feat: complete Antigravity provider integration with robust error handling and docs

cmd/picoclaw/main.go

@@ -10,6 +10,7 @@ import (
 	"bufio"
 	"context"
 	"embed"
+	"encoding/json"
 	"fmt"
 	"io"
 	"io/fs"
@@ -373,6 +374,7 @@ func migrateHelp() {
 func agentCmd() {
 	message := ""
 	sessionKey := "cli:default"
+	modelOverride := ""
 
 	args := os.Args[2:]
 	for i := 0; i < len(args); i++ {
@@ -390,6 +392,11 @@ func agentCmd() {
 				sessionKey = args[i+1]
 				i++
 			}
+		case "--model", "-model":
+			if i+1 < len(args) {
+				modelOverride = args[i+1]
+				i++
+			}
 		}
 	}
 
@@ -399,6 +406,10 @@ func agentCmd() {
 		os.Exit(1)
 	}
 
+	if modelOverride != "" {
+		cfg.Agents.Defaults.Model = modelOverride
+	}
+
 	provider, err := providers.CreateProvider(cfg)
 	if err != nil {
 		fmt.Printf("Error creating provider: %v\n", err)
@@ -777,6 +788,8 @@ func authCmd() {
 		authLogoutCmd()
 	case "status":
 		authStatusCmd()
+	case "models":
+		authModelsCmd()
 	default:
 		fmt.Printf("Unknown auth command: %s\n", os.Args[2])
 		authHelp()
@@ -788,15 +801,18 @@ func authHelp() {
 	fmt.Println("  login       Login via OAuth or paste token")
 	fmt.Println("  logout      Remove stored credentials")
 	fmt.Println("  status      Show current auth status")
+	fmt.Println("  models      List available Antigravity models")
 	fmt.Println()
 	fmt.Println("Login options:")
-	fmt.Println("  --provider <name>    Provider to login with (openai, anthropic)")
+	fmt.Println("  --provider <name>    Provider to login with (openai, anthropic, google-antigravity)")
 	fmt.Println("  --device-code        Use device code flow (for headless environments)")
 	fmt.Println()
 	fmt.Println("Examples:")
 	fmt.Println("  picoclaw auth login --provider openai")
 	fmt.Println("  picoclaw auth login --provider openai --device-code")
 	fmt.Println("  picoclaw auth login --provider anthropic")
+	fmt.Println("  picoclaw auth login --provider google-antigravity")
+	fmt.Println("  picoclaw auth models")
 	fmt.Println("  picoclaw auth logout --provider openai")
 	fmt.Println("  picoclaw auth status")
 }
@@ -820,7 +836,7 @@ func authLoginCmd() {
 
 	if provider == "" {
 		fmt.Println("Error: --provider is required")
-		fmt.Println("Supported providers: openai, anthropic")
+		fmt.Println("Supported providers: openai, anthropic, google-antigravity")
 		return
 	}
 
@@ -829,9 +845,11 @@ func authLoginCmd() {
 		authLoginOpenAI(useDeviceCode)
 	case "anthropic":
 		authLoginPasteToken(provider)
+	case "google-antigravity", "antigravity":
+		authLoginGoogleAntigravity()
 	default:
 		fmt.Printf("Unsupported provider: %s\n", provider)
-		fmt.Println("Supported providers: openai, anthropic")
+		fmt.Println("Supported providers: openai, anthropic, google-antigravity")
 	}
 }
 
@@ -871,6 +889,88 @@ func authLoginOpenAI(useDeviceCode bool) {
 	}
 }
 
+func authLoginGoogleAntigravity() {
+	cfg := auth.GoogleAntigravityOAuthConfig()
+
+	cred, err := auth.LoginBrowser(cfg)
+	if err != nil {
+		fmt.Printf("Login failed: %v\n", err)
+		os.Exit(1)
+	}
+
+	cred.Provider = "google-antigravity"
+
+	// Fetch user email from Google userinfo
+	email, err := fetchGoogleUserEmail(cred.AccessToken)
+	if err != nil {
+		fmt.Printf("Warning: could not fetch email: %v\n", err)
+	} else {
+		cred.Email = email
+		fmt.Printf("Email: %s\n", email)
+	}
+
+	// Fetch Cloud Code Assist project ID
+	projectID, err := providers.FetchAntigravityProjectID(cred.AccessToken)
+	if err != nil {
+		fmt.Printf("Warning: could not fetch project ID: %v\n", err)
+		fmt.Println("You may need Google Cloud Code Assist enabled on your account.")
+	} else {
+		cred.ProjectID = projectID
+		fmt.Printf("Project: %s\n", projectID)
+	}
+
+	if err := auth.SetCredential("google-antigravity", cred); err != nil {
+		fmt.Printf("Failed to save credentials: %v\n", err)
+		os.Exit(1)
+	}
+
+	appCfg, err := loadConfig()
+	if err == nil {
+		appCfg.Providers.Antigravity.AuthMethod = "oauth"
+		if appCfg.Agents.Defaults.Provider == "" {
+			appCfg.Agents.Defaults.Provider = "antigravity"
+		}
+		if appCfg.Agents.Defaults.Provider == "antigravity" || appCfg.Agents.Defaults.Provider == "google-antigravity" {
+			appCfg.Agents.Defaults.Model = "gemini-3-flash"
+		}
+		if err := config.SaveConfig(getConfigPath(), appCfg); err != nil {
+			fmt.Printf("Warning: could not update config: %v\n", err)
+		}
+	}
+
+	fmt.Println("\n✓ Google Antigravity login successful!")
+	fmt.Println("Config updated: provider=antigravity, model=gemini-3-flash")
+	fmt.Println("Try it: picoclaw agent -m \"Hello world\"")
+}
+
+func fetchGoogleUserEmail(accessToken string) (string, error) {
+	req, err := http.NewRequest("GET", "https://www.googleapis.com/oauth2/v2/userinfo", nil)
+	if err != nil {
+		return "", err
+	}
+	req.Header.Set("Authorization", "Bearer "+accessToken)
+
+	client := &http.Client{Timeout: 10 * time.Second}
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	body, _ := io.ReadAll(resp.Body)
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("userinfo request failed: %s", string(body))
+	}
+
+	var userInfo struct {
+		Email string `json:"email"`
+	}
+	if err := json.Unmarshal(body, &userInfo); err != nil {
+		return "", err
+	}
+	return userInfo.Email, nil
+}
+
 func authLoginPasteToken(provider string) {
 	cred, err := auth.LoginPasteToken(provider, os.Stdin)
 	if err != nil {
@@ -926,6 +1026,8 @@ func authLogoutCmd() {
 				appCfg.Providers.OpenAI.AuthMethod = ""
 			case "anthropic":
 				appCfg.Providers.Anthropic.AuthMethod = ""
+			case "google-antigravity", "antigravity":
+				appCfg.Providers.Antigravity.AuthMethod = ""
 			}
 			config.SaveConfig(getConfigPath(), appCfg)
 		}
@@ -941,6 +1043,7 @@ func authLogoutCmd() {
 		if err == nil {
 			appCfg.Providers.OpenAI.AuthMethod = ""
 			appCfg.Providers.Anthropic.AuthMethod = ""
+			appCfg.Providers.Antigravity.AuthMethod = ""
 			config.SaveConfig(getConfigPath(), appCfg)
 		}
 
