diff --git a/services/cross-runtime-queues/.gitignore b/services/cross-runtime-queues/.gitignore
new file mode 100644
index 0000000000..84aa34b3c2
--- /dev/null
+++ b/services/cross-runtime-queues/.gitignore
@@ -0,0 +1,29 @@
+# frontend
+frontend/.next/
+frontend/node_modules/
+frontend/*.log
+frontend/*.tsbuildinfo
+frontend/next-env.d.ts
+frontend/package-lock.json
+
+# python
+backend/.venv/
+backend/**/__pycache__/
+backend/**/*.py[cod]
+backend/**/*.egg-info/
+backend/.pytest_cache/
+backend/.queue-results.sqlite3
+backend/.queue-results.sqlite3-*
+
+# environment files
+.env
+.env*.local
+frontend/.env
+frontend/.env*.local
+backend/.env
+backend/.env*.local
+
+# common
+.vercel/
+.DS_Store
+.vercel
diff --git a/services/cross-runtime-queues/README.md b/services/cross-runtime-queues/README.md
new file mode 100644
index 0000000000..831aa76ce8
--- /dev/null
+++ b/services/cross-runtime-queues/README.md
@@ -0,0 +1,65 @@
+# Next.js + FastAPI Queues
+
+Minimal example showing [Vercel Services](https://vercel.com/docs/services)
+with [Vercel Queues](https://vercel.com/docs/queues):
+
+- `frontend` (Next.js) mounted at `/`
+- `backend` (FastAPI) mounted at `/api/python`
+
+It demonstrates:
+
+1. Next.js publishing a message for a Python subscriber
+2. Python publishing a message for a Next.js callback
+3. Next.js publishing one message to both runtimes
+
+## How it works
+
+Each producer creates a task before publishing a message. The queue delivers
+the message to the configured subscriber, which stores its result in
+[Vercel Runtime Cache](https://vercel.com/docs/runtime-cache). The frontend
+polls the FastAPI service until every expected subscriber has completed.
+
+The fanout example uses separate consumer groups for the Next.js callback and
+Python subscriber, so both receive a copy of the same message.
+
+## Project structure
+
+```txt
+cross-runtime-queues/
+├── backend/       # FastAPI producer, subscribers, and result store
+├── frontend/      # Next.js UI, producers, and queue callbacks
+└── vercel.json    # Service routing and Next.js queue triggers
+```
+
+## Services config
+
+Configuration in `vercel.json`:
+
+- routes `/(.*)` to `frontend`
+- routes `/api/python/(.*)` to `backend`
+- binds `backend` to `frontend` as `BACKEND_URL`
+- registers the Next.js callbacks as `queue/v2beta` triggers
+
+Python subscribers are configured in `backend/pyproject.toml`.
+
+## Run locally
+
+Install the frontend and Python dependencies:
+
+```bash
+cd frontend
+npm install
+cd ../backend
+python -m venv .venv
+source .venv/bin/activate
+pip install -e .
+cd ..
+```
+
+Start the development server:
+
+```bash
+npx vercel dev
+```
+
+The application is now available at `http://localhost:3000`.
