fix: require antigravity project id

internal/auth/antigravity/auth.go

@@ -48,10 +48,76 @@ func NewAntigravityAuth(cfg *config.Config, httpClient *http.Client) *Antigravit
 	}
 }
 
-func (o *AntigravityAuth) loadCodeAssistUserAgent() string {
+func (o *AntigravityAuth) shortUserAgent() string {
+	return misc.AntigravityRequestUserAgent("")
+}
+
+func (o *AntigravityAuth) nodeUserAgent() string {
 	return misc.AntigravityLoadCodeAssistUserAgent("")
 }
 
+func antigravityLoadCodeAssistMetadata() map[string]string {
+	return map[string]string{
+		"ideType": "ANTIGRAVITY",
+	}
+}
+
+func antigravityControlPlaneMetadata(userAgent string) map[string]string {
+	return map[string]string{
+		"ide_type":    "ANTIGRAVITY",
+		"ide_version": misc.AntigravityVersionFromUserAgent(userAgent),
+		"ide_name":    "antigravity",
+	}
+}
+
+func extractCloudaicompanionProject(data map[string]any) string {
+	if data == nil {
+		return ""
+	}
+	for _, key := range []string{"cloudaicompanionProject", "projectId", "project"} {
+		switch value := data[key].(type) {
+		case string:
+			if trimmed := strings.TrimSpace(value); trimmed != "" {
+				return trimmed
+			}
+		case map[string]any:
+			if id, ok := value["id"].(string); ok {
+				if trimmed := strings.TrimSpace(id); trimmed != "" {
+					return trimmed
+				}
+			}
+		}
+	}
+	return ""
+}
+
+func defaultAntigravityTierID(loadResp map[string]any) string {
+	if tiers, okTiers := loadResp["allowedTiers"].([]any); okTiers {
+		for _, rawTier := range tiers {
+			tier, okTier := rawTier.(map[string]any)
+			if !okTier {
+				continue
+			}
+			if isDefault, okDefault := tier["isDefault"].(bool); !okDefault || !isDefault {
+				continue
+			}
+			if id, okID := tier["id"].(string); okID {
+				if trimmed := strings.TrimSpace(id); trimmed != "" {
+					return trimmed
+				}
+			}
+		}
+	}
+	if currentTier, okTier := loadResp["currentTier"].(map[string]any); okTier {
+		if id, okID := currentTier["id"].(string); okID {
+			if trimmed := strings.TrimSpace(id); trimmed != "" {
+				return trimmed
+			}
+		}
+	}
+	return "free-tier"
+}
+
 // BuildAuthURL generates the OAuth authorization URL.
 func (o *AntigravityAuth) BuildAuthURL(state, redirectURI string) string {
 	if strings.TrimSpace(redirectURI) == "" {
@@ -123,7 +189,7 @@ func (o *AntigravityAuth) FetchUserInfo(ctx context.Context, accessToken string)
 		return "", fmt.Errorf("antigravity userinfo: create request: %w", err)
 	}
 	req.Header.Set("Authorization", "Bearer "+accessToken)
-	req.Header.Set("User-Agent", o.loadCodeAssistUserAgent())
+	req.Header.Set("User-Agent", o.shortUserAgent())
 
 	resp, errDo := o.httpClient.Do(req)
 	if errDo != nil {
@@ -159,13 +225,9 @@ func (o *AntigravityAuth) FetchUserInfo(ctx context.Context, accessToken string)
 
