Codex Plan Apply

Belmont: Codex Plan Apply

Use this skill only when the user provides a BELMONT_PLAN_PACKET produced by a Codex plan-mode Belmont planning session.

This is a Codex compatibility adapter. Other agents that can ask structured questions and write files in the same session should keep using product-plan and tech-plan directly.

Purpose

Codex plan mode provides keyboard-navigable structured questions, but may not be the right phase for writing planning files. This skill runs after the user leaves plan mode. It persists the already-approved planning output without reopening the interview.

Rules

1. Do NOT ask product or technical planning questions.
2. Do NOT infer missing PRD, PROGRESS, TECH_PLAN, or models.yaml content.
3. Do NOT edit source code.
4. Only write files under .belmont/.
5. Only write, create, or update files explicitly listed in the packet.
6. Preserve existing content unless the packet explicitly says a file should be replaced.
7. For update operations, edit the named sections only. Never replace a real existing file unless the packet explicitly marks it as a full-file replacement.
8. If the packet is incomplete, ambiguous, malformed, or lacks target paths, stop and ask the user to rerun the relevant Codex plan-mode skill.

Expected Packet Shape

The packet is plain Markdown in a fenced block:

```BELMONT_PLAN_PACKET
kind: product-plan | tech-plan
mode: create | update
feature_slug: <slug or none>
base_path: .belmont/features/<slug> | .belmont

files:
  - path: .belmont/features/<slug>/PRD.md
    operation: create | replace | update-section
    content: |
      ...
  - path: .belmont/features/<slug>/PROGRESS.md
    operation: create | replace | update-section
    content: |
      ...

post_apply:
  commit_message: belmont: update planning files after product planning
  next_prompt: /plan $belmont:tech-plan <feature>
```

YAML-like structure is preferred, but exact YAML parsing is not required. The key requirement is that each file path, operation, and content block is explicit enough to apply safely.

Workflow

1. Read the packet.
2. Validate that every target path is under .belmont/.
3. Validate that no source-code paths are listed.
4. Apply the file changes exactly as specified.
5. Run:

   git status --porcelain .belmont/
   

6. If .belmont/ is not git-ignored and the packet includes post_apply.commit_message, commit only .belmont/ changes:

   git check-ignore -q .belmont/ 2>/dev/null
   git add .belmont/
   git commit -m "<packet commit_message>"
   

   Skip the commit if .belmont/ is ignored or there are no .belmont/ changes.
7. Report the files written and the next prompt from post_apply.next_prompt.

Refusal Cases

Stop without editing if:

• No BELMONT_PLAN_PACKET is present.
• Any target path escapes .belmont/.
• The packet asks for source-code changes.
• The packet asks you to make new planning decisions.
• The packet conflicts with existing files and does not state whether to update or replace.