OpenSpec

Description

A lightweight specification-driven framework that helps define requirements in structured, human-readable format and track changes through spec deltas using Gherkin syntax. Bridges the gap between business requirements and implementation.

Activation Keywords

•openspec
•open spec
•spec-driven
•specification
•gherkin
•scenario
•requirement
•bdd
•given when then
•spec delta

Tools Used

•read: Read OpenSpec files
•write: Write and update OpenSpec files
•edit: Edit spec deltas
•memory: Store specifications for reference

Installation

Install OpenSpec CLI

bash

npm install -g openspec

Or via project:

bash

cd /path/to/project
npm install --save-dev openspec

Verify Installation

bash

openspec --version

Initialize Project

bash

# Create spec directory structure
openspec init

# Or create manually
mkdir -p openspec/{core,features}
touch openspec/README.md

Usage Patterns

Creating a New Spec

Basic spec:

gherkin

### Requirement: User registration
The system SHALL allow users to register with email and password.

#### Scenario: Successful registration
GIVEN a new user with valid email "user@example.com" and password "SecurePass123"
WHEN the user submits registration form
THEN a new user account is created
AND a verification email is sent
AND the user is redirected to verification page

#### Scenario: Duplicate email
GIVEN a user with email "existing@example.com" already exists
WHEN a new user tries to register with same email
THEN registration fails
AND an error message "Email already registered" is displayed

Spec delta (tracking changes):

gherkin

### Requirement: User authentication
- The system SHALL authenticate users with email and password.
+ The system SHALL authenticate users with email and password OR social login.

#### Scenario: Successful email login
GIVEN a registered user with email "user@example.com" and password "correct"
WHEN the user submits login credentials
THEN the user is authenticated
- AND the token expires in 1 hour
+ AND the token expires in 24 hours if "Remember me" is checked

+ #### Scenario: Social login
+ - GIVEN a user chooses to login with Google
+ - WHEN Google authentication is completed successfully
+ - THEN the user is authenticated
+ - AND a JWT token is returned
+ - AND token expires in 24 hours

Using OpenSpec with AI Coding Agents

With OpenCode:

code

Implement the following OpenSpec requirements ultrawork:

### Requirement: User authentication
The system SHALL authenticate users with email and password.

#### Scenario: Successful login
GIVEN a registered user with email "user@example.com" and password "password123"
WHEN the user submits login credentials
THEN the user is authenticated
AND a JWT token is returned
AND the token expires in 1 hour

With Claude Code:

code

Implement the OpenSpec requirements in openspec/auth.spec.md. Create the necessary controllers, models, and tests.

Generating Tests from Specs

Create test files:

code

Generate Jest test suites from the OpenSpec scenarios in openspec/core/auth.spec.md

Use scenarios as test cases:

javascript

describe('User Authentication', () => {
  test('Successful login', () => {
    // GIVEN a registered user
    const user = { email: 'user@example.com', password: 'password123' }
    // WHEN the user submits login
    const result = authenticate(user)
    // THEN the user is authenticated
    expect(result.token).toBeDefined()
  })
})

Code Review with Spec Deltas

Reviewer perspective:

code

Here's the spec delta:
- Old requirement: Token expires in 1 hour
+ New requirement: Token expires in 24 hours

Review the code changes against this delta. Does the implementation match?

Instructions for Agents

When user mentions OpenSpec or specifications:

1. Read Existing Specs

Check for existing specifications:

bash

# Find spec files
find openspec -name "*.spec.md"

# Read specific spec
read openspec/core/auth.spec.md

2. Understand Spec Syntax

OpenSpec uses Gherkin syntax:

Requirement:

gherkin

### Requirement: [Name]
The system SHALL [requirement description].

SHALL for mandatory, MAY for optional.

Scenario:

gherkin

#### Scenario: [Name]
GIVEN [initial state]
WHEN [action occurs]
THEN [expected outcome]
AND [additional outcome]

Spec Delta:

gherkin

- Removed line (with - prefix)
+ Added line (with + prefix)

3. Create New Specs

When creating specifications:

•Use clear requirement names
•Write complete scenarios (GIVEN-WHEN-THEN)
•Cover happy path, edge cases, errors
•Make scenarios testable
•Use SHALL for mandatory requirements

4. Update Specs with Deltas

When requirements change:

•Identify what changed
•Use - for removed items
•Use + for added items
•Keep both for comparison
•Commit deltas to version control

5. Implement from Specs

When implementing:

•Read the spec file
•Break down by requirements
•Implement each scenario
•Create tests matching scenarios
•Verify against spec deltas

6. Generate Tests

Convert scenarios to tests:

•Each GIVEN = test setup
•Each WHEN = test action
•Each THEN = test assertion

Context Files

OpenSpec uses these context files:

openspec/README.md

Overview of specification structure

openspec/core/

Core system specifications (auth, users, etc.)

openspec/features/

Feature specifications (dashboard, reports, etc.)

