diff --git a/.changeset/fix-community-world-specversion.md b/.changeset/fix-community-world-specversion.md
new file mode 100644
index 0000000000..b7abefca2a
--- /dev/null
+++ b/.changeset/fix-community-world-specversion.md
@@ -0,0 +1,9 @@
+---
+'@workflow/core': patch
+'@workflow/world': patch
+'@workflow/world-vercel': patch
+'@workflow/world-local': patch
+'@workflow/world-postgres': patch
+---
+
+Fix community world E2E tests by adding `specVersion` to the World interface so `start()` uses the safe baseline (v2) for worlds that don't declare their supported version
diff --git a/packages/core/e2e/e2e.test.ts b/packages/core/e2e/e2e.test.ts
index 6260a5cfdb..b0c3e05754 100644
--- a/packages/core/e2e/e2e.test.ts
+++ b/packages/core/e2e/e2e.test.ts
@@ -1549,9 +1549,12 @@ describe('e2e', () => {
       expect(flowBody).toEqual({
         healthy: true,
         endpoint: '/.well-known/workflow/v1/flow',
-        specVersion: SPEC_VERSION_CURRENT,
+        // specVersion comes from the World's declared specVersion (e.g. 3
+        // for world-vercel) or falls back to SPEC_VERSION_CURRENT (2).
+        specVersion: expect.any(Number),
         workflowCoreVersion: expect.any(String),
       });
+      expect(flowBody.specVersion).toBeGreaterThanOrEqual(SPEC_VERSION_CURRENT);
 
       // Test the step endpoint health check
       const stepHealthUrl = new URL(
@@ -1568,9 +1571,10 @@ describe('e2e', () => {
       expect(stepBody).toEqual({
         healthy: true,
         endpoint: '/.well-known/workflow/v1/step',
-        specVersion: SPEC_VERSION_CURRENT,
+        specVersion: expect.any(Number),
         workflowCoreVersion: expect.any(String),
       });
+      expect(stepBody.specVersion).toBeGreaterThanOrEqual(SPEC_VERSION_CURRENT);
     }
   );
 
diff --git a/packages/core/src/runtime.ts b/packages/core/src/runtime.ts
index 250955b482..902936b74f 100644
--- a/packages/core/src/runtime.ts
+++ b/packages/core/src/runtime.ts
@@ -97,7 +97,9 @@ export {
 export function workflowEntrypoint(
   workflowCode: string
 ): (req: Request) => Promise<Response> {
-  const handler = getWorldHandlers().createQueueHandler(
+  const { createQueueHandler, specVersion: worldSpecVersion } =
+    getWorldHandlers();
+  const handler = createQueueHandler(
     '__wkf_workflow_',
     async (message_, metadata) => {
       // Check if this is a health check message
@@ -106,7 +108,11 @@ export function workflowEntrypoint(
       // The stream name includes a unique correlationId that must be known by the caller.
       const healthCheck = parseHealthCheckPayload(message_);
       if (healthCheck) {
-        await handleHealthCheckMessage(healthCheck, 'workflow');
+        await handleHealthCheckMessage(
+          healthCheck,
+          'workflow',
+          worldSpecVersion
+        );
         return;
       }
 
@@ -615,7 +621,7 @@ export function workflowEntrypoint(
     }
   );
 
-  return withHealthCheck(handler);
+  return withHealthCheck(handler, worldSpecVersion);
 }
 
