Borrowing it
Nothing to install: this file belongs to yarlson/yarstack. 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/yarlson/yarstack/main/AGENTS.mdgit clone --depth 1 https://github.com/yarlson/yarstackWrote 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/yarlson/yarstack/agents-md)<a href="https://agentmods.dev/instructions/yarlson/yarstack/agents-md"><img src="https://agentmods.dev/badge/instructions/yarlson/yarstack/agents-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/yarlson/yarstack/agents-md"><img src="https://agentmods.dev/badge/instructions/yarlson/yarstack/agents-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 | $0.00758 | $0.00758 |
| Opus 5.5 | $0.00303 | $0.00303 |
| Sonnet 5.5 | $0.00152 | $0.00152 |
| Haiku 4.5 | $0.00076 | $0.00076 |
Grade A, and why
yarstack AGENTS.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 yesterday.
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 — 43 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Repository Rules
Commands
- Run
make validatebefore finalizing changes. - Run
make install-system-promptonly when the user explicitly requests changes to global agent guidance; it writes outside the repository. - Test installer changes with
YARSTACK_AGENT_HOMEpointed at a temporary directory. Do not test destructive paths against the real home directory.
Package invariants
- Keep each installable package self-contained under
plugins/<plugin-name>/. Marketplace installs are cached copies; runtime paths must not traverse outside the owning plugin root. - Follow
SKILL_FORMAT.mdwhen adding or changing skills. - Keep Codex metadata in
.codex-plugin/plugin.json, Claude metadata in.claude-plugin/plugin.json, and their marketplace schemas separate. - Keep each plugin's shared identity, author, repository, and version values aligned between its manifests.
- Do not change
0.1.0or any later explicit version unless the user requests a release/version change. When changing it, update both manifests for that plugin together. - Do not add a plugin-root
CLAUDE.md; Claude Code does not load it as plugin context. - Do not declare skills, hooks, agents, MCP servers, apps, assets, or capabilities before the corresponding package content and behavior exist.
- Keep every procedure in a skill. Agents under
plugins/<plugin-name>/agents/load only in Claude Code, because Codex plugins cannot ship agents. Use an agent as a worker that applies skills, and keep each skill usable without it.
Engineering guidance
- Treat
plugins/yarstack/agent-guidance/engineering-standards/standards.mdas the canonical source for the installed global guidance. - Preserve the guidance text unless the user explicitly requests prompt changes. When a rule changes, update its evidence entry in
plugins/yarstack/agent-guidance/engineering-standards/README.md. - Preserve installer idempotency, existing symlinks, preflight rejection of dangling symlinks, and backups before replacing differing files.
- Keep guidance installation explicit. Do not convert it into an automatic hook, startup action, or implicit plugin side effect.
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.
- yesterday Changed · +1 lines · +79 tokens per session b1af3221d26b
- 1mo ago First seen · 42 lines · 679 tokens per session scan A de9d570f8091
yarstack AGENTS.md is an instructions file published in the GitHub repository yarlson/yarstack (3 stars, last pushed today), licensed MIT. It adds 758 tokens to every session, about $0.0030 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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