diff --git a/open-sse/config/constants.js b/open-sse/config/constants.js
index e22c1b7..738ab0e 100644
--- a/open-sse/config/constants.js
+++ b/open-sse/config/constants.js
@@ -1,5 +1,24 @@
 import { platform, arch } from "os";
 
+function mapStainlessOs() {
+  switch (platform()) {
+    case "darwin": return "MacOS";
+    case "win32": return "Windows";
+    case "linux": return "Linux";
+    case "freebsd": return "FreeBSD";
+    default: return `Other::${platform()}`;
+  }
+}
+
+function mapStainlessArch() {
+  switch (arch()) {
+    case "x64": return "x64";
+    case "arm64": return "arm64";
+    case "ia32": return "x86";
+    default: return `other::${arch()}`;
+  }
+}
+
 // === GitHub Copilot Version Constants ===
 export const GITHUB_COPILOT = {
   VSCODE_VERSION: "1.110.0",
@@ -96,23 +115,23 @@ export const PROVIDERS = {
     format: "claude",
     headers: {
       "Anthropic-Version": "2023-06-01",
-      "Anthropic-Beta": "claude-code-20250219,oauth-2025-04-20,interleaved-thinking-2025-05-14,fine-grained-tool-streaming-2025-05-14,context-management-2025-06-27",
+      "Anthropic-Beta": "claude-code-20250219,oauth-2025-04-20,interleaved-thinking-2025-05-14,fine-grained-tool-streaming-2025-05-14,context-management-2025-06-27,prompt-caching-scope-2026-01-05",
       "Anthropic-Dangerous-Direct-Browser-Access": "true",
-      "User-Agent": "claude-cli/1.0.83 (external, cli)",
+      "User-Agent": "claude-cli/2.1.63 (external, cli)",
       "X-App": "cli",
       "X-Stainless-Helper-Method": "stream",
       "X-Stainless-Retry-Count": "0",
       "X-Stainless-Runtime-Version": "v24.3.0",
-      "X-Stainless-Package-Version": "0.55.1",
+      "X-Stainless-Package-Version": "0.74.0",
       "X-Stainless-Runtime": "node",
       "X-Stainless-Lang": "js",
-      "X-Stainless-Arch": "arm64",
-      "X-Stainless-Os": "MacOS",
-      "X-Stainless-Timeout": "60"
+      "X-Stainless-Arch": mapStainlessArch(),
+      "X-Stainless-Os": mapStainlessOs(),
+      "X-Stainless-Timeout": "600"
     },
     // Claude OAuth configuration
     clientId: "9d1c250a-e61b-44d9-88ed-5944d1962f5e",
-    tokenUrl: "https://console.anthropic.com/v1/oauth/token"
+    tokenUrl: "https://api.anthropic.com/v1/oauth/token"
   },
   gemini: {
     baseUrl: "https://generativelanguage.googleapis.com/v1beta/models",
@@ -376,7 +395,7 @@ export const PROVIDERS = {
 };
 
 // Claude system prompt
-export const CLAUDE_SYSTEM_PROMPT = "You are Claude Code, Anthropic's official CLI for Claude.";
+export const CLAUDE_SYSTEM_PROMPT = "You are a Claude agent, built on Anthropic's Claude Agent SDK.";
 
 // Antigravity default system prompt (required for API to work)
 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**";
@@ -392,8 +411,8 @@ export const OAUTH_ENDPOINTS = {
     auth: "https://auth.openai.com/oauth/authorize"
   },
   anthropic: {
-    token: "https://console.anthropic.com/v1/oauth/token",
-    auth: "https://console.anthropic.com/v1/oauth/authorize"
+    token: "https://api.anthropic.com/v1/oauth/token",
+    auth: "https://api.anthropic.com/v1/oauth/authorize"
   },
   qwen: {
     token: "https://chat.qwen.ai/api/v1/oauth2/token", // From CLIProxyAPI
diff --git a/open-sse/translator/helpers/claudeHelper.js b/open-sse/translator/helpers/claudeHelper.js
index efd8bcc..a06bab0 100644
--- a/open-sse/translator/helpers/claudeHelper.js
+++ b/open-sse/translator/helpers/claudeHelper.js
@@ -1,6 +1,7 @@
 // Claude helper functions for translator
 import { DEFAULT_THINKING_CLAUDE_SIGNATURE } from "../../config/defaultThinkingSignature.js";
 import { adjustMaxTokens } from "./maxTokensHelper.js";
+import { applyCloaking } from "../../utils/claudeCloaking.js";
 
 // Check if message has valid non-empty content
 export function hasValidContent(msg) {
@@ -79,7 +80,8 @@ export function fixToolUseOrdering(messages) {
 // - Filter empty messages
 // - Add thinking block for Anthropic endpoint (provider === "claude")
 // - Fix tool_use/tool_result ordering
-export function prepareClaudeRequest(body, provider = null) {
+// - Apply cloaking (billing header + fake user ID) for OAuth tokens
+export function prepareClaudeRequest(body, provider = null, apiKey = null) {
   // 1. System: remove all cache_control, add only to last block with ttl 1h
   if (body.system && Array.isArray(body.system)) {
     body.system = body.system.map((block, i) => {
@@ -186,6 +188,11 @@ export function prepareClaudeRequest(body, provider = null) {
     }
   }
 
+  // Apply cloaking for OAuth tokens (billing header + fake user ID)
+  if (provider === "claude" && apiKey) {
+    body = applyCloaking(body, apiKey);
+  }
+
   return body;
 }
 
diff --git a/open-sse/translator/index.js b/open-sse/translator/index.js
index 2bf8969..b1309e3 100644
--- a/open-sse/translator/index.js
+++ b/open-sse/translator/index.js
@@ -90,7 +90,8 @@ export function translateRequest(sourceFormat, targetFormat, model, body, stream
 