 // this is a no-op placeholder as the client is
diff --git a/packages/core/src/runtime/helpers.ts b/packages/core/src/runtime/helpers.ts
index b4597c6d07..7916997b33 100644
--- a/packages/core/src/runtime/helpers.ts
+++ b/packages/core/src/runtime/helpers.ts
@@ -95,7 +95,8 @@ function generateHealthCheckRunId(): string {
  */
 export async function handleHealthCheckMessage(
   healthCheck: HealthCheckPayload,
-  endpoint: 'workflow' | 'step'
+  endpoint: 'workflow' | 'step',
+  worldSpecVersion?: number
 ): Promise<void> {
   const world = getWorld();
   const streamName = getHealthCheckStreamName(healthCheck.correlationId);
@@ -103,7 +104,7 @@ export async function handleHealthCheckMessage(
     healthy: true,
     endpoint,
     correlationId: healthCheck.correlationId,
-    specVersion: SPEC_VERSION_CURRENT,
+    specVersion: worldSpecVersion ?? SPEC_VERSION_CURRENT,
     workflowCoreVersion,
     timestamp: Date.now(),
   });
@@ -377,7 +378,8 @@ const HEALTH_CHECK_CORS_HEADERS = {
  * based on the presence of a `__health` query parameter.
  */
 export function withHealthCheck(
-  handler: (req: Request) => Promise<Response>
+  handler: (req: Request) => Promise<Response>,
+  worldSpecVersion?: number
 ): (req: Request) => Promise<Response> {
   return async (req: Request) => {
     const url = new URL(req.url);
@@ -394,7 +396,7 @@ export function withHealthCheck(
         JSON.stringify({
           healthy: true,
           endpoint: url.pathname,
-          specVersion: SPEC_VERSION_CURRENT,
+          specVersion: worldSpecVersion ?? SPEC_VERSION_CURRENT,
           workflowCoreVersion,
         }),
         {
diff --git a/packages/core/src/runtime/start.test.ts b/packages/core/src/runtime/start.test.ts
index f0423db343..f8785f2dd3 100644
--- a/packages/core/src/runtime/start.test.ts
+++ b/packages/core/src/runtime/start.test.ts
@@ -1,5 +1,10 @@
 import { WorkflowRuntimeError, WorkflowWorldError } from '@workflow/errors';
-import { SPEC_VERSION_CURRENT, SPEC_VERSION_LEGACY } from '@workflow/world';
+import {
+  SPEC_VERSION_CURRENT,
+  SPEC_VERSION_LEGACY,
+  SPEC_VERSION_SUPPORTS_CBOR_QUEUE_TRANSPORT,
+  SPEC_VERSION_SUPPORTS_EVENT_SOURCING,
+} from '@workflow/world';
 import {
   afterEach,
   beforeEach,
@@ -10,8 +15,8 @@ import {
   vi,
 } from 'vitest';
 import type { Run } from './run.js';
-import { start } from './start.js';
 import type { WorkflowFunction } from './start.js';
+import { start } from './start.js';
 import { getWorld } from './world.js';
 
 // Mock @vercel/functions
@@ -109,11 +114,35 @@ describe('start', () => {
       vi.clearAllMocks();
     });
 
-    it('should use SPEC_VERSION_CURRENT when specVersion is not provided', async () => {
+    it('should use world.specVersion when available, falling back to SPEC_VERSION_SUPPORTS_EVENT_SOURCING', async () => {
       const validWorkflow = Object.assign(() => Promise.resolve('result'), {
         workflowId: 'test-workflow',
       });
 
+      // Mock world without specVersion → falls back to safe baseline (v2)
+      await start(validWorkflow, []);
+
+      expect(mockEventsCreate).toHaveBeenCalledWith(
+        expect.stringMatching(/^wrun_/),
+        expect.objectContaining({
+          eventType: 'run_created',
+          specVersion: SPEC_VERSION_SUPPORTS_EVENT_SOURCING,
+        }),
+        expect.objectContaining({
+          v1Compat: false,
+        })
+      );
+
+      vi.clearAllMocks();
+
+      // Mock world with specVersion 3 → uses it
+      vi.mocked(getWorld).mockReturnValue({
+        specVersion: SPEC_VERSION_CURRENT,
+        getDeploymentId: vi.fn().mockResolvedValue('deploy_123'),
+        events: { create: mockEventsCreate },
+        queue: mockQueue,
+      } as any);
+
       await start(validWorkflow, []);
 
       expect(mockEventsCreate).toHaveBeenCalledWith(
@@ -408,6 +437,8 @@ describe('start', () => {
       const mockEventsCreate = vi.fn().mockRejectedValue(serverError);
 
       vi.mocked(getWorld).mockReturnValue({
+        // World declares specVersion 3 to enable CBOR queue transport + runInput
+        specVersion: SPEC_VERSION_SUPPORTS_CBOR_QUEUE_TRANSPORT,
         getDeploymentId: vi.fn().mockResolvedValue('deploy_123'),
         events: { create: mockEventsCreate },
         queue: mockQueue,
@@ -423,7 +454,9 @@ describe('start', () => {
       expect(queuePayload.runInput).toBeDefined();
       expect(queuePayload.runInput.deploymentId).toBe('deploy_123');
       expect(queuePayload.runInput.workflowName).toBe('test-workflow');
-      expect(queuePayload.runInput.specVersion).toBe(SPEC_VERSION_CURRENT);
+      expect(queuePayload.runInput.specVersion).toBe(
+        SPEC_VERSION_SUPPORTS_CBOR_QUEUE_TRANSPORT
+      );
     });
 
