feat(antigravity): initial steps for Antigravity anti-ban alignment

Cherry-picked from decolua/9router#141 (author: LinearSakana / zx <me@char.moe>) - Implement client identity spoofing with numeric enums (ideType: 9, pluginType: 2) - Add runtime platform detection for User-Agent and metadata - Implement per-connection session ID caching (binary-compatible format) - Add ANTIGRAVITY_HEADERS (X-Client-Name, X-Client-Version, x-goog-api-client) - Add X-Machine-Session-Id header injection - Align metadata/mode parameters across all Antigravity API calls - Implement double injection for system prompt (raw + [ignore] wrapped) - Rename internal anti-loop header to x-request-source for anonymity Skipped: commit 6 (signature side-channel caching) — kept DEFAULT_THINKING_GEMINI_SIGNATURE Co-authored-by: Cursor <cursoragent@cursor.com>
2026-05-08 12:01:28 +00:00 · 2026-02-20 14:44:29 +07:00
parent 9fbd6e619d
commit a229d79158
11 changed files with 309 additions and 121 deletions
--- a/open-sse/config/constants.js
+++ b/open-sse/config/constants.js
@@ -1,3 +1,79 @@
+import { platform, arch } from "os";
+
+// === Antigravity Binary Alignment: Numeric Enums ===
+// Reference: Antigravity binary analysis - google.internal.cloud.code.v1internal.ClientMetadata
+
+// IDE Type enum (numeric values as expected by Cloud Code API)
+export const IDE_TYPE = {
+  UNSPECIFIED: 0,
+  JETSKI: 10,        // Internal codename for Gemini CLI
+  ANTIGRAVITY: 9,
+  PLUGINS: 7
+};
+
+// Platform enum (as specified in Antigravity binary)
+export const PLATFORM = {
+  UNSPECIFIED: 0,
+  DARWIN_AMD64: 1,
+  DARWIN_ARM64: 2,
+  LINUX_AMD64: 3,
+  LINUX_ARM64: 4,
+  WINDOWS_AMD64: 5
+};
+
+// Plugin type enum (as specified in Antigravity binary)
+export const PLUGIN_TYPE = {
+  UNSPECIFIED: 0,
+  CLOUD_CODE: 1,
+  GEMINI: 2
+};
+
+/**
+ * Get the platform enum value based on the current OS.
+ * @returns {number} Platform enum value
+ */
+export function getPlatformEnum() {
+  const os = platform();
+  const architecture = arch();
+
+  if (os === "darwin") {
+    return architecture === "arm64" ? PLATFORM.DARWIN_ARM64 : PLATFORM.DARWIN_AMD64;
+  } else if (os === "linux") {
+    return architecture === "arm64" ? PLATFORM.LINUX_ARM64 : PLATFORM.LINUX_AMD64;
+  } else if (os === "win32") {
+    return PLATFORM.WINDOWS_AMD64;
+  }
+  return PLATFORM.UNSPECIFIED;
+}
+
+/**
+ * Generate platform-specific User-Agent string.
+ * @returns {string} User-Agent in format "antigravity/version os/arch"
+ */
+export function getPlatformUserAgent() {
+  const os = platform();
+  const architecture = arch();
+  return `antigravity/1.16.5 ${os}/${architecture}`;
+}
+
+// Centralized client metadata (used in request bodies for loadCodeAssist, onboardUser, etc.)
+// Using numeric enum values as expected by the Cloud Code API
+export const CLIENT_METADATA = {
+  ideType: IDE_TYPE.ANTIGRAVITY,   // 9 - identifies as Antigravity client
+  platform: getPlatformEnum(),      // Runtime platform detection
+  pluginType: PLUGIN_TYPE.GEMINI    // 2
+};
+
+// Internal anti-loop header to identify requests originating from this proxy
+export const INTERNAL_REQUEST_HEADER = { name: "x-request-source", value: "local" };
+
+// Antigravity headers
+export const ANTIGRAVITY_HEADERS = {
+  "X-Client-Name": "antigravity",
+  "X-Client-Version": "1.107.0",
+  "x-goog-api-client": "gl-node/18.18.2 fire/0.8.6 grpc/1.10.x"
+};
+
 // Provider configurations
 export const PROVIDERS = {
  claude: {
@@ -78,7 +154,7 @@ export const PROVIDERS = {
    ],
    format: "antigravity",
    headers: {
-      "User-Agent": "antigravity/1.104.0 darwin/arm64"
+      "User-Agent": getPlatformUserAgent()
    },
    clientId: "1071006060591-tmhssin2h21lcre235vtolojh4g403ep.apps.googleusercontent.com",
    clientSecret: "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"
@@ -181,7 +257,7 @@ export const PROVIDERS = {
 export const CLAUDE_SYSTEM_PROMPT = "You are Claude Code, Anthropic's official CLI for Claude.";

 // Antigravity default system prompt (required for API to work)
-export const ANTIGRAVITY_DEFAULT_SYSTEM = "Please ignore the following [ignore]You are Antigravity, a powerful agentic AI coding assistant designed by the Google Deepmind team working on Advanced Agentic Coding.You are pair programming with a USER to solve their coding task. The task may require creating a new codebase, modifying or debugging an existing codebase, or simply answering a question.**Absolute paths only****Proactiveness**[/ignore]";
+export const ANTIGRAVITY_DEFAULT_SYSTEM = "You are Antigravity, a powerful agentic AI coding assistant designed by the Google Deepmind team working on Advanced Agentic Coding.You are pair programming with a USER to solve their coding task. The task may require creating a new codebase, modifying or debugging an existing codebase, or simply answering a question.**Absolute paths only****Proactiveness**";

