diff --git a/extensions/google-antigravity-auth/index.ts b/extensions/google-antigravity-auth/index.ts
index bd4bf9862..81d6ee9f7 100644
--- a/extensions/google-antigravity-auth/index.ts
+++ b/extensions/google-antigravity-auth/index.ts
@@ -435,3 +435,6 @@ const antigravityPlugin = {
 };
 
 export default antigravityPlugin;
+
+// Re-export refresh function
+export { refreshGoogleAntigravityCredentials } from "./refresh.js";
diff --git a/extensions/google-antigravity-auth/refresh.ts b/extensions/google-antigravity-auth/refresh.ts
new file mode 100644
index 000000000..e012e2d7b
--- /dev/null
+++ b/extensions/google-antigravity-auth/refresh.ts
@@ -0,0 +1,61 @@
+import { existsSync, readFileSync, realpathSync } from "node:fs";
+import { dirname, join } from "node:path";
+
+const GOOGLE_TOKEN_URL = "https://oauth2.googleapis.com/token";
+
+// OAuth constants - decoded from pi-ai's base64 encoded values to stay in sync
+const decode = (s: string) => Buffer.from(s, "base64").toString();
+const CLIENT_ID = decode(
+  "MTA3MTAwNjA2MDU5MS10bWhzc2luMmgyMWxjcmUyMzV2dG9sb2poNGc0MDNlcC5hcHBzLmdvb2dsZXVzZXJjb250ZW50LmNvbQ==",
+);
+const CLIENT_SECRET = decode("R09DU1BYLUs1OEZXUjQ4NkxkTEoxbUxCOHNYQzR6NnFEQWY=");
+
+export type GoogleAntigravityCredentials = {
+  access: string;
+  refresh: string;
+  expires: number;
+};
+
+export async function refreshGoogleAntigravityCredentials(
+  credentials: GoogleAntigravityCredentials,
+): Promise<GoogleAntigravityCredentials> {
+  if (!credentials.refresh?.trim()) {
+    throw new Error("Google Antigravity OAuth refresh token missing; re-authenticate.");
+  }
+
+  const response = await fetch(GOOGLE_TOKEN_URL, {
+    method: "POST",
+    headers: {
+      "Content-Type": "application/x-www-form-urlencoded",
+      Accept: "application/json",
+    },
+    body: new URLSearchParams({
+      grant_type: "refresh_token",
+      refresh_token: credentials.refresh,
+      client_id: CLIENT_ID,
+      client_secret: CLIENT_SECRET,
+    }),
+  });
+
+  if (!response.ok) {
+    const text = await response.text();
+    if (response.status === 400 || response.status === 401) {
+      throw new Error(
+        `Google Antigravity OAuth refresh token expired or invalid. Re-authenticate with \`clawdbot models auth login --provider google-antigravity\`.`,
+      );
+    }
+    throw new Error(`Google Antigravity OAuth refresh failed: ${text || response.statusText}`);
+  }
+
+  const payload = await response.json();
+  if (!payload.access_token || !payload.expires_in) {
+    throw new Error("Google Antigravity OAuth refresh response missing access token.");
+  }
+
+  return {
+    ...credentials,
+    access: payload.access_token,
+    refresh: payload.refresh_token || credentials.refresh,
+    expires: Date.now() + payload.expires_in * 1000,
+  };
+}
diff --git a/extensions/google-gemini-cli-auth/oauth.ts b/extensions/google-gemini-cli-auth/oauth.ts
index 2d923631a..2842c2d38 100644
--- a/extensions/google-gemini-cli-auth/oauth.ts
+++ b/extensions/google-gemini-cli-auth/oauth.ts
@@ -508,6 +508,9 @@ async function pollOperation(
   throw new Error("Operation polling timeout");
 }
 
+// Re-export refresh function
+export { refreshGoogleGeminiCliCredentials } from "./refresh.js";
+
 export async function loginGeminiCliOAuth(ctx: GeminiCliOAuthContext): Promise<GeminiCliOAuthCredentials> {
   const needsManual = shouldUseManualOAuthFlow(ctx.isRemote);
   await ctx.note(
diff --git a/extensions/google-gemini-cli-auth/refresh.ts b/extensions/google-gemini-cli-auth/refresh.ts
new file mode 100644
index 000000000..7cfc0b2b5
--- /dev/null
+++ b/extensions/google-gemini-cli-auth/refresh.ts
@@ -0,0 +1,125 @@
+import { existsSync, readFileSync, realpathSync } from "node:fs";
+import { delimiter, dirname, join } from "node:path";
+
+const GOOGLE_TOKEN_URL = "https://oauth2.googleapis.com/token";
+
+const CLIENT_ID_KEYS = ["CLAWDBOT_GEMINI_OAUTH_CLIENT_ID", "GEMINI_CLI_OAUTH_CLIENT_ID"];
