diff --git a/extensions/google/transport-stream.test.ts b/extensions/google/transport-stream.test.ts
index d85de02bbdf..320c1bf6ee2 100644
--- a/extensions/google/transport-stream.test.ts
+++ b/extensions/google/transport-stream.test.ts
@@ -292,6 +292,7 @@ describe("google transport stream", () => {
   });
 
   afterEach(() => {
+    vi.useRealTimers();
     vi.unstubAllEnvs();
   });
 
@@ -767,6 +768,29 @@ describe("google transport stream", () => {
     expect(tokenFetchMock).not.toHaveBeenCalled();
   });
 
+  it("does not cache google-auth ADC tokens when fallback expiry would exceed Date range", async () => {
+    const tempDir = await mkdtemp(path.join(os.tmpdir(), "openclaw-google-vertex-authlib-expiry-"));
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date(8_640_000_000_000_000));
+    vi.stubEnv("GOOGLE_APPLICATION_CREDENTIALS", "");
+    vi.stubEnv("HOME", path.join(tempDir, "home"));
+    vi.stubEnv("APPDATA", "");
+    googleAuthGetAccessTokenMock
+      .mockResolvedValueOnce("ya29.first-token")
+      .mockResolvedValueOnce("ya29.second-token");
+    const tokenFetchMock = vi.fn();
+
+    await expect(resolveGoogleVertexAuthorizedUserHeaders(tokenFetchMock)).resolves.toEqual({
+      Authorization: "Bearer ya29.first-token",
+    });
+    await expect(resolveGoogleVertexAuthorizedUserHeaders(tokenFetchMock)).resolves.toEqual({
+      Authorization: "Bearer ya29.second-token",
+    });
+
+    expect(googleAuthGetAccessTokenMock).toHaveBeenCalledTimes(2);
+    expect(tokenFetchMock).not.toHaveBeenCalled();
+  });
+
   it("uses google-auth-library bearer auth for Google Vertex credential marker requests", async () => {
     const tempDir = await mkdtemp(path.join(os.tmpdir(), "openclaw-google-vertex-authlib-stream-"));
     vi.stubEnv("GOOGLE_APPLICATION_CREDENTIALS", "");
diff --git a/extensions/google/vertex-adc.ts b/extensions/google/vertex-adc.ts
index 07a5d38ecbb..62399c11aab 100644
--- a/extensions/google/vertex-adc.ts
+++ b/extensions/google/vertex-adc.ts
@@ -2,7 +2,11 @@ import { existsSync, readFileSync } from "node:fs";
 import { readFile } from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
-import { resolveExpiresAtMsFromDurationSeconds } from "openclaw/plugin-sdk/number-runtime";
+import {
+  asDateTimestampMs,
+  resolveExpiresAtMsFromDurationMs,
+  resolveExpiresAtMsFromDurationSeconds,
+} from "openclaw/plugin-sdk/number-runtime";
 import { normalizeOptionalString } from "openclaw/plugin-sdk/string-coerce-runtime";
 
 type GoogleAuthorizedUserCredentials = {
@@ -32,6 +36,7 @@ const GOOGLE_VERTEX_OAUTH_SCOPE = "https://www.googleapis.com/auth/cloud-platfor
 // leaves the gateway.
 const GOOGLE_VERTEX_TOKEN_EXPIRY_BUFFER_MS = 60_000;
 const GOOGLE_VERTEX_DEFAULT_TOKEN_LIFETIME_SECONDS = 3600;
+const GOOGLE_VERTEX_AUTHLIB_TOKEN_CACHE_MS = 5 * 60_000;
 
 let cachedGoogleVertexAuthorizedUserToken: GoogleVertexAuthorizedUserToken | undefined;
 let cachedGoogleAuthClient:
@@ -43,18 +48,36 @@ let cachedGoogleAuthClient:
   | undefined;
 let cachedGoogleVertexAdcToken: GoogleVertexAdcToken | undefined;
 
