Add Antigravity workflow support

CHANGELOG.md

@@ -1,5 +1,11 @@
 # @fission-ai/openspec
 
+## Unreleased
+
+### Minor Changes
+
+- Add Antigravity slash command support so `openspec init` can generate `.agent/workflows/openspec-*.md` files with description-only frontmatter and `openspec update` refreshes existing workflows alongside Windsurf.
+
 ## 0.15.0
 
 ### Minor Changes

README.md

@@ -102,6 +102,7 @@ These tools have built-in OpenSpec commands. Select the OpenSpec integration whe
 | **OpenCode** | `/openspec-proposal`, `/openspec-apply`, `/openspec-archive` |
 | **Kilo Code** | `/openspec-proposal.md`, `/openspec-apply.md`, `/openspec-archive.md` (`.kilocode/workflows/`) |
 | **Qoder (CLI)** | `/openspec:proposal`, `/openspec:apply`, `/openspec:archive` (`.qoder/commands/openspec/`) — see [docs](https://qoder.com/cli) |
+| **Antigravity** | `/openspec-proposal`, `/openspec-apply`, `/openspec-archive` (`.agent/workflows/`) |
 | **Windsurf** | `/openspec-proposal`, `/openspec-apply`, `/openspec-archive` (`.windsurf/workflows/`) |
 | **Codex** | `/openspec-proposal`, `/openspec-apply`, `/openspec-archive` (global: `~/.codex/prompts`, auto-installed) |
 | **GitHub Copilot** | `/openspec-proposal`, `/openspec-apply`, `/openspec-archive` (`.github/prompts/`) |

openspec/changes/add-antigravity-support/proposal.md

@@ -0,0 +1,11 @@
+## Why
+Google is rolling out Antigravity, a Windsurf-derived IDE that discovers workflows from `.agent/workflows/*.md`. Today OpenSpec can only scaffold slash commands for Windsurf directories, so Antigravity users cannot run the proposal/apply/archive flows from the IDE.
+
+## What Changes
+- Add Antigravity as a selectable native tool in `openspec init` so it creates `.agent/workflows/openspec-proposal.md`, `openspec-apply.md`, and `openspec-archive.md` with YAML frontmatter containing only a `description` field plus the standard OpenSpec-managed body.
+- Ensure `openspec update` refreshes the body of any existing Antigravity workflows inside `.agent/workflows/` without creating missing files, mirroring the Windsurf behavior.
+- Share e2e/template coverage confirming the generator writes the proper directory, filename casing, and frontmatter format so Antigravity picks up the workflows.
+
+## Impact
+- Affected specs: `specs/cli-init`, `specs/cli-update`
+- Expected code: CLI init/update tool registries, slash-command templates, associated tests

openspec/changes/add-antigravity-support/specs/cli-init/spec.md

@@ -0,0 +1,9 @@
+## MODIFIED Requirements
+### Requirement: Slash Command Configuration
+The init command SHALL generate slash command files for supported editors using shared templates.
+
+#### Scenario: Generating slash commands for Antigravity
+- **WHEN** the user selects Antigravity during initialization
+- **THEN** create `.agent/workflows/openspec-proposal.md`, `.agent/workflows/openspec-apply.md`, and `.agent/workflows/openspec-archive.md`
+- **AND** ensure each file begins with YAML frontmatter that contains only a `description: <stage summary>` field followed by the shared OpenSpec workflow instructions wrapped in managed markers
+- **AND** populate the workflow body with the same proposal/apply/archive guidance used for other tools so Antigravity behaves like Windsurf while pointing to the `.agent/workflows/` directory

openspec/changes/add-antigravity-support/specs/cli-update/spec.md

@@ -0,0 +1,8 @@
+## MODIFIED Requirements
+### Requirement: Slash Command Updates
+The update command SHALL refresh existing slash command files for configured tools without creating new ones, and ensure the OpenCode archive command accepts change ID arguments.
+
+#### Scenario: Updating slash commands for Antigravity
+- **WHEN** `.agent/workflows/` contains `openspec-proposal.md`, `openspec-apply.md`, and `openspec-archive.md`
+- **THEN** refresh the OpenSpec-managed portion of each file so the workflow copy matches other tools while preserving the existing single-field `description` frontmatter
+- **AND** skip creating any missing workflow files during update, mirroring the behavior for Windsurf and other IDEs

