kn-debug

A structured method for debugging build failures, test failures, runtime crashes, integration problems, and blocked tasks. It classifies the issue, reproduces it, finds the root cause, fixes it, and records what was learned.

In plain words
What is it for?
Use it to triage errors, reproduce failures, diagnose causes, implement fixes, and capture lessons for later work.
Why use it?
It prevents developers from guessing at fixes before understanding what kind of failure occurred and why.

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/knowns-dev/knowns/kn-debug
Any agent
npx skills add knowns-dev/knowns --skill kn-debug
Clone the repo
git clone --depth 1 https://github.com/knowns-dev/knowns

Made for: Claude Code, Codex.

Per session 25 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,944 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00025 $0.01944
Opus 5 $0.00013 $0.00972
Sonnet 5 $0.00005 $0.00389
Haiku 4.5 $0.00003 $0.00194

Measured 2d ago against content hash df2418f4bee1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

kn-debug 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 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.

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.

internal/instructions/skills/kn-debug/SKILL.md · 265 lines

How it starts

The opening of the file, as written. The whole thing — 265 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Debugging

Systematic debugging: triage → reproduce → diagnose → fix → learn.

Announce: "Using kn-debug for [error/issue]."

Core principle: CLASSIFY FIRST → REPRODUCE → ROOT CAUSE → FIX → CAPTURE LEARNING.

When to Use

  • Build fails (compilation, type error, missing dependency)
  • Test fails (assertion mismatch, timeout, flaky)
  • Runtime crash or exception
  • Integration failure (API mismatch, env config, auth)
  • Task blocked with unclear cause
  • User says "debug this", "fix this error", "why is this failing"

Inputs

  • Error message, stack trace, or failing command
  • Optional: task ID (if debugging within a task context)

Step 1: Triage — Classify the Issue

Classify before investigating. Misclassifying wastes time.

Type Signals
Build failure Compilation error, type error, missing module, bundler failure
Test failure Assertion mismatch, snapshot diff, timeout, flaky intermittent
Runtime error Crash, uncaught exception, undefined behavior
Integration failure HTTP 4xx/5xx, env variable missing, API schema mismatch
Blocked task Circular dependency, conflicting changes, unclear requirement

Output: One-line classification: [TYPE] in [component]: [symptom]


Step 2: Check Known Patterns

Before deep investigation, search for known solutions (unified search includes docs, learnings, and memories):

mcp_knowns_search({ "action": "search", "query": "<keywords from classification>", "type": "doc" })

Also check learnings docs:

mcp_knowns_search({ "action": "search", "query": "<error pattern>", "type": "doc", "tag": "learning" })

Search memories for past debug patterns:

mcp_knowns_search({ "action": "search", "query": "<error pattern>", "type": "memory" })

If a known pattern matches → jump to Step 4 (Fix) using the documented resolution.


Step 3: Reproduce & Diagnose

3a. Reproduce

Run the exact failing command verbatim:

# Whatever failed — run it exactly
<failing-command> 2>&1

Read the full file on GitHub · 265 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. 2d ago First seen · 265 lines · 25 tokens per session scan A df2418f4bee1

Subscribe to this mod's changes

kn-debug is a skill published in the GitHub repository knowns-dev/knowns (241 stars, last pushed 6d ago), licensed MIT. It adds 25 tokens to every session and 1,944 once invoked, about $0.0001 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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