-function resolveAuthorizedUserTokenExpiresAtMs(value: unknown, nowMs: number): number {
-  if (typeof value === "number" && Number.isFinite(value)) {
-    return (
-      resolveExpiresAtMsFromDurationSeconds(Math.max(1, value), { nowMs }) ??
-      nowMs - GOOGLE_VERTEX_TOKEN_EXPIRY_BUFFER_MS
-    );
+function isGoogleVertexTokenFresh(expiresAtMsRaw: number, nowRaw = Date.now()): boolean {
+  const expiresAtMs = asDateTimestampMs(expiresAtMsRaw);
+  const nowMs = asDateTimestampMs(nowRaw);
+  if (expiresAtMs === undefined || nowMs === undefined) {
+    return false;
   }
-  return (
-    resolveExpiresAtMsFromDurationSeconds(GOOGLE_VERTEX_DEFAULT_TOKEN_LIFETIME_SECONDS, {
-      nowMs,
-    }) ?? nowMs - GOOGLE_VERTEX_TOKEN_EXPIRY_BUFFER_MS
+  const minFreshExpiresAtMs = resolveExpiresAtMsFromDurationMs(
+    GOOGLE_VERTEX_TOKEN_EXPIRY_BUFFER_MS,
+    { nowMs },
   );
+  return minFreshExpiresAtMs !== undefined && expiresAtMs > minFreshExpiresAtMs;
+}
+
+function resolveAuthorizedUserTokenExpiresAtMs(value: unknown, nowRaw: number): number | undefined {
+  const nowMs = asDateTimestampMs(nowRaw);
+  if (nowMs === undefined) {
+    return undefined;
+  }
+  const lifetimeSeconds =
+    typeof value === "number" && Number.isFinite(value)
+      ? Math.max(1, value)
+      : GOOGLE_VERTEX_DEFAULT_TOKEN_LIFETIME_SECONDS;
+  return resolveExpiresAtMsFromDurationSeconds(lifetimeSeconds, { nowMs }) ?? nowMs;
+}
+
+function resolveGoogleAuthLibraryTokenExpiresAtMs(nowRaw = Date.now()): number | undefined {
+  const nowMs = asDateTimestampMs(nowRaw);
+  return nowMs === undefined
+    ? undefined
+    : resolveExpiresAtMsFromDurationMs(GOOGLE_VERTEX_AUTHLIB_TOKEN_CACHE_MS, { nowMs });
 }
 
 export function resetGoogleVertexAuthorizedUserTokenCacheForTest(): void {
@@ -177,7 +200,7 @@ async function refreshGoogleVertexAuthorizedUserAccessToken(params: {
   if (
     cached?.credentialsPath === params.credentialsPath &&
     cached.refreshToken === refreshToken &&
-    cached.expiresAtMs - Date.now() > GOOGLE_VERTEX_TOKEN_EXPIRY_BUFFER_MS
+    isGoogleVertexTokenFresh(cached.expiresAtMs)
   ) {
     return cached.token;
   }
@@ -208,12 +231,15 @@ async function refreshGoogleVertexAuthorizedUserAccessToken(params: {
     throw new Error("Google Vertex ADC token refresh response did not include an access_token.");
   }
   const nowMs = Date.now();
-  cachedGoogleVertexAuthorizedUserToken = {
-    token,
-    expiresAtMs: resolveAuthorizedUserTokenExpiresAtMs(payload?.expires_in, nowMs),
-    credentialsPath: params.credentialsPath,
-    refreshToken,
-  };
+  const expiresAtMs = resolveAuthorizedUserTokenExpiresAtMs(payload?.expires_in, nowMs);
+  if (expiresAtMs !== undefined) {
+    cachedGoogleVertexAuthorizedUserToken = {
+      token,
+      expiresAtMs,
+      credentialsPath: params.credentialsPath,
+      refreshToken,
+    };
+  }
   return token;
 }
 
@@ -238,7 +264,7 @@ async function resolveGoogleVertexAccessTokenViaGoogleAuth(): Promise<string> {
   const auth = await cachedGoogleAuthClient.promise;
 
   const cached = cachedGoogleVertexAdcToken;
-  if (cached && cached.expiresAtMs - Date.now() > GOOGLE_VERTEX_TOKEN_EXPIRY_BUFFER_MS) {
+  if (cached && isGoogleVertexTokenFresh(cached.expiresAtMs)) {
     return cached.token;
   }
 
@@ -255,10 +281,13 @@ async function resolveGoogleVertexAccessTokenViaGoogleAuth(): Promise<string> {
   // `getAccessToken()` return type, so we cache for a conservative 5 minutes.
   // The library itself already refreshes well before its own internal expiry,
   // so this cache is mainly to avoid hot-loop calls into the auth client.
-  cachedGoogleVertexAdcToken = {
-    token: normalized,
-    expiresAtMs: Date.now() + 5 * 60_000,
-  };
+  const expiresAtMs = resolveGoogleAuthLibraryTokenExpiresAtMs();
+  if (expiresAtMs !== undefined) {
+    cachedGoogleVertexAdcToken = {
+      token: normalized,
+      expiresAtMs,
+    };
+  }
   return normalized;
 }