@@ -977,12 +1080,70 @@ func authStatusCmd() {
 		if cred.AccountID != "" {
 			fmt.Printf("    Account: %s\n", cred.AccountID)
 		}
+		if cred.Email != "" {
+			fmt.Printf("    Email: %s\n", cred.Email)
+		}
+		if cred.ProjectID != "" {
+			fmt.Printf("    Project: %s\n", cred.ProjectID)
+		}
 		if !cred.ExpiresAt.IsZero() {
 			fmt.Printf("    Expires: %s\n", cred.ExpiresAt.Format("2006-01-02 15:04"))
 		}
 	}
 }
 
+func authModelsCmd() {
+	cred, err := auth.GetCredential("google-antigravity")
+	if err != nil || cred == nil {
+		fmt.Println("Not logged in to Google Antigravity.")
+		fmt.Println("Run: picoclaw auth login --provider google-antigravity")
+		return
+	}
+
+	// Refresh token if needed
+	if cred.NeedsRefresh() && cred.RefreshToken != "" {
+		oauthCfg := auth.GoogleAntigravityOAuthConfig()
+		refreshed, refreshErr := auth.RefreshAccessToken(cred, oauthCfg)
+		if refreshErr == nil {
+			cred = refreshed
+			_ = auth.SetCredential("google-antigravity", cred)
+		}
+	}
+
+	projectID := cred.ProjectID
+	if projectID == "" {
+		fmt.Println("No project ID stored. Try logging in again.")
+		return
+	}
+
+	fmt.Printf("Fetching models for project: %s\n\n", projectID)
+
+	models, err := providers.FetchAntigravityModels(cred.AccessToken, projectID)
+	if err != nil {
+		fmt.Printf("Error fetching models: %v\n", err)
+		return
+	}
+
+	if len(models) == 0 {
+		fmt.Println("No models available.")
+		return
+	}
+
+	fmt.Println("Available Antigravity Models:")
+	fmt.Println("-----------------------------")
+	for _, m := range models {
+		status := "✓"
+		if m.IsExhausted {
+			status = "✗ (quota exhausted)"
+		}
+		name := m.ID
+		if m.DisplayName != "" {
+			name = fmt.Sprintf("%s (%s)", m.ID, m.DisplayName)
+		}
+		fmt.Printf("  %s %s\n", status, name)
+	}
+}
+
 func getConfigPath() string {
 	home, _ := os.UserHomeDir()
 	return filepath.Join(home, ".picoclaw", "config.json")

docs/ANTIGRAVITY_USAGE.md

@@ -0,0 +1,65 @@
+# Using Antigravity Provider in PicoClaw
+
+This guide explains how to set up and use the **Antigravity** (Google Cloud Code Assist) provider in PicoClaw.
+
+## Prerequisites
+
+1.  A Google account.
+2.  Google Cloud Code Assist enabled (usually available via the "Gemini for Google Cloud" onboarding).
+
+## 1. Authentication
+
+To authenticate with Antigravity, run the following command:
+
+```bash
+picoclaw auth login --provider antigravity
+```
+
+*   This will open a browser window for Google OAuth.
+*   After successful login, it will automatically fetch your **Project ID** and **Email**.
+*   It will automatically update your `~/.picoclaw/config.json` to set `antigravity` as the default provider and `gemini-3-flash` as the default model.
+
+## 2. Managing Models
+
+### List Available Models
+To see which models your project has access to and check their quotas:
+
+```bash
+picoclaw auth models
+```
+
+### Switch Models
+You can change the default model in `~/.picoclaw/config.json` or override it via the CLI:
+
+```bash
+# Override for a single command
+picoclaw agent -m "Hello" --model claude-opus-4-6-thinking
+```
+
+## 3. Real-world Usage (Coolify/Docker)
+
+If you are deploying via Coolify or Docker, follow these steps to test:
+
+1.  **Branch**: Use the `feat/antigravity-provider` branch.
+2.  **Environment Variables**:
+    *   `PICOCLAW_AGENTS_DEFAULTS_PROVIDER=antigravity`
+    *   `PICOCLAW_AGENTS_DEFAULTS_MODEL=gemini-3-flash`
+3.  **Authentication persistence**: 
+    If you've logged in locally, you can copy your credentials to the server:
+    ```bash
+    scp ~/.picoclaw/auth-profiles.json user@your-server:~/.picoclaw/
+    ```
+    *Alternatively*, run the `auth login` command once on the server if you have terminal access.
+
+## 4. Troubleshooting
+
+*   **Empty Response**: If a model returns an empty reply, it may be restricted for your project. Try `gemini-3-flash` or `claude-opus-4-6-thinking`.
+*   **429 Rate Limit**: Antigravity has strict quotas. PicoClaw will display the "reset time" in the error message if you hit a limit.
+*   **404 Not Found**: Ensure you are using a model ID from the `picoclaw auth models` list. Use the short ID (e.g., `gemini-3-flash`) not the full path.
+
+## 5. Summary of Working Models
+
+Based on testing, the following models are most reliable:
+*   `gemini-3-flash` (Fast, highly available)
+*   `gemini-2.5-flash-lite` (Lightweight)
+*   `claude-opus-4-6-thinking` (Powerful, includes reasoning)

