Borrowing it
Nothing to install: this file belongs to philipyaz/cos. 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/philipyaz/cos/main/CLAUDE.mdgit clone --depth 1 https://github.com/philipyaz/cosWrote 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/philipyaz/cos/claude-md)<a href="https://agentmods.dev/instructions/philipyaz/cos/claude-md"><img src="https://agentmods.dev/badge/instructions/philipyaz/cos/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/philipyaz/cos/claude-md"><img src="https://agentmods.dev/badge/instructions/philipyaz/cos/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 | $0.03495 | $0.03495 |
| Opus 5.5 | $0.01398 | $0.01398 |
| Sonnet 5.5 | $0.00699 | $0.00699 |
| Haiku 4.5 | $0.00349 | $0.00349 |
Grade A, and why
cos 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 1mo 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 — 166 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Cos — repo guide (read this first)
Cos — a personal "chief of staff": a writable board (board/, Next.js + a JSON store) for
work+life to-dos, a knowledge vault (vault/, the LLM-Wiki pattern), a prompt-injection
guard (guard/, FastAPI sidecar), semantic search (search/, sidecar), and MCP
servers (mcp/) that expose it all to agents. Feature docs live in the MkDocs site under
docs/ (Material theme, mkdocs.yml, published to GitHub Pages): e.g. docs/architecture/spec.md,
docs/features/board.md, docs/security/guard.md, docs/reference/search.md,
docs/architecture/hierarchy.md, docs/reference/migration.md. README.md (the repo
landing/quickstart) stays at the root.
Skills live in two trees, and the split is load-bearing. Put a setup skill in the repo-root
.claude/skills/ — Claude Code reads it live off disk and Cowork never sees it (cos-setup is the
single first-run orchestrator; each add-on ships its own <name>-mcp-setup skill). Put an
operator skill — anything a scheduled sweep runs or delegates to — in board/.claude/skills/,
and rebuild its bundle with node scripts/pack-skills.mjs after every edit. Cowork installs skills
only from board/.claude/skill-bundles/*.zip, so a delegation to a root-level skill is a silent
no-op there — not an error. Rebuilding a bundle does not install it: re-upload the .zip in
Cowork (Settings → Capabilities → Skills) after every rebuild. Nothing checks this, so until you do,
that skill's half of the feature is silently dead there while the repo stays green.
The bundles are committed binaries, so git cannot merge two branches that touched the same skill:
after any merge or rebase that brings in someone else's skill edit, re-run pack-skills.mjs and
commit the rebuilt .zip — a red pack-skills --check whose output says stale or missing there
means "rebuild", not "defect" (only an automation.json sync error from the packer itself is a defect).
Every setup/skill shell step begins with source "$(git rev-parse --show-toplevel)/config/load-config.sh",
which resolves REPO_ROOT from git and exports machine config from config/cos.env (generated by
cos-setup) — paths, ports, and URLs (REPO_ROOT, BREW_PREFIX, VAULT_DIR, BOARD_URL, the bridge/
sidecar ports + URLs, etc.) so nothing is hardcoded. The config/ dir splits by concern: cos.env
(machine paths/ports), secrets.env (the Anthropic API key), settings.json (board prefs), and
auto-sync.json (router switch); the loaders, secret-validation.mjs, auto-sync.json, and the
*.example files are committed — the live cos.env/secrets.env/settings.json are gitignored.
Secrets reach the two MCP clients by different binding paths (Claude Code re-reads secrets.env
per start; Cowork gets an inlined snapshot), so rotation is a two-step — see the "Cowork holds a
COPY of every secret" gotcha in mcp/CLAUDE.md.
mcp/CLAUDE.md— read it before touchingmcp/.board/.claude/CLAUDE.md— read it before writing or editing an operator skill.board/data/CLAUDE.md—board/data/is LIVE, irreplaceable user data; read it BEFORE touching anything there — never seedboard/dataon a machine with live data.
Multi-device — one hub, thin spokes. Cos is multi-device via hub & spoke: ONE machine (the
hub) runs the board and owns all state; every other device reaches it over Tailscale. To just
VIEW/use the board from another device you need nothing on that device — the hub runs the
production board (cd board && npm run build && npm run start, or the boardapp LaunchAgent —
never next dev behind a proxy) behind tailscale serve --bg 3000, and any tailnet device opens the
portless https://<hub>.<tailnet>.ts.net in a browser (full read/write UI — the browser writes
through the same HTTP API). You add a spoke (spoke-setup — the thin local stdio MCP wrappers
pointed at the hub's BOARD_URL) ONLY when you also want agents (Claude Code/Cowork) to drive the
board from that machine, since Cowork accepts only local stdio MCP servers (not a remote HTTP MCP
over the tailnet). Move the hub role to a different machine with hub-handover (the old one stays a
browser viewer, needing no spoke). Full runbook: docs/architecture/multi-device.md.
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.
- 1mo ago Changed · +3 lines · +54 tokens per session db1f731a1af0
- 1mo ago Changed · +2 lines · +60 tokens per session a7ef78d8152d
- 1mo ago Changed · +5 lines · +106 tokens per session 6493d1f204a0
- 1mo ago Changed · +3 lines · +45 tokens per session b4218459726b
- 1mo ago First seen · 153 lines · 3,230 tokens per session scan A 817ebf47af36
cos CLAUDE.md is an instructions file published in the GitHub repository philipyaz/cos (4 stars, last pushed 2d ago), licensed MIT. It adds 3,495 tokens to every session, about $0.0140 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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