skill-author

Author a new skill, the right way. Routed to when the user invokes /new-skill "<gap>".

Pre-flight

Read these, or STOP and surface the gap — never author on assumption:

• The <gap> argument. Absent → STOP and ask: "Describe the gap this skill would fill. What situation does no existing skill cover today?"
• ${CLAUDE_PLUGIN_ROOT}/skills/INDEX.md — the surface scan of every existing skill. This is the gap-overlap check in Phase 1 and the integration target in Phase 5. Never bulk-read the skill bodies.
• ${CLAUDE_PLUGIN_ROOT}/skills/commit-gate/SKILL.md and ${CLAUDE_PLUGIN_ROOT}/skills/tdd/SKILL.md — the canonical v2 format the authored skill must mirror. Read them before Phase 3.
• ${CLAUDE_PROJECT_DIR}/.codearbiter/CONTEXT.md — project context, only if the gap is project-specific. A generic skill needs no project state.

Phase 1 — Gap evidence · gate: BLOCK

A new skill is permanent surface area. It is not written until the gap is proven real and proven uncovered.

Restate the gap in one sentence. Then scan INDEX.md for overlap: if an existing skill's "Owns" column already covers this, STOP and name it — "The <name> skill already owns this; review it before requesting a new one."

If no skill covers it, demand evidence — one of:

• A — three specific cases where the gap blocked work: what was attempted, what happened with no skill, what it cost.
• B — one high-impact case with traceable evidence: a blocked PR, an introduced defect, a compliance finding, a repeated failure pattern.

Hypothetical cases do not count. Fewer than three (Option A) or no traceable evidence (Option B) → STOP and decline: "Insufficient evidence of a real, recurring gap. A skill adds permanent maintenance cost. Return with evidence and I'll author it."

Gate: the gap is restated, proven uncovered against INDEX.md, and backed by Option-A or Option-B evidence. Speculation does not pass.

Phase 2 — Scope · gate: BLOCK

Settle scope with the user before any prose is written. Ask, and wait for an explicit answer:

• Routed or dispatched? A skill is routed to (gated phases, lives at ${CLAUDE_PLUGIN_ROOT}/skills/<name>/SKILL.md). An agent is dispatched by a skill (a reviewer/author, lives at ${CLAUDE_PLUGIN_ROOT}/agents/<name>.md). If the gap is really a reviewer, this is the wrong skill — redirect to agent authoring.
• Command-invoked or internal? Does a user type /<name> to reach it, or does another skill route to it mid-workflow? A command needs a routing-table entry; an internal skill needs a named parent that routes to it.
• Single responsibility. State the one thing the skill owns in a sentence. If it needs "and" to describe its job, it is two skills — split it or pick one.

Confirm back: "I will write a [command-invoked / internal] skill at ${CLAUDE_PLUGIN_ROOT}/skills/<name>/SKILL.md, owning . [A /<name> command will be added to the routing table. / The <parent> skill will route to it.]"

Gate: explicit user agreement on routed-vs-dispatched, command-vs-internal, and a one-sentence single responsibility. Assumed answers do not pass.

Phase 3 — Authoring · gate: BLOCK

Write SKILL.md to the v2 house style — mirror commit-gate and tdd exactly. Start from ${CLAUDE_PLUGIN_ROOT}/skills/skill-author/references/skill-template.md. Required shape:

• Frontmatter — name: and description: only. Description is terse: what routes to it, the phase count, the gate. No cut doc refs, no trigger disclaimer.
• # <name> H1, then a one-line intro naming what routes to it (/<command> or the parent skill).
• ## Pre-flight — the docs to read or STOP on. Project state cites ${CLAUDE_PROJECT_DIR}/.codearbiter/<doc>; other skills cite ${CLAUDE_PLUGIN_ROOT}/skills/<name>; agents cite ${CLAUDE_PLUGIN_ROOT}/agents/<name>.md. Never guess a command — read it or STOP.
• ## Phase N — <title> · gate: BLOCK|STOP — sequential, each ending in a one-line Gate:. A phase with output that could be wrong has a gate; only a purely declarative phase may omit one.
• ## Hard rules — MUST NOT lines, one per rule, no duplication.

Authoring rules:

• Imperative, terse, no hedging. No "should", no "if it looks wrong". A gate is a concrete, checkable condition.
• Surviving project docs only: CONTEXT.md, tech-stack.md, coding-standards.md, specs/, plans/, security-controls.md, decisions/, overrides.log. Do not reference cut docs or cut skills.
• Terminology lock: a skill is routed to; an agent is dispatched. Never "trigger", "fires", or "runs".
• An out-of-scope finding gets one line with an inline [NEEDS-TRIAGE] marker.

