Borrowing it
Nothing to install: this file belongs to ymm-oss/fsl. 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/ymm-oss/fsl/main/CLAUDE.mdgit clone --depth 1 https://github.com/ymm-oss/fslWrote 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/ymm-oss/fsl/claude-md)<a href="https://agentmods.dev/instructions/ymm-oss/fsl/claude-md"><img src="https://agentmods.dev/badge/instructions/ymm-oss/fsl/claude-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/ymm-oss/fsl/claude-md"><img src="https://agentmods.dev/badge/instructions/ymm-oss/fsl/claude-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 | $0.00616 | $0.00616 |
| Opus 5.5 | $0.00246 | $0.00246 |
| Sonnet 5.5 | $0.00123 | $0.00123 |
| Haiku 4.5 | $0.00062 | $0.00062 |
Grade A, and why
fsl 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 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.
How it starts
The opening of the file, as written. The whole thing — 53 lines — stays where its author put it; the contents beside it link to each section on GitHub.
@AGENTS.md
Claude Code instructions
Sources of truth
- The working tree and verified repository artifacts are current state; conversation history is not.
- The native Rust workspace is authoritative. Treat
src/fslc/as a frozen compatibility/LSP surface unless the requested outcome explicitly crosses that boundary. - Accepted decisions live in
docs/design/DESIGN-*.md. Current task state lives in.claude/work/active.mdwhen that local file exists. - Do not treat proposals, plans, auto memory, or an earlier session's claims as implemented behavior.
Starting or resuming work
- Inspect
git status --shortand the relevant implementation before editing. - If
.claude/work/active.mdexists, compare it with the working tree and report stale claims. - For a substantial task, use
/task-startto create or refresh the task packet before implementation. - State the requested outcome, affected authority surface, invariant, and narrow verification plan.
- Do not read unrelated directories without a concrete reason.
Implementation policy
- Prefer the smallest contract-preserving change. Do not add fallback behavior or compatibility work unless the requirement or an established public contract calls for it.
- For new language behavior, change the Rust implementation first. Change the frozen Python reference only when an accepted compatibility decision requires both implementations to move.
- Preserve the runtime/solver dependency boundary and symbolic/concrete/BFS agreement.
- Keep CLI stdout machine-readable where the command contract requires JSON; diagnostics and progress belong on the established channel.
- Never suppress an error, weaken a spec, hand-edit a generated snapshot, or expand an allowlist merely to make a check green.
Verification and review
- Run the narrowest relevant Rust test or native
fslccommand first. - Inspect the diff and exercise the changed contract with positive, negative, and boundary evidence.
- Run broader Rust, compatibility, or browser gates in proportion to the affected surface.
- Use the specialized FSL reviewers after semantics, coupled language files, or specs change.
- To review a pull request that resolves an issue, use
/pr-review; it orchestrates the specialized reviewers and never merges. - Before ending or compacting substantial work, run
/checkpointand preserve exact test outcomes.
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 Changed · +1 tokens per session c12e5c578335
- 2mo ago First seen · 53 lines · 615 tokens per session scan A cf08548b14ec
fsl CLAUDE.md is an instructions file published in the GitHub repository ymm-oss/fsl (35 stars, last pushed today), licensed Apache-2.0. It adds 616 tokens to every session, about $0.0025 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.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
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Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
deno copilot-instructions.md
Copilot instructions for denoland/deno, covering deno development guide for github copilot, network access, high level overview, key directories and key files to understand first.