codex-system

name: codex-system description: | Use this skill whenever the user needs deep Rust reasoning — whether asked casually or formally, in Japanese or English. Trigger for: Rust compiler errors (E0382, E0505, E0507 etc. or "コンパイル通らない"), ownership/borrowing/lifetime questions ("moved value", "所有権", clone vs borrow), trait design or review ("トレイト設計", Repository pattern, method signatures, return types), Rust architecture planning (domain layer, usecase layer, hexagonal/DDD, Command/Query patterns), and implementation planning for Rust features ("実装計画", "設計したい"). Also trigger when the active profile assigns planner/reviewer/debugger/implementer roles to Codex. Do NOT trigger for simple Cargo.toml edits, cargo fmt/clippy fixes, test assertion updates, dependency version lookups, or non-Rust tasks. metadata: short-description: Consult Codex for Rust design & complex tasks

/codex-system — Codex CLI Consultation Skill

Skill for using Codex CLI as a specialist provider.

Check .claude/agent-profiles.json first. Use this skill only when the target capability is assigned to Codex.

Configuration

Before invoking Codex, read .claude/agent-profiles.json to resolve the model:

providers.codex.default_model  →  {model}  (e.g. "gpt-5.3-codex")

All templates below use {model} as a placeholder. Replace it with the actual value from agent-profiles.json.

Reasoning Effort

Append --config model_reasoning_effort="{effort}" to control reasoning depth:

timeout 180 codex exec --model {model} --config model_reasoning_effort="high" \
  --sandbox read-only --full-auto "{task}" 2>&1

Values: low, medium, high. Default varies by model. Use high for complex design/review tasks.

When to Use

• Rust trait/architecture design
• Ownership and lifetime planning
• Compiler error diagnosis (E-codes)
• Implementation planning (TDD-friendly)
• Complex Rust code review
• When planner / reviewer / debugger / implementer capability is assigned to Codex

Usage Patterns

Architecture Design

timeout 180 codex exec --model {model} --sandbox read-only --full-auto "
Design Rust architecture for: {feature description}

Current context:
- Architecture pattern: Hexagonal (Ports & Adapters)
- Async runtime: Tokio
- Error handling: thiserror

Provide:
1. Trait definitions (ports) with method signatures
2. Adapter structure (infra layer)
3. Ownership model (Arc<dyn Trait>, owned types)
4. Error type hierarchy
5. Module layout
" 2>&1

Ownership/Lifetime Design

timeout 180 codex exec --model {model} --sandbox read-only --full-auto "
Design the ownership model for:

{struct or function description}

Context: {how it's used, what it holds}

Provide:
1. Recommended ownership approach (owned vs borrowed vs Arc/Rc)
2. Lifetime annotations if needed
3. Alternative designs with trade-offs
4. Potential pitfalls
" 2>&1

Compiler Error Diagnosis

timeout 180 codex exec --model {model} --sandbox read-only --full-auto "
Diagnose this Rust compiler error:

Error code: {E0XXX}
Full error:
{paste full error message}

Relevant code:
{paste code snippet}

Analyze root cause (ownership/borrow/lifetime/trait bounds)
and suggest a fix that preserves the intended semantics.
" 2>&1

Implementation Planning

timeout 180 codex exec --model {model} --sandbox read-only --full-auto "
Create a TDD implementation plan for: {feature}

Requirements: {list of requirements}
Constraints: {crates to use, architecture patterns}

Output:
1. Step-by-step plan (domain types → traits → tests → impl → integration)
2. Key design decisions with rationale
3. Potential challenges and mitigations
" 2>&1

Code Review (Hybrid Prompt Pattern)

Embed design intent and change summary directly in the prompt; let Codex read files for details. This avoids Codex spending time searching the codebase while keeping the prompt concise. Use timeout 180 to prevent indefinite hangs (Codex file exploration can exceed 120s).

timeout 180 codex exec --model {model} --sandbox read-only --full-auto "
Review {feature name}. Report ONLY bugs or logic errors. Be concise.

## Design
{2-5 bullet points explaining the design intent and invariants}

## Changed files
{list of changed file paths}

## Key code (optional — include only if ~1KB or less)
{short code snippet of the core logic change}

Check for: logic errors, doc-code inconsistencies, edge cases, security issues.
" 2>&1

For larger diffs, use the file-based briefing pattern (see below) instead of inlining.

File-Based Briefing Pattern

Prefer writing content to a file over inline embedding when:

read-only sandbox can still read existing files — the file-based approach works without relaxing sandbox constraints.

Steps

1. Write the briefing file (Claude Code uses the Write tool)

   tmp/codex-briefing.md
   

2. Run Codex with a file reference

   timeout 180 codex exec --model {model} --sandbox read-only --full-auto \
     "Read tmp/codex-briefing.md and perform the task described there." 2>&1
   

3. Delete the briefing file (Claude Code uses Bash tool)

   rm tmp/codex-briefing.md
   

Briefing File Template

# Task

{task type: Architecture Design / Code Review / Compiler Error Diagnosis / etc.}

## Context

{feature name, relevant spec excerpt, architecture constraints}

## Input

{diff, error message, code snippet — verbatim}

## Output Required

{numbered list of what Codex should return}

Short queries (1–2 paragraphs) are fine as inline prompts. Use this file-based pattern when content is long or contains special characters.

Output Format

Codex will return structured output. Extract and relay to user in Japanese:

## Analysis
{Deep analysis of the Rust problem}

## Recommendation
{Clear, actionable recommendation with code if needed}

## Implementation Plan (if applicable)
1. {Step 1}
2. {Step 2}

## Rust Code Example
\`\`\`rust
{concrete Rust code}
\`\`\`

## Risks
{Potential issues to watch}

Iterative Review Loop

For review-fix-review cycles ("修正→レビュー→修正→…→指摘なし"):

1. First round: Use the hybrid prompt pattern — embed design intent and change summary, list changed files, let Codex read them
2. Fix findings: Add tests for each bug, implement fixes
3. Subsequent rounds: State what was fixed, ask Codex to verify the fix and check for remaining issues
4. Stop when Codex reports no bugs

Round 1 template (hybrid prompt)

timeout 180 codex exec --model {model} --sandbox read-only --full-auto "
Review {feature}. Report ONLY bugs or logic errors.

## Design
{design invariants}

## Changed files
{file list}

Check for: {checklist}
" 2>&1

Round N template (fix verification)

timeout 180 codex exec --model {model} --sandbox read-only --full-auto "
Previous review found: {finding summary}. Fixed by {fix description}. Test added.
Verify the fix in {file}:{line range}. Any remaining bugs?
" 2>&1

Tips

• Always use timeout 180 — Codex file exploration can exceed 120s
• Prefer 2>&1 over 2>/dev/null to capture diagnostics
• Instruct Codex "do not run Python code" if you want text-only analysis (faster)
• Codex may run code in read-only sandbox to verify edge cases — this is fine and often produces better findings
• Each round's prompt should reference only the delta, not the full history
• Keep inline prompts under ~1KB; for larger context, use the file-based briefing pattern

Execution Tips

• Model flag: read providers.codex.default_model from .claude/agent-profiles.json and pass as --model {model}
• Foreground preferred: 2>&1 captures both stdout and stderr reliably; 2>/dev/null may hide useful diagnostics
• Long prompts: always use the file-based briefing pattern — inline prompts over ~1KB risk shell escaping issues
• Short prompts: inline is fine for 1–2 paragraph queries

Notes

• Always ask in English for best results
• Pass full error messages including error codes
• Include relevant code context (not just the error line)
• Save important design decisions to .claude/docs/DESIGN.md