fix(antigravity): align provider fingerprint with IDE Desktop 2.1.1 (#2389)

Match captured official Antigravity IDE traffic: cloudcode-pa host,
antigravity/ide/2.1.1 User-Agent, IDE-shaped agent requestId, and drop
router-only stream/usage headers plus the legacy double system prompt.

Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/config/appConstants.js

@@ -1,5 +1,6 @@
 import { platform, arch } from "os";
 import { PROVIDERS, PROVIDER_OAUTH } from "./providers.js";
+import { ANTIGRAVITY_IDE_USER_AGENT } from "../providers/shared.js";
 
 // === Gemini CLI === derive từ registry gemini-cli.transport
 export const GEMINI_CLI_VERSION = PROVIDERS["gemini-cli"]?.cliVersion;
@@ -59,7 +60,7 @@ export function getPlatformEnum() {
 }
 
 export function getPlatformUserAgent() {
-  return `antigravity/1.104.0 ${platform()}/${arch()}`;
+  return ANTIGRAVITY_IDE_USER_AGENT;
 }
 
 export const CLIENT_METADATA = {
@@ -129,7 +130,7 @@ export const AG_DEFAULT_TOOLS = new Set([
 
 // Antigravity chat/stream headers
 export const ANTIGRAVITY_HEADERS = {
-  "User-Agent": `antigravity/1.107.0 ${platform()}/${arch()}`
+  "User-Agent": ANTIGRAVITY_IDE_USER_AGENT
 };
 
 // Cloud Code Assist API

open-sse/executors/antigravity.js

@@ -1,7 +1,7 @@
 import crypto from "crypto";
 import { BaseExecutor } from "./base.js";
 import { PROVIDERS } from "../config/providers.js";
-import { OAUTH_ENDPOINTS, ANTIGRAVITY_HEADERS, INTERNAL_REQUEST_HEADER, AG_DEFAULT_TOOLS, AG_TOOL_SUFFIX } from "../config/appConstants.js";
+import { OAUTH_ENDPOINTS, ANTIGRAVITY_HEADERS, AG_DEFAULT_TOOLS, AG_TOOL_SUFFIX } from "../config/appConstants.js";
 import { HTTP_STATUS } from "../config/runtimeConfig.js";
 import { resolveSessionId } from "../utils/sessionManager.js";
 import { proxyAwareFetch } from "../utils/proxyFetch.js";
@@ -18,7 +18,8 @@ function sanitizeFunctionName(name) {
 
 const MAX_RETRY_AFTER_MS = 10000;
 const ANTIGRAVITY_TRANSIENT_RETRY_MAX_MS = 15000;
-const MAX_ANTIGRAVITY_OUTPUT_TOKENS = 16384;
+const MAX_ANTIGRAVITY_OUTPUT_TOKENS = 64000;
+const ANTIGRAVITY_IDE_REQUEST_ID_RE = /^agent\/[^/]+\/\d+\/[^/]+\/\d+$/;
 
 const ANTIGRAVITY_TRANSIENT_ERROR_PATTERNS = [
   /high\s+traffic/i,
@@ -87,6 +88,27 @@ function parseImageConfig(model) {
   return config;
 }
 
