diff --git a/.changeset/fix-serverless-waituntil-cleanup.md b/.changeset/fix-serverless-waituntil-cleanup.md
new file mode 100644
index 000000000..9b7e6527f
--- /dev/null
+++ b/.changeset/fix-serverless-waituntil-cleanup.md
@@ -0,0 +1,9 @@
+---
+"@voltagent/serverless-hono": patch
+---
+
+fix(serverless-hono): defer waitUntil cleanup to prevent tool crashes in Cloudflare Workers
+
+The `finally` block in `toCloudflareWorker()`, `toVercelEdge()`, and `toDeno()` was calling `cleanup()` immediately when the Response was returned, before streaming and tool execution completed. This cleared the global `___voltagent_wait_until` while tools were still using it, causing crashes with time-consuming tools.
+
+Cleanup is now deferred through the platform's own `waitUntil()` so it runs only after all pending background work has settled.
diff --git a/packages/serverless-hono/src/serverless-provider.ts b/packages/serverless-hono/src/serverless-provider.ts
index 45eee1fcf..daf47242a 100644
--- a/packages/serverless-hono/src/serverless-provider.ts
+++ b/packages/serverless-hono/src/serverless-provider.ts
@@ -3,7 +3,69 @@ import type { Hono } from "hono";
 import { createServerlessApp } from "./app-factory";
 import type { ServerlessConfig, ServerlessRuntime } from "./types";
 import { detectServerlessRuntime } from "./utils/runtime-detection";
-import { withWaitUntil } from "./utils/wait-until-wrapper";
+import { type WaitUntilContext, withWaitUntil } from "./utils/wait-until-wrapper";
+
+type VoltAgentGlobal = typeof globalThis & {
+  ___voltagent_wait_until?: (promise: Promise<unknown>) => void;
+};
+
+/**
+ * Defers the waitUntil cleanup so the global stays alive while streaming and
+ * tool execution are still in progress.
+ *
+ * We wrap the global `___voltagent_wait_until` with a tracking proxy that
+ * records every promise registered by tools and observability exporters.
+ * Cleanup only runs after **all** tracked promises settle, guaranteeing the
+ * global is available for the entire lifetime of the request.
+ *
+ * If the platform context has no `waitUntil` (non-serverless), we fall back
+ * to immediate cleanup.
+ */
+export function deferCleanup(
+  context: WaitUntilContext | null | undefined,
+  cleanup: () => void,
+): void {
+  const waitUntil = context?.waitUntil;
+  if (!waitUntil || typeof waitUntil !== "function") {
+    cleanup();
+    return;
+  }
+
+  try {
+    const tracked: Promise<unknown>[] = [];
+    const originalWaitUntil = waitUntil.bind(context);
+    const globals = globalThis as VoltAgentGlobal;
+
+    // Replace the global with a tracking wrapper so every promise
+    // registered by tools / observability is captured.
+    const currentGlobal = globals.___voltagent_wait_until;
+    if (currentGlobal) {
+      globals.___voltagent_wait_until = (promise: Promise<unknown>) => {
+        tracked.push(promise);
+        originalWaitUntil(promise);
+      };
+    }
+
+    // Schedule cleanup to run only after every tracked promise settles.
+    const cleanupWhenDone = Promise.resolve().then(async () => {
+      // Wait in a loop — new promises may be registered while we wait.
+      let settled = 0;
+      while (settled < tracked.length) {
+        const batch = tracked.slice(settled);
+        await Promise.allSettled(batch);
+        settled += batch.length;
+      }
+      cleanup();
+    });
+
+    originalWaitUntil(cleanupWhenDone);
+  } catch {
+    // waitUntil can throw after the response is committed on some
+    // platforms — fall through to synchronous cleanup.
+    cleanup();
+  }
+}
+
 export class HonoServerlessProvider implements IServerlessProvider {
   private readonly deps: ServerProviderDeps;
   private readonly config?: ServerlessConfig;
@@ -42,14 +104,14 @@ export class HonoServerlessProvider implements IServerlessProvider {
         env: Record<string, unknown>,
         executionCtx: unknown,
       ): Promise<Response> => {
-        const cleanup = withWaitUntil(executionCtx as any);
+        const cleanup = withWaitUntil(executionCtx as WaitUntilContext | undefined);
 
         try {
           await this.ensureEnvironmentTarget(env);
           const app = await this.getApp();
           return await app.fetch(request, env as Record<string, unknown>, executionCtx as any);
         } finally {
-          cleanup();
+          deferCleanup(executionCtx as WaitUntilContext | undefined, cleanup);
         }
       },
     };
@@ -57,28 +119,28 @@ export class HonoServerlessProvider implements IServerlessProvider {
 
   toVercelEdge(): (request: Request, context?: unknown) => Promise<Response> {
     return async (request: Request, context?: unknown) => {
-      const cleanup = withWaitUntil(context as any);
+      const cleanup = withWaitUntil(context as WaitUntilContext | undefined);
 
       try {
         await this.ensureEnvironmentTarget(context as Record<string, unknown> | undefined);
         const app = await this.getApp();
         return await app.fetch(request, context as Record<string, unknown> | undefined);
       } finally {
-        cleanup();
+        deferCleanup(context as WaitUntilContext | undefined, cleanup);
       }
     };
   }
 
   toDeno(): (request: Request, info?: unknown) => Promise<Response> {
     return async (request: Request, info?: unknown) => {
-      const cleanup = withWaitUntil(info as any);
+      const cleanup = withWaitUntil(info as WaitUntilContext | undefined);
 
