fix(sveltekit): Resolve the Cloudflare execution context without event.platform (#24241)

`@sveltejs/adapter-cloudflare@8.0.0-next.7` no longer passes `platform`
to SvelteKit (sveltejs/kit#16754), so `initCloudflareSentryHandle` never
initialized the SDK and no events were sent, which broke the
`sveltekit-3-cloudflare-workers` E2E test.

Adds a `workerd` export condition whose entry registers `waitUntil` from
`cloudflare:workers` as the fallback execution context, keeping that
import out of the generic `worker` entry so other bundlers resolving
`worker` stay unaffected.

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

Author: chargome

packages/sveltekit/package.json

@@ -25,6 +25,10 @@
     },
     ".": {
       "types": "./build/types/index.types.d.ts",
+      "workerd": {
+        "import": "./build/esm/index.workerd.js",
+        "require": "./build/cjs/index.workerd.js"
+      },
       "worker": {
         "import": "./build/esm/index.worker.js",
         "require": "./build/cjs/index.worker.js"

packages/sveltekit/rollup.npm.config.mjs

@@ -6,6 +6,7 @@ export default makeNPMConfigVariants(
       'src/index.server.ts',
       'src/index.client.ts',
       'src/index.worker.ts',
+      'src/index.workerd.ts',
       'src/client/index.ts',
       // Browser-tracing variants, kept as standalone entrypoints so the `sentrySvelteKit()` plugin
       // (or the `exports` fallback) can select one per SvelteKit version.
@@ -18,7 +19,7 @@ export default makeNPMConfigVariants(
     packageSpecificConfig: {
       // Keep the variant subpath external so the transpiled output preserves the import for the
       // consumer to resolve (via `exports` or the `sentrySvelteKit()` plugin).
-      external: ['$app/state', '$app/stores', '@sentry/sveltekit/browser-tracing-variant'],
+      external: ['$app/state', '$app/stores', '@sentry/sveltekit/browser-tracing-variant', 'cloudflare:workers'],
       output: {
         dynamicImportInCjs: true,
       },

packages/sveltekit/src/index.workerd.ts

@@ -0,0 +1,14 @@
+import * as cloudflareWorkers from 'cloudflare:workers';
+import { setCloudflareExecutionContextFallback } from './server-common/utils';
+
+// `cloudflare:workers` only resolves in Cloudflare's own bundlers (wrangler, `@cloudflare/vite-plugin`),
+// which all select the `workerd` export condition. Consumers of the generic `worker` condition keep
+// getting `index.worker`, which has no such import and would otherwise fail to bundle.
+//
+// A namespace import keeps a missing `waitUntil` export (runtimes older than August 2025) a missing
+// property instead of a module linking error that would take the whole Worker down.
+setCloudflareExecutionContextFallback(() =>
+  typeof cloudflareWorkers.waitUntil === 'function' ? { waitUntil: cloudflareWorkers.waitUntil } : undefined,
+);
+
+export * from './worker';

packages/sveltekit/src/server-common/utils.ts

@@ -7,16 +7,36 @@ export type MinimalCloudflareExecutionContext = {
   waitUntil(promise: Promise<unknown>): void;
 };
 