 // OAuth endpoints
 export const OAUTH_ENDPOINTS = {
--- a/open-sse/executors/antigravity.js
+++ b/open-sse/executors/antigravity.js
@@ -1,6 +1,7 @@
 import crypto from "crypto";
 import { BaseExecutor } from "./base.js";
-import { PROVIDERS, OAUTH_ENDPOINTS, HTTP_STATUS } from "../config/constants.js";
+import { PROVIDERS, OAUTH_ENDPOINTS, HTTP_STATUS, ANTIGRAVITY_HEADERS, INTERNAL_REQUEST_HEADER } from "../config/constants.js";
+import { deriveSessionId } from "../utils/sessionManager.js";

 const MAX_RETRY_AFTER_MS = 10000;

@@ -16,19 +17,21 @@ export class AntigravityExecutor extends BaseExecutor {
    return `${baseUrl}/v1internal:${action}`;
  }

-  buildHeaders(credentials, stream = true) {
+  buildHeaders(credentials, stream = true, sessionId = null) {
    return {
      "Content-Type": "application/json",
      "Authorization": `Bearer ${credentials.accessToken}`,
      "User-Agent": this.config.headers?.["User-Agent"] || "antigravity/1.104.0 darwin/arm64",
-      "X-9Router-Source": "9router",
+      [INTERNAL_REQUEST_HEADER.name]: INTERNAL_REQUEST_HEADER.value,
+      ...ANTIGRAVITY_HEADERS,
+      ...(sessionId && { "X-Machine-Session-Id": sessionId }),
      ...(stream && { "Accept": "text/event-stream" })
    };
  }

  transformRequest(model, body, stream, credentials) {
    const projectId = credentials?.projectId || this.generateProjectId();
-    
+
    // Fix contents for Claude models via Antigravity
    const contents = body.request?.contents?.map(c => {
      let role = c.role;
@@ -51,13 +54,13 @@ export class AntigravityExecutor extends BaseExecutor {
    const transformedRequest = {
      ...body.request,
      ...(contents && { contents }),
-      sessionId: body.request?.sessionId || this.generateSessionId(),
+      sessionId: body.request?.sessionId || deriveSessionId(credentials?.email || credentials?.connectionId),
      safetySettings: undefined,
-      toolConfig: body.request?.tools?.length > 0 
+      toolConfig: body.request?.tools?.length > 0
        ? { functionCallingConfig: { mode: "VALIDATED" } }
        : body.request?.toolConfig
    };
-    
+
    return {
      ...body,
      project: projectId,
@@ -108,7 +111,7 @@ export class AntigravityExecutor extends BaseExecutor {
  }

  generateSessionId() {
-    return `-${Math.floor(Math.random() * 9_000_000_000_000_000_000)}`;
+    return crypto.randomUUID() + Date.now().toString();
  }

  parseRetryHeaders(headers) {
@@ -118,7 +121,7 @@ export class AntigravityExecutor extends BaseExecutor {
    if (retryAfter) {
      const seconds = parseInt(retryAfter, 10);
      if (!isNaN(seconds) && seconds > 0) return seconds * 1000;
-      
+
      const date = new Date(retryAfter);
      if (!isNaN(date.getTime())) {
        const diff = date.getTime() - Date.now();
@@ -167,9 +170,10 @@ export class AntigravityExecutor extends BaseExecutor {

    for (let urlIndex = 0; urlIndex < fallbackCount; urlIndex++) {
      const url = this.buildUrl(model, stream, urlIndex);
-      const headers = this.buildHeaders(credentials, stream);
      const transformedBody = this.transformRequest(model, body, stream, credentials);
-      
+      const sessionId = transformedBody.request?.sessionId;
+      const headers = this.buildHeaders(credentials, stream, sessionId);
+
      // Initialize retry counter for this URL
      if (!retryAttemptsByUrl[urlIndex]) {
        retryAttemptsByUrl[urlIndex] = 0;
@@ -200,7 +204,7 @@ export class AntigravityExecutor extends BaseExecutor {
          }

          if (retryMs && retryMs <= MAX_RETRY_AFTER_MS) {
-            log?.debug?.("RETRY", `${response.status} with Retry-After: ${Math.ceil(retryMs/1000)}s, waiting...`);
+            log?.debug?.("RETRY", `${response.status} with Retry-After: ${Math.ceil(retryMs / 1000)}s, waiting...`);
            await new Promise(resolve => setTimeout(resolve, retryMs));
            urlIndex--;
            continue;
@@ -211,15 +215,15 @@ export class AntigravityExecutor extends BaseExecutor {
            retryAttemptsByUrl[urlIndex]++;
            // Exponential backoff: 2s, 4s, 8s...
            const backoffMs = Math.min(1000 * (2 ** retryAttemptsByUrl[urlIndex]), MAX_RETRY_AFTER_MS);
-            log?.debug?.("RETRY", `429 auto retry ${retryAttemptsByUrl[urlIndex]}/${MAX_AUTO_RETRIES} after ${backoffMs/1000}s`);
+            log?.debug?.("RETRY", `429 auto retry ${retryAttemptsByUrl[urlIndex]}/${MAX_AUTO_RETRIES} after ${backoffMs / 1000}s`);
            await new Promise(resolve => setTimeout(resolve, backoffMs));
            urlIndex--;
            continue;
          }

