bar>  <URL>
  3. <SUB-ID-3> <repo:baz>  <URL>  ← carries ## Validation gate

Next:
  → /abc:ship-issue <PARENT-ID>       (serial single-loop; recommended)
  → /abc:ship-epic <PARENT-ID>        (parallel multi-repo; faster if no relations)

Linear link: <parent URL>

If Phase 2.5 flagged any missing cwd subdirectories, repeat the advisory:

⚠ Heads up: <cwd>/<repo-name>/ is missing.
  /abc:ship-issue resolves repo: labels against subdirectories of cwd.
  Invoke it from a cwd that has each <repo-name>/ as a subdirectory,
  or clone the missing repos first.

Notes on edge cases

• Sub-task with no acceptance criteria: ask the user to add them in the plan file, then re-run. AC is required for /abc:ship-issue to know when a ticket is done.
• Circular blocks (ST-1 blocks ST-2, ST-2 blocks ST-1): abort with a clear cycle description. Linear allows the relations, but the dependency graph is unworkable.
• Plan references a repo that has no sub-task: ignore — the parent's label union covers it.
• Multiple plans in cwd: ask the user to pick (Phase 0 auto-detect).
• Two plans contradict on a structural decision (e.g. one says split CMS into helper+UI, the other says one bundled sub-issue): Phase 1.5 surfaces via AskUserQuestion, recommends newer plan by mtime.
• Parent has existing sub-issues, user picks Append: warn that new sub-issues will land after existing ones in createdAt order, which means /abc:ship-issue will walk old → new. If the user wants new ones to go first, they need to manually reorder in Linear (no MCP exposes sortOrder).
• Loose-format plan with no `repo:` tag on a sub-task: halt and ask the user to add it. The skill won't guess.
• User wants to update an existing parent's description rather than add sub-issues — out of scope for v1. Tell them to edit in Linear directly.
• createdAt collision (two sub-issues share the same second): log a warning; the consumer's walk order is unspecified between collisions. Suggest comma-separated explicit ordering to /abc:ship-issue as a workaround.