 // FetchProjectID retrieves the project ID for the authenticated user via loadCodeAssist
 func (o *AntigravityAuth) FetchProjectID(ctx context.Context, accessToken string) (string, error) {
-	userAgent := o.loadCodeAssistUserAgent()
+	userAgent := o.shortUserAgent()
 	loadReqBody := map[string]any{
-		"metadata": map[string]string{
-			"ide_type":    "ANTIGRAVITY",
-			"ide_version": misc.AntigravityVersionFromUserAgent(userAgent),
-			"ide_name":    "antigravity",
-		},
+		"metadata": antigravityLoadCodeAssistMetadata(),
 	}
 
 	rawBody, errMarshal := json.Marshal(loadReqBody)
@@ -179,9 +241,9 @@ func (o *AntigravityAuth) FetchProjectID(ctx context.Context, accessToken string
 		return "", fmt.Errorf("create request: %w", err)
 	}
 	req.Header.Set("Authorization", "Bearer "+accessToken)
+	req.Header.Set("Accept", "*/*")
 	req.Header.Set("Content-Type", "application/json")
 	req.Header.Set("User-Agent", userAgent)
-	req.Header.Set("X-Goog-Api-Client", misc.AntigravityGoogAPIClientUA)
 
 	resp, errDo := o.httpClient.Do(req)
 	if errDo != nil {
@@ -207,40 +269,16 @@ func (o *AntigravityAuth) FetchProjectID(ctx context.Context, accessToken string
 		return "", fmt.Errorf("decode response: %w", errDecode)
 	}
 
-	// Extract projectID from response
-	projectID := ""
-	if id, ok := loadResp["cloudaicompanionProject"].(string); ok {
-		projectID = strings.TrimSpace(id)
-	}
-	if projectID == "" {
-		if projectMap, ok := loadResp["cloudaicompanionProject"].(map[string]any); ok {
-			if id, okID := projectMap["id"].(string); okID {
-				projectID = strings.TrimSpace(id)
-			}
-		}
-	}
+	projectID := extractCloudaicompanionProject(loadResp)
 
 	if projectID == "" {
-		tierID := "legacy-tier"
-		if tiers, okTiers := loadResp["allowedTiers"].([]any); okTiers {
-			for _, rawTier := range tiers {
-				tier, okTier := rawTier.(map[string]any)
-				if !okTier {
-					continue
-				}
-				if isDefault, okDefault := tier["isDefault"].(bool); okDefault && isDefault {
-					if id, okID := tier["id"].(string); okID && strings.TrimSpace(id) != "" {
-						tierID = strings.TrimSpace(id)
-						break
-					}
-				}
-			}
-		}
-
-		projectID, err = o.OnboardUser(ctx, accessToken, tierID)
+		projectID, err = o.OnboardUser(ctx, accessToken, defaultAntigravityTierID(loadResp))
 		if err != nil {
 			return "", err
 		}
+		if projectID == "" {
+			return "", fmt.Errorf("project id not found in loadCodeAssist or onboardUser response")
+		}
 		return projectID, nil
 	}
 
@@ -250,14 +288,10 @@ func (o *AntigravityAuth) FetchProjectID(ctx context.Context, accessToken string
 // OnboardUser attempts to fetch the project ID via onboardUser by polling for completion
 func (o *AntigravityAuth) OnboardUser(ctx context.Context, accessToken, tierID string) (string, error) {
 	log.Infof("Antigravity: onboarding user with tier: %s", tierID)
-	userAgent := o.loadCodeAssistUserAgent()
+	userAgent := o.nodeUserAgent()
 	requestBody := map[string]any{
-		"tierId": tierID,
-		"metadata": map[string]string{
-			"ide_type":    "ANTIGRAVITY",
-			"ide_version": misc.AntigravityVersionFromUserAgent(userAgent),
-			"ide_name":    "antigravity",
-		},
+		"tier_id":  tierID,
+		"metadata": antigravityControlPlaneMetadata(userAgent),
 	}
 
 	rawBody, errMarshal := json.Marshal(requestBody)
@@ -276,13 +310,14 @@ func (o *AntigravityAuth) OnboardUser(ctx context.Context, accessToken, tierID s
 		}
 		reqCtx, cancel = context.WithTimeout(reqCtx, 30*time.Second)
 
