debugging

A debugging method that requires a reproducible feedback loop before forming a theory, finding the underlying cause before changing code, and checking the possible effects afterward.

In plain words
What is it for?
Use it to investigate bugs with tests, HTTP checks, command-output comparisons, browser scripts, trace replays, small test harnesses, fuzz checks, or comparisons between code versions.
Why use it?
It helps prevent guesswork and fixes that hide the original problem while creating new ones elsewhere.

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/romiluz13/cc10x/debugging
Any agent
npx skills add romiluz13/cc10x --skill debugging
Clone the repo
git clone --depth 1 https://github.com/romiluz13/cc10x

Made for: Claude Code, Codex.

Per session 52 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,574 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. 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 $0.00052 $0.02574
Opus 5 $0.00026 $0.01287
Sonnet 5 $0.00010 $0.00515
Haiku 4.5 $0.00005 $0.00257

Measured 2d ago against content hash acda1cbfb648, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

debugging 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 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.

Makes network callslowCapability

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

2. `curl`/HTTP request with asserted response
plugins/cc10x/skills/debugging/SKILL.md · 187 lines

How it starts

The opening of the file, as written. The whole thing — 187 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Debugging

Feedback Loop FIRST: No hypothesis without a repro loop. No fix without root cause. No fix without blast radius scan.

Reference Files

  • references/investigation-hygiene.md — investigation discipline, evidence handling
  • references/root-cause-playbooks.md — scenario-specific debugging playbooks

Feedback Loop FIRST (Before Any Hypothesis)

A hypothesis without a repro loop is a guess. Before H1, build a fast, deterministic, agent-runnable signal that turns red on the bug.

Construction Ladder (try in rank order, stop at first that works — ordered by loop tightness: earlier rungs are faster and more deterministic)

  1. Failing automated test (unit/integration) — best: lives at a seam, reusable as RED
  2. curl/HTTP request with asserted response
  3. CLI snapshot diff (run command, diff stdout/stderr/exit)
  4. Headless browser script (real DOM/runtime crash)
  5. Trace replay (recorded request/log/event re-run)
  6. Throwaway harness (tiny script calling the suspect function)
  7. Property/fuzz check (when failing input is unknown)
  8. git bisect run (regression with existing test)
  9. Differential old-vs-new (last-good vs HEAD behavior diff)
  10. Human-in-the-loop (LAST resort: scripted manual steps)

Tighten the loop — treat it as a product. Once you have a loop, keep tightening:

  • Faster? Cache setup, skip unrelated init, narrow the test scope — sub-second beats sub-minute.
  • Sharper signal? Assert the exact failing fact, not a noisy superset — never just "didn't crash".
  • More deterministic? Pin time, seed RNG, isolate filesystem, freeze network — same input → same red, no drift. A 30-second flaky loop is barely better than none; a 2-second deterministic one is a debugging superpower.

Red-capable completion criteria — the loop is done when you can name one command (a script path, a test invocation, a curl) that you have already run at least once (paste the invocation and its output), and it is:

  • Red-capable — drives the actual bug code path and asserts the user's exact symptom (can go red on this bug, green once fixed). Not "runs without erroring".
  • Deterministic — same verdict every run (flaky bugs: a pinned, high reproduction rate).
  • Fast — seconds, not minutes.
  • Agent-runnable — you can run it unattended. No red-capable command, no hypothesis phase. If you catch yourself reading code to build a theory before this command exists, STOP.

Read the full file on GitHub · 187 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 · 187 lines · 52 tokens per session scan A acda1cbfb648

Subscribe to this mod's changes

debugging is a skill published in the GitHub repository romiluz13/cc10x (164 stars, last pushed 29d ago), licensed MIT. It adds 52 tokens to every session and 2,574 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 2026-08-30.

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