+function uuidFromSeed(seed) {
+  const bytes = crypto.createHash("sha256").update(String(seed || "antigravity")).digest().subarray(0, 16);
+  bytes[6] = (bytes[6] & 0x0f) | 0x50;
+  bytes[8] = (bytes[8] & 0x3f) | 0x80;
+  const hex = bytes.toString("hex");
+  return `${hex.slice(0, 8)}-${hex.slice(8, 12)}-${hex.slice(12, 16)}-${hex.slice(16, 20)}-${hex.slice(20)}`;
+}
+
+function buildIdeRequestId({ body, request, credentials, model, requestType }) {
+  if (ANTIGRAVITY_IDE_REQUEST_ID_RE.test(body?.requestId || "")) {
+    return body.requestId;
+  }
+
+  const sessionId = request?.sessionId || body?.request?.sessionId || credentials?._clientSessionId || credentials?.connectionId || credentials?.email || "anonymous";
+  const conversationId = uuidFromSeed(`antigravity:conversation:${sessionId}`);
+  const trajectoryId = uuidFromSeed(`antigravity:trajectory:${sessionId}:${model}:${requestType}`);
+  const contentCount = Array.isArray(request?.contents) ? request.contents.length : 1;
+  const step = Math.max(1, contentCount * 2 - 1);
+  return `agent/${conversationId}/${Date.now()}/${trajectoryId}/${step}`;
+}
+
 export class AntigravityExecutor extends BaseExecutor {
   constructor() {
     super("antigravity", PROVIDERS.antigravity);
@@ -104,14 +126,10 @@ export class AntigravityExecutor extends BaseExecutor {
   // sessionId comes from transformRequest output; base.execute runs transformRequest before
   // buildHeaders, so we read it from instance state cached there (fallback: explicit arg).
   buildHeaders(credentials, stream = true, sessionId = null) {
-    const sid = sessionId || this._lastSessionId;
     return {
       "Content-Type": "application/json",
       "Authorization": `Bearer ${credentials.accessToken}`,
       "User-Agent": this.config.headers?.["User-Agent"] || ANTIGRAVITY_HEADERS["User-Agent"],
-      [INTERNAL_REQUEST_HEADER.name]: INTERNAL_REQUEST_HEADER.value,
-      ...(sid && { "X-Machine-Session-Id": sid }),
-      "Accept": stream ? "text/event-stream" : "application/json"
     };
   }
 
@@ -142,25 +160,26 @@ export class AntigravityExecutor extends BaseExecutor {
       });
 
       this._lastSessionId = sessionId;
+      const request = {
+        contents,
+        generationConfig: {
+          temperature: 1.0,
+          topP: 0.95,
+          topK: 40,
+          maxOutputTokens: 8192,
+          imageConfig,
+        },
+        sessionId,
+        // No tools, no systemInstruction, no safetySettings for image gen
+      };
 
       return {
         project: projectId,
         model: cleanModel,
         userAgent: "antigravity",
         requestType: "image_gen",
-        requestId: `agent-${crypto.randomUUID()}`,
+        requestId: buildIdeRequestId({ body, request, credentials, model: cleanModel, requestType: "image_gen" }),
-        request: {
+        request,
-          contents,
-          generationConfig: {
-            temperature: 1.0,
-            topP: 0.95,
-            topK: 40,
-            maxOutputTokens: 8192,
-            imageConfig,
-          },
-          sessionId,
-          // No tools, no systemInstruction, no safetySettings for image gen
-        },
       };
     }
 
@@ -248,7 +267,7 @@ export class AntigravityExecutor extends BaseExecutor {
       model: model,
       userAgent: "antigravity",
       requestType: "agent",
-      requestId: `agent-${crypto.randomUUID()}`,
+      requestId: buildIdeRequestId({ body, request: transformedRequest, credentials, model, requestType: "agent" }),
       request: transformedRequest
     };
   }

open-sse/providers/registry/antigravity.js

@@ -1,5 +1,4 @@
-import { platform, arch } from "os";
+import { ANTIGRAVITY_IDE_BASE_URL, ANTIGRAVITY_IDE_USER_AGENT, ANTIGRAVITY_OAUTH_CLIENT } from "../shared.js";
-import { ANTIGRAVITY_OAUTH_CLIENT } from "../shared.js";
 
 export default {
   id: "antigravity",
@@ -20,13 +19,10 @@ export default {
   category: "oauth",
   serviceKinds: ["llm", "image"],
   transport: {
-    baseUrls: [
+    baseUrls: [ANTIGRAVITY_IDE_BASE_URL],
-      "https://daily-cloudcode-pa.googleapis.com",
-      "https://daily-cloudcode-pa.sandbox.googleapis.com",
-    ],
     format: "antigravity",
     headers: {
-      "User-Agent": "antigravity/1.107.0 darwin/arm64",
+      "User-Agent": ANTIGRAVITY_IDE_USER_AGENT,
     },
     retry: {
       "429": {

open-sse/providers/shared.js

@@ -54,6 +54,13 @@ export const KIMI_CODING_BASE_URL = "https://api.kimi.com/coding/v1/messages";
 export const OPENAI_COMPAT_BASE = "https://api.openai.com/v1";
 export const ANTHROPIC_COMPAT_BASE = "https://api.anthropic.com/v1";
 