-		endpointURL := fmt.Sprintf("%s/%s:onboardUser", APIEndpoint, APIVersion)
+		endpointURL := fmt.Sprintf("%s/%s:onboardUser", DailyAPIEndpoint, APIVersion)
 		req, errRequest := http.NewRequestWithContext(reqCtx, http.MethodPost, endpointURL, strings.NewReader(string(rawBody)))
 		if errRequest != nil {
 			cancel()
 			return "", fmt.Errorf("create request: %w", errRequest)
 		}
 		req.Header.Set("Authorization", "Bearer "+accessToken)
+		req.Header.Set("Accept", "*/*")
 		req.Header.Set("Content-Type", "application/json")
 		req.Header.Set("User-Agent", userAgent)
 		req.Header.Set("X-Goog-Api-Client", misc.AntigravityGoogAPIClientUA)
@@ -312,14 +347,7 @@ func (o *AntigravityAuth) OnboardUser(ctx context.Context, accessToken, tierID s
 			if done, okDone := data["done"].(bool); okDone && done {
 				projectID := ""
 				if responseData, okResp := data["response"].(map[string]any); okResp {
-					switch projectValue := responseData["cloudaicompanionProject"].(type) {
-					case map[string]any:
-						if id, okID := projectValue["id"].(string); okID {
-							projectID = strings.TrimSpace(id)
-						}
-					case string:
-						projectID = strings.TrimSpace(projectValue)
-					}
+					projectID = extractCloudaicompanionProject(responseData)
 				}
 
 				if projectID != "" {
@@ -346,5 +374,5 @@ func (o *AntigravityAuth) OnboardUser(ctx context.Context, accessToken, tierID s
 		return "", fmt.Errorf("http %d: %s", resp.StatusCode, responseErr)
 	}
 
-	return "", nil
+	return "", fmt.Errorf("onboard user did not complete after %d attempts", maxAttempts)
 }

