Borrowing it
Nothing to install: this file belongs to slopus/happy-agent. 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/slopus/happy-agent/main/AGENTS.mdgit clone --depth 1 https://github.com/slopus/happy-agentWrote 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/slopus/happy-agent/agents-md)<a href="https://agentmods.dev/instructions/slopus/happy-agent/agents-md"><img src="https://agentmods.dev/badge/instructions/slopus/happy-agent/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/slopus/happy-agent/agents-md"><img src="https://agentmods.dev/badge/instructions/slopus/happy-agent/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 | $0.06505 | $0.06505 |
| Opus 5.5 | $0.02602 | $0.02602 |
| Sonnet 5.5 | $0.01301 | $0.01301 |
| Haiku 4.5 | $0.00651 | $0.00651 |
Grade A, and why
happy-agent 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 9d 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 — 336 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Agent Instructions
Master plans
Read master-plans/00-master-plan.md first, before any other work. It explains how master plans are used and maintained. Then find every plan in master-plans/ relevant to your task and read each one in full before starting.
Master plans are dictated by the user and describe where the product is going, in what order, and what counts as done. They outrank conclusions drawn from the existing code. Do not create, edit, rename, or delete a file in master-plans/ unless the user explicitly asks for that change in the current task. When the code contradicts a master plan, report the contradiction instead of revising the plan.
All persistent plans must live in master-plans/ and follow the master-plan rules above. Do not create design documents, implementation plans, slash-command plan artifacts, or planning directories anywhere else in the repository, including docs/plans/.
Discussion notes that support or contextualize master plans must live only in
master-plans/notes/. Do not create these notes in the master-plans/ root,
in another documentation directory, or anywhere else in the repository.
API specification
Do not create, edit, rename, or delete any API.md file without direct human
input in the current task that explicitly authorizes the specific API
specification change.
packages/happy-agent/API.md is the authoritative Happy Agent API contract. Client types,
runtime schemas, daemon behavior, tests, and documentation must conform to it exactly. Never
invent, implement, preserve, or release behavior that deviates from the specification; stop and
request a human-directed specification change when the desired behavior is not already described.
Happy Agent API compatibility begins with protocol version 22. From version 22 onward, every API change must be backward-compatible and additive: never remove or rename an existing field, and never add a required field. New fields must be optional so older clients and daemons can ignore them safely. If a desired change cannot be made within those constraints, stop and request direct human guidance rather than breaking compatibility.
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.
- 9d ago Changed · +4 lines · +66 tokens per session 2bf522fbbaeb
- 13d ago Changed · +8 lines · +95 tokens per session 50f2b29e3548
- 14d ago Changed · +2 lines · +139 tokens per session 8512d9bcafd5
- 18d ago Changed · +8 lines · +115 tokens per session bdc9a4f26954
- 27d ago Changed · -22 lines · -416 tokens per session c7123ab0021b
- 1mo ago Changed · +4 lines · +80 tokens per session 3b40193208fe
- 2mo ago First seen · 332 lines · 6,426 tokens per session scan A 4a2f1e34975f
happy-agent AGENTS.md is an instructions file published in the GitHub repository slopus/happy-agent (38 stars, last pushed yesterday), licensed MIT. It adds 6,505 tokens to every session, about $0.0260 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.
happy-agent AGENTS.md compared with instructions from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| happy-agent AGENTS.mdslopus/happy-agent | Instructions file | 38 | yesterday | MIT | A | 6,505 | Codex, OpenCode |
| vscode buildNext.instructions.mdmicrosoft/vscode | Instructions file | 195k | yesterday | MIT | A | 9,719 | GitHub Copilot |
| next.js AGENTS.mdvercel/next.js | Instructions file | 143k | yesterday | MIT | A | 7,461 | Codex, OpenCode |
| langchain AGENTS.mdlangchain-ai/langchain | Instructions file | 149k | yesterday | MIT | A | 4,680 | Codex, OpenCode |
| vscode oss-third-party-notices.instructions.mdmicrosoft/vscode | Instructions file | 195k | yesterday | MIT | A | 5,516 | GitHub Copilot |
| vscode copilot-instructions.mdmicrosoft/vscode | Instructions file | 195k | yesterday | MIT | A | 3,093 | GitHub Copilot |
| deepseek-harness AGENTS.mddeepseek-ai/deepseek-harness | Instructions file | 274k | 2d ago | MIT | A | 4,313 | Codex, OpenCode |