+type CloudflareExecutionContextProvider = () => MinimalCloudflareExecutionContext | undefined;
+
+let fallbackExecutionContextProvider: CloudflareExecutionContextProvider | undefined;
+
+/**
+ * Registers where to get the execution context from when `platform` doesn't carry one.
+ *
+ * Since `8.0.0-next.7`, `@sveltejs/adapter-cloudflare` no longer passes a `platform` object to
+ * SvelteKit at all; `waitUntil` is imported from `cloudflare:workers` instead. That module only
+ * resolves under the `workerd` export condition, so the entry point for that condition registers it
+ * here instead of the shared worker code importing it directly.
+ *
+ * @see https://github.com/sveltejs/kit/pull/16754
+ */
+export function setCloudflareExecutionContextFallback(provider: CloudflareExecutionContextProvider | undefined): void {
+  fallbackExecutionContextProvider = provider;
+}
+
 /**
- * Reads the Cloudflare execution context off a SvelteKit `platform` object.
+ * Reads the Cloudflare execution context off a SvelteKit `platform` object, falling back to the
+ * provider registered via `setCloudflareExecutionContextFallback`.
  *
  * The property name differs by adapter version:
  * - `@sveltejs/adapter-cloudflare` <= 7 exposes it as `platform.context`
- * - `@sveltejs/adapter-cloudflare` 8 renamed it to `platform.ctx`
+ * - `@sveltejs/adapter-cloudflare` 8 renamed it to `platform.ctx`, and later prereleases dropped
+ *   `platform` altogether (see the fallback)
  *
- * We read both so that request isolation and `waitUntil`-based flushing keep working across the
- * adapter versions our peer range allows. Both accesses fail silently when the shape changes, so
- * dropping either one costs us events without surfacing an error.
+ * We read all of them so that request isolation and `waitUntil`-based flushing keep working across
+ * the adapter versions our peer range allows. Every access fails silently when the shape changes,
+ * so dropping any of them costs us events without surfacing an error.
  *
  * @see https://github.com/sveltejs/kit/pull/16668
  */
@@ -26,7 +46,7 @@ export function getCloudflareExecutionContext(platform: unknown): MinimalCloudfl
     context?: MinimalCloudflareExecutionContext;
   };
 
-  return ctx ?? context;
+  return ctx ?? context ?? fallbackExecutionContextProvider?.();
 }
 
 /**

packages/sveltekit/src/worker/cloudflare.ts

@@ -34,8 +34,11 @@ export function initCloudflareSentryHandle(options: CloudflareOptions): Handle {
   setAsyncLocalStorageAsyncContextStrategy();
 
   const handleInitSentry: Handle = ({ event, resolve }) => {
-    // if event.platform exists (should be there in a cloudflare worker), then do the cloudflare sentry init
-    if (event.platform) {
+    const context = getCloudflareExecutionContext(event.platform);
+
+    // Either signals a Cloudflare Worker: `event.platform` up to `adapter-cloudflare` 8.0.0-next.6, the
+    // execution context resolved through `cloudflare:workers` (see `index.workerd.ts`) after that.
+    if (event.platform || context) {
       // This is an optional local that the `sentryHandle` handler checks for to avoid double isolation
       // In Cloudflare the `wrapRequestHandler` function already takes care of
       // - request isolation
@@ -46,8 +49,8 @@ export function initCloudflareSentryHandle(options: CloudflareOptions): Handle {
         {
           options: opts,
           request: event.request,
-          // @ts-expect-error This will exist in Cloudflare
-          context: getCloudflareExecutionContext(event.platform),
+          // @ts-expect-error The SDK only ever calls `waitUntil`, the wrapper's type asks for the full context
+          context,
           // We don't want to capture errors here, as we want to capture them in the `sentryHandle` handler
           // where we can distinguish between redirects and actual errors.
           captureErrors: false,

packages/sveltekit/src/worker/cloudflareWorkers.d.ts

@@ -0,0 +1,6 @@
+// `@cloudflare/workers-types` declares this module, but pulling it in would also add Workers globals
+// that clash with the DOM lib the client half of this package is checked against. Only the export
+// the SDK reads is declared here; the declaration is build-time only and never emitted.
+declare module 'cloudflare:workers' {
+  export function waitUntil(promise: Promise<unknown>): void;
+}