internal/auth/antigravity/auth_test.go

@@ -0,0 +1,127 @@
+package antigravity
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+)
+
+type roundTripperFunc func(*http.Request) (*http.Response, error)
+
+func (f roundTripperFunc) RoundTrip(req *http.Request) (*http.Response, error) {
+	return f(req)
+}
+
+func TestFetchProjectIDFromLoadCodeAssist(t *testing.T) {
+	auth := NewAntigravityAuth(nil, &http.Client{Transport: roundTripperFunc(func(req *http.Request) (*http.Response, error) {
+		if req.URL.String() != "https://cloudcode-pa.googleapis.com/v1internal:loadCodeAssist" {
+			t.Fatalf("unexpected request URL: %s", req.URL.String())
+		}
+		assertLoadCodeAssistHeaders(t, req)
+		assertJSONContains(t, req, `"ideType":"ANTIGRAVITY"`)
+		return jsonResponse(`{"cloudaicompanionProject":"cogent-snow-4mnnp"}`), nil
+	})})
+
+	projectID, err := auth.FetchProjectID(context.Background(), "access-token")
+	if err != nil {
+		t.Fatalf("FetchProjectID error: %v", err)
+	}
+	if projectID != "cogent-snow-4mnnp" {
+		t.Fatalf("projectID = %q", projectID)
+	}
+}
+
+func TestFetchProjectIDFallsBackToDailyOnboardUser(t *testing.T) {
+	var sawOnboard bool
+	auth := NewAntigravityAuth(nil, &http.Client{Transport: roundTripperFunc(func(req *http.Request) (*http.Response, error) {
+		switch req.URL.String() {
+		case "https://cloudcode-pa.googleapis.com/v1internal:loadCodeAssist":
+			assertLoadCodeAssistHeaders(t, req)
+			return jsonResponse(`{"allowedTiers":[{"id":"free-tier","isDefault":true}]}`), nil
+		case "https://daily-cloudcode-pa.googleapis.com/v1internal:onboardUser":
+			sawOnboard = true
+			assertOnboardUserHeaders(t, req)
+			assertJSONContains(t, req, `"tier_id":"free-tier"`)
+			assertJSONContains(t, req, `"ide_type":"ANTIGRAVITY"`)
+			return jsonResponse(`{
+				"done": true,
+				"response": {
+					"cloudaicompanionProject": {
+						"id": "cogent-snow-4mnnp",
+						"name": "cogent-snow-4mnnp",
+						"projectNumber": "22597072101"
+					}
+				}
+			}`), nil
+		default:
+			t.Fatalf("unexpected request URL: %s", req.URL.String())
+			return nil, nil
+		}
+	})})
+
+	projectID, err := auth.FetchProjectID(context.Background(), "access-token")
+	if err != nil {
+		t.Fatalf("FetchProjectID error: %v", err)
+	}
+	if !sawOnboard {
+		t.Fatalf("expected onboardUser fallback")
+	}
+	if projectID != "cogent-snow-4mnnp" {
+		t.Fatalf("projectID = %q", projectID)
+	}
+}
+
+func assertLoadCodeAssistHeaders(t *testing.T, req *http.Request) {
+	t.Helper()
+	if got := req.Header.Get("Authorization"); got != "Bearer access-token" {
+		t.Fatalf("Authorization = %q", got)
+	}
+	if got := req.Header.Get("Accept"); got != "*/*" {
+		t.Fatalf("Accept = %q", got)
+	}
+	if got := req.Header.Get("X-Goog-Api-Client"); got != "" {
+		t.Fatalf("X-Goog-Api-Client = %q, want empty", got)
+	}
+	if got := req.Header.Get("User-Agent"); strings.Contains(got, "google-api-nodejs-client/") {
+		t.Fatalf("User-Agent = %q", got)
+	}
+}
+
+func assertOnboardUserHeaders(t *testing.T, req *http.Request) {
+	t.Helper()
+	if got := req.Header.Get("Authorization"); got != "Bearer access-token" {
+		t.Fatalf("Authorization = %q", got)
+	}
+	if got := req.Header.Get("Accept"); got != "*/*" {
+		t.Fatalf("Accept = %q", got)
+	}
+	if got := req.Header.Get("X-Goog-Api-Client"); got != "gl-node/22.21.1" {
+		t.Fatalf("X-Goog-Api-Client = %q", got)
+	}
+	if got := req.Header.Get("User-Agent"); !strings.Contains(got, "google-api-nodejs-client/10.3.0") {
+		t.Fatalf("User-Agent = %q", got)
+	}
+}
+
+func assertJSONContains(t *testing.T, req *http.Request, want string) {
+	t.Helper()
+	body, err := io.ReadAll(req.Body)
+	if err != nil {
+		t.Fatalf("read body: %v", err)
+	}
+	bodyText := string(body)
+	req.Body = io.NopCloser(strings.NewReader(bodyText))
+	if !strings.Contains(bodyText, want) {
+		t.Fatalf("body missing %s: %s", want, bodyText)
+	}
+}
+
+func jsonResponse(body string) *http.Response {
+	return &http.Response{
+		StatusCode: http.StatusOK,
+		Header:     make(http.Header),
+		Body:       io.NopCloser(strings.NewReader(body)),
+	}
+}

internal/auth/antigravity/constants.go

@@ -26,6 +26,7 @@ const (
 
 // Antigravity API configuration
 const (
-	APIEndpoint = "https://cloudcode-pa.googleapis.com"
-	APIVersion  = "v1internal"
+	APIEndpoint      = "https://cloudcode-pa.googleapis.com"
+	DailyAPIEndpoint = "https://daily-cloudcode-pa.googleapis.com"
+	APIVersion       = "v1internal"
 )

internal/runtime/executor/antigravity_executor.go

@@ -1412,6 +1412,41 @@ func (e *AntigravityExecutor) Refresh(ctx context.Context, auth *cliproxyauth.Au
 	return updated, nil
 }
 
