name: openspec-develop
description: "Implement OpenSpec change proposals. Use when: implementing approved changes, working through task lists, or checking implementation progress."
model: sonnet
allowed-tools: [Glob, Grep, Read, Edit, Write, Bash, TodoWrite, AskUserQuestion]

OpenSpec Develop

Implementation engine for approved OpenSpec proposals. Turns tasks.md checkboxes into working code.

Workflow: Explore → Implement → Mark

flowchart LR
    A["Read task"] --> B["Explore context"]
    B --> C["Implement"]
    C --> D["Mark ✅ in tasks.md"]
    D --> E{"More tasks?"}
    E -->|Yes| A
    E -->|No| F["Report complete"]

    classDef action fill:#C8E6C9,stroke:#388E3C,color:#000
    class A,B,C,D,F action

Critical: Mark checkbox immediately after each task. Enables crash recovery.

Exploration Strategy

Before implementation, consult openspec/project.md → Exploration Strategy section:

1. Context sources: Read primary files (project.md, proposal.md, specs)
2. Must-read files: CLAUDE.md, settings.json (project constraints)
3. Tools: Use configured codebase tools (Glob, Grep, Read, or MCP if enabled)
4. Pattern matching: Read existing similar files to match structure/style
5. Philosophy: Read Execution Philosophy section for current mode and principles

Commands

implement

Implement all pending tasks from tasks.md.

Input: $ARGUMENTS = change-id

Workflow:
1. Read openspec/changes/{change-id}/tasks.md
2. For each unchecked task (- [ ]):
a. Consult Exploration Strategy for context/tools
b. Read specs and must-read files
c. Explore codebase for patterns
d. Implement the task
e. Immediately mark checkbox: - [ ] → - [x]
3. When all complete: Report "All tasks complete. Ready for /openspec-test"

All complete:

✅ All tasks complete for {change-id}
Progress: {done}/{total} tasks
Ready for: /openspec-test {change-id}

task

Implement a specific task by number.

Input: $ARGUMENTS = change-id task-number (e.g., add-feature 1.3)

Workflow:
1. Read tasks.md, find task by number (e.g., 1.3)
2. If already checked: Report "Task {number} already complete"
3. If unchecked: Implement using same workflow as implement
4. Mark checkbox immediately after completion

Already complete:

⏭️ Task {number} already complete
Description: {task description}

status

Show implementation progress.

Input: $ARGUMENTS = change-id

Run:

openspec show {change-id}

Display task completion progress from CLI output.

Guardrails

Autonomous (no confirmation needed):
- Code generation matching specs
- File edits within scope
- Checkbox updates
- Pattern-matching existing code

Ask-first (pause and confirm):
- Architectural decisions not in specs
- New dependencies not mentioned
- Scope deviation >20% from proposal
- Files outside change scope

Scope check: Before creating files not mentioned in proposal.md, count affected files. If >20% more than proposal's "Affected files", ask:

⚠️ Scope expansion detected
Proposal mentions: {n} files
Implementation needs: {m} files ({percent}% more)

Proceed with expanded scope? [y/N]

Philosophy Check

Before implementing, read openspec/project.md → Execution Philosophy → mode.

During implementation, flag anti-patterns for current mode:

⚠️ Philosophy check ({mode} mode):
- Anti-pattern detected: {anti-pattern}
- Current action: {what you're about to do}
- Question: {is this necessary or gold-plating?}

Proceed anyway? [y/N]

Examples by mode:
- garage: Flag premature abstractions, over-engineering, excessive documentation
- scale: Flag missing tests, undocumented decisions, cowboy changes
- maintenance: Flag unnecessary refactors, feature creep, risky upgrades

Task Parsing

Parse tasks.md format:

## 1. Section Name
- [ ] 1.1 Task description here
- [x] 1.2 Already complete task
- [ ] 1.3 Another pending task

Match pattern: - \[([ x])\] (\d+\.\d+) (.+)$
- Group 1: checkbox state (space = pending, x = complete)
- Group 2: task number (e.g., 1.3)
- Group 3: task description

Checkbox Update

After completing task, edit tasks.md:
- Find: - [ ] {task-number} {description}
- Replace: - [x] {task-number} {description}

Use Edit tool for surgical update. Never rewrite entire file.