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).

Input: Optionally specify a change name. If omitted, MUST prompt for available changes.

Steps

•
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.
•
Find delta specs

Look for delta spec files in openspec/changes/<name>/specs/*/spec.md.

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

For each capability with a delta spec at openspec/changes/<name>/specs/<capability>/spec.md:

a. Read the delta spec to understand the intended changes

b. Read the main spec at 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
d. Create new main spec if capability doesn't exist yet:
- •Create openspec/specs/<capability>/spec.md
- •Add Purpose section (can be brief, mark as TBD)
- •Add Requirements section with the ADDED requirements
•
Show summary

After applying all changes, summarize:
- •Which capabilities were updated
- •What changes were made (requirements added/modified/removed/renamed)

Delta Spec Format Reference

markdown

## 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`

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

code

## 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
•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