+func (e *AntigravityExecutor) ShouldPrepareRequestAuth(auth *cliproxyauth.Auth) bool {
+	return antigravityProjectIDFromAuth(auth) == ""
+}
+
+func (e *AntigravityExecutor) PrepareRequestAuth(ctx context.Context, auth *cliproxyauth.Auth) (*cliproxyauth.Auth, error) {
+	if auth == nil || !e.ShouldPrepareRequestAuth(auth) {
+		return nil, nil
+	}
+
+	updated := auth.Clone()
+	token, refreshedAuth, errToken := e.ensureAccessToken(ctx, updated)
+	if errToken != nil {
+		return nil, errToken
+	}
+	if refreshedAuth != nil {
+		updated = refreshedAuth
+	}
+	if antigravityProjectIDFromAuth(updated) != "" {
+		return updated, nil
+	}
+
+	projectID, errProject := e.fetchAntigravityProjectID(ctx, updated, token)
+	if errProject != nil {
+		return nil, missingAntigravityProjectIDError(errProject)
+	}
+	if projectID == "" {
+		return nil, missingAntigravityProjectIDError(nil)
+	}
+	if updated.Metadata == nil {
+		updated.Metadata = make(map[string]any)
+	}
+	updated.Metadata["project_id"] = projectID
+	return updated, nil
+}
+
 // CountTokens counts tokens for the given request using the Antigravity API.
 func (e *AntigravityExecutor) CountTokens(ctx context.Context, auth *cliproxyauth.Auth, req cliproxyexecutor.Request, opts cliproxyexecutor.Options) (cliproxyexecutor.Response, error) {
 	baseModel := thinking.ParseSuffix(req.Model).ModelName
@@ -1737,34 +1772,67 @@ func (e *AntigravityExecutor) ensureAntigravityProjectID(ctx context.Context, au
 		return nil
 	}
 
-	if auth.Metadata["project_id"] != nil {
+	if antigravityProjectIDFromAuth(auth) != "" {
 		return nil
 	}
 
-	token := strings.TrimSpace(accessToken)
-	if token == "" {
-		token = metaStringValue(auth.Metadata, "access_token")
-	}
-	if token == "" {
-		return nil
-	}
-
-	httpClient := newAntigravityHTTPClient(ctx, e.cfg, auth, 0)
-	projectID, errFetch := sdkAuth.FetchAntigravityProjectID(ctx, token, httpClient)
+	projectID, errFetch := e.fetchAntigravityProjectID(ctx, auth, accessToken)
 	if errFetch != nil {
 		return errFetch
 	}
-	if strings.TrimSpace(projectID) == "" {
+	if projectID == "" {
 		return nil
 	}
 	if auth.Metadata == nil {
 		auth.Metadata = make(map[string]any)
 	}
-	auth.Metadata["project_id"] = strings.TrimSpace(projectID)
+	auth.Metadata["project_id"] = projectID
 
 	return nil
 }
 
+func (e *AntigravityExecutor) fetchAntigravityProjectID(ctx context.Context, auth *cliproxyauth.Auth, accessToken string) (string, error) {
+	token := strings.TrimSpace(accessToken)
+	if token == "" {
+		token = metaStringValue(auth.Metadata, "access_token")
+	}
+	if token == "" {
+		return "", nil
+	}
+
+	httpClient := newAntigravityHTTPClient(ctx, e.cfg, auth, 0)
+	projectID, errFetch := sdkAuth.FetchAntigravityProjectID(ctx, token, httpClient)
+	if errFetch != nil {
+		return "", errFetch
+	}
+	return strings.TrimSpace(projectID), nil
+}
+
+func (e *AntigravityExecutor) projectIDForRequest(_ context.Context, auth *cliproxyauth.Auth, _ string) (string, error) {
+	if projectID := antigravityProjectIDFromAuth(auth); projectID != "" {
+		return projectID, nil
+	}
+	return "", missingAntigravityProjectIDError(nil)
+}
+
+func antigravityProjectIDFromAuth(auth *cliproxyauth.Auth) string {
+	if auth == nil || auth.Metadata == nil {
+		return ""
+	}
+	if pid, ok := auth.Metadata["project_id"].(string); ok {
+		return strings.TrimSpace(pid)
+	}
+	return ""
+}
+
+func missingAntigravityProjectIDError(cause error) statusErr {
+	msg := "antigravity auth missing project_id"
+	if cause != nil {
+		msg = fmt.Sprintf("%s: %v", msg, cause)
+	}
+	return statusErr{code: http.StatusBadRequest, msg: msg}
+}
+
 func (e *AntigravityExecutor) updateAntigravityCreditsBalance(ctx context.Context, auth *cliproxyauth.Auth, accessToken string) {
 	if auth == nil || strings.TrimSpace(auth.ID) == "" {
 		return
@@ -1777,19 +1845,17 @@ func (e *AntigravityExecutor) updateAntigravityCreditsBalance(ctx context.Contex
 		return
 	}
 
