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, check if it can be inferred from conversation context. If vague or ambiguous you 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

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

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