diff --git a/open-sse/config/appConstants.js b/open-sse/config/appConstants.js
index 62e2f888..5ddf95ac 100644
--- a/open-sse/config/appConstants.js
+++ b/open-sse/config/appConstants.js
@@ -156,6 +156,13 @@ export const LOAD_CODE_ASSIST_HEADERS = {
   "Client-Metadata": JSON.stringify({ ideType: IDE_TYPE.ANTIGRAVITY, platform: getPlatformEnum(), pluginType: PLUGIN_TYPE.GEMINI }),
 };
 
+// Real Antigravity IDE doesn't send X-Goog-Api-Client/Client-Metadata on loadCodeAssist/onboardUser —
+// Google's backend fingerprints those and silently refuses to provision a cloudaicompanionProject.
+export const ANTIGRAVITY_LOAD_CODE_ASSIST_HEADERS = {
+  "Content-Type": "application/json",
+  "User-Agent": ANTIGRAVITY_IDE_USER_AGENT,
+};
+
 export const LOAD_CODE_ASSIST_METADATA = {
   ideType: IDE_TYPE.ANTIGRAVITY,
   platform: getPlatformEnum(),
diff --git a/open-sse/providers/registry/antigravity.js b/open-sse/providers/registry/antigravity.js
index a4ca7346..1a7c4347 100644
--- a/open-sse/providers/registry/antigravity.js
+++ b/open-sse/providers/registry/antigravity.js
@@ -76,8 +76,7 @@ export default {
     apiVersion: "v1internal",
     loadCodeAssistEndpoint: "https://cloudcode-pa.googleapis.com/v1internal:loadCodeAssist",
     onboardUserEndpoint: "https://cloudcode-pa.googleapis.com/v1internal:onboardUser",
-    loadCodeAssistUserAgent: "google-api-nodejs-client/9.15.1",
-    loadCodeAssistApiClient: "google-cloud-sdk vscode_cloudshelleditor/0.1",
+    loadCodeAssistUserAgent: ANTIGRAVITY_IDE_USER_AGENT,
     refreshLeadMs: 300000,
   },
   features: {
diff --git a/open-sse/services/projectId.js b/open-sse/services/projectId.js
index 3801ac69..84ab5a2b 100644
--- a/open-sse/services/projectId.js
+++ b/open-sse/services/projectId.js
@@ -7,7 +7,7 @@
  * This significantly reduces the risk of being flagged by Google's anti-abuse systems.
  */
 
-import { CLOUD_CODE_API, LOAD_CODE_ASSIST_HEADERS, LOAD_CODE_ASSIST_METADATA } from "../config/appConstants.js";
+import { CLOUD_CODE_API, LOAD_CODE_ASSIST_HEADERS, ANTIGRAVITY_LOAD_CODE_ASSIST_HEADERS, LOAD_CODE_ASSIST_METADATA } from "../config/appConstants.js";
 
 // ─── Cache ────────────────────────────────────────────────────────────────────
 // connectionId -> { projectId: string, fetchedAt: number }
@@ -157,9 +157,10 @@ export function removeConnection(connectionId) {
  */
 async function fetchProjectId(accessToken, signal, provider) {
     const endpoints = CLOUD_CODE_API[provider] || CLOUD_CODE_API["gemini-cli"];
+    const headers = provider === "antigravity" ? ANTIGRAVITY_LOAD_CODE_ASSIST_HEADERS : LOAD_CODE_ASSIST_HEADERS;
     const response = await fetch(endpoints.loadCodeAssist, {
         method: "POST",
-        headers: { ...LOAD_CODE_ASSIST_HEADERS, "Authorization": `Bearer ${accessToken}` },
+        headers: { ...headers, "Authorization": `Bearer ${accessToken}` },
         body: JSON.stringify({ metadata: LOAD_CODE_ASSIST_METADATA }),
         signal
     });
@@ -186,7 +187,7 @@ async function fetchProjectId(accessToken, signal, provider) {
         }
     }
 
-    return onboardUser(accessToken, tierID, signal, endpoints);
+    return onboardUser(accessToken, tierID, signal, endpoints, provider);
 }
 
 /**
@@ -197,10 +198,11 @@ async function fetchProjectId(accessToken, signal, provider) {
  * @param {AbortSignal} externalSignal  – propagated from the connection's AbortController
  * @returns {Promise<string|null>}
  */
-async function onboardUser(accessToken, tierID, externalSignal, endpoints) {
+async function onboardUser(accessToken, tierID, externalSignal, endpoints, provider) {
     console.log(`[ProjectId] Onboarding user with tier: ${tierID}`);
 
     const reqBody = { tierId: tierID, metadata: LOAD_CODE_ASSIST_METADATA };
+    const headers = provider === "antigravity" ? ANTIGRAVITY_LOAD_CODE_ASSIST_HEADERS : LOAD_CODE_ASSIST_HEADERS;
     const MAX_ATTEMPTS = 5;
 
     for (let attempt = 1; attempt <= MAX_ATTEMPTS; attempt++) {
@@ -216,7 +218,7 @@ async function onboardUser(accessToken, tierID, externalSignal, endpoints) {
         try {
             const response = await fetch(endpoints.onboardUser, {
                 method: "POST",
-                headers: { ...LOAD_CODE_ASSIST_HEADERS, "Authorization": `Bearer ${accessToken}` },
+                headers: { ...headers, "Authorization": `Bearer ${accessToken}` },
                 body: JSON.stringify(reqBody),
                 signal: localCtrl.signal
             });
diff --git a/src/lib/oauth/providers/antigravity.js b/src/lib/oauth/providers/antigravity.js
index 6cf28e81..10453ad8 100644
--- a/src/lib/oauth/providers/antigravity.js
+++ b/src/lib/oauth/providers/antigravity.js
@@ -39,13 +39,10 @@ const antigravity = {
     return await response.json();
   },
   postExchange: async (tokens) => {
-    // Numeric enums matching Antigravity binary ClientMetadata
     const loadHeaders = {
       "Authorization": `Bearer ${tokens.access_token}`,
       "Content-Type": "application/json",
       "User-Agent": ANTIGRAVITY_CONFIG.loadCodeAssistUserAgent,
-      "X-Goog-Api-Client": ANTIGRAVITY_CONFIG.loadCodeAssistApiClient,
-      "Client-Metadata": ANTIGRAVITY_CONFIG.loadCodeAssistClientMetadata,
       "x-request-source": "local",
     };
     const metadata = getOAuthClientMetadata();
diff --git a/src/lib/oauth/services/antigravity.js b/src/lib/oauth/services/antigravity.js
index cda6bde3..6540f055 100644
--- a/src/lib/oauth/services/antigravity.js
+++ b/src/lib/oauth/services/antigravity.js
@@ -85,8 +85,6 @@ export class AntigravityService {
       "Authorization": `Bearer ${accessToken}`,
       "Content-Type": "application/json",
       "User-Agent": this.config.loadCodeAssistUserAgent,
-      "X-Goog-Api-Client": this.config.loadCodeAssistApiClient,
-      "Client-Metadata": this.config.loadCodeAssistClientMetadata,
     };
   }