-	userAgent := resolveLoadCodeAssistUserAgent(auth)
+	userAgent := resolveUserAgent(auth)
 	loadReqBody, errMarshal := json.Marshal(map[string]any{
 		"metadata": map[string]string{
-			"ide_type":    "ANTIGRAVITY",
-			"ide_version": misc.AntigravityVersionFromUserAgent(userAgent),
-			"ide_name":    "antigravity",
+			"ideType": "ANTIGRAVITY",
 		},
 	})
 	if errMarshal != nil {
 		log.Debugf("antigravity executor: marshal loadCodeAssist request error: %v", errMarshal)
 		return
 	}
-	baseURL := buildBaseURL(auth)
+	baseURL := antigravityLoadCodeAssistBaseURL(auth)
 	endpointURL := strings.TrimSuffix(baseURL, "/") + "/v1internal:loadCodeAssist"
 	httpReq, errReq := http.NewRequestWithContext(ctx, http.MethodPost, endpointURL, bytes.NewReader(loadReqBody))
 	if errReq != nil {
@@ -1797,9 +1863,9 @@ func (e *AntigravityExecutor) updateAntigravityCreditsBalance(ctx context.Contex
 		return
 	}
 	httpReq.Header.Set("Authorization", "Bearer "+token)
+	httpReq.Header.Set("Accept", "*/*")
 	httpReq.Header.Set("Content-Type", "application/json")
 	httpReq.Header.Set("User-Agent", userAgent)
-	httpReq.Header.Set("X-Goog-Api-Client", misc.AntigravityGoogAPIClientUA)
 
 	httpClient := newAntigravityHTTPClient(ctx, e.cfg, auth, 0)
 	httpResp, errDo := httpClient.Do(httpReq)
@@ -1894,12 +1960,9 @@ func (e *AntigravityExecutor) buildRequest(ctx context.Context, auth *cliproxyau
 		requestURL.WriteString(url.QueryEscape(alt))
 	}
 
-	// Extract project_id from auth metadata if available
-	projectID := ""
-	if auth != nil && auth.Metadata != nil {
-		if pid, ok := auth.Metadata["project_id"].(string); ok {
-			projectID = strings.TrimSpace(pid)
-		}
+	projectID, errProject := e.projectIDForRequest(ctx, auth, token)
+	if errProject != nil {
+		return nil, errProject
 	}
 	payload = geminiToAntigravity(modelName, payload, projectID)
 	payload, _ = sjson.SetBytes(payload, "model", modelName)
@@ -2085,6 +2148,13 @@ func buildBaseURL(auth *cliproxyauth.Auth) string {
 	return antigravityBaseURLDaily
 }
 
+func antigravityLoadCodeAssistBaseURL(auth *cliproxyauth.Auth) string {
+	if base := resolveCustomAntigravityBaseURL(auth); base != "" {
+		return base
+	}
+	return antigravityBaseURLProd
+}
+
 func resolveHost(base string) string {
 	parsed, errParse := url.Parse(base)
 	if errParse != nil {
@@ -2323,11 +2393,10 @@ func geminiToAntigravity(modelName string, payload []byte, projectID string) []b
 	}
 	template, _ = sjson.SetBytes(template, "requestType", reqType)
 