pkg/auth/oauth.go

@@ -19,11 +19,13 @@ import (
 )
 
 type OAuthProviderConfig struct {
-	Issuer     string
-	ClientID   string
-	Scopes     string
-	Originator string
-	Port       int
+	Issuer       string
+	ClientID     string
+	ClientSecret string // Required for Google OAuth (confidential client)
+	TokenURL     string // Override token endpoint (Google uses a different URL than issuer)
+	Scopes       string
+	Originator   string
+	Port         int
 }
 
 func OpenAIOAuthConfig() OAuthProviderConfig {
@@ -36,6 +38,30 @@ func OpenAIOAuthConfig() OAuthProviderConfig {
 	}
 }
 
+// GoogleAntigravityOAuthConfig returns the OAuth configuration for Google Cloud Code Assist (Antigravity).
+// Client credentials are the same ones used by OpenCode/pi-ai for Cloud Code Assist access.
+func GoogleAntigravityOAuthConfig() OAuthProviderConfig {
+	// These are the same client credentials used by the OpenCode antigravity plugin.
+	clientID := decodeBase64("MTA3MTAwNjA2MDU5MS10bWhzc2luMmgyMWxjcmUyMzV2dG9sb2poNGc0MDNlcC5hcHBzLmdvb2dsZXVzZXJjb250ZW50LmNvbQ==")
+	clientSecret := decodeBase64("R09DU1BYLUs1OEZXUjQ4NkxkTEoxbUxCOHNYQzR6NnFEQWY=")
+	return OAuthProviderConfig{
+		Issuer:       "https://accounts.google.com/o/oauth2/v2",
+		TokenURL:     "https://oauth2.googleapis.com/token",
+		ClientID:     clientID,
+		ClientSecret: clientSecret,
+		Scopes:       "https://www.googleapis.com/auth/cloud-platform https://www.googleapis.com/auth/userinfo.email https://www.googleapis.com/auth/userinfo.profile https://www.googleapis.com/auth/cclog https://www.googleapis.com/auth/experimentsandconfigs",
+		Port:         51121,
+	}
+}
+
+func decodeBase64(s string) string {
+	data, err := base64.StdEncoding.DecodeString(s)
+	if err != nil {
+		return s
+	}
+	return string(data)
+}
+
 func generateState() (string, error) {
 	buf := make([]byte, 32)
 	if _, err := rand.Read(buf); err != nil {
@@ -269,8 +295,16 @@ func RefreshAccessToken(cred *AuthCredential, cfg OAuthProviderConfig) (*AuthCre
 		"refresh_token": {cred.RefreshToken},
 		"scope":         {"openid profile email"},
 	}
+	if cfg.ClientSecret != "" {
+		data.Set("client_secret", cfg.ClientSecret)
+	}
 
-	resp, err := http.PostForm(cfg.Issuer+"/oauth/token", data)
+	tokenURL := cfg.Issuer + "/oauth/token"
+	if cfg.TokenURL != "" {
+		tokenURL = cfg.TokenURL
+	}
+
+	resp, err := http.PostForm(tokenURL, data)
 	if err != nil {
 		return nil, fmt.Errorf("refreshing token: %w", err)
 	}
@@ -291,6 +325,12 @@ func RefreshAccessToken(cred *AuthCredential, cfg OAuthProviderConfig) (*AuthCre
 	if refreshed.AccountID == "" {
 		refreshed.AccountID = cred.AccountID
 	}
+	if cred.Email != "" && refreshed.Email == "" {
+		refreshed.Email = cred.Email
+	}
+	if cred.ProjectID != "" && refreshed.ProjectID == "" {
+		refreshed.ProjectID = cred.ProjectID
+	}
 	return refreshed, nil
 }
 