-          log?.debug?.("RETRY", `${response.status}, Retry-After ${retryMs ? `too long (${Math.ceil(retryMs/1000)}s)` : 'missing'}, trying fallback`);
+          log?.debug?.("RETRY", `${response.status}, Retry-After ${retryMs ? `too long (${Math.ceil(retryMs / 1000)}s)` : 'missing'}, trying fallback`);
          lastStatus = response.status;
-          
+
          if (urlIndex + 1 < fallbackCount) {
            continue;
          }
--- a/open-sse/services/usage.js
+++ b/open-sse/services/usage.js
@@ -2,6 +2,8 @@
 * Usage Fetcher - Get usage data from provider APIs
 */

+import { CLIENT_METADATA, getPlatformUserAgent } from "../config/constants.js";
+
 // GitHub API config
 const GITHUB_CONFIG = {
  apiVersion: "2022-11-28",
@@ -15,7 +17,7 @@ const ANTIGRAVITY_CONFIG = {
  tokenUrl: "https://oauth2.googleapis.com/token",
  clientId: "1071006060591-tmhssin2h21lcre235vtolojh4g403ep.apps.googleusercontent.com",
  clientSecret: "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",
-  userAgent: "antigravity/1.11.3 Darwin/arm64",
+  userAgent: getPlatformUserAgent(),
 };

 // Codex (OpenAI) API config
@@ -65,23 +67,23 @@ export async function getUsageForProvider(connection) {
 */
 function parseResetTime(resetValue) {
  if (!resetValue) return null;
-  
+
  try {
    // If it's already a Date object
    if (resetValue instanceof Date) {
      return resetValue.toISOString();
    }
-    
+
    // If it's a number (Unix timestamp in milliseconds)
    if (typeof resetValue === 'number') {
      return new Date(resetValue).toISOString();
    }
-    
+
    // If it's a string (ISO date or any parseable date string)
    if (typeof resetValue === 'string') {
      return new Date(resetValue).toISOString();
    }
-    
+
    return null;
  } catch (error) {
    console.warn(`Failed to parse reset time: ${resetValue}`, error);
@@ -98,7 +100,7 @@ async function getGitHubUsage(accessToken, providerSpecificData) {
    if (!accessToken) {
      throw new Error("No GitHub access token available. Please re-authorize the connection.");
    }
-    
+
    // copilot_internal/user API requires GitHub OAuth token, not copilotToken
    const response = await fetch("https://api.github.com/copilot_internal/user", {
      headers: {
@@ -123,7 +125,7 @@ async function getGitHubUsage(accessToken, providerSpecificData) {
      // Paid plan format
      const snapshots = data.quota_snapshots;
      const resetAt = parseResetTime(data.quota_reset_date);
-      
+
      return {
        plan: data.copilot_plan,
        resetDate: data.quota_reset_date,
@@ -138,7 +140,7 @@ async function getGitHubUsage(accessToken, providerSpecificData) {
      const monthlyQuotas = data.monthly_quotas || {};
      const usedQuotas = data.limited_user_quotas || {};
      const resetAt = parseResetTime(data.limited_user_reset_date);
-      
+
      return {
        plan: data.copilot_plan || data.access_type_sku,
        resetDate: data.limited_user_reset_date,
@@ -167,7 +169,7 @@ async function getGitHubUsage(accessToken, providerSpecificData) {

 function formatGitHubQuotaSnapshot(quota) {
  if (!quota) return { used: 0, total: 0, unlimited: true };
-  
+
  return {
    used: quota.entitlement - quota.remaining,
    total: quota.entitlement,
@@ -211,7 +213,7 @@ async function getAntigravityUsage(accessToken, providerSpecificData) {
  try {
    // First get project ID from subscription info
    const projectId = await getAntigravityProjectId(accessToken);
-    
+
    // Fetch quota data
    const response = await fetch(ANTIGRAVITY_CONFIG.quotaApiUrl, {
      method: "POST",
@@ -220,7 +222,11 @@ async function getAntigravityUsage(accessToken, providerSpecificData) {
        "User-Agent": ANTIGRAVITY_CONFIG.userAgent,
        "Content-Type": "application/json",
      },
-      body: JSON.stringify(projectId ? { project: projectId } : {}),
+      body: JSON.stringify({
+        ...(projectId ? { project: projectId } : {}),
+        metadata: CLIENT_METADATA,
+        mode: 1
+      }),
    });

    if (response.status === 403) {
@@ -233,7 +239,7 @@ async function getAntigravityUsage(accessToken, providerSpecificData) {

    const data = await response.json();
    const quotas = {};
-    
+
    // Parse model quotas (inspired by vscode-antigravity-cockpit)
    if (data.models) {
      // Filter only recommended/important models (must match PROVIDER_MODELS ag ids)
@@ -248,26 +254,26 @@ async function getAntigravityUsage(accessToken, providerSpecificData) {
        'gemini-3-flash',
        'gemini-2.5-flash',
      ];
-      
+
      for (const [modelKey, info] of Object.entries(data.models)) {
        // Skip models without quota info
        if (!info.quotaInfo) {
          continue;
        }
-        
+
        // Skip internal models and non-important models
        if (info.isInternal || !importantModels.includes(modelKey)) {
          continue;
        }
-        
+
        const remainingFraction = info.quotaInfo.remainingFraction || 0;
        const remainingPercentage = remainingFraction * 100;
-        
+
        // Convert percentage to used/total for UI compatibility
        const total = 1000; // Normalized base
        const remaining = Math.round(total * remainingFraction);
        const used = total - remaining;
-        
+
        // Use modelKey as key (matches PROVIDER_MODELS id)
        quotas[modelKey] = {
          used,
@@ -317,7 +323,7 @@ async function getAntigravitySubscriptionInfo(accessToken) {
        "User-Agent": ANTIGRAVITY_CONFIG.userAgent,
        "Content-Type": "application/json",
      },
-      body: JSON.stringify({ metadata: { ideType: "ANTIGRAVITY" } }),
+      body: JSON.stringify({ metadata: CLIENT_METADATA, mode: 1 }),
    });