packages/sveltekit/test/index.workerd.test.ts

@@ -0,0 +1,40 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { getCloudflareExecutionContext, setCloudflareExecutionContextFallback } from '../src/server-common/utils';
+
+describe('workerd entry point', () => {
+  afterEach(() => {
+    setCloudflareExecutionContextFallback(undefined);
+    vi.resetModules();
+    vi.doUnmock('cloudflare:workers');
+  });
+
+  it('registers `waitUntil` from `cloudflare:workers` as the fallback execution context', async () => {
+    const waitUntil = vi.fn();
+    vi.doMock('cloudflare:workers', () => ({ waitUntil }));
+
+    const workerdSdk = await import('../src/index.workerd');
+
+    const context = getCloudflareExecutionContext(undefined);
+    const task = Promise.resolve();
+    context?.waitUntil(task);
+
+    expect(waitUntil).toHaveBeenCalledWith(task);
+    expect(workerdSdk.initCloudflareSentryHandle).toBeTypeOf('function');
+  });
+
+  it('still prefers the execution context on `platform`', async () => {
+    vi.doMock('cloudflare:workers', () => ({ waitUntil: vi.fn() }));
+    await import('../src/index.workerd');
+
+    const ctx = { waitUntil: vi.fn() };
+
+    expect(getCloudflareExecutionContext({ ctx })).toBe(ctx);
+  });
+
+  it('resolves no execution context on runtimes where `waitUntil` is not importable', async () => {
+    vi.doMock('cloudflare:workers', () => ({}));
+    await import('../src/index.workerd');
+
+    expect(getCloudflareExecutionContext(undefined)).toBeUndefined();
+  });
+});

packages/sveltekit/test/server-common/handleError.test.ts

@@ -2,6 +2,7 @@ import * as SentryCore from '@sentry/core';
 import type { HandleServerError, RequestEvent } from '@sveltejs/kit';
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 import { handleErrorWithSentry } from '../../src/server-common/handleError';
+import { setCloudflareExecutionContextFallback } from '../../src/server-common/utils';
 
 const mockCaptureException = vi.spyOn(SentryCore, 'captureException').mockImplementation(() => 'xx');
 
@@ -158,6 +159,29 @@ describe('handleError (server)', () => {
 
       expect(mockCaptureException).toHaveBeenCalledTimes(1);
     });
+
+    // `@sveltejs/adapter-cloudflare` >= 8.0.0-next.7 passes no `platform` at all; the `workerd` entry point
+    // registers `waitUntil` from `cloudflare:workers` as the fallback instead
+    it('calls the fallback waitUntil if the event carries no platform', async () => {
+      const wrappedHandleError = handleErrorWithSentry();
+      const mockError = new Error('test');
+      const waitUntilSpy = vi.fn();
+      setCloudflareExecutionContextFallback(() => ({ waitUntil: waitUntilSpy }));
+
+      try {
+        await wrappedHandleError({
+          error: mockError,
+          event: { ...requestEvent, platform: undefined },
+          status: 500,
+          message: 'Internal Error',
+        });
+      } finally {
+        setCloudflareExecutionContextFallback(undefined);
+      }
+
+      expect(waitUntilSpy).toHaveBeenCalledTimes(1);
+      expect(waitUntilSpy).toHaveBeenCalledWith(expect.any(Promise));
+    });
   });
 });
 

packages/sveltekit/test/server-common/utils.test.ts

@@ -1,5 +1,9 @@
-import { describe, expect, it } from 'vitest';
-import { getTracePropagationData } from '../../src/server-common/utils';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import {
+  getCloudflareExecutionContext,
+  getTracePropagationData,
+  setCloudflareExecutionContextFallback,
+} from '../../src/server-common/utils';
 
