Add antigravity MCP install target

cmd/mcp/install.go

@@ -20,6 +20,7 @@ Supported targets:
   cursor      - Cursor editor
   claude      - Claude Desktop app
   claude-code - Claude Code CLI
+  antigravity - Google Antigravity
   windsurf    - Windsurf editor
   vscode      - Visual Studio Code
   goose       - Goose AI
@@ -119,6 +120,12 @@ func printPostInstallInstructions(target Target) {
 		pterm.Println("  1. Run '/mcp' in the Claude Code REPL to authenticate")
 		pterm.Println("  2. The Kernel tools will then be available")
 
+	case TargetAntigravity:
+		pterm.Info.Println("Next steps:")
+		pterm.Println("  1. Reload the Antigravity window")
+		pterm.Println("  2. Open agent settings and click 'Authenticate' next to kernel on the Customizations tab")
+		pterm.Println("  3. Paste the authorization code from your browser back into the settings panel")
+
 	case TargetWindsurf:
 		pterm.Info.Println("Next steps:")
 		pterm.Println("  1. Open Windsurf settings and navigate to MCP servers")

cmd/mcp/mcp.go

@@ -27,14 +27,15 @@ var MCPCmd = &cobra.Command{
 type Target string
 
 const (
-	TargetCursor     Target = "cursor"
-	TargetClaude     Target = "claude"
-	TargetClaudeCode Target = "claude-code"
-	TargetWindsurf   Target = "windsurf"
-	TargetVSCode     Target = "vscode"
-	TargetGoose      Target = "goose"
-	TargetZed        Target = "zed"
-	TargetFx         Target = "fx"
+	TargetCursor      Target = "cursor"
+	TargetClaude      Target = "claude"
+	TargetClaudeCode  Target = "claude-code"
+	TargetAntigravity Target = "antigravity"
+	TargetWindsurf    Target = "windsurf"
+	TargetVSCode      Target = "vscode"
+	TargetGoose       Target = "goose"
+	TargetZed         Target = "zed"
+	TargetFx          Target = "fx"
 )
 
 // KernelMCPURL is the URL for the Kernel MCP server
@@ -46,6 +47,7 @@ func AllTargets() []Target {
 		TargetCursor,
 		TargetClaude,
 		TargetClaudeCode,
+		TargetAntigravity,
 		TargetWindsurf,
 		TargetVSCode,
 		TargetGoose,
@@ -86,6 +88,8 @@ func getConfigPath(target Target) (string, error) {
 	case TargetClaudeCode:
 		// Claude Code uses the ~/.claude.json file
 		return filepath.Join(homeDir, ".claude.json"), nil
+	case TargetAntigravity:
+		return filepath.Join(homeDir, ".gemini", "config", "mcp_config.json"), nil
 	case TargetWindsurf:
 		return filepath.Join(homeDir, ".codeium", "windsurf", "mcp_config.json"), nil
 	case TargetVSCode:
@@ -327,6 +331,28 @@ func installForClaudeCode(configPath string) error {
 	return writeJSONFile(configPath, config)
 }
 
+// installForAntigravity installs MCP config for Google Antigravity
+func installForAntigravity(configPath string) error {
+	config, err := readJSONFile(configPath)
+	if err != nil {
+		return err
+	}
+
+	// Get or create mcpServers section
+	mcpServers, ok := config["mcpServers"].(map[string]interface{})
+	if !ok {
+		mcpServers = make(map[string]interface{})
+	}
+
+	// Antigravity keys remote servers off serverUrl; it ignores url and httpUrl
+	mcpServers["kernel"] = map[string]interface{}{
+		"serverUrl": KernelMCPURL,
+	}
+	config["mcpServers"] = mcpServers
+
+	return writeJSONFile(configPath, config)
+}
+
 // installForWindsurf installs MCP config for Windsurf
 func installForWindsurf(configPath string) error {
 	config, err := readJSONFile(configPath)
@@ -453,6 +479,8 @@ func Install(target Target) error {
 		return installForClaude(configPath)
 	case TargetClaudeCode:
 		return installForClaudeCode(configPath)
+	case TargetAntigravity:
+		return installForAntigravity(configPath)
 	case TargetWindsurf:
 		return installForWindsurf(configPath)
 	case TargetVSCode:

cmd/mcp/mcp_test.go

@@ -119,3 +119,95 @@ func TestInstallForFxClean(t *testing.T) {
 		t.Fatalf("config directory permissions = %o, want 700", got)
 	}
 }
+
+func TestInstallForAntigravity(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	t.Setenv("USERPROFILE", home)
+
+	configPath := filepath.Join(home, ".gemini", "config", "mcp_config.json")
+	if err := os.MkdirAll(filepath.Dir(configPath), 0755); err != nil {
+		t.Fatal(err)
+	}
+
+	existing := `{
+  "mcpServers": {
+    "existing": {
+      "serverUrl": "https://example.com/mcp"
+    }
+  },
+  "setting": "preserved"
+}`
+	if err := os.WriteFile(configPath, []byte(existing), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := Install(TargetAntigravity); err != nil {
+		t.Fatal(err)
+	}
+
+	data, err := os.ReadFile(configPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var config map[string]interface{}
+	if err := json.Unmarshal(data, &config); err != nil {
+		t.Fatal(err)
+	}
+	if config["setting"] != "preserved" {
+		t.Fatalf("setting = %v, want preserved", config["setting"])
+	}
+
+	servers, ok := config["mcpServers"].(map[string]interface{})
+	if !ok {
+		t.Fatalf("mcpServers = %#v, want object", config["mcpServers"])
+	}
+	if _, ok := servers["existing"]; !ok {
+		t.Fatal("existing MCP server was removed")
+	}
+
+	kernel, ok := servers["kernel"].(map[string]interface{})
+	if !ok {
+		t.Fatalf("kernel = %#v, want object", servers["kernel"])
+	}
+	if kernel["serverUrl"] != KernelMCPURL {
+		t.Fatalf("serverUrl = %v, want %s", kernel["serverUrl"], KernelMCPURL)
+	}
+	// Antigravity ignores url and httpUrl, so writing either would silently do nothing
+	if _, ok := kernel["url"]; ok {
+		t.Fatalf("kernel = %#v, want no url key", kernel)
+	}
+}
+
+func TestInstallForAntigravityClean(t *testing.T) {
+	home := t.TempDir()
+	t.Setenv("HOME", home)
+	t.Setenv("USERPROFILE", home)
+
+	if err := Install(TargetAntigravity); err != nil {
+		t.Fatal(err)
+	}
+
+	data, err := os.ReadFile(filepath.Join(home, ".gemini", "config", "mcp_config.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var config map[string]interface{}
+	if err := json.Unmarshal(data, &config); err != nil {
+		t.Fatal(err)
+	}
+
+	servers, ok := config["mcpServers"].(map[string]interface{})
+	if !ok {
+		t.Fatalf("mcpServers = %#v, want object", config["mcpServers"])
+	}
+	kernel, ok := servers["kernel"].(map[string]interface{})
+	if !ok {
+		t.Fatalf("kernel = %#v, want object", servers["kernel"])
+	}
+	if kernel["serverUrl"] != KernelMCPURL {
+		t.Fatalf("serverUrl = %v, want %s", kernel["serverUrl"], KernelMCPURL)
+	}
+}