     it('should throw when queue fails even if events.create succeeds', async () => {
diff --git a/packages/core/src/runtime/start.ts b/packages/core/src/runtime/start.ts
index ffe7d49981..8d7af65d44 100644
--- a/packages/core/src/runtime/start.ts
+++ b/packages/core/src/runtime/start.ts
@@ -8,8 +8,8 @@ import {
 import type { WorkflowInvokePayload, World } from '@workflow/world';
 import {
   isLegacySpecVersion,
-  SPEC_VERSION_CURRENT,
   SPEC_VERSION_SUPPORTS_CBOR_QUEUE_TRANSPORT,
+  SPEC_VERSION_SUPPORTS_EVENT_SOURCING,
 } from '@workflow/world';
 import { monotonicFactory } from 'ulid';
 import { importKey } from '../encryption.js';
@@ -172,7 +172,14 @@ export async function start<TArgs extends unknown[], TResult>(
       // Serialize current trace context to propagate across queue boundary
       const traceCarrier = await serializeTraceCarrier();
 
-      const specVersion = opts.specVersion ?? SPEC_VERSION_CURRENT;
+      // Use world-declared specVersion when available (our worlds set this),
+      // otherwise fall back to the safe baseline that community worlds handle.
+      // Community worlds built against older @workflow/world reject runs with
+      // specVersion > their SPEC_VERSION_CURRENT via requiresNewerWorld().
+      const specVersion =
+        opts.specVersion ??
+        world.specVersion ??
+        SPEC_VERSION_SUPPORTS_EVENT_SOURCING;
       const v1Compat = isLegacySpecVersion(specVersion);
 
       // Resolve encryption key for the new run. The runId has already been
diff --git a/packages/core/src/runtime/step-handler.ts b/packages/core/src/runtime/step-handler.ts
index 822f632a92..6bf0057a60 100644
--- a/packages/core/src/runtime/step-handler.ts
+++ b/packages/core/src/runtime/step-handler.ts
@@ -34,6 +34,7 @@ import {
   getErrorStack,
   normalizeUnknownError,
 } from '../types.js';
+import { MAX_QUEUE_DELIVERIES } from './constants.js';
 import {
   getQueueOverhead,
   getWorkflowQueueName,
@@ -42,12 +43,13 @@ import {
   queueMessage,
   withHealthCheck,
 } from './helpers.js';
-import { MAX_QUEUE_DELIVERIES } from './constants.js';
 import { getWorld, getWorldHandlers } from './world.js';
 
 const DEFAULT_STEP_MAX_RETRIES = 3;
 
-const stepHandler = getWorldHandlers().createQueueHandler(
+const { createQueueHandler, specVersion: worldSpecVersion } =
+  getWorldHandlers();
+const stepHandler = createQueueHandler(
   '__wkf_step_',
   async (message_, metadata) => {
     // Check if this is a health check message
@@ -56,7 +58,7 @@ const stepHandler = getWorldHandlers().createQueueHandler(
     // The stream name includes a unique correlationId that must be known by the caller.
     const healthCheck = parseHealthCheckPayload(message_);
     if (healthCheck) {
-      await handleHealthCheckMessage(healthCheck, 'step');
+      await handleHealthCheckMessage(healthCheck, 'step', worldSpecVersion);
       return;
     }
 
@@ -864,4 +866,4 @@ const stepHandler = getWorldHandlers().createQueueHandler(
  * for each step, this is temporary.
  */
 export const stepEntrypoint: (req: Request) => Promise<Response> =
-  /* @__PURE__ */ withHealthCheck(stepHandler);
+  /* @__PURE__ */ withHealthCheck(stepHandler, worldSpecVersion);
diff --git a/packages/core/src/runtime/world.ts b/packages/core/src/runtime/world.ts
index 4ca3339fee..524dc3cd7a 100644
--- a/packages/core/src/runtime/world.ts
+++ b/packages/core/src/runtime/world.ts
@@ -85,7 +85,10 @@ export const createWorld = (): World => {
  * Once we migrate to a file-based configuration (workflow.config.ts), we should
  * be able to re-combine getWorld and getWorldHandlers into one singleton.
  */
-export const getWorldHandlers = (): Pick<World, 'createQueueHandler'> => {
+export const getWorldHandlers = (): Pick<
+  World,
+  'createQueueHandler' | 'specVersion'
+> => {
   if (globalSymbols[StubbedWorldCache]) {
     return globalSymbols[StubbedWorldCache];
   }
@@ -93,6 +96,7 @@ export const getWorldHandlers = (): Pick<World, 'createQueueHandler'> => {
   globalSymbols[StubbedWorldCache] = _world;
   return {
     createQueueHandler: _world.createQueueHandler,
+    specVersion: _world.specVersion,
   };
 };
 
