Borrowing it
Nothing to install: this file belongs to meganemura/headsign. 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/meganemura/headsign/main/AGENTS.mdgit clone --depth 1 https://github.com/meganemura/headsignWrote 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/meganemura/headsign/agents-md)<a href="https://agentmods.dev/instructions/meganemura/headsign/agents-md"><img src="https://agentmods.dev/badge/instructions/meganemura/headsign/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/meganemura/headsign/agents-md"><img src="https://agentmods.dev/badge/instructions/meganemura/headsign/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 | $0.00445 | $0.00445 |
| Opus 5 | $0.00222 | $0.00222 |
| Sonnet 5 | $0.00089 | $0.00089 |
| Haiku 4.5 | $0.00044 | $0.00044 |
Grade A, and why
headsign 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 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.
What it actually says
Changing headsign
These instructions govern changes to headsign itself. They are not instructions for a consumer repository that uses the plugin.
Before changing runtime behavior, skills, workflow vocabulary, or product guidance, read ADR-0039 and the ADR that owns the behavior you will change. Use the ADR index to locate that decision. For optimization behavior, also read ADR-0038.
Carry these principles into the change:
- Design for more capable future models. Give the model objectives, constraints, facts, and authority. Keep semantic judgment with the model.
- Keep optimization enabled by default. Create an opportunity to improve the method; do not force edits or reward completed assessment records.
- Choose consequential outcomes over convenient nearby edits. A larger proposal or a justified decision to retain the method can be the right result.
- Permit an explicit future bet. State the assumed change, expected value, uncertainty, and reason to reconsider it. Verify present behavior separately.
- Keep the harness small. Justify added runtime responsibilities and instructions; consider what a stronger model lets us remove.
- Preserve the user's requested outcomes, authority, budget, and ability to stop. Reversible procedural repairs can use existing task authority.
Before handing over a design change, explain how it follows these principles and what observable behavior you verified. Scale the explanation to the change; do not create a separate report for a routine fix. Check for instructions that would make another agent follow an older, conflicting policy.
If the intended change conflicts with an accepted decision, identify the conflict and amend that ADR explicitly. Do not silently override it through code, a skill, or a local workaround. Preserve the user's authority over goals and constraints when proposing an amendment.
Give delegated agents the relevant ADR paths and these constraints in their task instructions. Ask reviewers to check policy alignment as well as behavior. Follow Maintenance for validation and distribution.
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 First seen · 41 lines · 445 tokens per session scan A 0419ceb0b435
headsign AGENTS.md is an instructions file published in the GitHub repository meganemura/headsign (1 stars, last pushed yesterday), licensed MIT. It adds 445 tokens to every session, about $0.0022 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 2026-09-13.
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