Borrowing it
Nothing to install: this file belongs to peters/horizon. 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/peters/horizon/main/.github/copilot-instructions.mdgit clone --depth 1 https://github.com/peters/horizonWrote 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/peters/horizon/copilot-instructions)<a href="https://agentmods.dev/instructions/peters/horizon/copilot-instructions"><img src="https://agentmods.dev/badge/instructions/peters/horizon/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/peters/horizon/copilot-instructions"><img src="https://agentmods.dev/badge/instructions/peters/horizon/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 | $0.00108 | $0.00108 |
| Opus 5.5 | $0.00043 | $0.00043 |
| Sonnet 5.5 | $0.00022 | $0.00022 |
| Haiku 4.5 | $0.00011 | $0.00011 |
Grade A, and why
horizon 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 3d 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
Code review instructions moved
The review rules are in docs/, which is the documentation home of this
repository. This file is a pointer only. It holds no review rule.
- Review scope:
docs/review/review-scope.md - Trust boundaries:
docs/review/trust-boundaries/ - How a review reads them:
docs/review/README.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.
- 3d ago Changed · -49 lines · -514 tokens per session aaaf1221c231
- 15d ago First seen · 58 lines · 622 tokens per session scan A 96f866d833ff
horizon copilot-instructions.md is an instructions file published in the GitHub repository peters/horizon (722 stars, last pushed today), licensed MIT. It adds 108 tokens to every session, about $0.0004 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 2026-10-13.
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Model-specific prompt authoring and registry guidelines.