+// Official Antigravity IDE Desktop 2.1.1 fingerprint captured from macOS arm64.
+// Keep this static even when 9router runs on Linux: the provider profile is
+// intentionally matching the IDE client, not the server host.
+export const ANTIGRAVITY_IDE_VERSION = "2.1.1";
+export const ANTIGRAVITY_IDE_BASE_URL = "https://cloudcode-pa.googleapis.com";
+export const ANTIGRAVITY_IDE_USER_AGENT = `antigravity/ide/${ANTIGRAVITY_IDE_VERSION} darwin/arm64`;
+
 // Antigravity OAuth client credentials (public CLI client — duplicated in usage.js + src/lib/oauth)
 export const ANTIGRAVITY_OAUTH_CLIENT = {
   clientId: "1071006060591-tmhssin2h21lcre235vtolojh4g403ep.apps.googleusercontent.com",

open-sse/services/usage/google.js

@@ -2,15 +2,15 @@
  * Google usage handlers (Gemini CLI + Antigravity)
  */
 
-import { CLIENT_METADATA, getPlatformUserAgent } from "../../config/appConstants.js";
+import { CLIENT_METADATA } from "../../config/appConstants.js";
-import { ANTIGRAVITY_OAUTH_CLIENT } from "../../providers/shared.js";
+import { ANTIGRAVITY_IDE_USER_AGENT, ANTIGRAVITY_IDE_VERSION, ANTIGRAVITY_OAUTH_CLIENT } from "../../providers/shared.js";
 import { U, parseResetTime, normalizeCloudCodeProjectId, fetchWithTimeout } from "./shared.js";
 
 // Antigravity API config (from Quotio) — urls from registry, oauth client + dynamic UA kept here
 const ANTIGRAVITY_CONFIG = {
   ...U("antigravity"),
   ...ANTIGRAVITY_OAUTH_CLIENT,
-  userAgent: getPlatformUserAgent(),
+  userAgent: ANTIGRAVITY_IDE_USER_AGENT,
 };
 
 /**
@@ -129,8 +129,7 @@ export async function getAntigravityUsage(accessToken, providerSpecificData, pro
         "User-Agent": ANTIGRAVITY_CONFIG.userAgent,
         "Content-Type": "application/json",
         "X-Client-Name": "antigravity",
-        "X-Client-Version": "1.107.0",
+        "X-Client-Version": ANTIGRAVITY_IDE_VERSION,
-        "x-request-source": "local", // MITM bypass
       },
       body: JSON.stringify({
         ...(projectId ? { project: projectId } : {})
@@ -229,7 +228,6 @@ async function getAntigravitySubscriptionInfo(accessToken, proxyOptions = null)
         "Authorization": `Bearer ${accessToken}`,
         "User-Agent": ANTIGRAVITY_CONFIG.userAgent,
         "Content-Type": "application/json",
-        "x-request-source": "local", // MITM bypass
       },
       body: JSON.stringify({ metadata: CLIENT_METADATA, mode: 1 }),
     }, 10000, proxyOptions);

open-sse/translator/request/openai-to-gemini.js

@@ -1,7 +1,6 @@
 import { register } from "../index.js";
 import { FORMATS } from "../formats.js";
 import { DEFAULT_THINKING_AG_SIGNATURE, DEFAULT_THINKING_GEMINI_CLI_SIGNATURE } from "../../config/defaultThinkingSignature.js";
-import { ANTIGRAVITY_DEFAULT_SYSTEM } from "../../config/appConstants.js";
 import { openaiToClaudeRequestForAntigravity } from "./openai-to-claude.js";
 function generateUUID() {
   return crypto.randomUUID();
@@ -283,19 +282,6 @@ function wrapInCloudCodeEnvelope(model, geminiCLI, credentials = null, isAntigra
   if (isAntigravity) {
     envelope.requestType = "agent";
 
