diff --git a/package-lock.json b/package-lock.json
index a6600b8..152e674 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -7,7 +7,9 @@
     "": {
       "name": "cc-gateway",
       "version": "0.1.0",
+      "license": "MIT",
       "dependencies": {
+        "https-proxy-agent": "^9.0.0",
         "yaml": "^2.7.0"
       },
       "devDependencies": {
@@ -468,6 +470,32 @@
         "undici-types": "~6.21.0"
       }
     },
+    "node_modules/agent-base": {
+      "version": "9.0.0",
+      "resolved": "https://registry.npmjs.org/agent-base/-/agent-base-9.0.0.tgz",
+      "integrity": "sha512-TQf59BsZnytt8GdJKLPfUZ54g/iaUL2OWDSFCCvMOhsHduDQxO8xC4PNeyIkVcA5KwL2phPSv0douC0fgWzmnA==",
+      "license": "MIT",
+      "engines": {
+        "node": ">= 20"
+      }
+    },
+    "node_modules/debug": {
+      "version": "4.4.3",
+      "resolved": "https://registry.npmjs.org/debug/-/debug-4.4.3.tgz",
+      "integrity": "sha512-RGwwWnwQvkVfavKVt22FGLw+xYSdzARwm0ru6DhTVA3umU5hZc28V3kO4stgYryrTlLpuvgI9GiijltAjNbcqA==",
+      "license": "MIT",
+      "dependencies": {
+        "ms": "^2.1.3"
+      },
+      "engines": {
+        "node": ">=6.0"
+      },
+      "peerDependenciesMeta": {
+        "supports-color": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/esbuild": {
       "version": "0.27.4",
       "resolved": "https://registry.npmjs.org/esbuild/-/esbuild-0.27.4.tgz",
@@ -538,6 +566,25 @@
         "url": "https://github.com/privatenumber/get-tsconfig?sponsor=1"
       }
     },
+    "node_modules/https-proxy-agent": {
+      "version": "9.0.0",
+      "resolved": "https://registry.npmjs.org/https-proxy-agent/-/https-proxy-agent-9.0.0.tgz",
+      "integrity": "sha512-/MVmHp58WkOypgFhCLk4fzpPcFQvTJ/e6LBI7irpIO2HfxUbpmYoHF+KzipzJpxxzJu7aJNWQ0xojJ/dzV2G5g==",
+      "license": "MIT",
+      "dependencies": {
+        "agent-base": "9.0.0",
+        "debug": "^4.3.4"
+      },
+      "engines": {
+        "node": ">= 20"
+      }
+    },
+    "node_modules/ms": {
+      "version": "2.1.3",
+      "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
+      "integrity": "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==",
+      "license": "MIT"
+    },
     "node_modules/resolve-pkg-maps": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/resolve-pkg-maps/-/resolve-pkg-maps-1.0.0.tgz",
diff --git a/package.json b/package.json
index e92a716..7ab5a41 100644
--- a/package.json
+++ b/package.json
@@ -14,6 +14,7 @@
     "test": "tsx tests/rewriter.test.ts"
   },
   "dependencies": {
+    "https-proxy-agent": "^9.0.0",
     "yaml": "^2.7.0"
   },
   "devDependencies": {
diff --git a/src/config.ts b/src/config.ts
index 34e022b..80f2318 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -17,6 +17,7 @@ export type Config = {
   }
   upstream: {
     url: string
+    proxy?: string
   }
   auth: {
     tokens: TokenEntry[]
diff --git a/src/index.ts b/src/index.ts
index 990a221..ededa4f 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,6 +1,7 @@
 import { loadConfig } from './config.js'
 import { setLogLevel, log } from './logger.js'
 import { initOAuth } from './oauth.js'
+import { initVersion } from './version.js'
 import { startProxy } from './proxy.js'
 
 const configPath = process.argv[2]
@@ -14,6 +15,9 @@ try {
   // Initialize OAuth first - gateway manages the token lifecycle
   await initOAuth(config.oauth.refresh_token)
 
+  // Sync version from npm registry (+ hourly auto-refresh)
+  await initVersion(config)
+
   startProxy(config)
 } catch (err) {
   console.error(`Fatal: ${err instanceof Error ? err.message : err}`)
