fsl: Agent for Claude Code

.claude/agents/fsl-test-diagnostician.md

fsl-test-diagnostician is an agent for Claude Code from ymm-oss/fsl. It costs 48 tokens per session (224 once invoked), scanned A, original, Apache-2.0.

A diagnostic workflow for understanding unclear or overly long Rust, browser, compatibility, or parity test output. It finds the first failure that caused the problem and reports the evidence without changing source files.

In plain words
What is it for?
Use it to record the failing command, status, test or code unit, likely cause, and a focused reproduction. It distinguishes product defects from dependency, environment, generated-file, and contract problems.
Why use it?
Test logs often contain follow-on errors that hide the original cause. This narrows the investigation to the smallest relevant test and implementation path.

Agent for Claude Code

Written for Claude Code: installed under .claude/. Also seen: model in frontmatter.

This is ymm-oss/fsl's own configuration. It tells Claude Code how to work on fsl 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 fsl configures →

View source ↗ ymm-oss/fsl
Reuse

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.

Copy the file
curl -O https://raw.githubusercontent.com/ymm-oss/fsl/main/.claude/agents/fsl-test-diagnostician.md
Clone the repo
git clone --depth 1 https://github.com/ymm-oss/fsl

Made for: Claude Code.

Wrote 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.

agentmods badge for fsl-test-diagnostician

README.md
[![agentmods](https://agentmods.dev/badge/agents/ymm-oss/fsl/fsl-test-diagnostician.svg)](https://agentmods.dev/agents/ymm-oss/fsl/fsl-test-diagnostician)
Your own site
<a href="https://agentmods.dev/agents/ymm-oss/fsl/fsl-test-diagnostician"><img src="https://agentmods.dev/badge/agents/ymm-oss/fsl/fsl-test-diagnostician.svg" alt="Measured on agentmods" height="20"></a>
Per session 48 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 224 The whole file, excluding the scripts and references it only reads on demand.
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 $0.00048 $0.00224
Opus 5 $0.00024 $0.00112
Sonnet 5 $0.00010 $0.00045
Haiku 4.5 $0.00005 $0.00022

Measured 8d ago against content hash 2be252d8e890, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

fsl-test-diagnostician 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 8d 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/agents/fsl-test-diagnostician.md · 21 lines

What it actually says

Diagnose a failing command without modifying source or generated artifacts.

  1. Record the exact command, exit status, first causal error, and failing test or crate.
  2. Separate primary failure from follow-on noise.
  3. Locate the smallest relevant implementation and test path; do not scan unrelated directories.
  4. Reproduce with the narrowest command that preserves the failure.
  5. Distinguish environment/dependency failure, stale generated artifact, contract mismatch, and product defect.
  6. If a full log exists, search it first and read only ranges around relevant errors.

Return root-cause hypothesis with confidence, exact evidence, minimal reproduction, affected contract, and the next discriminating check. Do not paste full logs or implement a fix.

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. 8d ago First seen · 21 lines · 48 tokens per session scan A 2be252d8e890

Subscribe to this mod's changes

fsl-test-diagnostician is an agent published in the GitHub repository ymm-oss/fsl (23 stars, last pushed today), licensed Apache-2.0. It adds 48 tokens to every session and 224 once invoked, about $0.0002 per session on Opus 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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