    if (!response.ok) return null;
@@ -345,7 +351,7 @@ async function getClaudeUsage(accessToken) {

    if (settingsResponse.ok) {
      const settings = await settingsResponse.json();
-      
+
      // Try usage endpoint if we have org info
      if (settings.organization_id) {
        const usageResponse = await fetch(
@@ -402,7 +408,7 @@ async function getCodexUsage(accessToken) {
    }

    const data = await response.json();
-    
+
    // Parse rate limit info
    const rateLimit = data.rate_limit || {};
    const primaryWindow = rateLimit.primary_window || {};
@@ -475,7 +481,7 @@ async function getKiroUsage(accessToken, providerSpecificData) {
    // Parse usage data from usageBreakdownList
    const usageList = data.usageBreakdownList || [];
    const quotaInfo = {};
-    
+
    // Parse reset time - supports multiple formats (nextDateReset, resetDate, etc.)
    const resetAt = parseResetTime(data.nextDateReset || data.resetDate);

@@ -483,7 +489,7 @@ async function getKiroUsage(accessToken, providerSpecificData) {
      const resourceType = breakdown.resourceType?.toLowerCase() || "unknown";
      const used = breakdown.currentUsageWithPrecision || 0;
      const total = breakdown.usageLimitWithPrecision || 0;
-      
+
      quotaInfo[resourceType] = {
        used,
        total,
@@ -496,7 +502,7 @@ async function getKiroUsage(accessToken, providerSpecificData) {
      if (breakdown.freeTrialInfo) {
        const freeUsed = breakdown.freeTrialInfo.currentUsageWithPrecision || 0;
        const freeTotal = breakdown.freeTrialInfo.usageLimitWithPrecision || 0;
-        
+
        quotaInfo[`${resourceType}_freetrial`] = {
          used: freeUsed,
          total: freeTotal,
--- a/open-sse/translator/helpers/geminiHelper.js
+++ b/open-sse/translator/helpers/geminiHelper.js
@@ -35,7 +35,7 @@ export const DEFAULT_SAFETY_SETTINGS = [
 // Convert OpenAI content to Gemini parts
 export function convertOpenAIContentToParts(content) {
  const parts = [];
-  
+
  if (typeof content === "string") {
    parts.push({ text: content });
  } else if (Array.isArray(content)) {
@@ -57,7 +57,7 @@ export function convertOpenAIContentToParts(content) {
      }
    }
  }
-  
+
  return parts;
 }

@@ -85,9 +85,9 @@ export function generateRequestId() {
  return `agent-${crypto.randomUUID()}`;
 }

-// Generate session ID
+// Generate session ID (binary-compatible format: UUID + timestamp)
 export function generateSessionId() {
-  return `-${Math.floor(Math.random() * 9000000000000000000)}`;
+  return crypto.randomUUID() + Date.now().toString();
 }

 // Generate project ID
@@ -102,7 +102,7 @@ export function generateProjectId() {
 // Helper: Remove unsupported keywords recursively from object/array
 function removeUnsupportedKeywords(obj, keywords) {
  if (!obj || typeof obj !== "object") return;
-  
+
  if (Array.isArray(obj)) {
    for (const item of obj) {
      removeUnsupportedKeywords(item, keywords);
@@ -126,12 +126,12 @@ function removeUnsupportedKeywords(obj, keywords) {
 // Convert const to enum
 function convertConstToEnum(obj) {
  if (!obj || typeof obj !== "object") return;
-  
+
  if (obj.const !== undefined && !obj.enum) {
    obj.enum = [obj.const];
    delete obj.const;
  }
-  
+
  for (const value of Object.values(obj)) {
    if (value && typeof value === "object") {
      convertConstToEnum(value);
@@ -142,11 +142,11 @@ function convertConstToEnum(obj) {
 // Convert enum values to strings (Gemini requires string enum values)
 function convertEnumValuesToStrings(obj) {
  if (!obj || typeof obj !== "object") return;
-  
+
  if (obj.enum && Array.isArray(obj.enum)) {
    obj.enum = obj.enum.map(v => String(v));
  }
-  
+
  for (const value of Object.values(obj)) {
    if (value && typeof value === "object") {
      convertEnumValuesToStrings(value);
@@ -157,10 +157,10 @@ function convertEnumValuesToStrings(obj) {
 // Merge allOf schemas
 function mergeAllOf(obj) {
  if (!obj || typeof obj !== "object") return;
-  
+
  if (obj.allOf && Array.isArray(obj.allOf)) {
    const merged = {};
-    
+
    for (const item of obj.allOf) {
      if (item.properties) {
        if (!merged.properties) merged.properties = {};
@@ -175,12 +175,12 @@ function mergeAllOf(obj) {
        }
      }
    }
-    
+
    delete obj.allOf;
    if (merged.properties) obj.properties = { ...obj.properties, ...merged.properties };
    if (merged.required) obj.required = [...(obj.required || []), ...merged.required];
  }
-  
+
  for (const value of Object.values(obj)) {
    if (value && typeof value === "object") {
      mergeAllOf(value);
@@ -192,12 +192,12 @@ function mergeAllOf(obj) {
 function selectBest(items) {
  let bestIdx = 0;
  let bestScore = -1;
-  
+
  for (let i = 0; i < items.length; i++) {
    const item = items[i];
    let score = 0;
    const type = item.type;
-    
+
    if (type === "object" || item.properties) {
      score = 3;
    } else if (type === "array" || item.items) {
@@ -205,20 +205,20 @@ function selectBest(items) {
    } else if (type && type !== "null") {
      score = 1;
    }
-    
+
    if (score > bestScore) {
      bestScore = score;
      bestIdx = i;
    }
  }
-  
+
  return bestIdx;
 }

