/openspec-apply-change

name: openspec-apply-change
description: Implement tasks from an OpenSpec change. Use when the user wants to start implementing, continue implementation, or work through tasks.
license: MIT
compatibility: Requires openspec CLI.
metadata:
  author: openspec
  version: "1.0"
  generatedBy: "1.3.1"
  internal: true

Implement tasks from an OpenSpec change.

**Input**: Optionally specify a change name. If omitted, check if it can be inferred from conversation context. If vague or ambiguous you MUST prompt for available changes.

**Steps**

1. **Select the change**

If a name is provided, use it. Otherwise:

• Infer from conversation context if the user mentioned a change
• Auto-select if only one active change exists
• If ambiguous, run `openspec list --json` to get available changes and use the **AskUserQuestion tool** to let the user select

Always announce: "Using change: <name>" and how to override (e.g., `/opsx:apply <other>`).

2. **Check status to understand the schema**

   openspec status --change "<name>" --json

Parse the JSON to understand:

• `schemaName`: The workflow being used (e.g., "spec-driven")
• Which artifact contains the tasks (typically "tasks" for spec-driven, check status for others)

3. **Get apply instructions**

   openspec instructions apply --change "<name>" --json

This returns:

• `contextFiles`: artifact ID -> array of concrete file paths (varies by schema - could be proposal/specs/design/tasks or spec/tests/implementation/docs)
• Progress (total, complete, remaining)
• Task list with status
• Dynamic instruction based on current state

**Handle states:**

• If `state: "blocked"` (missing artifacts): show message, suggest using openspec-continue-change
• If `state: "all_done"`: congratulate, suggest archive
• Otherwise: proceed to implementation

4. **Read context files**

Read every file path listed under `contextFiles` from the apply instructions output. The files depend on the schema being used:

• **spec-driven**: proposal, specs, design, tasks
• Other schemas: follow the contextFiles from CLI output

5. **Show current progress**

Display:

• Schema being used
• Progress: "N/M tasks complete"
• Remaining tasks overview
• Dynamic instruction from CLI

6. **Implement tasks (loop until done or blocked)**

For each pending task:

• Show which task is being worked on
• Make the code changes required
• Keep changes minimal and focused
• Mark task complete in the tasks file: `- [ ]` → `- [x]`
• Continue to next task

**Pause if:**

• Task is unclear → ask for clarification
• Implementation reveals a design issue → suggest updating artifacts
• Error or blocker encountered → report and wait for guidance
• User interrupts

7. **On completion or pause, show status**

Display:

• Tasks completed this session
• Overall progress: "N/M tasks complete"
• If all done: suggest archive
• If paused: explain why and wait for guidance

**Output During Implementation**

## Implementing: <change-name> (schema: <schema-name>)

Working on task 3/7: <task description>
[...implementation happening...]
✓ Task complete

Working on task 4/7: <task description>
[...implementation happening...]
✓ Task complete

**Output On Completion**

## Implementation Complete

**Change:** <change-name>
**Schema:** <schema-name>
**Progress:** 7/7 tasks complete ✓

### Completed This Session
- [x] Task 1
- [x] Task 2
...

All tasks complete! Ready to archive this change.

**Output On Pause (Issue Encountered)**

## Implementation Paused

**Change:** <change-name>
**Schema:** <schema-name>
**Progress:** 4/7 tasks complete

### Issue Encountered
<description of the issue>

**Options:**
1. <option 1>
2. <option 2>
3. Other approach

What would you like to do?

**Guardrails**

• Keep going through tasks until done or blocked
• Always read context files before starting (from the apply instructions output)
• If task is ambiguous, pause and ask before implementing
• If implementation reveals issues, pause and suggest artifact updates
• Keep code changes minimal and scoped to each task
• Update task checkbox immediately after completing each task
• Pause on errors, blockers, or unclear requirements - don't guess
• Use contextFiles from CLI output, don't assume specific file names

**Fluid Workflow Integration**

This skill supports the "actions on a change" model:

• **Can be invoked anytime**: Before all artifacts are done (if tasks exist), after partial implementation, interleaved with other actions
• **Allows artifact updates**: If implementation reveals design issues, suggest updating artifacts - not phase-locked, work fluidly