diff --git a/packages/start-server-core/src/request-response.ts b/packages/start-server-core/src/request-response.ts
index f8de03aa566..ab2b129b9d5 100644
--- a/packages/start-server-core/src/request-response.ts
+++ b/packages/start-server-core/src/request-response.ts
@@ -103,12 +103,37 @@ function attachResponseHeaders<T>(
   event: H3Event,
 ): MaybePromise<T> {
   if (isPromiseLike(value)) {
-    return value.then((resolved) => {
-      if (resolved instanceof Response) {
-        mergeEventResponseHeaders(resolved, event)
-      }
-      return resolved
-    })
+    return value.then(
+      (resolved) => {
+        if (resolved instanceof Response) {
+          mergeEventResponseHeaders(resolved, event)
+        }
+        return resolved
+      },
+      (error) => {
+        const eventStatus = event.res.status
+        if (eventStatus) {
+          const eventStatusText = event.res.statusText
+          const response =
+            error instanceof Response
+              ? new Response(error.body, {
+                  status: eventStatus,
+                  statusText: eventStatusText || error.statusText,
+                  headers: error.headers,
+                })
+              : new Response(
+                  error instanceof Error ? error.message : String(error),
+                  {
+                    status: eventStatus,
+                    statusText: eventStatusText || '',
+                  },
+                )
+          mergeEventResponseHeaders(response, event)
+          return response as T
+        }
+        throw error
+      },
+    )
   }
 
   if (value instanceof Response) {
diff --git a/packages/start-server-core/tests/request-response.test.ts b/packages/start-server-core/tests/request-response.test.ts
new file mode 100644
index 00000000000..4a81ba0f2e6
--- /dev/null
+++ b/packages/start-server-core/tests/request-response.test.ts
@@ -0,0 +1,89 @@
+import { describe, expect, it } from 'vitest'
+
+import {
+  getRequest,
+  requestHandler,
+  setResponseStatus,
+} from '../src/request-response'
+
+describe('setResponseStatus + throw preserves status code', () => {
+  it('should preserve status code when handler throws an Error after setResponseStatus', async () => {
+    const handler = requestHandler(async (_request: Request) => {
+      setResponseStatus(401)
+      throw new Error('Unauthorized')
+    })
+
+    const request = new Request('http://localhost/test')
+    const response = await handler(request, {})
+
+    expect(response.status).toBe(401)
+    expect(await response.text()).toBe('Unauthorized')
+  })
+
+  it('should preserve status code when handler throws a bare Response after setResponseStatus', async () => {
+    const handler = requestHandler(async (_request: Request) => {
+      setResponseStatus(429, 'Too Many Requests')
+      throw new Response('Rate limited')
+    })
+
+    const request = new Request('http://localhost/test')
+    const response = await handler(request, {})
+
+    expect(response.status).toBe(429)
+  })
+
+  it('should preserve status code when thrown Response already has same status', async () => {
+    const handler = requestHandler(async (_request: Request) => {
+      setResponseStatus(403)
+      throw new Response('Forbidden', { status: 403 })
+    })
+
+    const request = new Request('http://localhost/test')
+    const response = await handler(request, {})
+
+    expect(response.status).toBe(403)
+  })
+
+  it('should transfer event status when handler returns non-Response value', async () => {
+    const handler = requestHandler(async (_request: Request) => {
+      setResponseStatus(204)
+      return null as any
+    })
+
+    const request = new Request('http://localhost/test')
+    const response = await handler(request, {})
+
+    expect(response.status).toBe(204)
+  })
+
+  it('should return 500 when handler throws without setResponseStatus', async () => {
+    const handler = requestHandler(async (_request: Request) => {
+      throw new Error('unexpected failure')
+    })
+
+    const request = new Request('http://localhost/test')
+    const response = await handler(request, {})
+
+    expect(response.status).toBe(500)
+  })
+})
+
+describe('requestHandler basic behavior', () => {
+  it('should handle async handler returning a Response', async () => {
+    const handler = requestHandler(async (_request: Request) => {
+      return new Response('Hello', { status: 200 })
+    })
+
+    const request = new Request('http://localhost/test')
+    const response = await handler(request, {})
+
+    expect(response.status).toBe(200)
+    expect(await response.text()).toBe('Hello')
+  })
+
+  it('should throw when accessing event outside requestHandler context', async () => {
+    expect(() => getRequest()).toThrow(
+      'No StartEvent found in AsyncLocalStorage',
+    )
+  })
+})