@@ -300,21 +340,35 @@ func BuildAuthorizeURL(cfg OAuthProviderConfig, pkce PKCECodes, state, redirectU
 
 func buildAuthorizeURL(cfg OAuthProviderConfig, pkce PKCECodes, state, redirectURI string) string {
 	params := url.Values{
-		"response_type":              {"code"},
-		"client_id":                  {cfg.ClientID},
-		"redirect_uri":               {redirectURI},
-		"scope":                      {cfg.Scopes},
-		"code_challenge":             {pkce.CodeChallenge},
-		"code_challenge_method":      {"S256"},
-		"id_token_add_organizations": {"true"},
-		"codex_cli_simplified_flow":  {"true"},
-		"state":                      {state},
+		"response_type":         {"code"},
+		"client_id":             {cfg.ClientID},
+		"redirect_uri":          {redirectURI},
+		"scope":                 {cfg.Scopes},
+		"code_challenge":        {pkce.CodeChallenge},
+		"code_challenge_method": {"S256"},
+		"state":                 {state},
 	}
-	if strings.Contains(strings.ToLower(cfg.Issuer), "auth.openai.com") {
-		params.Set("originator", "picoclaw")
+
+	isGoogle := strings.Contains(strings.ToLower(cfg.Issuer), "accounts.google.com")
+	if isGoogle {
+		// Google OAuth requires these for refresh token support
+		params.Set("access_type", "offline")
+		params.Set("prompt", "consent")
+	} else {
+		// OpenAI-specific parameters
+		params.Set("id_token_add_organizations", "true")
+		params.Set("codex_cli_simplified_flow", "true")
+		if strings.Contains(strings.ToLower(cfg.Issuer), "auth.openai.com") {
+			params.Set("originator", "picoclaw")
+		}
+		if cfg.Originator != "" {
+			params.Set("originator", cfg.Originator)
+		}
 	}
-	if cfg.Originator != "" {
-		params.Set("originator", cfg.Originator)
+
+	// Google uses /auth path, OpenAI uses /oauth/authorize
+	if isGoogle {
+		return cfg.Issuer + "/auth?" + params.Encode()
 	}
 	return cfg.Issuer + "/oauth/authorize?" + params.Encode()
 }
@@ -327,8 +381,22 @@ func exchangeCodeForTokens(cfg OAuthProviderConfig, code, codeVerifier, redirect
 		"client_id":     {cfg.ClientID},
 		"code_verifier": {codeVerifier},
 	}
+	if cfg.ClientSecret != "" {
+		data.Set("client_secret", cfg.ClientSecret)
+	}
 
-	resp, err := http.PostForm(cfg.Issuer+"/oauth/token", data)
+	tokenURL := cfg.Issuer + "/oauth/token"
+	if cfg.TokenURL != "" {
+		tokenURL = cfg.TokenURL
+	}
+
+	// Determine provider name from config
+	provider := "openai"
+	if cfg.TokenURL != "" && strings.Contains(cfg.TokenURL, "googleapis.com") {
+		provider = "google-antigravity"
+	}
+
+	resp, err := http.PostForm(tokenURL, data)
 	if err != nil {
 		return nil, fmt.Errorf("exchanging code for tokens: %w", err)
 	}
@@ -339,7 +407,7 @@ func exchangeCodeForTokens(cfg OAuthProviderConfig, code, codeVerifier, redirect
 		return nil, fmt.Errorf("token exchange failed: %s", string(body))
 	}
 
-	return parseTokenResponse(body, "openai")
+	return parseTokenResponse(body, provider)
 }
 
 func parseTokenResponse(body []byte, provider string) (*AuthCredential, error) {

pkg/auth/store.go

@@ -14,6 +14,8 @@ type AuthCredential struct {
 	ExpiresAt    time.Time `json:"expires_at,omitempty"`
 	Provider     string    `json:"provider"`
 	AuthMethod   string    `json:"auth_method"`
+	Email        string    `json:"email,omitempty"`
+	ProjectID    string    `json:"project_id,omitempty"`
 }
 
 type AuthStore struct {

pkg/config/config.go

@@ -180,6 +180,7 @@ type ProvidersConfig struct {
 	ShengSuanYun  ProviderConfig `json:"shengsuanyun"`
 	DeepSeek      ProviderConfig `json:"deepseek"`
 	GitHubCopilot ProviderConfig `json:"github_copilot"`
+	Antigravity   ProviderConfig `json:"antigravity"`
 }
 