-	// Use real project ID from auth if available, otherwise generate random (legacy fallback)
 	if projectID != "" {
 		template, _ = sjson.SetBytes(template, "project", projectID)
 	} else {
-		template, _ = sjson.SetBytes(template, "project", generateProjectID())
+		template, _ = sjson.DeleteBytes(template, "project")
 	}
 
 	if isImageModel {
@@ -2376,14 +2445,3 @@ func generateStableSessionID(payload []byte) string {
 	}
 	return generateSessionID()
 }
-
-func generateProjectID() string {
-	adjectives := []string{"useful", "bright", "swift", "calm", "bold"}
-	nouns := []string{"fuze", "wave", "spark", "flow", "core"}
-	randSourceMutex.Lock()
-	adj := adjectives[randSource.Intn(len(adjectives))]
-	noun := nouns[randSource.Intn(len(nouns))]
-	randSourceMutex.Unlock()
-	randomPart := strings.ToLower(uuid.NewString())[:5]
-	return adj + "-" + noun + "-" + randomPart
-}

internal/runtime/executor/antigravity_executor_buildrequest_test.go

@@ -4,7 +4,10 @@ import (
 	"context"
 	"encoding/json"
 	"io"
+	"net/http"
+	"strings"
 	"testing"
+	"time"
 
 	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
 )
@@ -90,6 +93,82 @@ func TestAntigravityBuildRequest_SkipsSchemaSanitizationWithEmptyToolsArray(t *t
 	assertNonSchemaRequestPreserved(t, body)
 }
 
+func TestAntigravityBuildRequest_UsesAuthProjectID(t *testing.T) {
+	body := buildRequestBodyFromRawPayload(t, "gemini-3.1-pro", []byte(`{
+		"request": {
+			"contents": [
+				{
+					"role": "user",
+					"parts": [{"text": "hello"}]
+				}
+			]
+		}
+	}`))
+
+	if got, ok := body["project"].(string); !ok || got != "project-1" {
+		t.Fatalf("project should come from auth metadata, got=%v", body["project"])
+	}
+}
+
+func TestAntigravityPrepareRequestAuth_FetchesMissingProjectID(t *testing.T) {
+	executor := &AntigravityExecutor{}
+	auth := &cliproxyauth.Auth{Metadata: map[string]any{
+		"access_token": "token",
+		"expired":      time.Now().Add(1 * time.Hour).Format(time.RFC3339),
+	}}
+	ctx := context.WithValue(context.Background(), "cliproxy.roundtripper", roundTripperFunc(func(req *http.Request) (*http.Response, error) {
+		if req.URL.String() != "https://cloudcode-pa.googleapis.com/v1internal:loadCodeAssist" {
+			t.Fatalf("unexpected project discovery request: %s", req.URL.String())
+		}
+		if got := req.Header.Get("X-Goog-Api-Client"); got != "" {
+			t.Fatalf("X-Goog-Api-Client = %q, want empty", got)
+		}
+		raw, errRead := io.ReadAll(req.Body)
+		if errRead != nil {
+			t.Fatalf("read discovery body: %v", errRead)
+		}
+		if !strings.Contains(string(raw), `"ideType":"ANTIGRAVITY"`) {
+			t.Fatalf("unexpected discovery body: %s", string(raw))
+		}
+		return &http.Response{
+			StatusCode: http.StatusOK,
+			Header:     make(http.Header),
+			Body:       io.NopCloser(strings.NewReader(`{"cloudaicompanionProject":"fetched-project"}`)),
+		}, nil
+	}))
+
+	updated, err := executor.PrepareRequestAuth(ctx, auth)
+	if err != nil {
+		t.Fatalf("PrepareRequestAuth error: %v", err)
+	}
+	if updated == nil {
+		t.Fatalf("PrepareRequestAuth returned nil auth")
+	}
+	if _, ok := auth.Metadata["project_id"]; ok {
+		t.Fatalf("original auth metadata should not be mutated")
+	}
+	if got, ok := updated.Metadata["project_id"].(string); !ok || got != "fetched-project" {
+		t.Fatalf("updated auth metadata project_id = %v, want fetched-project", updated.Metadata["project_id"])
+	}
+}
+
+func TestAntigravityBuildRequest_RejectsMissingProjectID(t *testing.T) {
+	executor := &AntigravityExecutor{}
+	auth := &cliproxyauth.Auth{Metadata: map[string]any{}}
+
+	_, err := executor.buildRequest(context.Background(), auth, "token", "gemini-3.1-pro", []byte(`{"request":{}}`), false, "", "https://example.com")
+	if err == nil {
+		t.Fatalf("buildRequest should fail when auth has no project_id")
+	}
+	status, ok := err.(interface{ StatusCode() int })
+	if !ok {
+		t.Fatalf("error should expose status code, got %T", err)
+	}
+	if got := status.StatusCode(); got != http.StatusBadRequest {
+		t.Fatalf("status code = %d, want %d", got, http.StatusBadRequest)
+	}
+}
+
 func assertNonSchemaRequestPreserved(t *testing.T, body map[string]any) {
 	t.Helper()
 