diff --git a/src/proxy.ts b/src/proxy.ts
index c4ed8a4..6d5dfba 100644
--- a/src/proxy.ts
+++ b/src/proxy.ts
@@ -185,7 +185,7 @@ function buildVerificationPayload(config: Config) {
     system: [
       {
         type: 'text',
-        text: `x-anthropic-billing-header: cc_version=2.1.81.a1b; cc_entrypoint=cli;`,
+        text: `x-anthropic-billing-header: cc_version=${config.env.version}.a1b; cc_entrypoint=cli;`,
       },
       {
         type: 'text',
diff --git a/src/version.ts b/src/version.ts
new file mode 100644
index 0000000..feccfe9
--- /dev/null
+++ b/src/version.ts
@@ -0,0 +1,85 @@
+import { request as httpsRequest } from 'https'
+import { HttpsProxyAgent } from 'https-proxy-agent'
+import type { Config } from './config.js'
+import { log } from './logger.js'
+
+const REGISTRY_URL = 'https://registry.npmjs.org/@anthropic-ai/claude-code'
+const REFRESH_INTERVAL = 60 * 60 * 1000 // 1 hour
+const TIMEOUT = 5_000
+
+type NpmRegistryInfo = {
+  'dist-tags': { latest: string }
+  time: Record<string, string>
+}
+
+function fetchLatestVersion(proxyAgent?: HttpsProxyAgent<string>): Promise<{ version: string; buildTime: string }> {
+  return new Promise((resolve, reject) => {
+    const url = new URL(REGISTRY_URL)
+    const req = httpsRequest(
+      {
+        hostname: url.hostname,
+        port: 443,
+        path: url.pathname,
+        method: 'GET',
+        headers: {
+          'Accept': 'application/vnd.npm.install-v1+json',
+        },
+        timeout: TIMEOUT,
+        ...(proxyAgent ? { agent: proxyAgent } : {}),
+      },
+      (res) => {
+        const chunks: Buffer[] = []
+        res.on('data', (chunk) => chunks.push(chunk))
+        res.on('end', () => {
+          try {
+            const data = JSON.parse(Buffer.concat(chunks).toString('utf-8')) as NpmRegistryInfo
+            const latest = data['dist-tags']?.latest
+            if (!latest) {
+              reject(new Error('No latest version in registry response'))
+              return
+            }
+            const buildTime = data.time?.[latest] || new Date().toISOString()
+            resolve({ version: latest, buildTime })
+          } catch (err) {
+            reject(new Error(`Failed to parse registry response: ${err}`))
+          }
+        })
+      },
+    )
+    req.on('timeout', () => {
+      req.destroy()
+      reject(new Error('Registry request timed out'))
+    })
+    req.on('error', reject)
+    req.end()
+  })
+}
+
+function applyVersion(config: Config, version: string, buildTime: string) {
+  config.env.version = version
+  config.env.version_base = version
+  config.env.build_time = buildTime
+}
+
+async function syncVersion(config: Config, proxyAgent?: HttpsProxyAgent<string>): Promise<void> {
+  try {
+    const { version, buildTime } = await fetchLatestVersion(proxyAgent)
+    const prev = config.env.version
+    applyVersion(config, version, buildTime)
+    if (prev !== version) {
+      log('info', `Version synced: ${prev} -> ${version} (build: ${buildTime})`)
+    } else {
+      log('debug', `Version unchanged: ${version}`)
+    }
+  } catch (err) {
+    log('warn', `Version sync failed, keeping ${config.env.version}: ${err}`)
+  }
+}
+
+export async function initVersion(config: Config): Promise<void> {
+  const proxyAgent = config.upstream.proxy ? new HttpsProxyAgent(config.upstream.proxy) : undefined
+  await syncVersion(config, proxyAgent)
+
+  setInterval(() => syncVersion(config, proxyAgent), REFRESH_INTERVAL)
+  log('info', `Version auto-refresh scheduled every ${REFRESH_INTERVAL / 60000} min`)
+}