 // Flatten anyOf/oneOf
 function flattenAnyOfOneOf(obj) {
  if (!obj || typeof obj !== "object") return;
-  
+
  if (obj.anyOf && Array.isArray(obj.anyOf) && obj.anyOf.length > 0) {
    const nonNullSchemas = obj.anyOf.filter(s => s && s.type !== "null");
    if (nonNullSchemas.length > 0) {
@@ -228,7 +228,7 @@ function flattenAnyOfOneOf(obj) {
      Object.assign(obj, selected);
    }
  }
-  
+
  if (obj.oneOf && Array.isArray(obj.oneOf) && obj.oneOf.length > 0) {
    const nonNullSchemas = obj.oneOf.filter(s => s && s.type !== "null");
    if (nonNullSchemas.length > 0) {
@@ -238,7 +238,7 @@ function flattenAnyOfOneOf(obj) {
      Object.assign(obj, selected);
    }
  }
-  
+
  for (const value of Object.values(obj)) {
    if (value && typeof value === "object") {
      flattenAnyOfOneOf(value);
@@ -249,12 +249,12 @@ function flattenAnyOfOneOf(obj) {
 // Flatten type arrays
 function flattenTypeArrays(obj) {
  if (!obj || typeof obj !== "object") return;
-  
+
  if (obj.type && Array.isArray(obj.type)) {
    const nonNullTypes = obj.type.filter(t => t !== "null");
    obj.type = nonNullTypes.length > 0 ? nonNullTypes[0] : "string";
  }
-  
+
  for (const value of Object.values(obj)) {
    if (value && typeof value === "object") {
      flattenTypeArrays(value);
@@ -266,28 +266,28 @@ function flattenTypeArrays(obj) {
 // Reference: CLIProxyAPI/internal/util/gemini_schema.go
 export function cleanJSONSchemaForAntigravity(schema) {
  if (!schema || typeof schema !== "object") return schema;
-  
+
  // Mutate directly (schema is only used once per request)
  let cleaned = schema;
-  
+
  // Phase 1: Convert and prepare
  convertConstToEnum(cleaned);
  convertEnumValuesToStrings(cleaned);
-  
+
  // Phase 2: Flatten complex structures
  mergeAllOf(cleaned);
  flattenAnyOfOneOf(cleaned);
  flattenTypeArrays(cleaned);
-  
+
  // Phase 3: Remove all unsupported keywords at ALL levels (including inside arrays)
  removeUnsupportedKeywords(cleaned, UNSUPPORTED_SCHEMA_CONSTRAINTS);
-  
+
  // Phase 4: Cleanup required fields recursively
  function cleanupRequired(obj) {
    if (!obj || typeof obj !== "object") return;
-    
+
    if (obj.required && Array.isArray(obj.required) && obj.properties) {
-      const validRequired = obj.required.filter(field => 
+      const validRequired = obj.required.filter(field =>
        Object.prototype.hasOwnProperty.call(obj.properties, field)
      );
      if (validRequired.length === 0) {
@@ -296,7 +296,7 @@ export function cleanJSONSchemaForAntigravity(schema) {
        obj.required = validRequired;
      }
    }
-    
+
    // Recurse into nested objects
    for (const value of Object.values(obj)) {
      if (value && typeof value === "object") {
@@ -304,13 +304,13 @@ export function cleanJSONSchemaForAntigravity(schema) {
      }
    }
  }
-  
+
  cleanupRequired(cleaned);
-  
+
  // Phase 5: Add placeholder for empty object schemas (Antigravity requirement)
  function addPlaceholders(obj) {
    if (!obj || typeof obj !== "object") return;
-    
+
    if (obj.type === "object") {
      if (!obj.properties || Object.keys(obj.properties).length === 0) {
        obj.properties = {
@@ -322,7 +322,7 @@ export function cleanJSONSchemaForAntigravity(schema) {
        obj.required = ["reason"];
      }
    }
-    
+
    // Recurse into nested objects
    for (const value of Object.values(obj)) {
      if (value && typeof value === "object") {
@@ -330,9 +330,9 @@ export function cleanJSONSchemaForAntigravity(schema) {
      }
    }
  }
-  
+
  addPlaceholders(cleaned);
-  
+
  return cleaned;
 }

--- a/open-sse/translator/request/openai-to-gemini.js
+++ b/open-sse/translator/request/openai-to-gemini.js
@@ -18,6 +18,7 @@ import {
  generateProjectId,
  cleanJSONSchemaForAntigravity
 } from "../helpers/geminiHelper.js";
+import { deriveSessionId } from "../../utils/sessionManager.js";

