---
name: coauthor
description: "Resolve the Co-Authored-By trailer policy for the active repo."
argument-hint: "[--mode=runtime|project|disabled]"
user-invocable: true
disable-model-invocation: false
---

# /coauthor

## Canonical algorithm

1. Read the `vcs.coauthor` config block (`mode` ∈ `runtime|project|disabled`) and the caller-supplied `mode` / `runtime` / `message_text` args.
2. Run the canonical resolver (`resolve_coauthor_trailer`) to turn the config + the explicit runtime opt-in into a `Co-Authored-By:` trailer line (or `None` when trailers are disabled).
3. On `mode=runtime` with no resolvable runtime (no explicit opt-in and no usable default identity), degrade to `status=needs_user` so the runtime adapter surfaces a `coauthor resolve` prompt rather than guessing.

This skill is a thin surface over the shipped co-author policy machinery; it does not reimplement trailer resolution.

## Pre-flight checklist

- [ ] Never invent an author identity — `disabled` mode rejects an existing trailer in `message_text`.
- [ ] No PII beyond the canonical author block.

## Decision surfaces

`status=needs_user` routes to a `coauthor resolve` `AskUserQuestion` when the runtime cannot be resolved.

## Output contract

Skill envelope with `header.skill = "/coauthor"`. Body carries mode, runtime, and the resolved trailer (or a reason on the needs_user path).