diff --git a/packages/world-local/src/index.ts b/packages/world-local/src/index.ts
index ccc28f8188..3eb9cee622 100644
--- a/packages/world-local/src/index.ts
+++ b/packages/world-local/src/index.ts
@@ -2,7 +2,7 @@ import { promises as fs } from 'node:fs';
 import { rm } from 'node:fs/promises';
 import path from 'node:path';
 import type { World } from '@workflow/world';
-import { reenqueueActiveRuns } from '@workflow/world';
+import { reenqueueActiveRuns, SPEC_VERSION_CURRENT } from '@workflow/world';
 import type { Config } from './config.js';
 import { config } from './config.js';
 import {
@@ -29,7 +29,7 @@ export {
   parseVersion,
 } from './init.js';
 
-export { type DirectHandler } from './queue.js';
+export type { DirectHandler } from './queue.js';
 
 export type LocalWorld = World & {
   /** Register a direct in-process handler for a queue prefix, bypassing HTTP. */
@@ -64,6 +64,7 @@ export function createLocalWorld(args?: Partial<Config>): LocalWorld {
   const queue = createQueue(mergedConfig);
   const storage = createStorage(mergedConfig.dataDir, tag);
   return {
+    specVersion: SPEC_VERSION_CURRENT,
     ...queue,
     ...createStorage(mergedConfig.dataDir, tag),
     ...instrumentObject('world.streams', {
diff --git a/packages/world-postgres/src/index.ts b/packages/world-postgres/src/index.ts
index 62e1530138..31fb1d84ac 100644
--- a/packages/world-postgres/src/index.ts
+++ b/packages/world-postgres/src/index.ts
@@ -1,5 +1,5 @@
 import type { Storage, World } from '@workflow/world';
-import { reenqueueActiveRuns } from '@workflow/world';
+import { reenqueueActiveRuns, SPEC_VERSION_CURRENT } from '@workflow/world';
 import { Pool } from 'pg';
 import type { PostgresWorldConfig } from './config.js';
 import { createClient, type Drizzle } from './drizzle/index.js';
@@ -57,6 +57,7 @@ export function createWorld(
   const streamer = createStreamer(pool, drizzle);
 
   return {
+    specVersion: SPEC_VERSION_CURRENT,
     ...storage,
     ...streamer,
     ...queue,
diff --git a/packages/world-vercel/src/index.ts b/packages/world-vercel/src/index.ts
index 896fede377..f15c480869 100644
--- a/packages/world-vercel/src/index.ts
+++ b/packages/world-vercel/src/index.ts
@@ -1,4 +1,5 @@
 import type { World } from '@workflow/world';
+import { SPEC_VERSION_SUPPORTS_CBOR_QUEUE_TRANSPORT } from '@workflow/world';
 import { createGetEncryptionKeyForRun } from './encryption.js';
 import { instrumentObject } from './instrumentObject.js';
 import { createQueue } from './queue.js';
@@ -24,6 +25,7 @@ export function createVercelWorld(config?: APIConfig): World {
     config?.projectConfig?.projectId || process.env.VERCEL_PROJECT_ID;
 
   return {
+    specVersion: SPEC_VERSION_SUPPORTS_CBOR_QUEUE_TRANSPORT,
     ...createQueue(config),
     ...createStorage(config),
     ...instrumentObject('world.streams', createStreamer(config)),
diff --git a/packages/world/src/interfaces.ts b/packages/world/src/interfaces.ts
index c9628a9685..cd650c07a1 100644
--- a/packages/world/src/interfaces.ts
+++ b/packages/world/src/interfaces.ts
@@ -233,6 +233,17 @@ export interface Storage {
  * The "World" interface represents how Workflows are able to communicate with the outside world.
  */
 export interface World extends Queue, Storage, Streamer {
+  /**
+   * The highest spec version this World supports.
+   *
+   * When set, `start()` creates runs at this version so world-specific
+   * features (e.g., CBOR queue transport) are enabled automatically.
+   * When omitted, runs default to `SPEC_VERSION_SUPPORTS_EVENT_SOURCING` (2),
+   * the safe baseline that all worlds — including community worlds on
+   * older @workflow/world versions — are expected to handle.
+   */
+  specVersion?: number;
+
   /**
    * A function that will be called to start any background tasks needed by the World implementation.
    * For example, in the case of a queue backed World, this would start the queue processing.