       try {
         await this.ensureEnvironmentTarget(info as Record<string, unknown> | undefined);
         const app = await this.getApp();
         return await app.fetch(request, info as Record<string, unknown> | undefined);
       } finally {
-        cleanup();
+        deferCleanup(info as WaitUntilContext | undefined, cleanup);
       }
     };
   }
diff --git a/packages/serverless-hono/src/utils/defer-cleanup.spec.ts b/packages/serverless-hono/src/utils/defer-cleanup.spec.ts
new file mode 100644
index 000000000..c892db541
--- /dev/null
+++ b/packages/serverless-hono/src/utils/defer-cleanup.spec.ts
@@ -0,0 +1,158 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { deferCleanup } from "../serverless-provider";
+import type { WaitUntilContext } from "./wait-until-wrapper";
+
+type VoltAgentGlobal = typeof globalThis & {
+  ___voltagent_wait_until?: (promise: Promise<unknown>) => void;
+};
+
+describe("deferCleanup", () => {
+  let originalWaitUntil: ((promise: Promise<unknown>) => void) | undefined;
+
+  beforeEach(() => {
+    const globals = globalThis as VoltAgentGlobal;
+    originalWaitUntil = globals.___voltagent_wait_until;
+  });
+
+  afterEach(() => {
+    const globals = globalThis as VoltAgentGlobal;
+    globals.___voltagent_wait_until = originalWaitUntil;
+  });
+
+  it("should defer cleanup until all tracked promises settle", async () => {
+    const cleanup = vi.fn();
+    const registeredPromises: Promise<unknown>[] = [];
+    const context: WaitUntilContext = {
+      waitUntil: vi.fn((p: Promise<unknown>) => {
+        registeredPromises.push(p);
+      }),
+    };
+
+    // Set up a global so the tracking wrapper can intercept
+    const globals = globalThis as VoltAgentGlobal;
+    globals.___voltagent_wait_until = context.waitUntil?.bind(context);
+
+    // Simulate a background tool promise that takes time
+    let resolveToolPromise!: () => void;
+    const toolPromise = new Promise<void>((r) => {
+      resolveToolPromise = r;
+    });
+
+    deferCleanup(context, cleanup);
+
+    // Simulate tool registering via the global after deferCleanup
+    globals.___voltagent_wait_until?.(toolPromise);
+
+    // cleanup should NOT have run yet — tool is still pending
+    await Promise.resolve(); // flush microtasks
+    expect(cleanup).not.toHaveBeenCalled();
+
+    // Now resolve the tool promise
+    resolveToolPromise();
+    await Promise.allSettled(registeredPromises);
+
+    expect(cleanup).toHaveBeenCalledTimes(1);
+  });
+
+  it("should fall back to synchronous cleanup when context is null", () => {
+    const cleanup = vi.fn();
+
+    deferCleanup(null, cleanup);
+
+    expect(cleanup).toHaveBeenCalledTimes(1);
+  });
+
+  it("should fall back to synchronous cleanup when context is undefined", () => {
+    const cleanup = vi.fn();
+
+    deferCleanup(undefined, cleanup);
+
+    expect(cleanup).toHaveBeenCalledTimes(1);
+  });
+
+  it("should fall back to synchronous cleanup when context has no waitUntil", () => {
+    const cleanup = vi.fn();
+
+    deferCleanup({} as unknown as WaitUntilContext, cleanup);
+
+    expect(cleanup).toHaveBeenCalledTimes(1);
+  });
+
+  it("should fall back to synchronous cleanup when waitUntil throws", () => {
+    const cleanup = vi.fn();
+    const context: WaitUntilContext = {
+      waitUntil: vi.fn(() => {
+        throw new Error("Cannot call waitUntil after response committed");
+      }),
+    };
+
+    deferCleanup(context, cleanup);
+
+    expect(cleanup).toHaveBeenCalledTimes(1);
+  });
+
+  it("should not throw when waitUntil throws", () => {
+    const cleanup = vi.fn();
+    const context: WaitUntilContext = {
+      waitUntil: vi.fn(() => {
+        throw new Error("platform error");
+      }),
+    };
+
+    expect(() => deferCleanup(context, cleanup)).not.toThrow();
+  });
+
+  it("should handle context with non-function waitUntil", () => {
+    const cleanup = vi.fn();
+    const context = { waitUntil: "not a function" } as unknown as WaitUntilContext;
+
+    deferCleanup(context, cleanup);
+
+    expect(cleanup).toHaveBeenCalledTimes(1);
+  });
+
+  it("should handle late-registered promises", async () => {
+    const cleanup = vi.fn();
+    const registeredPromises: Promise<unknown>[] = [];
+    const context: WaitUntilContext = {
+      waitUntil: vi.fn((p: Promise<unknown>) => {
+        registeredPromises.push(p);
+      }),
+    };
+
+    const globals = globalThis as VoltAgentGlobal;
+    globals.___voltagent_wait_until = context.waitUntil?.bind(context);
+
+    let resolveFirst!: () => void;
+    const firstPromise = new Promise<void>((r) => {
+      resolveFirst = r;
+    });
+
+    let resolveSecond!: () => void;
+    const secondPromise = new Promise<void>((r) => {
+      resolveSecond = r;
+    });
+
+    deferCleanup(context, cleanup);
+
+    // Register first background task
+    globals.___voltagent_wait_until?.(firstPromise);
+
+    // Resolve first — but second hasn't been registered yet
+    resolveFirst();
+    await Promise.resolve();
+    await Promise.resolve();
+
+    // Register second task AFTER first settled (late registration)
+    globals.___voltagent_wait_until?.(secondPromise);
+
+    // cleanup should still NOT have run
+    expect(cleanup).not.toHaveBeenCalled();
+
+    // Now resolve second
+    resolveSecond();
+    await Promise.allSettled(registeredPromises);
+
+    expect(cleanup).toHaveBeenCalledTimes(1);
+  });
+});