 const MOCK_REQUEST_EVENT: any = {
   request: {
@@ -48,3 +52,39 @@ describe('getTracePropagationData', () => {
     expect(baggage).toBeUndefined();
   });
 });
+
+describe('getCloudflareExecutionContext', () => {
+  afterEach(() => {
+    setCloudflareExecutionContextFallback(undefined);
+  });
+
+  it.each([
+    ['context', 'adapter-cloudflare <= 7'],
+    ['ctx', 'adapter-cloudflare 8'],
+  ])('reads platform.%s (%s)', platformKey => {
+    const ctx = { waitUntil: vi.fn() };
+
+    expect(getCloudflareExecutionContext({ [platformKey]: ctx })).toBe(ctx);
+  });
+
+  it('returns undefined without a platform and without a registered fallback', () => {
+    expect(getCloudflareExecutionContext(undefined)).toBeUndefined();
+    expect(getCloudflareExecutionContext({})).toBeUndefined();
+  });
+
+  // `adapter-cloudflare` >= 8.0.0-next.7 passes no `platform` object at all
+  it('falls back to the registered provider when the platform carries no execution context', () => {
+    const fallbackCtx = { waitUntil: vi.fn() };
+    setCloudflareExecutionContextFallback(() => fallbackCtx);
+
+    expect(getCloudflareExecutionContext(undefined)).toBe(fallbackCtx);
+    expect(getCloudflareExecutionContext({})).toBe(fallbackCtx);
+  });
+
+  it('prefers the execution context on the platform over the fallback', () => {
+    const ctx = { waitUntil: vi.fn() };
+    setCloudflareExecutionContextFallback(() => ({ waitUntil: vi.fn() }));
+
+    expect(getCloudflareExecutionContext({ ctx })).toBe(ctx);
+  });
+});

packages/sveltekit/test/worker/cloudflare.test.ts

@@ -1,7 +1,8 @@
 import * as SentryCloudflare from '@sentry/cloudflare';
 import { _INTERNAL_wrapRequestHandler as wrapRequestHandler } from '@sentry/cloudflare';
 import type { Carrier, GLOBAL_OBJ } from '@sentry/core';
-import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { setCloudflareExecutionContextFallback } from '../../src/server-common/utils';
 import { initCloudflareSentryHandle } from '../../src/worker';
 
 vi.mock('@sentry/cloudflare', async importOriginal => {
@@ -27,6 +28,10 @@ describe('initCloudflareSentryHandle', () => {
     vi.mocked(wrapRequestHandler).mockClear();
   });
 
+  afterEach(() => {
+    setCloudflareExecutionContextFallback(undefined);
+  });
+
   it('sets the async context strategy when called', () => {
     vi.spyOn(SentryCloudflare, 'setAsyncLocalStorageAsyncContextStrategy');
 
@@ -85,6 +90,31 @@ describe('initCloudflareSentryHandle', () => {
     expect(locals._sentrySkipRequestIsolation).toBe(true);
   });
 
+  // `@sveltejs/adapter-cloudflare` >= 8.0.0-next.7 passes no `platform` at all; the `workerd` entry point
+  // registers `waitUntil` from `cloudflare:workers` as the fallback instead
+  it('calls wrapRequestHandler with the fallback execution context, if no platform data is set', async () => {
+    const { options, event, resolve, request } = getHandlerInput();
+    // @ts-expect-error - removing platform data
+    delete event.platform;
+    const fallbackContext = { waitUntil: vi.fn() };
+    setCloudflareExecutionContextFallback(() => fallbackContext);
+
+    // @ts-expect-error - resolving an empty object is enough for this test
+    vi.mocked(wrapRequestHandler).mockImplementationOnce((_, cb) => cb());
+
+    const handle = initCloudflareSentryHandle(options);
+
+    // @ts-expect-error - only passing a partial event object
+    await handle({ event, resolve });
+
+    expect(wrapRequestHandler).toHaveBeenCalledTimes(1);
+    expect(wrapRequestHandler).toHaveBeenCalledWith(
+      expect.objectContaining({ request, context: fallbackContext, captureErrors: false }),
+      expect.any(Function),
+    );
+    expect(resolve).toHaveBeenCalledTimes(1);
+  });
+
   it('falls back to resolving the event, if no platform data is set', async () => {
     const { options, event, resolve } = getHandlerInput();
     // @ts-expect-error - removing platform data