Headroom is a library, proxy, and MCP server that compresses tool outputs, logs, files, retrieval chunks, and conversation history before they reach a language model. It helps coding agents use fewer context tokens while keeping the original content available locally when needed. Its catalogue add-ons support using Headroom with agent workflows.
Borrowing it
Nothing to install: this file belongs to headroomlabs-ai/headroom. 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/headroomlabs-ai/headroom/main/.github/copilot-instructions.mdgit clone --depth 1 https://github.com/headroomlabs-ai/headroomWrote 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/headroomlabs-ai/headroom/copilot-instructions)<a href="https://agentmods.dev/instructions/headroomlabs-ai/headroom/copilot-instructions"><img src="https://agentmods.dev/badge/instructions/headroomlabs-ai/headroom/copilot-instructions/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/headroomlabs-ai/headroom/copilot-instructions"><img src="https://agentmods.dev/badge/instructions/headroomlabs-ai/headroom/copilot-instructions.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 | $0.00138 | $0.00138 |
| Opus 5.5 | $0.00055 | $0.00055 |
| Sonnet 5.5 | $0.00028 | $0.00028 |
| Haiku 4.5 | $0.00014 | $0.00014 |
Grade A, and why
headroom copilot-instructions.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.
What it actually says
When performing a pull request review in this repository:
- Treat
.github/PULL_REQUEST_TEMPLATE.mdandCONTRIBUTING.mdas required policy, not optional guidance. - Flag pull requests that do not include concrete "Real Behavior Proof" with environment, exact commands or steps, observed result, and what was not tested.
- Be strict about contributor verification: missing tests, missing runtime evidence, or placeholder PR text should be called out.
- For user-facing, release, dependency, workflow, or security-sensitive changes, prefer blocking feedback over optional suggestions.
- Focus on correctness, safety, and whether the PR is actually ready for human maintainer review.
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 First seen · 8 lines · 138 tokens per session scan A ded6a77597b9
headroom copilot-instructions.md is an instructions file published in the GitHub repository headroomlabs-ai/headroom (75,453 stars, last pushed today), licensed Apache-2.0. It adds 138 tokens to every session, about $0.0006 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 2026-08-30.
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