 // Core: Convert OpenAI request to Gemini format (base for all variants)
 function openaiToGeminiBase(model, body, stream) {
@@ -259,7 +260,7 @@ function wrapInCloudCodeEnvelope(model, geminiCLI, credentials = null, isAntigra
    userAgent: isAntigravity ? "antigravity" : "gemini-cli",
    requestId: isAntigravity ? `agent-${generateUUID()}` : generateRequestId(),
    request: {
-      sessionId: generateSessionId(),
+      sessionId: isAntigravity ? deriveSessionId(credentials?.email || credentials?.connectionId) : generateSessionId(),
      contents: geminiCLI.contents,
      systemInstruction: geminiCLI.systemInstruction,
      generationConfig: geminiCLI.generationConfig,
@@ -272,11 +273,16 @@ function wrapInCloudCodeEnvelope(model, geminiCLI, credentials = null, isAntigra
    envelope.requestType = "agent";

    // Inject required default system prompt for Antigravity
-    const defaultPart = { text: ANTIGRAVITY_DEFAULT_SYSTEM };
+    // 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(defaultPart);
+      envelope.request.systemInstruction.parts.unshift(...systemParts);
    } else {
-      envelope.request.systemInstruction = { role: "user", parts: [defaultPart] };
+      envelope.request.systemInstruction = { role: "user", parts: systemParts };
    }

    // Add toolConfig for Antigravity
@@ -304,7 +310,7 @@ function wrapInCloudCodeEnvelopeForClaude(model, claudeRequest, credentials = nu
    requestId: `agent-${generateUUID()}`,
    requestType: "agent",
    request: {
-      sessionId: generateSessionId(),
+      sessionId: deriveSessionId(credentials?.email || credentials?.connectionId),
      contents: [],
      generationConfig: {
        temperature: claudeRequest.temperature || 1,
@@ -378,9 +384,11 @@ function wrapInCloudCodeEnvelopeForClaude(model, claudeRequest, credentials = nu
    }
  }

-  // Add system instruction (Antigravity default)
-  const defaultPart = { text: ANTIGRAVITY_DEFAULT_SYSTEM };
-  const systemParts = [defaultPart];
+  // Add system instruction (Antigravity default - double injection)
+  const systemParts = [
+    { text: ANTIGRAVITY_DEFAULT_SYSTEM },
+    { text: `Please ignore the following [ignore]${ANTIGRAVITY_DEFAULT_SYSTEM}[/ignore]` }
+  ];

  if (claudeRequest.system) {
    if (Array.isArray(claudeRequest.system)) {
--- a/open-sse/utils/sessionManager.js
+++ b/open-sse/utils/sessionManager.js
@@ -0,0 +1,66 @@
+/**
+ * Session Manager for Antigravity Cloud Code
+ *
+ * Handles session ID generation and caching for prompt caching continuity.
+ * Mimics the Antigravity binary behavior: generates a session ID at startup
+ * and keeps it for the process lifetime, scoped per account/connection.
+ *
+ * Reference: antigravity-claude-proxy/src/cloudcode/session-manager.js
+ */
+
+import crypto from "crypto";
+
+// Runtime storage for session IDs (per connection/account)
+// Key: connectionId (email or identifier), Value: sessionId
+const runtimeSessionStore = new Map();
+
+/**
+ * Get or create a session ID for the given connection.
+ *
+ * The binary generates a session ID once at startup: `rs() + Date.now()`.
+ * Since 9router is long-running, we simulate this "per-launch" behavior by
+ * storing a generated ID in memory for each connection.
+ *
+ * - If 9router restarts, the ID changes (matching binary restart behavior).
+ * - Within a running instance, the ID is stable for that connection.
+ * - This enables prompt caching while using the EXACT random logic of the binary.
+ *
+ * @param {string} connectionId - The connection identifier (email or unique ID)
+ * @returns {string} A stable session ID string matching binary format
+ */
+export function deriveSessionId(connectionId) {
+    if (!connectionId) {
+        // Fallback for requests without a connection identifier
+        return generateBinaryStyleId();
+    }
+
+    // Check if we already have a session ID for this connection in this process run
+    if (runtimeSessionStore.has(connectionId)) {
+        return runtimeSessionStore.get(connectionId);
+    }
+
+    // Generate a new ID using the binary's exact logic
+    const newSessionId = generateBinaryStyleId();
+
+    // Store it for future requests from this connection
+    runtimeSessionStore.set(connectionId, newSessionId);
+
+    return newSessionId;
+}
+
+/**
+ * Generate a Session ID using the binary's exact logic.
+ * Format: `rs() + Date.now()` where `rs()` is randomUUID
+ *
+ * @returns {string} A session ID in binary format
+ */
+export function generateBinaryStyleId() {
+    return crypto.randomUUID() + Date.now().toString();
+}
+
+/**
+ * Clears all session IDs (e.g. useful for testing or explicit reset)
+ */
+export function clearSessionStore() {
+    runtimeSessionStore.clear();
+}
--- a/src/lib/oauth/constants/oauth.js
+++ b/src/lib/oauth/constants/oauth.js
@@ -1,6 +1,20 @@
 /**
 * OAuth Configuration Constants
 */
+import { platform, arch } from "os";
+
+/**
+ * Get the platform enum value based on the current OS.
+ * Matches Antigravity binary's ClientMetadata.Platform enum.
+ */
+function getOAuthPlatformEnum() {
+  const os = platform();
+  const architecture = arch();
+  if (os === "darwin") return architecture === "arm64" ? 2 : 1;
+  if (os === "linux") return architecture === "arm64" ? 4 : 3;
+  if (os === "win32") return 5;
+  return 0;
+}

