diagnose

diagnose is a skill for Claude Code, Codex from ntaffzii/Skill-Agents. It costs 55 tokens per session (549 once invoked), scanned A, original, MIT.

A step-by-step process for finding the underlying cause of bugs, failed tests, crashes, incorrect results, and performance problems.

In plain words
What is it for?
Use it to reproduce and minimise failures, test competing explanations, add targeted investigation, and verify that the confirmed fix addresses the reported issue.
Why use it?
It encourages a reproducible, small test case and evidence-based hypotheses before code is changed, reducing the risk of fixing the wrong problem.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to reproduce and minimise failures, test competing explanations, add targeted investigation, and verify that the confirmed fix addresses the reported issue.

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Install with agentmods
npx agentmods add skills/ntaffzii/skill-agents/diagnose
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add ntaffzii/Skill-Agents --skill diagnose
Clone the repo
git clone --depth 1 https://github.com/ntaffzii/Skill-Agents

Made for: Claude Code, Codex.

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 diagnose

README.md
[![agentmods](https://agentmods.dev/badge/skills/ntaffzii/skill-agents/diagnose.svg)](https://agentmods.dev/skills/ntaffzii/skill-agents/diagnose)
Your own site
<a href="https://agentmods.dev/skills/ntaffzii/skill-agents/diagnose"><img src="https://agentmods.dev/badge/skills/ntaffzii/skill-agents/diagnose.svg" alt="Measured on agentmods" height="20"></a>
Per session 55 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 549 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. 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 $0.00055 $0.00549
Opus 5 $0.00028 $0.00275
Sonnet 5 $0.00011 $0.00110
Haiku 4.5 $0.00006 $0.00055

Measured 7d ago against content hash 845c4edb42f6, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

diagnose scanned grade A with 1 finding 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 7d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- Prefer a fast deterministic signal: failing test, CLI command, curl script, browser script, replay harness, or benchmark.
skills/engineering/diagnose/SKILL.md · 71 lines

How it starts

The opening of the file, as written. The whole thing — 71 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Diagnose

Use this skill to find root cause before changing code.

Core Rule

Build a reliable feedback loop before committing to a hypothesis. If there is no runnable signal, create one or explain exactly what is missing.

Mantra

Reproduce, trace, falsify, validate.

Workflow

  1. Reproduce

    • Capture exact steps, inputs, environment, command, request, fixture, or UI path.
    • Prefer a fast deterministic signal: failing test, CLI command, curl script, browser script, replay harness, or benchmark.
    • If flaky, raise the reproduction rate with loops, stress, narrowed timing, pinned seeds, or isolated state.
  2. Minimize

    • Reduce the repro to the smallest case that still shows the bug.
    • Confirm the minimized failure is the same symptom the user reported.
    • Avoid fixing a nearby but different failure.
  3. Generate hypotheses

    • List 3 to 5 ranked hypotheses before testing.
    • For each, state a falsifiable prediction.
    • Prefer the hypothesis that explains every observed breadcrumb, not only the latest one.
  4. Instrument

    • Test one variable at a time.
    • Prefer debugger or REPL inspection when available.
    • Use targeted logs only at boundaries that distinguish hypotheses.
    • Tag temporary logs with a unique prefix such as [DEBUG-a4f2].
    • Keep a short ledger of experiments and observations when the investigation has more than one branch.
  5. Fix

    • Write or preserve a regression signal before the fix when a correct seam exists.
    • Apply the smallest change that addresses the root cause.
    • Re-run the original repro and the minimized repro.
  6. Clean up

    • Remove temporary instrumentation.
    • Delete throwaway harnesses or move them to a clearly named debug location.
    • State the root cause, mechanism, fix, and verification.

Stop Conditions

Stop and ask for missing artifacts when:

  • The issue cannot be reproduced locally.
  • The only repro depends on an external system the agent cannot access.
  • The user has logs, HAR files, screenshots, traces, or environment details that are required.

Read the full file on GitHub · 71 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. 7d ago First seen · 71 lines · 55 tokens per session scan A 845c4edb42f6

Subscribe to this mod's changes

diagnose is a skill published in the GitHub repository ntaffzii/Skill-Agents (4 stars, last pushed 5d ago), licensed MIT. It adds 55 tokens to every session and 549 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.