openspec/changes/add-antigravity-support/tasks.md

@@ -0,0 +1,12 @@
+## 1. CLI init support
+- [x] 1.1 Surface Antigravity in the native-tool picker (interactive + `--tools`) so it toggles alongside other IDEs.
+- [x] 1.2 Generate `.agent/workflows/openspec-proposal.md`, `openspec-apply.md`, and `openspec-archive.md` with YAML frontmatter restricted to a single `description` field for each stage and wrap the body in OpenSpec markers.
+- [x] 1.3 Confirm workspace scaffolding covers missing directory creation and re-run scenarios so repeated init refreshes the managed block.
+
+## 2. CLI update support
+- [x] 2.1 Detect existing Antigravity workflow files during `openspec update` and refresh only the managed body, skipping creation when files are missing.
+- [x] 2.2 Ensure update logic preserves the `description` frontmatter block exactly as written by init, including case and spacing, and refreshes body templates alongside other tools.
+
+## 3. Templates and tests
+- [x] 3.1 Add shared template entries for Antigravity that reuse the Windsurf copy but target `.agent/workflows` plus the description-only frontmatter requirement.
+- [x] 3.2 Expand automated coverage (unit or integration) verifying init and update produce the expected file paths and frontmatter + body markers for Antigravity.

src/core/config.ts

@@ -30,6 +30,7 @@ export const AI_TOOLS: AIToolOption[] = [
   { name: 'OpenCode', value: 'opencode', available: true, successLabel: 'OpenCode' },
   { name: 'Kilo Code', value: 'kilocode', available: true, successLabel: 'Kilo Code' },
   { name: 'Qoder (CLI)', value: 'qoder', available: true, successLabel: 'Qoder' },
+  { name: 'Antigravity', value: 'antigravity', available: true, successLabel: 'Antigravity' },
   { name: 'Windsurf', value: 'windsurf', available: true, successLabel: 'Windsurf' },
   { name: 'Codex', value: 'codex', available: true, successLabel: 'Codex' },
   { name: 'GitHub Copilot', value: 'github-copilot', available: true, successLabel: 'GitHub Copilot' },

src/core/configurators/slash/antigravity.ts

@@ -0,0 +1,28 @@
+import { SlashCommandConfigurator } from './base.js';
+import { SlashCommandId } from '../../templates/index.js';
+
+const FILE_PATHS: Record<SlashCommandId, string> = {
+  proposal: '.agent/workflows/openspec-proposal.md',
+  apply: '.agent/workflows/openspec-apply.md',
+  archive: '.agent/workflows/openspec-archive.md'
+};
+
+const DESCRIPTIONS: Record<SlashCommandId, string> = {
+  proposal: 'Scaffold a new OpenSpec change and validate strictly.',
+  apply: 'Implement an approved OpenSpec change and keep tasks in sync.',
+  archive: 'Archive a deployed OpenSpec change and update specs.'
+};
+
+export class AntigravitySlashCommandConfigurator extends SlashCommandConfigurator {
+  readonly toolId = 'antigravity';
+  readonly isAvailable = true;
+
+  protected getRelativePath(id: SlashCommandId): string {
+    return FILE_PATHS[id];
+  }
+
+  protected getFrontmatter(id: SlashCommandId): string | undefined {
+    const description = DESCRIPTIONS[id];
+    return `---\ndescription: ${description}\n---`;
+  }
+}

src/core/configurators/slash/registry.ts

@@ -17,6 +17,7 @@ import { CrushSlashCommandConfigurator } from './crush.js';
 import { CostrictSlashCommandConfigurator } from './costrict.js';
 import { QwenSlashCommandConfigurator } from './qwen.js';
 import { RooCodeSlashCommandConfigurator } from './roocode.js';
+import { AntigravitySlashCommandConfigurator } from './antigravity.js';
 
 export class SlashCommandRegistry {
   private static configurators: Map<string, SlashCommandConfigurator> = new Map();
@@ -40,6 +41,7 @@ export class SlashCommandRegistry {
     const costrict = new CostrictSlashCommandConfigurator();
     const qwen = new QwenSlashCommandConfigurator();
     const roocode = new RooCodeSlashCommandConfigurator();
+    const antigravity = new AntigravitySlashCommandConfigurator();
 
     this.configurators.set(claude.toolId, claude);
     this.configurators.set(codeBuddy.toolId, codeBuddy);
@@ -59,6 +61,7 @@ export class SlashCommandRegistry {
     this.configurators.set(costrict.toolId, costrict);
     this.configurators.set(qwen.toolId, qwen);
     this.configurators.set(roocode.toolId, roocode);
+    this.configurators.set(antigravity.toolId, antigravity);
   }
 
   static register(configurator: SlashCommandConfigurator): void {

test/core/init.test.ts

@@ -213,6 +213,50 @@ describe('InitCommand', () => {
       expect(archiveContent).toContain('Run `openspec archive <id> --yes`');
     });
 
