rigor: Skill for Claude Code

Implement one issue as a lane

You are a lane: one issue, one worktree, one Draft PR. The coordinator plans the batch, reviews your PR and lands it (docs/agents/parallel-lanes.md). The brief gives you the issue, the worktree branch, any decision already settled and anything withdrawn; this skill gives you everything else. A brief that contradicts this skill wins for that lane.

Before you write code

1. Create the worktree the brief names with nix develop --command bin/rigor-worktree <branch> origin/master (add --with-references when a gate you run reads references/) and work only there.
2. Reproduce the issue on the fresh origin/master. When the premise is already fixed, or the work needs a decision on contribution-flow.md's serious list, stop and report; open no PR.

While you work

• Scope. Change only what the issue asks. Report anything wider for the coordinator to file. Leave the review, gh pr ready, the merge, bin/land-pr and other PRs to the coordinator, whatever AGENTS.md says about landing.
• Environment. Every command through nix develop --command; stdin from /dev/null for rspec and rigor; this worktree's bundle exec exe/rigor as the oracle; references/ read-only; scratch files under the worktree's tmp/. No git stash, no git submodule deinit, no pkill/killall; stop only processes you started, and leave none running when you report. No version bump, no edit to CHANGELOG.md, never rake release. Leave # rigor: and # rubocop: lines alone; in fixtures they are suppression directives. A survey target gets a private copy (docs/agents/measurement.md); run one heavy job at a time.
• Commits. Use the configured identity: never --author= or GIT_AUTHOR_*/GIT_COMMITTER_*. Add no tool attribution trailers. A fix of an external report carries the reporter's Co-Authored-By trailer from the brief on every fix commit, the fragment included, and the fragment ends with thank you @handle! (docs/agents/contribution-flow.md § "Branches and pull requests").
• Gate. make verify-changed </dev/null in the foreground, re-run after the last edit. Never make verify, make check or the whole suite. A change to dispatch, scope resolution or the discovery tables also runs spec/rigor/scope/ancestry_walker_detection_spec.rb and spec/rigor/declaration_facts/producers_spec.rb.
• Mutation table. For every new or changed example, remove the line of the fix it pins and show it fails: commit first, mutate with perl -pi -e (the Flake's sed -i '' edits nothing), prove the edit with git diff --stat, restore with git checkout HEAD -- <path>. An example that survives every removal is a labelled guard or is rewritten. The shapes that survive are in docs/agents/measurement.md § "Specs and gates that pass without checking".
• Honest gates. When a provenance pin, residue count or other gate moves, stop and report the row and what rigor sig-gen --print proposes. A # sig-gen gap: or # authored: marker, a gap_issues.yml row or a moved pin needs the brief's authorisation; the rules are ADR-107 and docs/agents/type-authoring.md. Copy no type into a declaration without checking it against every write site. Code keeps the shape it would have without the gate. Keep each rewritten spec's original assertion.
• Engine cost. For an engine change, run tool/engine_alloc_ab.rb against the merge base. A rise above pr_allocations_pct in bench/thresholds.yml is reported with where it comes from; the coordinator decides whether it lands (docs/agents/parallel-lanes.md step 6).
• Reach. After deleting or renaming a method, git grep --untracked -nw <name> -- ':!references'.
• Claims. The PR body, doc edits and changelog fragment say what the specs pin and no more. A binding doc under docs/type-specification/ or docs/internal-spec/ changes with the behaviour. Every user-facing change gets a changelog.d/ fragment, in a second push once the PR exists. A fixed fragment needs the broken behaviour to have shipped: find the commit that introduced it (git log -S, blame or bisect), and git merge-base --is-ancestor <commit> "$(git describe --tags --abbrev=0 origin/master)" must exit 0; an unshipped regression gets none. A new CLI output form is run as a user would: against the command's documented contract (1-based columns, argument order), combined with its other input forms, and past any cap it adds. cli.rb's help and docs/manual/ change in the same PR; make docs-check covers neither.
• Decisions. Make only the decisions the brief delegates, and record each in an approval-queue.d/ entry (its README has the format). Stop and report every other open choice for the coordinator to rule on.
• Known limits. When the PR deliberately gives up soundness or precision that a later change could win back (a floor that drops a fact, a decline to Dynamic, a cap, a rule or guard that withholds findings), add a "Known limits" section to the PR body with, per limit, its Kind, Why, Cost (a minimal example) and Revisit when (docs/agents/triage-labels.md § "Known limitations"), and name each in a few words on the report's Known limits line, not again under "for the coordinator to file". Re-send the line with a fix-round reply whenever it changes. An ordinary fallback for a shape the issue never asked about is not a known limit, and neither is one nobody will lift: say that in the spec instead.
• Closing keywords. Fixes #N only when the PR closes all of #N, on its own line, in the PR body and commit messages alike; otherwise Refs #N. Start every GitHub body with a one-line note that it was AI-generated.