Borrowing it
Nothing to install: this file belongs to noontide-co/mainbranch. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/noontide-co/mainbranch/main/CLAUDE.mdgit clone --depth 1 https://github.com/noontide-co/mainbranchWrote 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.
[](https://agentmods.dev/instructions/noontide-co/mainbranch/claude-md)<a href="https://agentmods.dev/instructions/noontide-co/mainbranch/claude-md"><img src="https://agentmods.dev/badge/instructions/noontide-co/mainbranch/claude-md.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00711 | $0.00711 |
| Opus 5 | $0.00356 | $0.00356 |
| Sonnet 5 | $0.00142 | $0.00142 |
| Haiku 4.5 | $0.00071 | $0.00071 |
Grade A, and why
mainbranch CLAUDE.md 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 8d ago.
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.
How it starts
The opening of the file, as written. The whole thing — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Claude Code Instructions
Read AGENTS.md first. It is the shared operating contract for all agents
working in this repository.
This file only adds Claude Code-specific guidance for the Main Branch engine repo.
Repository Role
This is the public noontide-co/mainbranch engine repository. It contains the
mb CLI, bundled agent-runtime skills, docs, fixtures, tests, and release
metadata.
It is not a user's business repo. Business data belongs in the repo created by
mb onboard or mb init, not in this engine checkout.
Product Loop To Preserve
Main Branch's current daily loop is: open a business repo, start Claude Code,
run /mb-start or follow generated repo instructions, ground the agent in
mb facts, route business input into primitives such as bets, research,
decisions, pushes, playbooks, outcomes, and checkpoints, then close with
/mb-end or checkpoint guidance so the durable memory lands in git.
mb is the deterministic control and enforcement plane. Claude Code skills are
the judgment-heavy execution layer. Keep user-facing guidance in business
language first, and treat issues, branches, pull requests, commits, graph links,
and provider state as the technical memory layer underneath the business loop.
How to Work Here
- Follow
AGENTS.mdfor product shape, scope, public/private boundaries, branch discipline, validation, and PR expectations. - Use
README.md,docs/,decisions/, tests, and GitHub issues as durable context. - Keep local scratch files out of durable product docs and commits.
- Run
scripts/check.shfrom the repo root before pushing code or docs that could affect packaged behavior. - If you change first-run, skill discovery,
mb init,mb onboard,mb start,mb status,mb update, or bundled skills, add the relevant fixture/package/runtime smoke evidence described inAGENTS.md.
Engine vs Business Repo
When a user is operating Main Branch, they should be in their business repo:
cd path/to/my-business
mb status
mb start --launch
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.
- 8d ago First seen · 77 lines · 711 tokens per session scan A 7c33d68f5e60
mainbranch CLAUDE.md is an instructions file published in the GitHub repository noontide-co/mainbranch (39 stars, last pushed 24d ago), licensed MIT. It adds 711 tokens to every session, about $0.0036 per session on Opus 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 2026-08-30.
Other instructions, from other repositories
codex AGENTS.md
AGENTS.md instructions for openai/codex, covering rust/codex-rs, the codex-core crate, code review rules, crate api surface and model visible context.
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, applying the notice (cutover) and fallback chain (never fail the build).
spec-kit AGENTS.md
AGENTS.md instructions for github/spec-kit, covering agents.md, about spec kit and specify, quickstart — add a new integration in 5 steps, integration architecture and integrationmanifest — file tracking.