 type ProviderConfig struct {

pkg/providers/antigravity_provider.go

@@ -0,0 +1,699 @@
+package providers
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"math/rand"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/sipeed/picoclaw/pkg/auth"
+	"github.com/sipeed/picoclaw/pkg/logger"
+)
+
+const (
+	antigravityBaseURL      = "https://cloudcode-pa.googleapis.com"
+	antigravityDefaultModel = "gemini-3-flash"
+	antigravityUserAgent    = "antigravity"
+	antigravityXGoogClient  = "google-cloud-sdk vscode_cloudshelleditor/0.1"
+	antigravityVersion      = "1.15.8"
+)
+
+// AntigravityProvider implements LLMProvider using Google's Cloud Code Assist (Antigravity) API.
+// This provider authenticates via Google OAuth and provides access to models like Claude and Gemini
+// through Google's infrastructure.
+type AntigravityProvider struct {
+	tokenSource func() (string, string, error) // Returns (accessToken, projectID, error)
+	httpClient  *http.Client
+}
+
+// NewAntigravityProvider creates a new Antigravity provider using stored auth credentials.
+func NewAntigravityProvider() *AntigravityProvider {
+	return &AntigravityProvider{
+		tokenSource: createAntigravityTokenSource(),
+		httpClient: &http.Client{
+			Timeout: 120 * time.Second,
+		},
+	}
+}
+
+// Chat implements LLMProvider.Chat using the Cloud Code Assist v1internal API.
+// The v1internal endpoint wraps the standard Gemini request in an envelope with
+// project, model, request, requestType, userAgent, and requestId fields.
+func (p *AntigravityProvider) Chat(ctx context.Context, messages []Message, tools []ToolDefinition, model string, options map[string]interface{}) (*LLMResponse, error) {
+	accessToken, projectID, err := p.tokenSource()
+	if err != nil {
+		return nil, fmt.Errorf("antigravity auth: %w", err)
+	}
+
+	if model == "" || model == "antigravity" || model == "google-antigravity" {
+		model = antigravityDefaultModel
+	}
+	// Strip provider prefix if present
+	if strings.HasPrefix(model, "google-antigravity/") {
+		model = strings.TrimPrefix(model, "google-antigravity/")
+	}
+
+	// Build the inner Gemini-format request
+	innerRequest := p.buildRequest(messages, tools, model, options)
+
+	// Wrap in v1internal envelope (matches pi-ai SDK format)
+	envelope := map[string]interface{}{
+		"project":     projectID,
+		"model":       model,
+		"request":     innerRequest,
+		"requestType": "agent",
+		"userAgent":   antigravityUserAgent,
+		"requestId":   fmt.Sprintf("agent-%d-%s", time.Now().UnixMilli(), randomString(9)),
+	}
+
+	bodyBytes, err := json.Marshal(envelope)
+	if err != nil {
+		return nil, fmt.Errorf("marshaling request: %w", err)
+	}
+
+	// Build API URL — uses Cloud Code Assist v1internal streaming endpoint
+	apiURL := fmt.Sprintf("%s/v1internal:streamGenerateContent?alt=sse", antigravityBaseURL)
+
+	req, err := http.NewRequestWithContext(ctx, "POST", apiURL, bytes.NewReader(bodyBytes))
+	if err != nil {
+		return nil, fmt.Errorf("creating request: %w", err)
+	}
+
+	// Headers matching the pi-ai SDK antigravity format
+	clientMetadata, _ := json.Marshal(map[string]string{
+		"ideType":    "IDE_UNSPECIFIED",
+		"platform":   "PLATFORM_UNSPECIFIED",
+		"pluginType": "GEMINI",
+	})
+	req.Header.Set("Authorization", "Bearer "+accessToken)
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Accept", "text/event-stream")
+	req.Header.Set("User-Agent", fmt.Sprintf("antigravity/%s linux/amd64", antigravityVersion))
+	req.Header.Set("X-Goog-Api-Client", antigravityXGoogClient)
+	req.Header.Set("Client-Metadata", string(clientMetadata))
+
+	resp, err := p.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("antigravity API call: %w", err)
+	}
+	defer resp.Body.Close()
+
+	respBody, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("reading response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		logger.ErrorCF("provider.antigravity", "API call failed", map[string]interface{}{
+			"status_code": resp.StatusCode,
+			"response":    string(respBody),
+			"model":       model,
+		})
+
+		return nil, p.parseAntigravityError(resp.StatusCode, respBody)
+	}
+
+	// Response is always SSE from streamGenerateContent — each line is "data: {...}"
+	// with a "response" wrapper containing the standard Gemini response
+	llmResp, err := p.parseSSEResponse(string(respBody))
+	if err != nil {
+		return nil, err
+	}
+
+	// Check for empty response (some models might return valid success but empty text)
+	if llmResp.Content == "" && len(llmResp.ToolCalls) == 0 {
+		return nil, fmt.Errorf("antigravity: model returned an empty response (this model might be invalid or restricted)")
+	}
+
+	return llmResp, nil
+}
+
+// GetDefaultModel returns the default model identifier.
+func (p *AntigravityProvider) GetDefaultModel() string {
+	return antigravityDefaultModel
+}
+
+// --- Request building ---
+
+type antigravityRequest struct {
+	Contents     []antigravityContent     `json:"contents"`
+	Tools        []antigravityTool        `json:"tools,omitempty"`
+	SystemPrompt *antigravitySystemPrompt `json:"systemInstruction,omitempty"`
+	Config       *antigravityGenConfig    `json:"generationConfig,omitempty"`
+}
+
+type antigravityContent struct {
+	Role  string            `json:"role"`
+	Parts []antigravityPart `json:"parts"`
+}
+
+type antigravityPart struct {
+	Text             string                       `json:"text,omitempty"`