   // Final step: prepare request for Claude format endpoints
   if (targetFormat === FORMATS.CLAUDE) {
-    result = prepareClaudeRequest(result, provider);
+    const apiKey = credentials?.accessToken || credentials?.apiKey || null;
+    result = prepareClaudeRequest(result, provider, apiKey);
   }
 
   return result;
diff --git a/open-sse/translator/request/openai-to-claude.js b/open-sse/translator/request/openai-to-claude.js
index 05ab08f..e2e9663 100644
--- a/open-sse/translator/request/openai-to-claude.js
+++ b/open-sse/translator/request/openai-to-claude.js
@@ -3,8 +3,9 @@ import { FORMATS } from "../formats.js";
 import { CLAUDE_SYSTEM_PROMPT } from "../../config/constants.js";
 import { adjustMaxTokens } from "../helpers/maxTokensHelper.js";
 
-// Prefix for Claude OAuth tool names to avoid conflicts
-const CLAUDE_OAUTH_TOOL_PREFIX = "proxy_";
+// Empty prefix matches real Claude Code behavior (no tool name prefix).
+// Previously "proxy_" was used but this is a detectable fingerprint difference.
+const CLAUDE_OAUTH_TOOL_PREFIX = "";
 
 // Convert OpenAI request to Claude format
 export function openaiToClaudeRequest(model, body, stream) {
diff --git a/open-sse/utils/claudeCloaking.js b/open-sse/utils/claudeCloaking.js
new file mode 100644
index 0000000..8cb490d
--- /dev/null
+++ b/open-sse/utils/claudeCloaking.js
@@ -0,0 +1,60 @@
+import { createHash, randomBytes } from "crypto";
+
+const CLAUDE_VERSION = "2.1.63";
+
+// Generate billing header matching real Claude Code format:
+// x-anthropic-billing-header: cc_version=<ver>.<build>; cc_entrypoint=cli; cch=<hash>;
+function generateBillingHeader(payload) {
+  const content = JSON.stringify(payload);
+  const cch = createHash("sha256").update(content).digest("hex").slice(0, 5);
+  const buildHash = randomBytes(2).toString("hex").slice(0, 3);
+  return `x-anthropic-billing-header: cc_version=${CLAUDE_VERSION}.${buildHash}; cc_entrypoint=cli; cch=${cch};`;
+}
+
+// Generate a random UUID v4
+function generateFakeUserID() {
+  const bytes = randomBytes(16);
+  bytes[6] = (bytes[6] & 0x0f) | 0x40;
+  bytes[8] = (bytes[8] & 0x3f) | 0x80;
+  const hex = bytes.toString("hex");
+  return `${hex.slice(0,8)}-${hex.slice(8,12)}-${hex.slice(12,16)}-${hex.slice(16,20)}-${hex.slice(20)}`;
+}
+
+/**
+ * Apply Claude cloaking to request body:
+ * 1. Inject billing header as first system block
+ * 2. Inject fake user ID into metadata
+ *
+ * Only applies when using OAuth token (sk-ant-oat).
+ * @param {object} body - Claude API request body
+ * @param {string} apiKey - API key or OAuth token
+ * @returns {object} Modified body
+ */
+export function applyCloaking(body, apiKey) {
+  if (!apiKey || !apiKey.includes("sk-ant-oat")) return body;
+
+  const result = { ...body };
+
+  // Inject billing header as system[0], preserve existing system blocks
+  const billingText = generateBillingHeader(body);
+  const billingBlock = { type: "text", text: billingText };
+
+  if (Array.isArray(result.system)) {
+    // Skip if already injected
+    if (!result.system[0]?.text?.startsWith("x-anthropic-billing-header:")) {
+      result.system = [billingBlock, ...result.system];
+    }
+  } else if (typeof result.system === "string") {
+    result.system = [billingBlock, { type: "text", text: result.system }];
+  } else {
+    result.system = [billingBlock];
+  }
+
+  // Inject fake user ID into metadata
+  const existingUserId = result.metadata?.user_id;
+  if (!existingUserId) {
+    result.metadata = { ...result.metadata, user_id: generateFakeUserID() };
+  }
+
+  return result;
+}
diff --git a/src/lib/oauth/constants/oauth.js b/src/lib/oauth/constants/oauth.js
index 3e52c5d..ee20dd1 100644
--- a/src/lib/oauth/constants/oauth.js
+++ b/src/lib/oauth/constants/oauth.js
@@ -20,7 +20,7 @@ function getOAuthPlatformEnum() {
 export const CLAUDE_CONFIG = {
   clientId: "9d1c250a-e61b-44d9-88ed-5944d1962f5e",
   authorizeUrl: "https://claude.ai/oauth/authorize",
-  tokenUrl: "https://console.anthropic.com/v1/oauth/token",
+  tokenUrl: "https://api.anthropic.com/v1/oauth/token",
   scopes: ["org:create_api_key", "user:profile", "user:inference"],
   codeChallengeMethod: "S256",
 };
diff --git a/src/mitm/server.js b/src/mitm/server.js
index 7f9d52a..e2f774f 100644
--- a/src/mitm/server.js
+++ b/src/mitm/server.js
@@ -140,6 +140,7 @@ async function passthrough(req, res, bodyBuffer) {
 async function intercept(req, res, bodyBuffer, mappedModel) {
   try {
     const body = JSON.parse(bodyBuffer.toString());
+    console.log("🚀 ~ intercept ~ body:", body)
     body.model = mappedModel;
 
     const response = await fetch(ROUTER_URL, {