debug-like-expert

A methodical debugging mode for difficult software problems. It gathers evidence, tests possible causes, and verifies the result instead of relying on a quick guess.

In plain words
What is it for?
Use it to investigate complex bugs across projects such as Python, JavaScript, Rust, Swift, C++, Go, and Java. It scans the project context and applies a structured root-cause process.
Why use it?
It helps when ordinary troubleshooting has not found the cause or when assumptions about the code may be misleading.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/cfircoo/claude-code-toolkit/debug-like-expert
Any agent
npx skills add cfircoo/claude-code-toolkit --skill debug-like-expert
Clone the repo
git clone --depth 1 https://github.com/cfircoo/claude-code-toolkit

Made for: Claude Code, Codex.

Per session 44 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,488 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 1 finding. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 $0.00044 $0.02488
Opus 5 $0.00022 $0.01244
Sonnet 5 $0.00009 $0.00498
Haiku 4.5 $0.00004 $0.00249

Measured 2d ago against content hash 89e3feb89745, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

debug-like-expert scanned grade B 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 2d 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.

Enumerates other installed skillsmediumAgent snooping

Other skills' SKILL.md files reveal prompts, capabilities and secrets that should be invisible to peers.

ls ~/.claude/skills/expertise/ 2>/dev/null | head -5
Origin

This is a copy

100% identical to debug-like-expert — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/debug-like-expert/SKILL.md · 310 lines

How it starts

The opening of the file, as written. The whole thing — 310 lines — stays where its author put it; the contents beside it link to each section on GitHub.

The skill emphasizes treating code you wrote with MORE skepticism than unfamiliar code, as cognitive biases about "how it should work" can blind you to actual implementation errors. Use scientific method to systematically identify root causes rather than applying quick fixes.

<context_scan> Run on every invocation to detect domain-specific debugging expertise:

# What files are we debugging?
echo "FILE_TYPES:"
find . -maxdepth 2 -type f 2>/dev/null | grep -E '\.(py|js|jsx|ts|tsx|rs|swift|c|cpp|go|java)$' | head -10

# Check for domain indicators
[ -f "package.json" ] && echo "DETECTED: JavaScript/Node project"
[ -f "Cargo.toml" ] && echo "DETECTED: Rust project"
[ -f "setup.py" ] || [ -f "pyproject.toml" ] && echo "DETECTED: Python project"
[ -f "*.xcodeproj" ] || [ -f "Package.swift" ] && echo "DETECTED: Swift/macOS project"
[ -f "go.mod" ] && echo "DETECTED: Go project"

# Scan for available domain expertise
echo "EXPERTISE_SKILLS:"
ls ~/.claude/skills/expertise/ 2>/dev/null | head -5

Present findings before starting investigation. </context_scan>

<domain_expertise> Domain-specific expertise lives in ~/.claude/skills/expertise/

Domain skills contain comprehensive knowledge including debugging, testing, performance, and common pitfalls. Before investigation, determine if domain expertise should be loaded.

<scan_domains>

ls ~/.claude/skills/expertise/ 2>/dev/null

This reveals available domain expertise (e.g., macos-apps, iphone-apps, python-games, unity-games).

If no expertise skills found: Proceed without domain expertise (graceful degradation). The skill works fine with general debugging methodology. </scan_domains>

<inference_rules> If user's description or codebase contains domain keywords, INFER the domain:

Keywords/Files Domain Skill
"Python", "game", "pygame", ".py" + game loop expertise/python-games
"React", "Next.js", ".jsx/.tsx" expertise/nextjs-ecommerce
"Rust", "cargo", ".rs" files expertise/rust-systems
"Swift", "macOS", ".swift" + AppKit/SwiftUI expertise/macos-apps
"iOS", "iPhone", ".swift" + UIKit expertise/iphone-apps
"Unity", ".cs" + Unity imports expertise/unity-games
"SuperCollider", ".sc", ".scd" expertise/supercollider
"Agent SDK", "claude-agent" expertise/with-agent-sdk

If domain inferred, confirm:

Detected: [domain] issue → expertise/[skill-name]
Load this debugging expertise? (Y / see other options / none)

</inference_rules>

<no_inference> If no domain obvious, present options:

What type of project are you debugging?

Available domain expertise:
1. macos-apps - macOS Swift (SwiftUI, AppKit, debugging, testing)
2. iphone-apps - iOS Swift (UIKit, debugging, performance)
3. python-games - Python games (Pygame, physics, performance)
4. unity-games - Unity (C#, debugging, optimization)
[... any others found in build/]

N. None - proceed with general debugging methodology
C. Create domain expertise for this domain

Select:

</no_inference>

<load_domain> When domain selected, READ all references from that skill:

cat ~/.claude/skills/expertise/[domain]/references/*.md 2>/dev/null

This loads comprehensive domain knowledge BEFORE investigation:

  • Common issues and error patterns
  • Domain-specific debugging tools and techniques
  • Testing and verification approaches
  • Performance profiling and optimization
  • Known pitfalls and anti-patterns
  • Platform-specific considerations

Announce: "Loaded [domain] expertise. Investigating with domain-specific context."

If domain skill not found: Inform user and offer to proceed with general methodology or create the expertise. </load_domain>

<when_to_load> Domain expertise should be loaded BEFORE investigation when domain is known.

Read the full file on GitHub · 310 lines

Files

What ships with it

5 files 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. 2d ago First seen · 310 lines · 44 tokens per session scan B 89e3feb89745

Subscribe to this mod's changes

debug-like-expert is a skill published in the GitHub repository cfircoo/claude-code-toolkit (17 stars, last pushed 5mo ago), licensed MIT. It adds 44 tokens to every session and 2,488 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it B with 1 finding (enumerates other installed skills). It is 100% identical to debug-like-expert, differing in 0 lines, and is treated as a copy.

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