diff --git a/src/agents/embedded-agent-runner/google-prompt-cache.test.ts b/src/agents/embedded-agent-runner/google-prompt-cache.test.ts
index 5e99f2a9057..f9b87ac8b61 100644
--- a/src/agents/embedded-agent-runner/google-prompt-cache.test.ts
+++ b/src/agents/embedded-agent-runner/google-prompt-cache.test.ts
@@ -385,6 +385,53 @@ describe("google prompt cache", () => {
     expect(getCapturedPayload()?.cachedContent).toBe("cachedContents/system-cache-3");
   });
 
+  it("does not bypass failed-cache backoff when the process clock is invalid", async () => {
+    const systemPromptDigest = crypto.createHash("sha256").update("Follow policy.").digest("hex");
+    const sessionManager = makeSessionManager([
+      {
+        id: "entry-1",
+        parentId: null,
+        timestamp: new Date(1_000).toISOString(),
+        type: "custom",
+        customType: "openclaw.google-prompt-cache",
+        data: {
+          status: "failed",
+          timestamp: 1_000,
+          provider: "google",
+          modelId: "gemini-3.1-pro-preview",
+          modelApi: "google-generative-ai",
+          baseUrl: "https://generativelanguage.googleapis.com/v1beta",
+          systemPromptDigest,
+          cacheRetention: "long",
+          retryAfter: Date.parse("2030-01-01T00:00:00.000Z"),
+        },
+      },
+    ]);
+    const fetchMock = createCacheFetchMock({
+      name: "cachedContents/system-cache-invalid-clock",
+      expireTime: "2030-01-01T00:00:00.000Z",
+    });
+    const innerStreamFn = vi.fn(() => "stream" as never);
+
+    const wrapped = await preparePromptCacheStream({
+      fetchMock,
+      now: Number.NaN,
+      sessionManager,
+      streamFn: innerStreamFn,
+    });
+
+    await Promise.resolve(
+      wrapped?.(
+        makeGoogleModel(),
+        { systemPrompt: "Follow policy.", messages: [] } as never,
+        {} as never,
+      ),
+    );
+
+    expect(fetchMock).not.toHaveBeenCalled();
+    expect(innerStreamFn).toHaveBeenCalledTimes(1);
+  });
+
   it("stays out of the way when cachedContent is already configured explicitly", async () => {
     const fetchMock = vi.fn();
 
diff --git a/src/agents/embedded-agent-runner/google-prompt-cache.ts b/src/agents/embedded-agent-runner/google-prompt-cache.ts
index ec32dbcb6be..273f6ef67c4 100644
--- a/src/agents/embedded-agent-runner/google-prompt-cache.ts
+++ b/src/agents/embedded-agent-runner/google-prompt-cache.ts
@@ -3,6 +3,11 @@ import { parseGeminiAuth } from "../../infra/gemini-auth.js";
 import { normalizeGoogleApiBaseUrl } from "../../infra/google-api-base-url.js";
 import { streamWithPayloadPatch } from "../../llm/providers/stream-wrappers/stream-payload-utils.js";
 import type { Model } from "../../llm/types.js";
+import {
+  asDateTimestampMs,
+  isFutureDateTimestampMs,
+  resolveExpiresAtMsFromDurationMs,
+} from "../../shared/number-coercion.js";
 import { normalizeOptionalString } from "../../shared/string-coerce.js";
 import { buildGuardedModelFetch } from "../provider-transport-fetch.js";
 import type { StreamFn } from "../runtime/index.js";
@@ -185,8 +190,7 @@ function parseExpireTimeMs(expireTime: string | undefined): number | null {
   if (!expireTime) {
     return null;
   }
-  const timestamp = Date.parse(expireTime);
-  return Number.isFinite(timestamp) ? timestamp : null;
+  return asDateTimestampMs(Date.parse(expireTime)) ?? null;
 }
 
 function convertManagedGoogleTools(tools: NonNullable<GooglePromptCacheContext["tools"]>) {
@@ -342,7 +346,10 @@ async function ensureGooglePromptCache(
   deps: GooglePromptCacheDeps,
 ): Promise<string | null> {
   const baseUrl = normalizeGoogleApiBaseUrl(params.model.baseUrl);
-  const now = deps.now?.() ?? Date.now();
+  const now = asDateTimestampMs(deps.now?.() ?? Date.now());
+  if (now === undefined) {
+    return null;
+  }
   const systemPromptDigest = digestSystemPrompt(params.systemPrompt);
   const matchKey = buildGooglePromptCacheMatchKey({
     provider: params.provider,
@@ -354,7 +361,10 @@ async function ensureGooglePromptCache(
   });
   const latestEntry = readLatestGooglePromptCacheEntry(params.sessionManager, matchKey);
 
-  if (latestEntry?.status === "failed" && latestEntry.retryAfter > now) {
+  if (
+    latestEntry?.status === "failed" &&
+    isFutureDateTimestampMs(latestEntry.retryAfter, { nowMs: now })
+  ) {
     return null;
   }
 
@@ -362,7 +372,7 @@ async function ensureGooglePromptCache(
   const refreshWindowMs = resolveGooglePromptCacheRefreshWindowMs(params.cacheRetention);
   if (latestEntry?.status === "ready" && latestEntry.cachedContent) {
     const expiresAt = parseExpireTimeMs(latestEntry.expireTime);
-    const isExpired = expiresAt !== null && expiresAt <= now;
+    const isExpired = expiresAt !== null && !isFutureDateTimestampMs(expiresAt, { nowMs: now });
     if (!isExpired) {
       const needsRefresh = expiresAt !== null && expiresAt - now <= refreshWindowMs;
       if (!needsRefresh) {
@@ -420,7 +430,8 @@ async function ensureGooglePromptCache(
       systemPromptDigest,
       cacheConfigDigest: params.cacheConfigDigest,
       cacheRetention: params.cacheRetention,
-      retryAfter: now + GOOGLE_PROMPT_CACHE_RETRY_BACKOFF_MS,
+      retryAfter:
+        resolveExpiresAtMsFromDurationMs(GOOGLE_PROMPT_CACHE_RETRY_BACKOFF_MS, { nowMs: now }) ?? 0,
     });
     return null;
   }