@@ -172,13 +251,19 @@ func buildRequestBodyFromRawPayload(t *testing.T, modelName string, payload []by
 	t.Helper()
 
 	executor := &AntigravityExecutor{}
-	auth := &cliproxyauth.Auth{}
+	auth := &cliproxyauth.Auth{Metadata: map[string]any{"project_id": "project-1"}}
 
 	req, err := executor.buildRequest(context.Background(), auth, "token", modelName, payload, false, "", "https://example.com")
 	if err != nil {
 		t.Fatalf("buildRequest error: %v", err)
 	}
 
+	return requestBody(t, req)
+}
+
+func requestBody(t *testing.T, req *http.Request) map[string]any {
+	t.Helper()
+
 	raw, err := io.ReadAll(req.Body)
 	if err != nil {
 		t.Fatalf("read request body error: %v", err)

internal/runtime/executor/antigravity_executor_credits_test.go

@@ -444,24 +444,25 @@ func TestUpdateAntigravityCreditsBalance_LoadCodeAssistUserAgent(t *testing.T) {
 	t.Cleanup(resetAntigravityCreditsRetryState)
 
 	exec := NewAntigravityExecutor(&config.Config{})
-	const userAgent = "antigravity/1.23.2 windows/amd64 google-api-nodejs-client/10.3.0"
+	const configuredUserAgent = "antigravity/1.23.2 windows/amd64 google-api-nodejs-client/10.3.0"
+	const loadCodeAssistUserAgent = "antigravity/1.23.2 windows/amd64"
 	auth := &cliproxyauth.Auth{
 		ID:         "auth-load-code-assist-ua",
-		Attributes: map[string]string{"user_agent": userAgent},
+		Attributes: map[string]string{"user_agent": configuredUserAgent},
 	}
 	ctx := context.WithValue(context.Background(), "cliproxy.roundtripper", roundTripperFunc(func(req *http.Request) (*http.Response, error) {
 		if req.URL.String() != "https://cloudcode-pa.googleapis.com/v1internal:loadCodeAssist" {
 			t.Fatalf("unexpected request url %s", req.URL.String())
 		}
-		if got := req.Header.Get("User-Agent"); got != userAgent {
-			t.Fatalf("User-Agent = %q, want %q", got, userAgent)
+		if got := req.Header.Get("User-Agent"); got != loadCodeAssistUserAgent {
+			t.Fatalf("User-Agent = %q, want %q", got, loadCodeAssistUserAgent)
 		}
-		if got := req.Header.Get("X-Goog-Api-Client"); got != "gl-node/22.21.1" {
-			t.Fatalf("X-Goog-Api-Client = %q, want %q", got, "gl-node/22.21.1")
+		if got := req.Header.Get("X-Goog-Api-Client"); got != "" {
+			t.Fatalf("X-Goog-Api-Client = %q, want empty", got)
 		}
 		body, _ := io.ReadAll(req.Body)
 		_ = req.Body.Close()
-		if string(body) != `{"metadata":{"ide_name":"antigravity","ide_type":"ANTIGRAVITY","ide_version":"1.23.2"}}` {
+		if string(body) != `{"metadata":{"ideType":"ANTIGRAVITY"}}` {
 			t.Fatalf("loadCodeAssist body = %s", string(body))
 		}
 		return &http.Response{