+const CLIENT_SECRET_KEYS = [
+  "CLAWDBOT_GEMINI_OAUTH_CLIENT_SECRET",
+  "GEMINI_CLI_OAUTH_CLIENT_SECRET",
+];
+
+export type GeminiCliOAuthCredentials = {
+  access: string;
+  refresh: string;
+  expires: number;
+  email?: string;
+  projectId: string;
+};
+
+function resolveEnv(keys: string[]): string | undefined {
+  for (const key of keys) {
+    const value = process.env[key]?.trim();
+    if (value) return value;
+  }
+  return undefined;
+}
+
+function findInPath(name: string): string | null {
+  const exts = process.platform === "win32" ? [".cmd", ".bat", ".exe", ""] : [""];
+  const paths = process.env.PATH?.split(delimiter) || [];
+  for (const dir of paths) {
+    for (const ext of exts) {
+      const full = join(dir, name + ext);
+      if (existsSync(full)) return full;
+    }
+  }
+  return null;
+}
+
+function resolveCredentials(): { clientId: string; clientSecret: string | undefined } {
+  const envClientId = resolveEnv(CLIENT_ID_KEYS);
+  const envClientSecret = resolveEnv(CLIENT_SECRET_KEYS);
+  if (envClientId) {
+    return { clientId: envClientId, clientSecret: envClientSecret };
+  }
+
+  // Try to extract from Gemini CLI
+  try {
+    const geminiPath = findInPath("gemini");
+    if (geminiPath) {
+      const resolvedPath = realpathSync(geminiPath);
+      const geminiCliDir = dirname(dirname(resolvedPath));
+      const searchPaths = [
+        join(geminiCliDir, "node_modules", "@google", "gemini-cli-core", "dist", "src", "code_assist", "oauth2.js"),
+        join(geminiCliDir, "node_modules", "@google", "gemini-cli-core", "dist", "code_assist", "oauth2.js"),
+      ];
+      for (const p of searchPaths) {
+        if (existsSync(p)) {
+          const content = readFileSync(p, "utf8");
+          const idMatch = content.match(/(\d+-[a-z0-9]+\.apps\.googleusercontent\.com)/);
+          const secretMatch = content.match(/(GOCSPX-[A-Za-z0-9_-]+)/);
+          if (idMatch && secretMatch) {
+            return { clientId: idMatch[1], clientSecret: secretMatch[1] };
+          }
+        }
+      }
+    }
+  } catch {
+    // Extraction failed
+  }
+
+  throw new Error(
+    "Gemini CLI OAuth credentials not found. Set GEMINI_CLI_OAUTH_CLIENT_ID and GEMINI_CLI_OAUTH_CLIENT_SECRET, or ensure gemini-cli is installed.",
+  );
+}
+
+export async function refreshGoogleGeminiCliCredentials(
+  credentials: GeminiCliOAuthCredentials,
+): Promise<GeminiCliOAuthCredentials> {
+  if (!credentials.refresh?.trim()) {
+    throw new Error("Google Gemini CLI OAuth refresh token missing; re-authenticate.");
+  }
+
+  const { clientId, clientSecret } = resolveCredentials();
+
+  const body = new URLSearchParams({
+    grant_type: "refresh_token",
+    refresh_token: credentials.refresh,
+    client_id: clientId,
+  });
+  if (clientSecret) {
+    body.set("client_secret", clientSecret);
+  }
+
+  const response = await fetch(GOOGLE_TOKEN_URL, {
+    method: "POST",
+    headers: {
+      "Content-Type": "application/x-www-form-urlencoded",
+      Accept: "application/json",
+    },
+    body,
+  });
+
+  if (!response.ok) {
+    const text = await response.text();
+    if (response.status === 400 || response.status === 401) {
+      throw new Error(
+        `Google Gemini CLI OAuth refresh token expired or invalid. Re-authenticate with \`clawdbot models auth login --provider google-gemini-cli\`.`,
+      );
+    }
+    throw new Error(`Google Gemini CLI OAuth refresh failed: ${text || response.statusText}`);
+  }
+
+  const payload = await response.json();
+  if (!payload.access_token || !payload.expires_in) {
+    throw new Error("Google Gemini CLI OAuth refresh response missing access token.");
+  }
+
+  return {
+    ...credentials,
+    access: payload.access_token,
+    refresh: payload.refresh_token || credentials.refresh,
+    expires: Date.now() + payload.expires_in * 1000,
+  };
+}