A workflow for turning an approved software direction into tested branch work. It plans changes, sends the plan to an isolated implementer, reviews the result, and stops before merging it into the main branch.

For initializing repository conventions, planning approved features, dispatching implementation work, verifying a feature branch, and preparing an explicitly approved merge.

It separates planning, implementation, review, and merging so unfinished or unsuitable work does not enter the main codebase automatically. It also requires product or scope decisions to be escalated when evidence cannot resolve them.

arc — Skill for Claude Code and Codex by emilvaintrub/ShowRunner

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add emilvaintrub/ShowRunner --skill arc

Clone the repo

git clone --depth 1 https://github.com/emilvaintrub/ShowRunner

Made for: Claude Code, Codex.

Or install showrunner, the plugin that ships this one along with the rest of its 7 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/emilvaintrub/showrunner/arc/github.svg)](https://agentmods.dev/skills/emilvaintrub/showrunner/arc)

Your own site

<a href="https://agentmods.dev/skills/emilvaintrub/showrunner/arc"><img src="https://agentmods.dev/badge/skills/emilvaintrub/showrunner/arc/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/emilvaintrub/showrunner/arc"><img src="https://agentmods.dev/badge/skills/emilvaintrub/showrunner/arc.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 73 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 670 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00073	$0.00670
Opus 5.5	$0.00029	$0.00268
Sonnet 5.5	$0.00015	$0.00134
Haiku 4.5	$0.00007	$0.00067

Measured today against content hash ca6182042067, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

arc scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured today.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

showrunner/arc/SKILL.md · 60 lines

How it starts

The opening of the file, as written. The whole thing — 60 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Arc

Turn approved direction into verified branch work. Resolve conventions from evidence, escalate product or scope calls, and never merge automatically.

Load

Read ../core/lifecycle.md and ../core/method.md.
Read the active project's .claude/showrunner/config.md and the state ledger it names in lifecycle.state_file (default .claude/showrunner/state.md).
Read method.md.
For run, load ../core/dispatch.md.
For verify or merge, load ../core/merge.md. For verify, also load ../gates/audit.md, and ../gates/wow-check.md when the arc touches UI and the creative gate is enabled.
Load only the templates required by the requested command.

Route

Arc runs lifecycle stages 7-10 (arc-plan, step0, build, verify) and executes the merge ceremony. The conductor chains them: plan flows into run, run into verify, and verify SHIP into the Sentry security stage, without the owner asking.

init: inspect repository mechanics and fill the Arc config section.
plan: consume approved direction, resolve conventions, and render an implementation prompt.
run: execute plan, dispatch a cold implementer, review Step 0, collect evidence, and stop before merge.
verify: independently review the exact feature tip and issue SHIP, FIX, or REDESIGN.
merge: after SHIP, required smoke, and explicit approval, execute the shared two-commit ceremony.

Use templates/questions.md for human decisions, templates/spec.md for Arc-owned planning, templates/impl-prompt.md for dispatch, templates/ship-report.md for completion, and templates/merge.md for merge readiness.

Hard Stops

Never plan from a source whose handoff ledger row is missing; a raw brief goes to intake, not to Arc.
Never rewrite approved Forge sections 1-8 while consuming sections 9-11.
Never dispatch before the front-loaded decision gate resolves.
Never authorize edits before Step 0 approval.
Never widen scope silently.
Never accept static inspection as required physical or operational smoke.
Never issue SHIP without binding the verdict to the exact feature tip.
Never merge without independent SHIP, required smoke, and explicit human approval.
Never import facts or wording from another project.

Read the full file on GitHub · 60 lines

Files

What ships with it

7 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

today Changed · +1 lines ca6182042067
1mo ago Changed · +10 lines d6b59290f2c0
2mo ago First seen · 49 lines · 73 tokens per session scan A 0bdcdc2a1153

Subscribe to this mod's changes

arc is a skill published in the GitHub repository emilvaintrub/ShowRunner (2 stars, last pushed yesterday), licensed MIT. It adds 73 tokens to every session and 670 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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