 // Claude OAuth Configuration (Authorization Code Flow with PKCE)
 export const CLAUDE_CONFIG = {
@@ -83,9 +97,17 @@ export const ANTIGRAVITY_CONFIG = {
  onboardUserEndpoint: "https://cloudcode-pa.googleapis.com/v1internal:onboardUser",
  loadCodeAssistUserAgent: "google-api-nodejs-client/9.15.1",
  loadCodeAssistApiClient: "google-cloud-sdk vscode_cloudshelleditor/0.1",
-  loadCodeAssistClientMetadata: `{"ideType":"IDE_UNSPECIFIED","platform":"PLATFORM_UNSPECIFIED","pluginType":"GEMINI"}`,
+  loadCodeAssistClientMetadata: JSON.stringify({ ideType: 9, platform: getOAuthPlatformEnum(), pluginType: 2 }),
 };

+/**
+ * Get client metadata using numeric enum values for API calls.
+ * @returns {{ ideType: number, platform: number, pluginType: number }}
+ */
+export function getOAuthClientMetadata() {
+  return { ideType: 9, platform: getOAuthPlatformEnum(), pluginType: 2 };
+}
+
 // OpenAI OAuth Configuration (Authorization Code Flow with PKCE)
 export const OPENAI_CONFIG = {
  clientId: "app_EMoamEEZ73f0CkXaXp7hrann",
--- a/src/lib/oauth/providers.js
+++ b/src/lib/oauth/providers.js
@@ -14,6 +14,7 @@ import {
  GITHUB_CONFIG,
  KIRO_CONFIG,
  CURSOR_CONFIG,
+  getOAuthClientMetadata,
 } from "./constants/oauth";

 // Provider configurations
@@ -184,7 +185,8 @@ const PROVIDERS = {
              "Content-Type": "application/json",
            },
            body: JSON.stringify({
-              metadata: { ideType: "IDE_UNSPECIFIED", platform: "PLATFORM_UNSPECIFIED", pluginType: "GEMINI" },
+              metadata: getOAuthClientMetadata(),
+              mode: 1,
            }),
          }
        );
@@ -254,7 +256,7 @@ const PROVIDERS = {
        "X-Goog-Api-Client": ANTIGRAVITY_CONFIG.loadCodeAssistApiClient,
        "Client-Metadata": ANTIGRAVITY_CONFIG.loadCodeAssistClientMetadata,
      };
-      const metadata = { ideType: "IDE_UNSPECIFIED", platform: "PLATFORM_UNSPECIFIED", pluginType: "GEMINI" };
+      const metadata = getOAuthClientMetadata();

      // Fetch user info
      const userInfoRes = await fetch(`${ANTIGRAVITY_CONFIG.userInfoUrl}?alt=json`, {
@@ -269,7 +271,7 @@ const PROVIDERS = {
        const loadRes = await fetch(ANTIGRAVITY_CONFIG.loadCodeAssistEndpoint, {
          method: "POST",
          headers,
-          body: JSON.stringify({ metadata }),
+          body: JSON.stringify({ metadata, mode: 1 }),
        });
        if (loadRes.ok) {
          const data = await loadRes.json();
@@ -295,7 +297,7 @@ const PROVIDERS = {
            const onboardRes = await fetch(ANTIGRAVITY_CONFIG.onboardUserEndpoint, {
              method: "POST",
              headers,
-              body: JSON.stringify({ tierId, metadata, cloudaicompanionProject: projectId }),
+              body: JSON.stringify({ tierId, metadata, cloudaicompanionProject: projectId, mode: 1 }),
            });
            if (onboardRes.ok) {
              const result = await onboardRes.json();
@@ -727,9 +729,9 @@ export function generateAuthData(providerName, redirectUri) {
 */
 export async function exchangeTokens(providerName, code, redirectUri, codeVerifier, state) {
  const provider = getProvider(providerName);
-  
+
  const tokens = await provider.exchangeToken(provider.config, code, redirectUri, codeVerifier, state);
-  
+
  let extra = null;
  if (provider.postExchange) {
    extra = await provider.postExchange(tokens);
@@ -761,9 +763,9 @@ export async function pollForToken(providerName, deviceCode, codeVerifier, extra
  if (provider.flowType !== "device_code") {
    throw new Error(`Provider ${providerName} does not support device code flow`);
  }
-  
+
  const result = await provider.pollToken(provider.config, deviceCode, codeVerifier, extraData);
-  
+
  if (result.ok) {
    // For device code flows, success is only when we have an access token
    if (result.data.access_token) {
@@ -777,23 +779,23 @@ export async function pollForToken(providerName, deviceCode, codeVerifier, extra
      // Check if it's still pending authorization
      if (result.data.error === 'authorization_pending' || result.data.error === 'slow_down') {
        // This is not a failure, just still waiting
-        return { 
-          success: false, 
-          error: result.data.error, 
+        return {
+          success: false,
+          error: result.data.error,
          errorDescription: result.data.error_description || result.data.message,
          pending: result.data.error === 'authorization_pending'
        };
      } else {
        // Actual error
-        return { 
-          success: false, 
-          error: result.data.error || 'no_access_token', 
-          errorDescription: result.data.error_description || result.data.message || 'No access token received' 
+        return {
+          success: false,
+          error: result.data.error || 'no_access_token',
+          errorDescription: result.data.error_description || result.data.message || 'No access token received'
        };
      }
    }
  }
-  
+
  return { success: false, error: result.data.error, errorDescription: result.data.error_description };
 }

