Sync delta specs from a change to main specs.

This is an agent-driven operation - you will read delta specs and directly edit main specs to apply the changes. This allows intelligent merging (e.g., adding a scenario without copying the entire requirement).

Store selection: If the user names a store (a store is a standalone OpenSpec repo registered on this machine) or the work lives in one, run openspec store list --json to discover registered store ids, then pass --store <id> on the commands that read or write specs and changes (new change, status, instructions, list, show, validate, archive, doctor, context). Other commands do not take the flag. Hints printed by commands already carry the flag; keep it on follow-ups. Without a store, commands act on the nearest local openspec/ root.

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. If no change name provided, prompt for selection

   Run openspec list --json to get available changes. Use the AskUserQuestion tool to let the user select.

   Show changes that have delta specs (under specs/ directory).

   IMPORTANT: Do NOT guess or auto-select a change. Always let the user choose.

2. Resolve change context

   Run:

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

   The JSON includes planningHome.root. Main specs live under <planningHome.root>/openspec/specs/ — use that (store-aware) root for every main-spec path below, not a hardcoded repo path. When a store is selected it points at the store, not the current repository.

3. Find delta specs

   Use artifactPaths.specs.existingOutputPaths from the status JSON as the list of delta spec files.

   Each delta spec file contains sections like:

   • ## ADDED Requirements - New requirements to add
   • ## MODIFIED Requirements - Changes to existing requirements
   • ## REMOVED Requirements - Requirements to remove
   • ## RENAMED Requirements - Requirements to rename (FROM:/TO: format)

   If no delta specs found, inform user and stop.

4. For each delta spec, apply changes to main specs

   For each capability delta spec path returned by the CLI (these may belong to a selected store, not the repo):

   a. Read the delta spec to understand the intended changes

   b. Read the main spec at <planningHome.root>/openspec/specs/<capability>/spec.md (may not exist yet)

   c. Apply changes intelligently:

   ADDED Requirements:

   • If requirement doesn't exist in main spec → add it
   • If requirement already exists → update it to match (treat as implicit MODIFIED)

   MODIFIED Requirements:

   • Find the requirement in main spec
   • Apply the changes - this can be:
     • Adding new scenarios (don't need to copy existing ones)
     • Modifying existing scenarios
     • Changing the requirement description
   • Preserve scenarios/content not mentioned in the delta

   REMOVED Requirements:

   • Remove the entire requirement block from main spec

   RENAMED Requirements:

   • Find the FROM requirement, rename to TO

   ## Purpose in the delta:

   • The main spec already has one and it is authoritative - leave it alone (this is what openspec archive does; it warns and moves on)

   d. Create new main spec if capability doesn't exist yet:

   • Create <planningHome.root>/openspec/specs/<capability>/spec.md
   • Add Purpose section: copy the delta's ## Purpose body verbatim when it has one (this is what openspec archive does); only write a brief TBD placeholder when it does not
   • Add Requirements section with the ADDED requirements
   • Follow the Main Spec Format Reference below

5. Show summary

   After applying all changes, summarize:

   • Which capabilities were updated
   • What changes were made (requirements added/modified/removed/renamed)
   • Any new main spec left with a TBD Purpose placeholder, so it gets written now rather than lingering

Delta Spec Format Reference

## Purpose

Only on a delta that introduces a brand-new capability. Seeds the new main spec.

## ADDED Requirements

### Requirement: New Feature
The system SHALL do something new.

#### Scenario: Basic case
- **WHEN** user does X
- **THEN** system does Y

## MODIFIED Requirements

### Requirement: Existing Feature
#### Scenario: New scenario to add
- **WHEN** user does A
- **THEN** system does B

## REMOVED Requirements

### Requirement: Deprecated Feature

## RENAMED Requirements

- FROM: `### Requirement: Old Name`
- TO: `### Requirement: New Name`

Main Spec Format Reference

Main specs are what the delta merges INTO. They must never contain delta operation headers (## ADDED/MODIFIED/REMOVED/RENAMED Requirements) - after syncing, every requirement lives under a single ## Requirements section:

# <capability> Specification

## Purpose
Short description of what this capability does and why it exists.

## Requirements

### Requirement: New Feature
The system SHALL do something new.

#### Scenario: Basic case
- **WHEN** user does X
- **THEN** system does Y

Key Principle: Intelligent Merging

Unlike programmatic merging, you can apply partial updates:

• To add a scenario, just include that scenario under MODIFIED - don't copy existing scenarios
• The delta represents intent, not a wholesale replacement
• Use your judgment to merge changes sensibly

Output On Success

## Specs Synced: <change-name>

Updated main specs:

**<capability-1>**:
- Added requirement: "New Feature"
- Modified requirement: "Existing Feature" (added 1 scenario)

**<capability-2>**:
- Created new spec file
- Added requirement: "Another Feature"

Main specs are now updated. The change remains active - archive when implementation is complete.

Guardrails

• Read both delta and main specs before making changes
• Preserve existing content not mentioned in delta
• Never copy a delta file into a main spec as-is - merge its content so the main spec keeps the Main Spec Format Reference structure, with no delta operation headers
• If something is unclear, ask for clarification
• Show what you're changing as you go
• The operation should be idempotent - running twice should give same result