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dev-challenge: Instructions file for Claude Code

CLAUDE.md

dev-challenge CLAUDE.md is an instructions file for Claude Code from micheltlutz/dev-challenge. It costs 543 tokens per session, scanned A, original, MIT.

Project instructions for the micheltlutz/dev-challenge coding exercises, including how to read challenge requirements, use commands, and choose between mentoring and solving.

In plain words
What is it for?
Use them when starting a challenge, checking whether a solution passes, suggesting the next task, or reviewing changes against the stated requirements.
Why use it?
They prevent answers based on incomplete files and help keep guidance aligned with each exercise's specification and acceptance criteria.

Instructions file for Claude Code

Written for Claude Code: the file is CLAUDE.md. Also seen: mentions CLAUDE.md; mentions subagents; mentions Claude Code.

This is micheltlutz/dev-challenge's own configuration. It tells Claude Code how to work on dev-challenge itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything dev-challenge configures →

not rated 33repo 5d ago A scan 543 tokens original MIT
View source ↗ micheltlutz/dev-challenge micheltlutz.me
Reuse

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.

Copy the file
curl -O https://raw.githubusercontent.com/micheltlutz/dev-challenge/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/micheltlutz/dev-challenge

Made for: Claude Code.

Wrote this? Show the measurements

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Per session 543 This file is loaded in full into every session.
When invoked 543 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00543 $0.00543
Opus 5.5 $0.00217 $0.00217
Sonnet 5.5 $0.00109 $0.00109
Haiku 4.5 $0.00054 $0.00054

Measured 2mo ago against content hash f80bbf99b4aa, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

dev-challenge CLAUDE.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.

CLAUDE.md · 58 lines

How it starts

The opening of the file, as written. The whole thing — 58 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

@AGENTS.md

Everything above applies. What follows is Claude Code specific.

The one rule to internalise

Read specs/challenges/<id>/spec.md and acceptance.md before answering anything about what a challenge requires. Never answer from readme_files/ (redirect stubs) or from how such an API usually works.

And decide which job you are doing — mentoring a learner or improving the lab. The default when someone is working through a challenge is to coach, not to hand over the implementation. See "First: which job are you doing?" in AGENTS.md.

Slash commands

Command What it does
/challenge <id> Load a challenge's spec, criteria and design tokens, and start work on it
/verify [id] Run the harness and explain failures in terms of the criteria
/next Suggest what to do next from the dependency graph and what currently passes

/challenge <id> --solve switches to solver mode explicitly.

Subagents

Agent Use it for
challenge-mentor Reviewing a learner's work without solving it for them
spec-auditor Checking a spec change against the contract before a PR

Skills

Skill Loads when
challenge-workflow Someone is working through a challenge
design-fidelity Comparing an implemented UI against the tokens and mockups
spec-authoring Adding or editing a challenge in specs/

MCP

.mcp.json declares an optional Figma Dev Mode server. With it, you can pull real node specs instead of inferring layout from a PNG. It needs the user's own Figma token and is inert without one — the sampled tokens in specs/design/tokens.json are the fallback, and they are good enough for every challenge.

Working in this repo

  • The venv is at ./venv. Use ./venv/bin/python, or activate it.
  • Before saying you are done, run what CI runs (see Commands in AGENTS.md).
  • dev-challenge.db is generated. Change scripts/seed.py and regenerate; do not hand-edit it.
  • specs/openapi.json and specs/design/tokens.css are generated. Same rule.

Read the full file on GitHub · 58 lines

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.

  1. 2mo ago First seen · 58 lines · 543 tokens per session scan A f80bbf99b4aa

Subscribe to this mod's changes

dev-challenge CLAUDE.md is an instructions file published in the GitHub repository micheltlutz/dev-challenge (33 stars, last pushed 5d ago), licensed MIT. It adds 543 tokens to every session, about $0.0022 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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Related

dev-challenge CLAUDE.md compared with instructions from other repositories

dev-challenge CLAUDE.md next to 6 instructions from other repositories
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dev-challenge CLAUDE.mdmicheltlutz/dev-challengeInstructions file335d agoMITA543Claude Code
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