--- a/src/lib/oauth/services/antigravity.js
+++ b/src/lib/oauth/services/antigravity.js
@@ -1,4 +1,5 @@
 import crypto from "crypto";
+import { platform, arch } from "os";
 import open from "open";
 import { ANTIGRAVITY_CONFIG } from "../constants/oauth.js";
 import { getServerCredentials } from "../config/index.js";
@@ -92,12 +93,20 @@ export class AntigravityService {

  /**
   * Get metadata object for API calls
+   * Uses numeric enum values matching Antigravity binary specifications
   */
  getMetadata() {
+    const os = platform();
+    const architecture = arch();
+    let platformEnum = 0; // UNSPECIFIED
+    if (os === "darwin") platformEnum = architecture === "arm64" ? 2 : 1;
+    else if (os === "linux") platformEnum = architecture === "arm64" ? 4 : 3;
+    else if (os === "win32") platformEnum = 5;
+
    return {
-      ideType: "IDE_UNSPECIFIED",
-      platform: "PLATFORM_UNSPECIFIED",
-      pluginType: "GEMINI",
+      ideType: 9,        // ANTIGRAVITY
+      platform: platformEnum,
+      pluginType: 2,     // GEMINI
    };
  }

@@ -108,7 +117,7 @@ export class AntigravityService {
    const response = await fetch(this.config.loadCodeAssistEndpoint, {
      method: "POST",
      headers: this.getApiHeaders(accessToken),
-      body: JSON.stringify({ metadata: this.getMetadata() }),
+      body: JSON.stringify({ metadata: this.getMetadata(), mode: 1 }),
    });

    if (!response.ok) {
@@ -117,7 +126,7 @@ export class AntigravityService {
    }

    const data = await response.json();
-    
+
    // Extract project ID
    let projectId = data.cloudaicompanionProject;
    if (typeof projectId === 'object' && projectId !== null && projectId.id) {
@@ -149,6 +158,7 @@ export class AntigravityService {
        tierId,
        metadata: this.getMetadata(),
        cloudaicompanionProject: projectId,
+        mode: 1,
      }),
    });

@@ -166,7 +176,7 @@ export class AntigravityService {
  async completeOnboarding(accessToken, projectId, tierId, maxRetries = 10) {
    for (let i = 0; i < maxRetries; i++) {
      const result = await this.onboardUser(accessToken, projectId, tierId);
-      
+
      if (result.done === true) {
        // Extract final project ID from response
        let finalProjectId = projectId;
@@ -301,7 +311,7 @@ export class AntigravityService {

      // Load Code Assist to get project ID and tier
      const { projectId, tierId } = await this.loadCodeAssist(tokens.access_token);
-      
+
      if (!projectId) {
        throw new Error("No Google Cloud Project found. Please ensure you have a GCP project with Gemini Code Assist enabled.");
      }
--- a/src/lib/oauth/services/gemini.js
+++ b/src/lib/oauth/services/gemini.js
@@ -1,6 +1,6 @@
 import crypto from "crypto";
 import open from "open";
-import { GEMINI_CONFIG } from "../constants/oauth.js";
+import { GEMINI_CONFIG, getOAuthClientMetadata } from "../constants/oauth.js";
 import { getServerCredentials } from "../config/index.js";
 import { startLocalServer } from "../utils/server.js";
 import { spinner as createSpinner } from "../utils/ui.js";
@@ -71,18 +71,11 @@ export class GeminiCLIService {
          "Content-Type": "application/json",
          "User-Agent": "google-api-nodejs-client/9.15.1",
          "X-Goog-Api-Client": "google-cloud-sdk vscode_cloudshelleditor/0.1",
-          "Client-Metadata": JSON.stringify({
-            ideType: "IDE_UNSPECIFIED",
-            platform: "PLATFORM_UNSPECIFIED",
-            pluginType: "GEMINI"
-          })
+          "Client-Metadata": JSON.stringify(getOAuthClientMetadata())
        },
        body: JSON.stringify({
-          metadata: {
-            ideType: "IDE_UNSPECIFIED",
-            platform: "PLATFORM_UNSPECIFIED",
-            pluginType: "GEMINI"
-          }
+          metadata: getOAuthClientMetadata(),
+          mode: 1
        })
      }
    );
@@ -93,7 +86,7 @@ export class GeminiCLIService {
    }

    const data = await response.json();
-    
+
    // Extract project ID
    let projectId = "";
    if (typeof data.cloudaicompanionProject === "string") {
--- a/src/mitm/server.js
+++ b/src/mitm/server.js
@@ -6,6 +6,7 @@ const { promisify } = require("util");
 const os = require("os");

 // Configuration
+const INTERNAL_REQUEST_HEADER = { name: "x-request-source", value: "local" };
 const TARGET_HOST = "daily-cloudcode-pa.googleapis.com";
 const LOCAL_PORT = 443;
 const ROUTER_URL = "http://localhost:20128/v1/chat/completions";
@@ -174,7 +175,7 @@ const server = https.createServer(sslOptions, async (req, res) => {
  if (bodyBuffer.length > 0) saveRequestLog(req.url, bodyBuffer);

  // Anti-loop: requests from 9Router bypass interception
-  if (req.headers["x-9router-source"] === "9router") {
+  if (req.headers[INTERNAL_REQUEST_HEADER.name] === INTERNAL_REQUEST_HEADER.value) {
    return passthrough(req, res, bodyBuffer);
  }