+    it('should create Antigravity workflows when Antigravity is selected', async () => {
+      queueSelections('antigravity', DONE);
+
+      await initCommand.execute(testDir);
+
+      const agProposal = path.join(
+        testDir,
+        '.agent/workflows/openspec-proposal.md'
+      );
+      const agApply = path.join(
+        testDir,
+        '.agent/workflows/openspec-apply.md'
+      );
+      const agArchive = path.join(
+        testDir,
+        '.agent/workflows/openspec-archive.md'
+      );
+
+      expect(await fileExists(agProposal)).toBe(true);
+      expect(await fileExists(agApply)).toBe(true);
+      expect(await fileExists(agArchive)).toBe(true);
+
+      const proposalContent = await fs.readFile(agProposal, 'utf-8');
+      expect(proposalContent).toContain('---');
+      expect(proposalContent).toContain('description: Scaffold a new OpenSpec change and validate strictly.');
+      expect(proposalContent).toContain('<!-- OPENSPEC:START -->');
+      expect(proposalContent).toContain('**Guardrails**');
+      expect(proposalContent).not.toContain('auto_execution_mode');
+
+      const applyContent = await fs.readFile(agApply, 'utf-8');
+      expect(applyContent).toContain('---');
+      expect(applyContent).toContain('description: Implement an approved OpenSpec change and keep tasks in sync.');
+      expect(applyContent).toContain('<!-- OPENSPEC:START -->');
+      expect(applyContent).toContain('Work through tasks sequentially');
+      expect(applyContent).not.toContain('auto_execution_mode');
+
+      const archiveContent = await fs.readFile(agArchive, 'utf-8');
+      expect(archiveContent).toContain('---');
+      expect(archiveContent).toContain('description: Archive a deployed OpenSpec change and update specs.');
+      expect(archiveContent).toContain('<!-- OPENSPEC:START -->');
+      expect(archiveContent).toContain('Run `openspec archive <id> --yes`');
+      expect(archiveContent).not.toContain('auto_execution_mode');
+    });
+
     it('should always create AGENTS.md in project root', async () => {
       queueSelections(DONE);
 
@@ -854,6 +898,18 @@ describe('InitCommand', () => {
       expect(wsChoice.configured).toBe(true);
     });
 
+    it('should mark Antigravity as already configured during extend mode', async () => {
+      queueSelections('antigravity', DONE, 'antigravity', DONE);
+      await initCommand.execute(testDir);
+      await initCommand.execute(testDir);
+
+      const secondRunArgs = mockPrompt.mock.calls[1][0];
+      const antigravityChoice = secondRunArgs.choices.find(
+        (choice: any) => choice.value === 'antigravity'
+      );
+      expect(antigravityChoice.configured).toBe(true);
+    });
+
     it('should mark Codex as already configured during extend mode', async () => {
       queueSelections('codex', DONE, 'codex', DONE);
       await initCommand.execute(testDir);

test/core/update.test.ts

@@ -467,6 +467,38 @@ Old body
     consoleSpy.mockRestore();
   });
 
+  it('should refresh existing Antigravity workflows', async () => {
+    const agPath = path.join(
+      testDir,
+      '.agent/workflows/openspec-apply.md'
+    );
+    await fs.mkdir(path.dirname(agPath), { recursive: true });
+    const initialContent = `---
+description: Implement an approved OpenSpec change and keep tasks in sync.
+---
+
+<!-- OPENSPEC:START -->
+Old body
+<!-- OPENSPEC:END -->`;
+    await fs.writeFile(agPath, initialContent);
+
+    const consoleSpy = vi.spyOn(console, 'log');
+
+    await updateCommand.execute(testDir);
+
+    const updated = await fs.readFile(agPath, 'utf-8');
+    expect(updated).toContain('Work through tasks sequentially');
+    expect(updated).not.toContain('Old body');
+    expect(updated).toContain('description: Implement an approved OpenSpec change and keep tasks in sync.');
+    expect(updated).not.toContain('auto_execution_mode: 3');
+
+    const [logMessage] = consoleSpy.mock.calls[0];
+    expect(logMessage).toContain(
+      'Updated slash commands: .agent/workflows/openspec-apply.md'
+    );
+    consoleSpy.mockRestore();
+  });
+
   it('should refresh existing Codex prompts', async () => {
     const codexPath = path.join(
       testDir,