code-investigate

A deep code investigation that asks Claude and Codex to analyse the same implementation independently, then combines their findings.

In plain words
What is it for?
Use it to trace how a feature works, follow data through the code, investigate an implementation, and confirm conclusions from two perspectives.
Why use it?
It reduces the risk of relying on one incomplete reading when you need to understand unfamiliar or complicated code.

Skill for Claude CodeCodex

Part of the sd0x-dev-flow plugin — 40 skills, 16 agents, 5 hooks shipped together

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/sd0xdev/sd0x-harness/code-investigate
Any agent
npx skills add sd0xdev/sd0x-harness --skill code-investigate
Clone the repo
git clone --depth 1 https://github.com/sd0xdev/sd0x-harness

Made for: Claude Code, Codex.

Or install sd0x-dev-flow, the plugin that ships this one along with the rest of its 40 skills, 16 agents, 5 hooks.

Per session 52 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,267 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 $0.00052 $0.01267
Opus 5 $0.00026 $0.00633
Sonnet 5 $0.00010 $0.00253
Haiku 4.5 $0.00005 $0.00127

Measured 3d ago against content hash 355cd1cb17d0, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

code-investigate 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.

skills/code-investigate/SKILL.md · 159 lines

How it starts

The opening of the file, as written. The whole thing — 159 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Code Investigate Skill

Trigger

  • Keywords: investigate code, how feature works, trace implementation, dual confirmation, deep dive, how code works, what this code does, code research

When NOT to Use

  • Just need quick lookup (use Grep/Glob directly)
  • Code review (use codex-review)
  • System verification (use feature-verify)
  • Git history tracking (use git-investigate)

Core Principle

Codex must explore independently. Feeding Claude's conclusions to Codex is prohibited.
┌─────────────────┐     ┌─────────────────┐
│ Claude Explores  │     │ Codex Explores   │
│ Independently    │     │ Independently    │
│   (Phase 1-2)   │     │    (Phase 3)     │
└────────┬────────┘     └────────┬────────┘
         │                       │
         ▼                       ▼
   ┌───────────┐           ┌───────────┐
   │ Claude    │           │ Codex     │
   │ Conclusion│           │ Conclusion│
   └─────┬─────┘           └─────┬─────┘
         │                       │
         └───────────┬───────────┘
                     ▼
              ┌─────────────┐
              │ Consolidated│
              │   Report    │
              │  (Phase 4)  │
              └─────────────┘

Workflow

Phase Name Action Output
1 Claude Explore Grep/Glob/Read to search code Related files list
2 Claude Conclude Analyze logic, form understanding Initial conclusion (internal)
3 Codex Explore Invoke Codex MCP to explore independently Codex analysis report
4 Integrate Compare both perspectives, mark differences Consolidated report

Codex Invocation Rules

Required Parameters

Parameter Value Description
sandbox read-only Force read-only
approval-policy never Auto-execute
cwd Project root Exploration start point

Read the full file on GitHub · 159 lines

Files

What ships with it

2 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. 3d ago First seen · 159 lines · 52 tokens per session scan A 355cd1cb17d0

Subscribe to this mod's changes

code-investigate is a skill published in the GitHub repository sd0xdev/sd0x-harness (188 stars, last pushed today), licensed MIT. It adds 52 tokens to every session and 1,267 once invoked, about $0.0003 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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