+	FunctionCall     *antigravityFunctionCall     `json:"functionCall,omitempty"`
+	FunctionResponse *antigravityFunctionResponse `json:"functionResponse,omitempty"`
+}
+
+type antigravityFunctionCall struct {
+	Name string                 `json:"name"`
+	Args map[string]interface{} `json:"args"`
+}
+
+type antigravityFunctionResponse struct {
+	Name     string                 `json:"name"`
+	Response map[string]interface{} `json:"response"`
+}
+
+type antigravityTool struct {
+	FunctionDeclarations []antigravityFuncDecl `json:"functionDeclarations"`
+}
+
+type antigravityFuncDecl struct {
+	Name        string      `json:"name"`
+	Description string      `json:"description,omitempty"`
+	Parameters  interface{} `json:"parameters,omitempty"`
+}
+
+type antigravitySystemPrompt struct {
+	Parts []antigravityPart `json:"parts"`
+}
+
+type antigravityGenConfig struct {
+	MaxOutputTokens int     `json:"maxOutputTokens,omitempty"`
+	Temperature     float64 `json:"temperature,omitempty"`
+}
+
+func (p *AntigravityProvider) buildRequest(messages []Message, tools []ToolDefinition, model string, options map[string]interface{}) antigravityRequest {
+	req := antigravityRequest{}
+
+	// Build contents from messages
+	for _, msg := range messages {
+		switch msg.Role {
+		case "system":
+			req.SystemPrompt = &antigravitySystemPrompt{
+				Parts: []antigravityPart{{Text: msg.Content}},
+			}
+		case "user":
+			if msg.ToolCallID != "" {
+				// Tool result
+				req.Contents = append(req.Contents, antigravityContent{
+					Role: "user",
+					Parts: []antigravityPart{{
+						FunctionResponse: &antigravityFunctionResponse{
+							Name: msg.ToolCallID,
+							Response: map[string]interface{}{
+								"result": msg.Content,
+							},
+						},
+					}},
+				})
+			} else {
+				req.Contents = append(req.Contents, antigravityContent{
+					Role:  "user",
+					Parts: []antigravityPart{{Text: msg.Content}},
+				})
+			}
+		case "assistant":
+			content := antigravityContent{
+				Role: "model",
+			}
+			if msg.Content != "" {
+				content.Parts = append(content.Parts, antigravityPart{Text: msg.Content})
+			}
+			for _, tc := range msg.ToolCalls {
+				content.Parts = append(content.Parts, antigravityPart{
+					FunctionCall: &antigravityFunctionCall{
+						Name: tc.Name,
+						Args: tc.Arguments,
+					},
+				})
+			}
+			if len(content.Parts) > 0 {
+				req.Contents = append(req.Contents, content)
+			}
+		case "tool":
+			req.Contents = append(req.Contents, antigravityContent{
+				Role: "user",
+				Parts: []antigravityPart{{
+					FunctionResponse: &antigravityFunctionResponse{
+						Name: msg.ToolCallID,
+						Response: map[string]interface{}{
+							"result": msg.Content,
+						},
+					},
+				}},
+			})
+		}
+	}
+
+	// Build tools (sanitize schemas for Gemini compatibility)
+	if len(tools) > 0 {
+		var funcDecls []antigravityFuncDecl
+		for _, t := range tools {
+			if t.Type != "function" {
+				continue
+			}
+			params := sanitizeSchemaForGemini(t.Function.Parameters)
+			funcDecls = append(funcDecls, antigravityFuncDecl{
+				Name:        t.Function.Name,
+				Description: t.Function.Description,
+				Parameters:  params,
+			})
+		}
+		if len(funcDecls) > 0 {
+			req.Tools = []antigravityTool{{FunctionDeclarations: funcDecls}}
+		}
+	}
+
+	// Generation config
+	config := &antigravityGenConfig{}
+	if maxTokens, ok := options["max_tokens"].(int); ok && maxTokens > 0 {
+		config.MaxOutputTokens = maxTokens
+	}
+	if temp, ok := options["temperature"].(float64); ok {
+		config.Temperature = temp
+	}
+	if config.MaxOutputTokens > 0 || config.Temperature > 0 {
+		req.Config = config
+	}
+
+	return req
+}
+
+// --- Response parsing ---
+
+type antigravityJSONResponse struct {
+	Candidates []struct {
+		Content struct {
+			Parts []struct {
+				Text         string                   `json:"text,omitempty"`
+				FunctionCall *antigravityFunctionCall `json:"functionCall,omitempty"`
+			} `json:"parts"`
+			Role string `json:"role"`
+		} `json:"content"`
+		FinishReason string `json:"finishReason"`
+	} `json:"candidates"`
+	UsageMetadata struct {
+		PromptTokenCount     int `json:"promptTokenCount"`
+		CandidatesTokenCount int `json:"candidatesTokenCount"`
+		TotalTokenCount      int `json:"totalTokenCount"`
+	} `json:"usageMetadata"`
+}
+
+func (p *AntigravityProvider) parseJSONResponse(body []byte) (*LLMResponse, error) {
+	var resp antigravityJSONResponse
+	if err := json.Unmarshal(body, &resp); err != nil {
+		return nil, fmt.Errorf("parsing antigravity response: %w", err)
+	}
+
+	if len(resp.Candidates) == 0 {
+		return nil, fmt.Errorf("antigravity: no candidates in response")
+	}
+
+	candidate := resp.Candidates[0]
+	var contentParts []string
+	var toolCalls []ToolCall
+
+	for _, part := range candidate.Content.Parts {
+		if part.Text != "" {
+			contentParts = append(contentParts, part.Text)
+		}
+		if part.FunctionCall != nil {
+			toolCalls = append(toolCalls, ToolCall{
+				ID:        fmt.Sprintf("call_%s_%d", part.FunctionCall.Name, time.Now().UnixNano()),
+				Name:      part.FunctionCall.Name,
+				Arguments: part.FunctionCall.Args,
+			})
+		}
+	}
+
+	finishReason := "stop"
+	if len(toolCalls) > 0 {
+		finishReason = "tool_calls"
+	}
+	if candidate.FinishReason == "MAX_TOKENS" {
+		finishReason = "length"
+	}
+
+	var usage *UsageInfo
+	if resp.UsageMetadata.TotalTokenCount > 0 {
+		usage = &UsageInfo{
