Immutable. This exact content is served forever at /api/v1/blob/615bc34889a9a434.
---
name: codex-implement
description: "Implement features via Codex MCP. Use when: writing new code from specs, implementing features, Codex-driven development. Not for: code review (use codex-code-review), architecture advice (use codex-architect). Output: implemented code + review loop."
allowed-tools: mcp__codex__codex, mcp__codex__codex-reply, Bash(git:*), Read, Grep, Glob, Edit, Write, AskUserQuestion, Skill
---
# Codex Implement Skill
## Trigger
- Keywords: codex implement, implement feature, codex write code, implement from spec
## When NOT to Use
- Architecture advice only (use `/codex-architect`)
- Code review (use `/codex-review-fast`)
- Bug fix (use `/bug-fix`)
- Simple one-line change (edit directly)
## Workflow
```
Parse args → Decompose → Collect context → Iterate items → Review loop → Done
↕
codex → diff → confirm
↕
reject/modify → codex-reply
```
### Step 1: Parse & Decompose
**`--spec` provided**: Read spec/request doc, extract individual items.
**Arguments without `--spec`**: Use directly as single item.
**No arguments**: Ask user for requirement, target file, reference files.
Break into **implementation items** — each one logical unit (interface, method, endpoint), implementable in dependency order, small enough for one Codex call.
Present plan before starting:
```
| # | Item | Target File | Depends On |
|---|-------------------|----------------------|------------|
| 1 | Define interfaces | src/interface/x.ts | - |
| 2 | Core logic | src/service/x.ts | 1 |
| 3 | Controller/Route | src/controller/x.ts | 2 |
Proceed?
```
### Step 2: Collect Context (Claude, NOT Codex)
Claude researches the codebase before calling Codex:
1. Read `.claude/CLAUDE.md` (fallback `CLAUDE.md`) — tech stack, conventions, test commands
2. Read target file (if exists) and context files
3. Search similar implementations
4. Read 2-3 similar files for patterns
Summarize as `PROJECT_CONTEXT` for Codex.
### Step 3: Iterative Implementation
Implement **one item at a time**, in dependency order.
#### 3a: First item — new session
See `references/codex-prompts.md` for the full prompt template.
Call `mcp__codex__codex` with `sandbox: 'workspace-write'`, `approval-policy: 'on-failure'`.
**Save the returned `threadId`.**
#### 3b: Confirm each item
After each Codex call: `git diff` → ask user:
| Choice | Action |
|--------|--------|
| Accept | Proceed to next item (3c) |
| Reject | `git checkout .` affected files, re-attempt (max 2 retries, then ⛔) |
| Modify | `codex-reply` with feedback → loop back to 3b |
#### 3c: Subsequent items — same thread
Use `mcp__codex__codex-reply` with saved `threadId`. See `references/codex-prompts.md`.
Repeat 3b → 3c until all items done.
### Step 4: Final Confirmation
`git diff` full changeset → user confirms.
### Step 5: Review Loop (Codex-in-the-loop)
**⚠️ @CLAUDE.md auto-loop: fix → re-review → ... → ✅ PASS ⚠️**
| Step | Command | On fail |
|------|---------|---------|
| 1 | `/codex-review-fast` | `codex-reply` to fix → re-review |
| 2 | `/precommit` | `codex-reply` to fix → re-run |
Issues found → **use same Codex thread to fix** (not manual). See `references/codex-prompts.md` for fix prompt.
Max 3 rounds per step. Still failing → report blocker.
#### Test Requirements
| Change Type | Required Tests |
|-------------|---------------|
| New service/provider | Unit (happy + error + edge) |
| New API endpoint | Unit + integration |
| Modified logic | Existing pass + new logic tests |
| Bug fix scenario | Regression test |
If Codex omitted tests → `codex-reply` to request them.
## Output
```markdown
## Codex Implementation Report
### Implementation Items
| # | Item | Target File | Status |
|---|------|-------------|--------|
| 1 | ... | ... | ✅/❌ |
### Change Summary
| File | Operation | Description |
|------|-----------|-------------|
| ... | Create/Modify | ... |
### Review Result
<codex-review-fast output>
### Gate
✅ Complete / ⛔ Needs modification
```
## Verification
- [ ] All items implemented and confirmed
- [ ] Tests included for each item
- [ ] `/codex-review-fast` passed
- [ ] `/precommit` passed
## Examples
```
/codex-implement "Add a method to calculate fees"
/codex-implement "Implement wallet service" --spec docs/features/wallet/2-tech-spec.md
/codex-implement "Add getUserBalance method" --target src/service/wallet.service.ts
/codex-implement "Implement cache logic" --target src/service/cache.ts --context src/service/redis.ts
```