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/arroyo-gonzalo/codex-devkit/bug-investigationnpx skills add Arroyo-Gonzalo/codex-devkit --skill bug-investigationgit clone --depth 1 https://github.com/Arroyo-Gonzalo/codex-devkitWrote 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/arroyo-gonzalo/codex-devkit/bug-investigation)<a href="https://agentmods.dev/skills/arroyo-gonzalo/codex-devkit/bug-investigation"><img src="https://agentmods.dev/badge/skills/arroyo-gonzalo/codex-devkit/bug-investigation.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 | $0.00044 | $0.00830 |
| Opus 5 | $0.00022 | $0.00415 |
| Sonnet 5 | $0.00009 | $0.00166 |
| Haiku 4.5 | $0.00004 | $0.00083 |
Grade A, and why
bug-investigation 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 — 177 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Bug Investigation
Purpose
Identify the root cause of a defect and correct it with the smallest safe change.
Do not begin by modifying code based only on assumptions.
Investigation workflow
1. Establish the problem
Determine:
- expected behavior;
- actual behavior;
- affected environment;
- reproduction conditions;
- frequency;
- error messages, logs, or stack traces;
- whether the issue is new or previously existed.
When information is incomplete, inspect available evidence before requesting additional details.
2. Reproduce the failure
Attempt to reproduce the issue using the narrowest practical scenario.
Prefer:
- a focused failing test;
- a minimal request;
- a specific command;
- a small data fixture;
- an isolated execution path.
Do not perform broad changes merely to reproduce the problem.
If reproduction is not possible, clearly state the limitation and continue using available evidence.
3. Trace the execution path
Inspect the relevant path from input to failure.
Identify:
- entry point;
- validation;
- transformations;
- business logic;
- persistence operations;
- external integrations;
- error handling;
- response generation.
Read only the files necessary to understand that path.
4. Gather evidence
Use evidence from:
- error messages;
- stack traces;
- logs;
- failing tests;
- configuration;
- recent changes;
- version history when relevant;
- database state;
- network requests;
- runtime behavior.
Distinguish observed facts from assumptions.
5. Form hypotheses
Create a short list of plausible causes.
Prioritize hypotheses using:
- available evidence;
- proximity to the failure;
- recent changes;
- likelihood;
- ability to verify safely.
Do not present speculation as a confirmed cause.
6. Verify the most likely cause
Test the highest-confidence hypothesis before changing production code.
Verification may include:
- adding a focused test;
- inspecting values at the failure boundary;
- running a narrow command;
- comparing expected and actual data;
- checking configuration;
- reviewing a recent diff.
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 · 177 lines · 44 tokens per session scan A 79793d196db7
bug-investigation is a skill published in the GitHub repository Arroyo-Gonzalo/codex-devkit (2 stars, last pushed 1mo ago), licensed MIT. It adds 44 tokens to every session and 830 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 2026-08-31.
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