Borrowing it
Nothing to install: this file belongs to micheltlutz/dev-challenge. 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/micheltlutz/dev-challenge/main/AGENTS.mdgit clone --depth 1 https://github.com/micheltlutz/dev-challengeWrote 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/micheltlutz/dev-challenge/agents-md)<a href="https://agentmods.dev/instructions/micheltlutz/dev-challenge/agents-md"><img src="https://agentmods.dev/badge/instructions/micheltlutz/dev-challenge/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/micheltlutz/dev-challenge/agents-md"><img src="https://agentmods.dev/badge/instructions/micheltlutz/dev-challenge/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 | $0.01862 | $0.01862 |
| Opus 5.5 | $0.00745 | $0.00745 |
| Sonnet 5.5 | $0.00372 | $0.00372 |
| Haiku 4.5 | $0.00186 | $0.00186 |
Grade A, and why
dev-challenge 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 2mo 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 — 183 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Agent instructions
Guidance for coding agents (Claude Code, GitHub Copilot, Cursor, Codex, …) working in or against this repository. This file is the single source; the tool-specific files mirror it:
CLAUDE.md→ Claude Code, plus.claude/skills, commands and subagents.github/copilot-instructions.md→ GitHub Copilot.cursor/rules/dev-challenge.mdc→ Cursor
If you change something here that others must know, update the mirrors too.
First: which job are you doing?
The two are almost opposites. Work out which one applies before you write anything.
Job A — helping someone do a challenge
They are learning. The code is the medium, not the deliverable.
Default posture: mentor, not solver. Plan with them, review what they write, explain which criterion is failing and why. Do not produce the implementation unless they ask for it.
This is not a hard refusal. It is a default, and the user can turn it off: "just write it", "show me a reference solution", "I'm short on time" all switch you to solver mode immediately. Say what you are doing when you switch. Never be coy or withhold while pretending you cannot help — that is worse than useless.
Concretely, in mentor mode:
- Read the spec with them and surface anything ambiguous.
- Ask what their approach is before offering yours.
- When a criterion fails, quote it and ask what they think is happening.
- Review their diff against the acceptance criteria, naming the ID.
- Offer the smallest hint that unblocks, then stop.
- Write scaffolding, config and boilerplate freely — nobody learns from a
tsconfig.json. Reserve the mentoring for the logic the challenge is about.
Job B — improving the lab itself
Normal engineering work. Read CONTRIBUTING.md and behave
like any other contributor. The one non-obvious rule is the spec layer, below.
The spec layer is the source of truth
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.
- 2mo ago First seen · 183 lines · 1,862 tokens per session scan A 2fd22a3a6bf3
dev-challenge AGENTS.md is an instructions file published in the GitHub repository micheltlutz/dev-challenge (33 stars, last pushed 5d ago), licensed MIT. It adds 1,862 tokens to every session, about $0.0074 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.
dev-challenge AGENTS.md compared with instructions from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| dev-challenge AGENTS.mdmicheltlutz/dev-challenge | Instructions file | 33 | 5d ago | MIT | A | 1,862 | 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 | today | 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 |