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.
npx agentmods add skills/zstevovich/claude-apd/apd-debugnpx skills add zstevovich/claude-apd --skill apd-debuggit clone --depth 1 https://github.com/zstevovich/claude-apdWrote 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.
[](https://agentmods.dev/skills/zstevovich/claude-apd/apd-debug)<a href="https://agentmods.dev/skills/zstevovich/claude-apd/apd-debug"><img src="https://agentmods.dev/badge/skills/zstevovich/claude-apd/apd-debug.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00126 | $0.01513 |
| Opus 5 | $0.00063 | $0.00757 |
| Sonnet 5 | $0.00025 | $0.00303 |
| Haiku 4.5 | $0.00013 | $0.00151 |
Grade A, and why
apd-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 5d 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.
How it starts
The opening of the file, as written. The whole thing — 124 lines — stays where its author put it; the contents beside it link to each section on GitHub.
APD Systematic Debugging (Codex)
Do this BEFORE re-running any pipeline phase.
When to use / When to skip
Use when:
- A test failed (unit, integration, or end-to-end)
- A build or compile failed
- The verifier step blocked the pipeline
- The reviewer raised a critical finding
- You are about to re-run a pipeline phase after a verifier failure (MANDATORY)
Skip when:
- The "failure" is actually expected behaviour (test marked skip/expected-fail)
- You haven't run the failing command yourself yet (run it first, get a real error message)
- The issue is a known intermittent and you have a tracking ticket — escalate, don't loop
The Iron Law
NO FIXES WITHOUT ROOT CAUSE INVESTIGATION FIRST
Guessing is not debugging. If you have not completed Phase 1, you cannot propose a fix.
Four phases
Phase 1 — root cause investigation
- Read the error fully. Don't skip the stack trace. Note file:line references, exception types, and the exact command that produced it.
- Reproduce reliably. Can you trigger the failure consistently? If not, find a repro first — intermittent fixes are almost never fixes.
- Check recent changes.
git diff, recent commits on this pipeline. - Trace the data flow. Where does the bad value originate? What transformation produced it?
Phase 2 — pattern analysis
- Find working examples of similar code in this codebase.
- Compare systematically — what is different between the working path and the broken path?
- List every difference. Don't skip with "that can't matter" — the subtle ones are usually the answer.
Phase 3 — hypothesis and controlled test
- State the hypothesis as a sentence. "I think X causes Y because Z."
- Test with the smallest possible change. One variable at a time.
- Verify. Did it resolve the failure? If not, form a NEW hypothesis — don't layer fixes.
- 3+ failed hypotheses → STOP and escalate to the user with a clear summary of what you tried and what you learned.
What ships with it
4 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.
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.
- 5d ago First seen · 124 lines · 126 tokens per session scan A 02ca66347f2b
apd-debug is a skill published in the GitHub repository zstevovich/claude-apd (5 stars, last pushed 1mo ago), licensed MIT. It adds 126 tokens to every session and 1,513 once invoked, about $0.0006 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 2026-08-31.
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