implementation

What this skill does

# Implementation

Pick the next feature. Build it. Verify it. Ship it.

## Gotchas

| Gotcha | What happens | Do instead |
|--------|-------------|------------|
| Committing before verify passes | Broken code lands in history, needs revert or fixup | Always run verify.sh first — commit only on exit 0 |
| Reading full feature-list.json | Burns context tokens as feature list grows (33+ features) | Use `feature.py next` to get just the one feature you need |
| Script fails, agent rewrites it | Loses project-specific customizations from /init-project | Read the script, fix the broken command — never recreate |
| Forgetting to update AGENTS.md | Architecture/Key Files drift from actual codebase | Check if you added/removed modules — update if so |

## Workflow

### 1. Pick Feature

```bash
python .codex/scripts/feature.py next
```

Returns the highest-priority pending feature whose dependencies are resolved. If no features ready, stop and tell the user.

### 2. Implement

- Read the project AGENTS.md for architecture, key files, and conventions
- Read existing code before modifying — understand the patterns in use
- Write the implementation following project conventions
- Write tests — happy path + at least one error path

The goal is working code with tests, not perfect code. Ship, then iterate.

### 3. Verify

```bash
bash .codex/scripts/verify.sh
```

Runs lint → test → build in order, stops at first failure. Fix the issue, rerun from top. Only proceed to commit when exit code is 0.

If `verify.sh` is missing or stale, run the checks from AGENTS.md Commands table manually.

### 4. Commit

Stage only the files you changed. Commit with the feature ID:

```
feat(FT-XXX): short description of what was built
```

### 5. Update & Mark Done

- If you added/removed modules, models, or key files → update AGENTS.md (Architecture, Key Files, Commands)
- If the feature revealed new verification needs → update `.codex/scripts/verify.sh`
- Mark done:

```bash
python .codex/scripts/feature.py done FT-XXX
```

## Scripts Reference

Scripts live in `.codex/scripts/`. Created by `/init-project`, tailored per project.

| Script | What it does | When to update |
|--------|-------------|----------------|
| `feature.py` | Feature CRUD: `next`, `get`, `done`, `add`, `list`, `summary`. Reads/writes `.codex/progress/feature-list.json`. | Never — project-agnostic |
| `verify.sh` | Runs lint → test → build in order, `set -e` stops at first failure. Exit 0 = all pass. | When a feature adds a new check (e.g., type check, new linter, integration test command) |
| `dev-server.sh` | Installs deps + starts dev server. | When dependencies change, entry point moves, or a new service is added |

**If a script fails:** read it, fix the broken command, do NOT delete and rewrite. The structure (set -e, echo headers, command order) is intentional and project-specific.

## Rules

- **Never commit with failing checks** — broken commits create revert churn that wastes more time than the fix
- **Never skip tests for production code** — untested code is unverified code, and the agent can't self-correct without tests
- **Read files before editing** — modifying code you haven't read produces wrong assumptions and wasted iterations
- **One feature per cycle** — context switching mid-feature leads to half-finished work in both
- **Never recreate scripts from scratch** — they contain project-specific customizations from /init-project that you can't rederive