diagnose

diagnose is a skill for Claude Code from aldianriski/lean-flow. It costs 70 tokens per session (1,593 once invoked), scanned A, original, MIT.

A debugging guide for investigating defects, unexpected behaviour, failing tests, and performance regressions through reproduction, evidence gathering, hypothesis testing, fixing, and cleanup.

In plain words
What is it for?
Use it to reproduce failures, capture useful diagnostic evidence, test possible causes, add regression tests, and document the resulting fix.
Why use it?
It gives debugging a repeatable feedback loop and reduces the risk of guessing at causes or exposing secrets in logs and traces.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Part of the lean-flow plugin — 15 skills shipped together

Good fit Use it to reproduce failures, capture useful diagnostic evidence, test possible causes, add regression tests, and document the resulting fix.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/aldianriski/lean-flow/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 aldianriski/lean-flow --skill diagnose
Clone the repo
git clone --depth 1 https://github.com/aldianriski/lean-flow

Made for: Claude Code.

Or install lean-flow, the plugin that ships this one along with the rest of its 15 skills.

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/aldianriski/lean-flow/diagnose.svg)](https://agentmods.dev/skills/aldianriski/lean-flow/diagnose)
Your own site
<a href="https://agentmods.dev/skills/aldianriski/lean-flow/diagnose"><img src="https://agentmods.dev/badge/skills/aldianriski/lean-flow/diagnose.svg" alt="Measured on agentmods" height="20"></a>
Per session 70 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,593 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 $0.00070 $0.01593
Opus 5 $0.00035 $0.00796
Sonnet 5 $0.00014 $0.00319
Haiku 4.5 $0.00007 $0.00159

Measured 8d ago against content hash b2b48a0d615e, 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 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.

Makes network callslowCapability

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

- Prefer an **automated test** at the seam that reaches the bug; then curl/HTTP, CLI snapshot-diff, headless browser, replay a captured trace, a throwaway harness, fuzz, `git bisect run`, or a differential loop. Full men
skills/diagnose/SKILL.md · 95 lines

How it starts

The opening of the file, as written. The whole thing — 95 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Diagnose

A discipline for hard bugs. The rate of feedback is your speed limit — build the loop first. Skip a phase only when you can explicitly justify it.

Redact before you show

Every phase below produces an artifact and then shows it — loop output, a captured trace, a log dump, a replayed payload, a HITL transcript. Those carry auth headers, tokens, connection strings and PII by default, and a debugging session is exactly where they get pasted into a chat, an issue, or a commit message. Redact first, and prefer the mechanism over the reminder:

  • Build the loop against environment variables so the credential stays in the environment rather than in the command you show. That removes the whole class; redacting afterwards removes instances.
  • Quote only the signal-carrying lines of a captured artifact — never a whole HAR file or log dump.
  • Whatever must still be shown gets <REDACTED> in place of the secret, before it is shown.
  • If the redacted output is no longer enough to diagnose the bug, say so and ask — never widen what you paste to compensate.

Phase 1 — Build a feedback loop

This is the skill — everything else just consumes the signal. Get a fast, deterministic, agent-runnable pass/fail signal for the bug and you will find the cause. Spend disproportionate effort here; be aggressive, refuse to give up.

  • Prefer an automated test at the seam that reaches the bug; then curl/HTTP, CLI snapshot-diff, headless browser, replay a captured trace, a throwaway harness, fuzz, git bisect run, or a differential loop. Full menu → ${CLAUDE_SKILL_DIR}/references/feedback-loops.md.
  • Iterate on the loop — faster, sharper signal, more deterministic. A 2-second deterministic loop beats a 30-second flaky one.
  • Non-deterministic bug? Raise the reproduction rate (loop 100×, parallelise, stress), don't chase a clean one-shot repro.
  • Genuinely can't build one? Stop, list what you tried, ask for env access / a captured artifact / instrumentation permission. Do not hypothesise without a loop.

Read the full file on GitHub · 95 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 95 lines · 70 tokens per session scan A b2b48a0d615e

Subscribe to this mod's changes

diagnose is a skill published in the GitHub repository aldianriski/lean-flow (5 stars, last pushed 9d ago), licensed MIT. It adds 70 tokens to every session and 1,593 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.

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