Configuration

Project Structure

code

project/
├── openspec/
│   ├── core/
│   │   ├── auth.spec.md
│   │   ├── users.spec.md
│   │   └── sessions.spec.md
│   ├── features/
│   │   ├── dashboard.spec.md
│   │   └── reports.spec.md
│   └── README.md
├── src/
├── tests/
└── package.json

Spec Template

markdown

# Feature: [Feature Name]

## Requirements

### Requirement: [Requirement Name]
The system SHALL [requirement description].

#### Scenario: [Scenario Name]
GIVEN [initial state]
WHEN [action occurs]
THEN [expected outcome]
AND [additional outcomes]

### Requirement: Another requirement
...

Advanced Features

Spec Validation

code

Validate that all tests in the test suite correspond to scenarios in the OpenSpec files. Report any missing or extra test cases.

Spec Coverage

code

Calculate spec coverage: percentage of OpenSpec scenarios that have corresponding tests passing.

Spec-Driven Refactoring

code

Analyze the codebase against openspec/ requirements. Identify areas where implementation doesn't match spec and suggest fixes.

Common Patterns

Authentication Spec

gherkin

### Requirement: User authentication
The system SHALL authenticate users with email and password.

#### Scenario: Successful login
GIVEN a registered user with valid credentials
WHEN the user submits login
THEN authentication succeeds
AND a JWT token is returned

#### Scenario: Wrong password
GIVEN a registered user
WHEN the user submits wrong password
THEN authentication fails
AND an error is returned

API Endpoint Spec

gherkin

### Requirement: Get user profile
The system SHALL provide user profile data via API.

#### Scenario: Get own profile
GIVEN an authenticated user
WHEN the user requests /api/users/me
THEN user profile data is returned
AND status code is 200

#### Scenario: Unauthorized access
GIVEN an unauthenticated request
WHEN requesting /api/users/me
THEN status code is 401
AND error message is returned

Data Validation Spec

gherkin

### Requirement: Email validation
The system SHALL validate email addresses during registration.

#### Scenario: Valid email
GIVEN a user provides "user@example.com"
WHEN submitting registration
THEN email is accepted

#### Scenario: Invalid email
GIVEN a user provides "invalid-email"
WHEN submitting registration
THEN registration fails
AND "Invalid email" error is shown

Error Handling

Invalid Spec Syntax

code

If spec has syntax errors:
  1. Check each scenario has GIVEN-WHEN-THEN
  2. Verify proper indentation
  3. Ensure requirement descriptions are clear
  4. Use spec validation tool: openspec validate

Missing Scenarios

code

If implementation doesn't match spec:
  1. Compare implementation against spec scenarios
  2. Identify missing functionality
  3. Add missing scenarios or update implementation
  4. Re-run tests

Conflicting Deltas

code

If spec deltas have conflicts:
  1. Review the changes (- and + lines)
  2. Resolve conflicts by choosing correct state
  3. Update spec without conflicting lines
  4. Clear the delta once resolved

Best Practices

1. Write Testable Scenarios

Each scenario should be:

•Specific and clear
•Testable via automation
•Independent of other scenarios
•Focused on single behavior

2. Use SHALL/MAY Correctly

•SHALL: Mandatory requirement
•MAY: Optional feature
•SHALL NOT: Forbidden behavior

3. Cover All Cases

For each requirement, cover:

•Happy path (success case)
•Edge cases (boundary conditions)
•Error cases (failure modes)

4. Keep Deltas Clean

•Clear deltas after implementation
•Use version control to track changes
•Document why changes were made

5. Use with AI Agents

•Provide specs as input to agents
•Use spec deltas to track changes
•Generate tests from scenarios
•Review code against specs

Examples

Example 1: Initial Spec

gherkin

### Requirement: User registration
The system SHALL allow users to register with email and password.

#### Scenario: Successful registration
GIVEN a new user with valid email and password
WHEN the user submits registration
THEN account is created
AND verification email is sent

Example 2: Spec Delta

gherkin

### Requirement: User registration
The system SHALL allow users to register with email and password.
+ The system SHALL support optional phone number.

#### Scenario: Successful registration
GIVEN a new user with valid email and password
- WHEN the user submits registration
+ WHEN the user submits registration with optional phone number
THEN account is created
AND verification email is sent

Example 3: Implementation Request

code

User: "Implement the OpenSpec spec for user authentication"

Agent:
1. Reads openspec/core/auth.spec.md
2. Identifies requirements and scenarios
3. Creates auth controller
4. Implements login endpoint
5. Adds validation
6. Creates tests for each scenario
7. Runs tests
8. Reports completion

Limitations

•Doesn't generate code automatically (requires AI agent)
•Needs discipline to keep specs updated
•Can be verbose for simple features
•Learning curve for Gherkin syntax

Resources

•OpenSpec Website: https://openspec.dev/
•Gherkin Syntax: https://cucumber.io/docs/gherkin/reference/
•BDD Best Practices: https://cucumber.io/docs/bdd/

Related Skills

•opencode: OpenSpec integration for implementation
•claude-code: Can implement OpenSpec specs
•obsidian: For storing and organizing specs

Notes

•OpenSpec is particularly effective when paired with AI coding agents
•The spec delta format makes changes easy to review
•Gherkin syntax is familiar to many developers and BDD practitioners
•Specs can live alongside code as documentation
•Perfect for TDD/BDD workflows