diff --git a/services/cross-runtime-queues/backend/main.py b/services/cross-runtime-queues/backend/main.py
new file mode 100644
index 0000000000..5c83a7f13f
--- /dev/null
+++ b/services/cross-runtime-queues/backend/main.py
@@ -0,0 +1,109 @@
+from datetime import datetime, timezone
+from typing import Any, Literal
+from uuid import uuid4
+
+from fastapi import FastAPI, HTTPException
+from pydantic import BaseModel
+from vercel.queue import send
+
+from store import result_store
+
+
+class DemoMessage(BaseModel):
+    text: str
+    sentAt: str | None = None
+
+
+class TaskRecord(BaseModel):
+    taskId: str
+    expectedConsumers: list[Literal["nextjs", "python"]]
+    messageId: str | None = None
+
+
+class Completion(BaseModel):
+    result: dict[str, Any]
+
+
+app = FastAPI(title="Cross-runtime Vercel Queues demo")
+
+
+def task_key(task_id: str) -> str:
+    return f"task:{task_id}"
+
+
+def completion_key(task_id: str, consumer: str) -> str:
+    return f"task:{task_id}:completion:{consumer}"
+
+
+@app.put("/api/python/tasks/{task_id}", status_code=204)
+async def put_task(task_id: str, task: TaskRecord) -> None:
+    if task.taskId != task_id:
+        raise HTTPException(status_code=400, detail="Task ID mismatch")
+    await result_store.set(task_key(task_id), task.model_dump())
+
+
+@app.delete("/api/python/tasks/{task_id}", status_code=204)
+async def delete_task(task_id: str) -> None:
+    await result_store.delete(task_key(task_id))
+
+
+@app.put(
+    "/api/python/tasks/{task_id}/completions/{consumer}",
+    status_code=204,
+)
+async def put_completion(
+    task_id: str,
+    consumer: Literal["nextjs", "python"],
+    completion: Completion,
+) -> None:
+    await result_store.set(
+        completion_key(task_id, consumer),
+        completion.model_dump(),
+    )
+
+
+@app.get("/api/python/tasks/{task_id}")
+async def get_task(task_id: str) -> dict[str, Any]:
+    task = await result_store.get(task_key(task_id))
+    if task is None:
+        raise HTTPException(status_code=404, detail="Task not found")
+
+    completions: dict[str, Any] = {}
+    for consumer in task["expectedConsumers"]:
+        completion = await result_store.get(completion_key(task_id, consumer))
+        if completion is not None:
+            completions[consumer] = completion
+
+    return {
+        **task,
+        "status": (
+            "completed"
+            if len(completions) == len(task["expectedConsumers"])
+            else "pending"
+        ),
+        "completions": completions,
+    }
+
+
+@app.post("/api/python/messages/python-to-next")
+async def send_to_next(message: DemoMessage) -> TaskRecord:
+    task_id = str(uuid4())
+    payload = message.model_dump()
+    payload["sentAt"] = payload["sentAt"] or datetime.now(timezone.utc).isoformat()
+    payload["taskId"] = task_id
+    task = TaskRecord(
+        taskId=task_id,
+        expectedConsumers=["nextjs"],
+    )
+
+    await result_store.set(task_key(task_id), task.model_dump())
+    try:
+        message_id = await send("demo-python-to-next", payload)
+    except Exception:
+        await result_store.delete(task_key(task_id))
+        raise
+
+    task.messageId = message_id
+    await result_store.set(task_key(task_id), task.model_dump())
+
+    return task
diff --git a/services/cross-runtime-queues/backend/pyproject.toml b/services/cross-runtime-queues/backend/pyproject.toml
new file mode 100644
index 0000000000..039f28e73a
--- /dev/null
+++ b/services/cross-runtime-queues/backend/pyproject.toml
@@ -0,0 +1,16 @@
+[project]
+name = "queues-python-backend"
+version = "0.1.0"
+requires-python = ">=3.11"
+dependencies = [
+  "fastapi",
+  "pydantic",
+  "vercel-cache",
+  "vercel-queue",
+]
+
+[tool.vercel]
+entrypoint = "main:app"
+
+[[tool.vercel.subscribers]]
+entrypoint = "subscribers"
diff --git a/services/cross-runtime-queues/backend/store.py b/services/cross-runtime-queues/backend/store.py
new file mode 100644
index 0000000000..07b740d27f
--- /dev/null
+++ b/services/cross-runtime-queues/backend/store.py
@@ -0,0 +1,102 @@
+import asyncio
+import json
+import os
+import sqlite3
+import time
+from contextlib import contextmanager
+from pathlib import Path
+from typing import Any, Iterator
+
+from vercel.cache import AsyncRuntimeCache
+
+RESULT_TTL_SECONDS = 3600
+LOCAL_DATABASE_PATH = Path(__file__).with_name(".queue-results.sqlite3")
+
+
+class ResultStore:
+    def __init__(self) -> None:
+        self._runtime_cache = AsyncRuntimeCache(namespace="cross-runtime-queues")
+        self._use_runtime_cache = bool(
+            os.getenv("VERCEL") and os.getenv("VERCEL_ENV") != "development"
+        )
+
+    async def set(self, key: str, value: dict[str, Any]) -> None:
+        if self._use_runtime_cache:
+            await self._runtime_cache.set(
+                key,
+                value,
+                {"ttl": RESULT_TTL_SECONDS},
+            )
+            return
+
+        await asyncio.to_thread(self._set_local, key, value)
+
+    async def get(self, key: str) -> dict[str, Any] | None:
+        if self._use_runtime_cache:
+            return await self._runtime_cache.get(key)
+
+        return await asyncio.to_thread(self._get_local, key)
+
+    async def delete(self, key: str) -> None:
+        if self._use_runtime_cache:
+            await self._runtime_cache.delete(key)
+            return
+
+        await asyncio.to_thread(self._delete_local, key)
+
+    @contextmanager
+    def _connect(self) -> Iterator[sqlite3.Connection]:
+        connection = sqlite3.connect(LOCAL_DATABASE_PATH, timeout=5)
+        try:
+            connection.execute(
+                """
+                CREATE TABLE IF NOT EXISTS queue_results (
+                    key TEXT PRIMARY KEY,
+                    value TEXT NOT NULL,
+                    expires_at REAL NOT NULL
+                )
+                """
+            )
+            yield connection
+            connection.commit()
+        finally:
+            connection.close()
+
+    def _set_local(self, key: str, value: dict[str, Any]) -> None:
+        with self._connect() as connection:
+            connection.execute(
+                """
+                INSERT INTO queue_results (key, value, expires_at)
+                VALUES (?, ?, ?)
