gemini-cli/docs/cli/spec-driven-development.md

# Spec-Driven Development (SDD)

**Measure twice, code once.**

Spec-Driven Development (SDD) is a built-in methodology for Gemini CLI that
enables **Context-Driven Development**. Inspired by [Conductor], it turns Gemini
CLI into a proactive project manager that follows a strict protocol to specify,
plan, and implement software features and bug fixes.

Instead of just writing code, SDD ensures a consistent, high-quality lifecycle
for every task: **Context -> Spec & Plan -> Implement**.

The philosophy behind SDD is simple: control your code. By treating context as a
managed artifact alongside your code, you transform your repository into a
single source of truth that drives every agent interaction with deep, persistent
project awareness.

## Features

- **Plan before you build**: Create specs and plans that guide the agent for new
  and existing codebases.
- **Maintain context**: Ensure AI follows style guides, tech stack choices, and
  product goals.
- **Iterate safely**: Review plans before code is written, keeping you firmly in
  the loop.
- **Work as a team**: Set project-level context for your product, tech stack,
  and workflow preferences that become a shared foundation for your team.
- **Build on existing projects**: Intelligent initialization for both new
  (Greenfield) and existing (Brownfield) projects.
- **Smart revert**: A git-aware revert command that understands logical units of
  work (tracks, phases, tasks) rather than just commit hashes.

## Usage

SDD is designed to manage the entire lifecycle of your development tasks. It is
one of the [planning workflows](./plan-mode.md#planning-workflows) supported by
Gemini CLI.

**Note on Token Consumption:** SDD's context-driven approach involves reading
and analyzing your project's context, specifications, and plans. This can lead
to increased token consumption, especially in larger projects or during
extensive planning and implementation phases. You can check the token
consumption in the current session by running `/stats model`.

### 1. Set Up the Project (Run Once)

When you run `/spec setup`, SDD helps you define the core components of your
project context. This context is then used for building new components or
features by you or anyone on your team.

- **Product**: Define project context (e.g. users, product goals, high-level
  features).
- **Product guidelines**: Define standards (e.g. prose style, brand messaging,
  visual identity).
- **Tech stack**: Configure technical preferences (e.g. language, database,
  frameworks).
- **Workflow**: Set team preferences (e.g. TDD, commit strategy).

**Generated Artifacts:**

- `.gemini/specs/product.md`
- `.gemini/specs/product-guidelines.md`
- `.gemini/specs/tech-stack.md`
- `.gemini/specs/workflow.md`
- `.gemini/specs/code_styleguides/`
- `.gemini/specs/tracks.md`

```bash
/spec setup
```

### 2. Start a New Track (Feature or Bug)

When you’re ready to take on a new feature or bug fix, run `/spec create`. This
initializes a **track** — a high-level unit of work. SDD helps you generate two
critical artifacts:

- **Specs**: The detailed requirements for the specific job. What are we
  building and why?
- **Plan**: An actionable to-do list containing phases, tasks, and sub-tasks.

**Generated Artifacts:**

- `.gemini/specs/tracks/<track_id>/spec.md`
- `.gemini/specs/tracks/<track_id>/plan.md`
- `.gemini/specs/tracks/<track_id>/metadata.json`

```bash
/spec create
# OR with a description
/spec create "Add a dark mode toggle to the settings page"
```

### 3. Implement the Track

Once you approve the plan, run `/spec implement`. Your coding agent then works
through the `plan.md` file, checking off tasks as it completes them.

**Updated Artifacts:**

- `.gemini/specs/tracks.md` (Status updates)
- `.gemini/specs/tracks/<track_id>/plan.md` (Status updates)
- Project context files (Synchronized on completion)

```bash
/spec implement
```

SDD will:

1.  Select the next pending task.
2.  Follow the defined workflow (e.g., TDD: Write Test -> Fail -> Implement ->
    Pass).
3.  Update the status in the plan as it progresses.
4.  **Verify Progress**: Guide you through a manual verification step at the end
    of each phase to ensure everything works as expected.

During implementation, you can also:

- **Check status**: Get a high-level overview of your project's progress.
  ```bash
  /spec status
  ```
- **Revert work**: Undo a feature or a specific task if needed.

  ```bash
  /spec revert
  ```

- **Review work**: Review completed work against guidelines and the plan.
  ```bash
  /spec review
  ```

## Commands Reference

| Command           | Description                                                                       | Artifacts                                                                                                                                                        |
| :---------------- | :-------------------------------------------------------------------------------- | :--------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `/spec setup`     | Scaffolds the project and sets up the SDD environment. Run this once per project. | `.gemini/specs/product.md`<br>`.gemini/specs/product-guidelines.md`<br>`.gemini/specs/tech-stack.md`<br>`.gemini/specs/workflow.md`<br>`.gemini/specs/tracks.md` |
| `/spec create`    | Starts a new feature or bug track. Generates `spec.md` and `plan.md`.             | `.gemini/specs/tracks/<id>/spec.md`<br>`.gemini/specs/tracks/<id>/plan.md`<br>`.gemini/specs/tracks.md`                                                          |
| `/spec implement` | Executes the tasks defined in the current track's plan.                           | `.gemini/specs/tracks.md`<br>`.gemini/specs/tracks/<id>/plan.md`                                                                                                 |
| `/spec status`    | Displays the current progress of the tracks file and active tracks.               | Reads `.gemini/specs/tracks.md`                                                                                                                                  |
| `/spec revert`    | Reverts a track, phase, or task by analyzing git history.                         | Reverts git history                                                                                                                                              |
| `/spec review`    | Reviews completed work against guidelines and the plan.                           | Reads `plan.md`, `product-guidelines.md`                                                                                                                         |

[Conductor]: https://github.com/gemini-cli-extensions/conductor