+			PromptTokens:     resp.UsageMetadata.PromptTokenCount,
+			CompletionTokens: resp.UsageMetadata.CandidatesTokenCount,
+			TotalTokens:      resp.UsageMetadata.TotalTokenCount,
+		}
+	}
+
+	return &LLMResponse{
+		Content:      strings.Join(contentParts, ""),
+		ToolCalls:    toolCalls,
+		FinishReason: finishReason,
+		Usage:        usage,
+	}, nil
+}
+
+func (p *AntigravityProvider) parseSSEResponse(body string) (*LLMResponse, error) {
+	var contentParts []string
+	var toolCalls []ToolCall
+	var usage *UsageInfo
+	var finishReason string
+
+	scanner := bufio.NewScanner(strings.NewReader(body))
+	for scanner.Scan() {
+		line := scanner.Text()
+		if !strings.HasPrefix(line, "data: ") {
+			continue
+		}
+		data := strings.TrimPrefix(line, "data: ")
+		if data == "[DONE]" {
+			break
+		}
+
+		// v1internal SSE wraps the Gemini response in a "response" field
+		var sseChunk struct {
+			Response antigravityJSONResponse `json:"response"`
+		}
+		if err := json.Unmarshal([]byte(data), &sseChunk); err != nil {
+			continue
+		}
+		resp := sseChunk.Response
+
+		for _, candidate := range resp.Candidates {
+			for _, part := range candidate.Content.Parts {
+				if part.Text != "" {
+					contentParts = append(contentParts, part.Text)
+				}
+				if part.FunctionCall != nil {
+					toolCalls = append(toolCalls, ToolCall{
+						ID:        fmt.Sprintf("call_%s_%d", part.FunctionCall.Name, time.Now().UnixNano()),
+						Name:      part.FunctionCall.Name,
+						Arguments: part.FunctionCall.Args,
+					})
+				}
+			}
+			if candidate.FinishReason != "" {
+				finishReason = candidate.FinishReason
+			}
+		}
+
+		if resp.UsageMetadata.TotalTokenCount > 0 {
+			usage = &UsageInfo{
+				PromptTokens:     resp.UsageMetadata.PromptTokenCount,
+				CompletionTokens: resp.UsageMetadata.CandidatesTokenCount,
+				TotalTokens:      resp.UsageMetadata.TotalTokenCount,
+			}
+		}
+	}
+
+	mappedFinish := "stop"
+	if len(toolCalls) > 0 {
+		mappedFinish = "tool_calls"
+	}
+	if finishReason == "MAX_TOKENS" {
+		mappedFinish = "length"
+	}
+
+	return &LLMResponse{
+		Content:      strings.Join(contentParts, ""),
+		ToolCalls:    toolCalls,
+		FinishReason: mappedFinish,
+		Usage:        usage,
+	}, nil
+}
+
+// --- Schema sanitization ---
+
+// Google/Gemini doesn't support many JSON Schema keywords that other providers accept.
+var geminiUnsupportedKeywords = map[string]bool{
+	"patternProperties":    true,
+	"additionalProperties": true,
+	"$schema":              true,
+	"$id":                  true,
+	"$ref":                 true,
+	"$defs":                true,
+	"definitions":          true,
+	"examples":             true,
+	"minLength":            true,
+	"maxLength":            true,
+	"minimum":              true,
+	"maximum":              true,
+	"multipleOf":           true,
+	"pattern":              true,
+	"format":               true,
+	"minItems":             true,
+	"maxItems":             true,
+	"uniqueItems":          true,
+	"minProperties":        true,
+	"maxProperties":        true,
+}
+
+func sanitizeSchemaForGemini(schema map[string]interface{}) map[string]interface{} {
+	if schema == nil {
+		return nil
+	}
+
+	result := make(map[string]interface{})
+	for k, v := range schema {
+		if geminiUnsupportedKeywords[k] {
+			continue
+		}
+		// Recursively sanitize nested objects
+		switch val := v.(type) {
+		case map[string]interface{}:
+			result[k] = sanitizeSchemaForGemini(val)
+		case []interface{}:
+			sanitized := make([]interface{}, len(val))
+			for i, item := range val {
+				if m, ok := item.(map[string]interface{}); ok {
+					sanitized[i] = sanitizeSchemaForGemini(m)
+				} else {
+					sanitized[i] = item
+				}
+			}
+			result[k] = sanitized
+		default:
+			result[k] = v
+		}
+	}
+
+	// Ensure top-level has type: "object" if properties are present
+	if _, hasProps := result["properties"]; hasProps {
+		if _, hasType := result["type"]; !hasType {
+			result["type"] = "object"
+		}
+	}
+
+	return result
+}
+
+// --- Token source ---
+
+func createAntigravityTokenSource() func() (string, string, error) {
+	return func() (string, string, error) {
+		cred, err := auth.GetCredential("google-antigravity")
+		if err != nil {
+			return "", "", fmt.Errorf("loading auth credentials: %w", err)
+		}
+		if cred == nil {
+			return "", "", fmt.Errorf("no credentials for google-antigravity. Run: picoclaw auth login --provider google-antigravity")
+		}
+
+		// Refresh if needed
+		if cred.NeedsRefresh() && cred.RefreshToken != "" {
+			oauthCfg := auth.GoogleAntigravityOAuthConfig()
+			refreshed, err := auth.RefreshAccessToken(cred, oauthCfg)
+			if err != nil {
+				return "", "", fmt.Errorf("refreshing token: %w", err)
+			}
+			refreshed.Email = cred.Email
+			if refreshed.ProjectID == "" {
+				refreshed.ProjectID = cred.ProjectID
+			}
+			if err := auth.SetCredential("google-antigravity", refreshed); err != nil {
+				return "", "", fmt.Errorf("saving refreshed token: %w", err)
+			}
+			cred = refreshed
+		}
+
+		if cred.IsExpired() {
+			return "", "", fmt.Errorf("antigravity credentials expired. Run: picoclaw auth login --provider google-antigravity")
+		}
+
+		projectID := cred.ProjectID
+		if projectID == "" {
+			// Try to fetch project ID from API
+			fetchedID, err := FetchAntigravityProjectID(cred.AccessToken)
+			if err != nil {
