Borrowing it
Nothing to install: this file belongs to matteocervelli/llms. 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/matteocervelli/llms/main/.claude/skills/diagnose/SKILL.mdgit clone --depth 1 https://github.com/matteocervelli/llmsWrote 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/skills/matteocervelli/llms/diagnose)<a href="https://agentmods.dev/skills/matteocervelli/llms/diagnose"><img src="https://agentmods.dev/badge/skills/matteocervelli/llms/diagnose/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/skills/matteocervelli/llms/diagnose"><img src="https://agentmods.dev/badge/skills/matteocervelli/llms/diagnose.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 | $0.00040 | $0.01880 |
| Opus 5.5 | $0.00016 | $0.00752 |
| Sonnet 5.5 | $0.00008 | $0.00376 |
| Haiku 4.5 | $0.00004 | $0.00188 |
Grade A, and why
diagnose 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 — 253 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Diagnose Skill
Purpose
Investigation skill for bugs where the root cause is unknown. When you don't know why
something is broken — just that it is — use /diagnose before reaching for /fix.
Key mechanism: spawns a fresh-context debugger subagent (Task tool) alongside a /review solve
companion analysis. The main agent orchestrates, stays clean, and synthesizes results. Debug
sessions persist in .claude/debug/<slug>.md so they survive context compaction and can be resumed.
Not for: applying a fix you already understand (use /fix), or quick one-line patches (use /quick).
When to Use
/quick |
/fix |
/diagnose |
/implementation |
|
|---|---|---|---|---|
| Root cause known? | Yes | Yes | No | Yes |
| Code changes | Yes | Yes | No (read-only) | Yes |
| Subagent isolation | No | No | Yes (fresh 200k context) | No |
| Companion analysis | No | No | Yes (/review solve) | No |
| Output | Commit | Commit | Root cause report | PR |
Usage
/diagnose "auth token not working" # start new session
/diagnose --resume auth-token # resume session by slug
/diagnose --list # show all active sessions
/diagnose --close auth-token # mark session resolved
/diagnose --issue 42 # pull symptoms from GitHub issue
/diagnose --issue 42 "login fails on iOS" # issue + free-form description
Workflow
Step 1: Collect Symptoms
Ask the user for (or pull from gh issue view <N> if --issue provided):
- Expected — what should happen
- Actual — what is happening
- Error — exact error message or stack trace (if any)
- Timeline — when did this start, what changed recently
- Reproduction — minimal steps to reproduce
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 First seen · 253 lines · 40 tokens per session scan A 8f2ad4dbc55e
diagnose is a skill published in the GitHub repository matteocervelli/llms (25 stars, last pushed 5mo ago), licensed MIT. It adds 40 tokens to every session and 1,880 once invoked, about $0.0002 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 2026-09-03.
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