Borrowing it
Nothing to install: this file belongs to randomittin/heimdall. 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/randomittin/heimdall/main/AGENTS.mdgit clone --depth 1 https://github.com/randomittin/heimdallWrote 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/randomittin/heimdall/agents-md)<a href="https://agentmods.dev/instructions/randomittin/heimdall/agents-md"><img src="https://agentmods.dev/badge/instructions/randomittin/heimdall/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/randomittin/heimdall/agents-md"><img src="https://agentmods.dev/badge/instructions/randomittin/heimdall/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 | $0.01175 | $0.01175 |
| Opus 5.5 | $0.00470 | $0.00470 |
| Sonnet 5.5 | $0.00235 | $0.00235 |
| Haiku 4.5 | $0.00118 | $0.00118 |
Grade A, and why
heimdall 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 7d 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 — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Working in the Heimdall repo
Heimdall is the watchman: it gates other people's repos. So the bar here is the bar we sell. Read this before your first edit.
The rules that actually block you
- No stub, placeholder, TODO, or skeleton code. A
PreToolUsehook scans every Claude Code write for unfinished code shapes (empty bodies, not-implemented throws,# TODOcomments) and refuses the write — but that hook only fires inside a live Claude Code session.bin/heimdall-gate-run'spre-commitphase backs it up at the git layer: it re-scans the staged diff against the same shared shapes (bin/lib/heimdall-stub-patterns.sh), so the ban holds no matter which tool — or human — makes the commit. If you cannot implement something fully, say so — faking it is the one failure mode this repo exists to catch. - Tests are bash. One file per surface:
test/<name>.test.sh, run withbash test/<name>.test.sh. Exit 0 = green. A test printsPASS/FAILlines and a count. Follow the shape of a neighbouring test rather than inventing a harness. - Every assertion must be falsifiable. Before you call a test done, break the thing it covers and watch it go RED, then revert and watch it go GREEN. A test that cannot fail is not a gate — it is decoration.
- Test once, at the end. Run only the test file(s) you add or edit, once, after
your changes are written; the full sweep (
bash test/run-all.sh) runs once, on the final frozen tree, immediately before the landing commit — see CLAUDE.md "When the full gate runs". The break-it-and-watch-it-go-RED check above is a run on a different tree, not a repeat. - Batch before you sweep. Merge every pending agent result first, then run ONE sweep; never merge anything between a green sweep and its push, and never start a second sweep while one runs — see CLAUDE.md "When the full gate runs".
- Quality gates run before push (
heimdall-state check-quality-gates): tests green, lint clean, no untested changes.
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.
- 7d ago Changed · +3 lines · +57 tokens per session 013dfbf8527b
- 10d ago Changed · +5 lines · +98 tokens per session 6cc437d47c77
- 1mo ago First seen · 74 lines · 1,020 tokens per session scan A e2ecdf3e1bce
heimdall AGENTS.md is an instructions file published in the GitHub repository randomittin/heimdall (5 stars, last pushed 6d ago), licensed MIT. It adds 1,175 tokens to every session, about $0.0047 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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