+				logger.WarnCF("provider.antigravity", "Could not fetch project ID, using fallback", map[string]interface{}{
+					"error": err.Error(),
+				})
+				projectID = "rising-fact-p41fc" // Default fallback (same as OpenCode)
+			} else {
+				projectID = fetchedID
+				cred.ProjectID = projectID
+				_ = auth.SetCredential("google-antigravity", cred)
+			}
+		}
+
+		return cred.AccessToken, projectID, nil
+	}
+}
+
+// FetchAntigravityProjectID retrieves the Google Cloud project ID from the loadCodeAssist endpoint.
+func FetchAntigravityProjectID(accessToken string) (string, error) {
+	reqBody, _ := json.Marshal(map[string]interface{}{
+		"metadata": map[string]interface{}{
+			"ideType":    "IDE_UNSPECIFIED",
+			"platform":   "PLATFORM_UNSPECIFIED",
+			"pluginType": "GEMINI",
+		},
+	})
+
+	req, err := http.NewRequest("POST", antigravityBaseURL+"/v1internal:loadCodeAssist", bytes.NewReader(reqBody))
+	if err != nil {
+		return "", err
+	}
+	req.Header.Set("Authorization", "Bearer "+accessToken)
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("User-Agent", antigravityUserAgent)
+	req.Header.Set("X-Goog-Api-Client", antigravityXGoogClient)
+
+	client := &http.Client{Timeout: 15 * time.Second}
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	body, _ := io.ReadAll(resp.Body)
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("loadCodeAssist failed: %s", string(body))
+	}
+
+	var result struct {
+		CloudAICompanionProject string `json:"cloudaicompanionProject"`
+	}
+	if err := json.Unmarshal(body, &result); err != nil {
+		return "", err
+	}
+
+	if result.CloudAICompanionProject == "" {
+		return "", fmt.Errorf("no project ID in loadCodeAssist response")
+	}
+
+	return result.CloudAICompanionProject, nil
+}
+
+// FetchAntigravityModels fetches available models from the Cloud Code Assist API.
+func FetchAntigravityModels(accessToken, projectID string) ([]AntigravityModelInfo, error) {
+	reqBody, _ := json.Marshal(map[string]interface{}{
+		"project": projectID,
+	})
+
+	req, err := http.NewRequest("POST", antigravityBaseURL+"/v1internal:fetchAvailableModels", bytes.NewReader(reqBody))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Authorization", "Bearer "+accessToken)
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("User-Agent", antigravityUserAgent)
+	req.Header.Set("X-Goog-Api-Client", antigravityXGoogClient)
+
+	client := &http.Client{Timeout: 15 * time.Second}
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	body, _ := io.ReadAll(resp.Body)
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("fetchAvailableModels failed (HTTP %d): %s", resp.StatusCode, truncateString(string(body), 200))
+	}
+
+	var result struct {
+		Models map[string]struct {
+			DisplayName string `json:"displayName"`
+			QuotaInfo   struct {
+				RemainingFraction interface{} `json:"remainingFraction"`
+				ResetTime         string      `json:"resetTime"`
+				IsExhausted       bool        `json:"isExhausted"`
+			} `json:"quotaInfo"`
+		} `json:"models"`
+	}
+	if err := json.Unmarshal(body, &result); err != nil {
+		return nil, fmt.Errorf("parsing models response: %w", err)
+	}
+
+	var models []AntigravityModelInfo
+	for id, info := range result.Models {
+		models = append(models, AntigravityModelInfo{
+			ID:          id,
+			DisplayName: info.DisplayName,
+			IsExhausted: info.QuotaInfo.IsExhausted,
+		})
+	}
+
+	return models, nil
+}
+
+type AntigravityModelInfo struct {
+	ID          string `json:"id"`
+	DisplayName string `json:"display_name"`
+	IsExhausted bool   `json:"is_exhausted"`
+}
+
+// --- Helpers ---
+
+func truncateString(s string, maxLen int) string {
+	if len(s) <= maxLen {
+		return s
+	}
+	return s[:maxLen] + "..."
+}
+
+func randomString(n int) string {
+	const letters = "abcdefghijklmnopqrstuvwxyz0123456789"
+	b := make([]byte, n)
+	for i := range b {
+		b[i] = letters[rand.Intn(len(letters))]
+	}
+	return string(b)
+}
+
+func (p *AntigravityProvider) parseAntigravityError(statusCode int, body []byte) error {
+	var errResp struct {
+		Error struct {
+			Code    int                      `json:"code"`
+			Message string                   `json:"message"`
+			Status  string                   `json:"status"`
+			Details []map[string]interface{} `json:"details"`
+		} `json:"error"`
+	}
+
+	if err := json.Unmarshal(body, &errResp); err != nil {
+		return fmt.Errorf("antigravity API error (HTTP %d): %s", statusCode, truncateString(string(body), 500))
+	}
+
+	msg := errResp.Error.Message
+	if statusCode == 429 {
+		// Try to extract quota reset info
+		for _, detail := range errResp.Error.Details {
+			if typeVal, ok := detail["@type"].(string); ok && strings.HasSuffix(typeVal, "ErrorInfo") {
+				if metadata, ok := detail["metadata"].(map[string]interface{}); ok {
+					if delay, ok := metadata["quotaResetDelay"].(string); ok {
+						return fmt.Errorf("antigravity rate limit exceeded: %s (reset in %s)", msg, delay)
+					}
+				}
+			}
+		}
+		return fmt.Errorf("antigravity rate limit exceeded: %s", msg)
+	}
+
+	return fmt.Errorf("antigravity API error (%s): %s", errResp.Error.Status, msg)
+}

pkg/providers/http_provider.go

@@ -331,6 +331,8 @@ func CreateProvider(cfg *config.Config) (LLMProvider, error) {
 				apiBase = "localhost:4321"
 			}
 			return NewGitHubCopilotProvider(apiBase, cfg.Providers.GitHubCopilot.ConnectMode, model)
+		case "antigravity", "google-antigravity":
+			return NewAntigravityProvider(), nil
 
 		}