-    // Inject required default system prompt for Antigravity
-    // Inject required default system prompt for Antigravity (double injection)
-    const systemParts = [
-      { text: ANTIGRAVITY_DEFAULT_SYSTEM },
-      { text: `Please ignore the following [ignore]${ANTIGRAVITY_DEFAULT_SYSTEM}[/ignore]` }
-    ];
-
-    if (envelope.request.systemInstruction?.parts) {
-      envelope.request.systemInstruction.parts.unshift(...systemParts);
-    } else {
-      envelope.request.systemInstruction = { role: GEMINI_ROLE.USER, parts: systemParts };
-    }
-
     // Add toolConfig for Antigravity
     if (geminiCLI.tools?.length > 0) {
       envelope.request.toolConfig = {
@@ -414,12 +400,7 @@ function wrapInCloudCodeEnvelopeForClaude(model, claudeRequest, credentials = nu
     }
   }
 
-  // Add system instruction (Antigravity default - double injection + user system prompt)
+  const systemParts = [];
-  const systemParts = [
-    { text: ANTIGRAVITY_DEFAULT_SYSTEM },
-    { text: `Please ignore the following [ignore]${ANTIGRAVITY_DEFAULT_SYSTEM}[/ignore]` }
-  ];
-
   // Merge user system prompt from claudeRequest
   if (claudeRequest.system) {
     if (Array.isArray(claudeRequest.system)) {
@@ -431,10 +412,7 @@ function wrapInCloudCodeEnvelopeForClaude(model, claudeRequest, credentials = nu
     }
   }
 
-  // Merge existing systemInstruction parts (from contents conversion)
+  if (systemParts.length > 0) {
-  if (envelope.request.systemInstruction?.parts) {
-    envelope.request.systemInstruction.parts.unshift(...systemParts);
-  } else {
     envelope.request.systemInstruction = { role: GEMINI_ROLE.USER, parts: systemParts };
   }
 
@@ -463,4 +441,3 @@ export function openaiToAntigravityRequest(model, body, stream, credentials = nu
 register(FORMATS.OPENAI, FORMATS.GEMINI, openaiToGeminiRequest, null);
 register(FORMATS.OPENAI, FORMATS.GEMINI_CLI, (model, body, stream, credentials) => wrapInCloudCodeEnvelope(model, openaiToGeminiCLIRequest(model, body, stream), credentials), null);
 register(FORMATS.OPENAI, FORMATS.ANTIGRAVITY, openaiToAntigravityRequest, null);
-

tests/translator/bugs-antigravity.test.js

@@ -4,6 +4,8 @@ import "./registerAll.js";
 import { translateRequest, translateResponse, initState } from "../../open-sse/translator/index.js";
 import { FORMATS } from "../../open-sse/translator/formats.js";
 import { AntigravityExecutor } from "../../open-sse/executors/antigravity.js";
+import { openaiToAntigravityRequest } from "../../open-sse/translator/request/openai-to-gemini.js";
+import { ANTIGRAVITY_DEFAULT_SYSTEM } from "../../open-sse/config/appConstants.js";
 
 const AG2O = (req) =>
   translateRequest(FORMATS.ANTIGRAVITY, FORMATS.OPENAI, "m", { request: req }, true, null, null);
@@ -106,4 +108,32 @@ describe("Antigravity executor", () => {
     const query = out.request.tools[0].functionDeclarations[0].parameters.properties.query;
     expect(query).toEqual({ type: "string", description: "Search query" });
   });
+
+  it("does not inject the legacy Antigravity default system prompt for Gemini-backed models", () => {
+    const out = openaiToAntigravityRequest("gemini-3.5-flash-low", {
+      messages: [
+        { role: "system", content: "USER_SYSTEM_PROMPT" },
+        { role: "user", content: "hello" },
+      ],
+    }, true, { projectId: "project-1", connectionId: "conn-1" });
+
+    const system = JSON.stringify(out.request.systemInstruction);
+    expect(system).toContain("USER_SYSTEM_PROMPT");
+    expect(system).not.toContain(ANTIGRAVITY_DEFAULT_SYSTEM);
+    expect(system).not.toContain("Please ignore the following [ignore]");
+  });
+
+  it("does not inject the legacy Antigravity default system prompt for Claude-backed models", () => {
+    const out = openaiToAntigravityRequest("claude-opus-4-6-thinking", {
+      messages: [
+        { role: "system", content: "USER_SYSTEM_PROMPT" },
+        { role: "user", content: "hello" },
+      ],
+    }, true, { projectId: "project-1", connectionId: "conn-1" });
+
+    const system = JSON.stringify(out.request.systemInstruction);
+    expect(system).toContain("USER_SYSTEM_PROMPT");
+    expect(system).not.toContain(ANTIGRAVITY_DEFAULT_SYSTEM);
+    expect(system).not.toContain("Please ignore the following [ignore]");
+  });
 });