Phase 4 — Self-review · gate: BLOCK

Re-read the authored skill against the v2 quality bar. Each line below is a checkable defect, not a vibe:

• Single responsibility — the skill owns one thing. If a phase belongs to a different job, it is the wrong skill; cut it.
• Concrete gates — every non-declarative phase ends in a Gate: line stating a checkable condition. "Looks good" / "seems right" is not a gate; rewrite it.
• House-style prose — terse, imperative, matches commit-gate/tdd. Strip hedging and filler.
• No duplicated rules — a rule stated in a phase is not restated in Hard rules, and Hard rules carry no duplicates. State each rule once.
• Format conformance — frontmatter is name+description, plus disable-model-invocation: true ONLY on a chain-internal skill (never user-typed, reached solely via routing-table path loads — see ADR-0028); H1 matches name; phases are numbered with · gate:; paths use ${CLAUDE_PLUGIN_ROOT} / ${CLAUDE_PROJECT_DIR} correctly; no cut docs/skills, no legacy ${FRAMEWORK_ROOT}/${PROJECT_ROOT}/.agents/ paths.
• Frontmatter scalar quoting — any frontmatter scalar that starts with [ or {, or contains ": " or " | ", MUST be JSON-quoted (the _yaml_safe_scalar predicate the surface generator applies to codex/pi wrappers; the claude surface ships frontmatter verbatim, so the author quotes it at the source).
• No trigger language — "routed to" / "dispatched" only, and no ## Trigger disclaimer block.
• Evidence lenses (issue #612) — each checked where the skill's shape triggers it, skipped where it does not:
  • A gate an agent is tempted to skip carries a rationalization guard AT the decision point — the known excuses paired with rebuttals. The best rebuttal carries its own instrument: a check the agent can run that falsifies the excuse either way. A tempting gate with no guard is a defect.
  • An acceptance or verification step names what is READ, never what is claimed — "the subagent reports green" is a defect; "the runner's output shows green" is not.
  • A user-facing ask leads with a recommendation AND its strongest counter-consideration.
  • A rule a tested helper could enforce is mechanized rather than accreted as prose — the helper enforces, the prose explains.
  • A rule whose literal reading has an exploitable edge names what it protects.
• Behavior-changing gate revisions are validated, not assumed — an A/B pass (fixed scenarios, rubrics written before any output exists, both versions run under identical conditions) scaled to the change's blast radius, with results recorded in the PR (issue #612's method).

Compile the findings, fix each, and re-read once. Present the corrected skill and the findings list to the user.

Gate: zero open self-review defects, and the user has seen the corrected skill. An unaddressed defect blocks Phase 5.

Phase 5 — Routing integration · gate: BLOCK

A skill no one routes to is dead code. Wire it in.

• Add a row to ${CLAUDE_PLUGIN_ROOT}/skills/INDEX.md: skill name (linked), "Routed to by", and "Owns" (the one-sentence responsibility from Phase 2).
• Add the skill to the routing table — the invocation cue (the /<command> or condition), the primary route, any dispatched agents, the hard gate. For a command-invoked skill, also register the /<command> in the command reference.
• For an internal skill, update the named parent so it routes to the new skill explicitly.

Verify no broken references: every path the skill cites resolves. INDEX.md row parity and routing-table dangling-route freedom are no longer a hand-check here — .github/scripts/check_routing_index_parity.py enforces both mechanically in CI (issue #592); a missing row, an orphan row, or a route to a name that does not exist fails the build.

Hand off to commit-gate — never git commit directly. The skill change ships only through the commit gate.

Gate: INDEX.md and the routing table updated, no broken references, and the change handed to commit-gate. CI's routing-parity check is the authority on row/route correctness, not a self-report.

Hard rules

• MUST NOT author a skill before the gap is proven uncovered against INDEX.md and backed by Option-A or Option-B evidence.
• MUST NOT begin authoring without explicit user agreement on scope (routed-vs-dispatched, command-vs-internal, single responsibility).
• MUST NOT emit a skill whose phases lack concrete Gate: lines, or whose Hard rules duplicate phase rules.
• MUST NOT use trigger language ("trigger", "fires", "runs") or a ## Trigger disclaimer — a skill is routed to, an agent dispatched.
• MUST NOT reference a cut doc, cut skill, or a legacy .agents/ / ${FRAMEWORK_ROOT} / ${PROJECT_ROOT} path in an authored skill.
• MUST NOT ship a skill without an INDEX.md row and a routing entry.
• MUST NOT commit the new skill directly — hand off to commit-gate.