Borrowing it
Nothing to install: this file belongs to ARCASSystems/FounderOS. 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/ARCASSystems/FounderOS/main/CLAUDE.mdgit clone --depth 1 https://github.com/ARCASSystems/FounderOSWrote 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/arcassystems/founderos/claude-md)<a href="https://agentmods.dev/instructions/arcassystems/founderos/claude-md"><img src="https://agentmods.dev/badge/instructions/arcassystems/founderos/claude-md/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.
<a href="https://agentmods.dev/instructions/arcassystems/founderos/claude-md"><img src="https://agentmods.dev/badge/instructions/arcassystems/founderos/claude-md.svg" alt="Reviewed on agentmods" width="80" 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 | $0.10414 | $0.10414 |
| Opus 5.5 | $0.04166 | $0.04166 |
| Sonnet 5.5 | $0.02083 | $0.02083 |
| Haiku 4.5 | $0.01041 | $0.01041 |
Grade A, and why
FounderOS 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 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.
How it starts
The opening of the file, as written. The whole thing — 345 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Founder OS - Claude Code Plugin
This is the generic Founder OS plugin. Install it to give Claude Code the context of who you are, how you work, what you are building, and what you need help with.
What This Is
Founder OS is a Claude Code plugin that installs an operating system for one founder: your identity, your roles, your priorities, your cadence, your scars - so the AI you work with stops treating you like an anonymous user and starts working like a chief of staff who has been with you for five years.
It is NOT a framework. It is NOT a multi-tenant AI platform. It is a product you install once and run every day.
Positioning non-negotiables
- The public Founder OS product is single-founder software. ARCAS's enterprise offering has a separate company and per-employee layer. Do not conflate the two, and do not frame the public product as team or collaboration software.
- Founder OS is plain markdown any capable agent can read and drive. Claude Code is the reference runtime we validate against, and where slash commands and hooks run. We do not ship a separate product per agent: no ChatGPT-Projects pack, no per-agent skills pack. The same markdown OS is read by whatever agent the user brings. See "Runtime honesty" below for the per-skill
Runs on:contract. - Keep the product's established hook framing. Do not invent demo-length claims, and do not paste private brand internals into this public repo. Match the wording already used elsewhere in this repo.
Quick Start
Say "set up Founder OS" to personalize this for your situation. If you prefer a slash command, it depends on how you installed: /setup on a ZIP or git-clone install, /founder-os:setup on a plugin install.
The wizard asks you questions about who you are, what you run, what tools you use, and what is slowing you down. From your answers it generates all the operating files in this repo - personalized to you. Takes 15-20 minutes the first time.
Updates
Founder OS ships with /founder-os:update to pull the latest System Layer files (skills, templates, commands, hooks) without touching your personal data. Run it whenever you want. The command tells you what is changing before applying.
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 · +14 lines · +1,018 tokens per session 482d36a90c9a
- 17d ago Changed · -2 lines · +90 tokens per session 71e1562b8ae2
- 20d ago Changed · +131 tokens per session 42e1ad4f7b83
- 22d ago Changed · +2 lines · +150 tokens per session 7f2738132e5b
- 1mo ago First seen · 331 lines · 9,025 tokens per session scan A 1419f70383d9
FounderOS CLAUDE.md is an instructions file published in the GitHub repository ARCASSystems/FounderOS (6 stars, last pushed yesterday), licensed MIT. It adds 10,414 tokens to every session, about $0.0417 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.
Other instructions, from other repositories
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.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
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 copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
deepseek-harness AGENTS.md
AGENTS.md instructions for deepseek-ai/deepseek-harness, covering agents.md, pre-stable apis and released session data, repository layout, commands and host sandbox failures.