tests/unit/antigravity-retry-hook.test.js

@@ -1,6 +1,7 @@
 // Guards D3: antigravity 429/503 retry merged into base via computeRetryDelay hook.
 import { describe, it, expect } from "vitest";
 import { AntigravityExecutor } from "../../open-sse/executors/antigravity.js";
+import antigravity from "../../open-sse/providers/registry/antigravity.js";
 
 const MAX = 10000;
 function res(status, headers = {}, body = null) {
@@ -66,9 +67,35 @@ describe("antigravity computeRetryDelay hook (D3)", () => {
     expect(out.request.tools[0].functionDeclarations.map(fn => fn.name)).toEqual(["read_file"]);
   });
 
-  it("buildHeaders includes cached session id after transformRequest", () => {
+  it("registry uses the official IDE cloudcode host and user agent", () => {
+    expect(antigravity.transport.baseUrls).toEqual(["https://cloudcode-pa.googleapis.com"]);
+    expect(antigravity.transport.headers["User-Agent"]).toBe("antigravity/ide/2.1.1 darwin/arm64");
+  });
+
+  it("buildHeaders matches official IDE stream headers", () => {
     ag._lastSessionId = "sess-123";
     const h = ag.buildHeaders({ accessToken: "tok" }, true);
-    expect(h["X-Machine-Session-Id"]).toBe("sess-123");
+    expect(h["User-Agent"]).toBe("antigravity/ide/2.1.1 darwin/arm64");
+    expect(h["Content-Type"]).toBe("application/json");
+    expect(h["Authorization"]).toBe("Bearer tok");
+    expect(h).not.toHaveProperty("X-Machine-Session-Id");
+    expect(h).not.toHaveProperty("x-request-source");
+    expect(h).not.toHaveProperty("Accept");
+  });
+
+  it("transforms chat requests with official IDE requestId shape and 64000 token cap", () => {
+    const out = ag.transformRequest("claude-opus-4-6-thinking", {
+      request: {
+        contents: [
+          { role: "user", parts: [{ text: "hi" }] },
+          { role: "model", parts: [{ text: "hello" }] },
+        ],
+        generationConfig: { maxOutputTokens: 90000 },
+        sessionId: "-3750763034362895579",
+      },
+    }, true, { projectId: "project-1", connectionId: "conn-1" });
+
+    expect(out.requestId).toMatch(/^agent\/[0-9a-f-]{36}\/\d{13}\/[0-9a-f-]{36}\/\d+$/);
+    expect(out.request.generationConfig.maxOutputTokens).toBe(64000);
   });
 });

tests/unit/antigravity-usage-headers.test.js

@@ -0,0 +1,30 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+const proxyAwareFetch = vi.fn(async (url) => ({
+  ok: true,
+  status: 200,
+  json: async () => url.includes(":loadCodeAssist")
+    ? { cloudaicompanionProject: "project-1", currentTier: { name: "Pro" } }
+    : { models: {} },
+  text: async () => "{}",
+}));
+
+vi.mock("../../open-sse/utils/proxyFetch.js", () => ({
+  proxyAwareFetch,
+}));
+
+describe("Antigravity usage headers", () => {
+  beforeEach(() => proxyAwareFetch.mockClear());
+
+  it("uses the official IDE user agent and omits router-only source headers", async () => {
+    const { getAntigravityUsage } = await import("../../open-sse/services/usage/google.js");
+
+    await getAntigravityUsage("access-token", {});
+
+    expect(proxyAwareFetch).toHaveBeenCalledTimes(2);
+    for (const [, options] of proxyAwareFetch.mock.calls) {
+      expect(options.headers["User-Agent"]).toBe("antigravity/ide/2.1.1 darwin/arm64");
+      expect(options.headers).not.toHaveProperty("x-request-source");
+    }
+  });
+});