log-driven-debugging

log-driven-debugging is a skill for Claude Code, Codex from patrick-fu/awesome-skills. It costs 37 tokens per session (1,056 once invoked), scanned A, original, MIT.

A debugging method for a bug that can be reproduced by running the same scenario again. It adds carefully chosen log messages, asks the user to rerun the case, and uses the returned output to locate the failure.

In plain words
What is it for?
Use it to trace a hard-to-reproduce error, inspect the path an execution takes, and narrow down the failing layer before fixing it.
Why use it?
It replaces guesswork when reading the code is not enough to show which part of the program breaks.

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/patrick-fu/awesome-skills/log-driven-debugging
Any agent
npx skills add patrick-fu/awesome-skills --skill log-driven-debugging
Clone the repo
git clone --depth 1 https://github.com/patrick-fu/awesome-skills

Made for: Claude Code, Codex.

Per session 37 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,056 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 $0.00037 $0.01056
Opus 5 $0.00018 $0.00528
Sonnet 5 $0.00007 $0.00211
Haiku 4.5 $0.00004 $0.00106

Measured 3d ago against content hash 8307cb2f1d64, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

log-driven-debugging 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 3d 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.

log-driven-debugging/SKILL.md · 157 lines

How it starts

The opening of the file, as written. The whole thing — 157 lines — stays where its author put it; the contents beside it link to each section on GitHub.

When the bug is slippery, stop guessing and build observability.

This skill is for situations where:

  • the visible symptom is known, but the actual failure layer is not
  • static code reading is no longer enough
  • one execution with good logs can collapse a large search space

The workflow is simple:

  1. decide where to instrument
  2. add high-signal logs
  3. have the user rerun the scenario
  4. analyze the returned logs
  5. only then propose or implement the real fix

First move

Before adding any logs, ask the user for a log prefix.

This is required, not optional. Explain why briefly: the prefix makes the new logs searchable and prevents them from being lost in normal application output.

Good prefixes look like:

  • Patrick
  • MyDebug
  • DebugTrace

Prefer a short prefix that:

  • is unique in the current codebase
  • is easy to grep
  • is unlikely to collide with existing production logs

If the user does not care, ask for one and wait. Do not silently invent a prefix unless the user explicitly delegates that choice.

Logging strategy

Do not scatter random prints everywhere. Instrument the execution path deliberately.

Choose logs around:

  • entry points where the user action first enters the system
  • state transitions where data changes shape
  • serialization or conversion boundaries
  • async handoff points
  • final outbound effects such as send, save, render, request, or callback

For each log, include enough structure to reconstruct the flow:

  • the shared prefix
  • a timestamp
  • a short tag for the subsystem or phase
  • the minimum fields needed to compare expected vs actual behavior

Treat the timestamp as part of the standard format, not a nice-to-have. For tricky bugs, ordering is often as important as values.

Prefer logs that answer:

  • Did this code path run?
  • In what order did the steps happen?
  • What data existed at this point?
  • Where did duplication, loss, mutation, or branching first appear?

Avoid:

  • giant object dumps unless they are truly needed
  • vague messages like "here" or "called"
  • logging so much that the signal disappears

Read the full file on GitHub · 157 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. 3d ago First seen · 157 lines · 37 tokens per session scan A 8307cb2f1d64

Subscribe to this mod's changes

log-driven-debugging is a skill published in the GitHub repository patrick-fu/awesome-skills (57 stars, last pushed today), licensed MIT. It adds 37 tokens to every session and 1,056 once invoked, about $0.0002 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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