+                ON CONFLICT(key) DO UPDATE SET
+                    value = excluded.value,
+                    expires_at = excluded.expires_at
+                """,
+                (key, json.dumps(value), time.time() + RESULT_TTL_SECONDS),
+            )
+
+    def _get_local(self, key: str) -> dict[str, Any] | None:
+        with self._connect() as connection:
+            row = connection.execute(
+                "SELECT value, expires_at FROM queue_results WHERE key = ?",
+                (key,),
+            ).fetchone()
+            if row is None:
+                return None
+
+            value, expires_at = row
+            if expires_at <= time.time():
+                connection.execute(
+                    "DELETE FROM queue_results WHERE key = ?",
+                    (key,),
+                )
+                return None
+
+            return json.loads(value)
+
+    def _delete_local(self, key: str) -> None:
+        with self._connect() as connection:
+            connection.execute("DELETE FROM queue_results WHERE key = ?", (key,))
+
+
+result_store = ResultStore()
diff --git a/services/cross-runtime-queues/backend/subscribers.py b/services/cross-runtime-queues/backend/subscribers.py
new file mode 100644
index 0000000000..fea1413506
--- /dev/null
+++ b/services/cross-runtime-queues/backend/subscribers.py
@@ -0,0 +1,50 @@
+from typing import Any
+
+from vercel.queue import Message, subscribe
+
+from store import result_store
+
+
+async def complete_task(
+    message: Message[dict[str, Any]],
+    consumer: str,
+) -> None:
+    task_id = str(message.payload["taskId"])
+    await result_store.set(
+        f"task:{task_id}:completion:{consumer}",
+        {
+            "result": {
+                "messageId": message.message_id,
+                "deliveryCount": message.metadata.delivery_count,
+                "received": message.payload,
+            },
+        },
+    )
+
+
+@subscribe(topic="demo-next-to-python")
+async def receive_from_next(message: Message[dict[str, Any]]) -> None:
+    await complete_task(message, "python")
+    print(
+        "[python consumer] received from Next.js",
+        {
+            "payload": message.payload,
+            "message_id": message.message_id,
+            "delivery_count": message.metadata.delivery_count,
+            "topic": message.metadata.topic,
+        },
+    )
+
+
+@subscribe(topic="demo-fanout")
+async def receive_fanout(message: Message[dict[str, Any]]) -> None:
+    await complete_task(message, "python")
+    print(
+        "[python fanout consumer] received a copy",
+        {
+            "payload": message.payload,
+            "message_id": message.message_id,
+            "consumer_group": message.metadata.consumer_group,
+            "delivery_count": message.metadata.delivery_count,
+        },
+    )
diff --git a/services/cross-runtime-queues/frontend/eslint.config.mjs b/services/cross-runtime-queues/frontend/eslint.config.mjs
new file mode 100644
index 0000000000..6407a8442c
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/eslint.config.mjs
@@ -0,0 +1,9 @@
+import { defineConfig, globalIgnores } from "eslint/config";
+import nextVitals from "eslint-config-next/core-web-vitals";
+import nextTypeScript from "eslint-config-next/typescript";
+
+export default defineConfig([
+  ...nextVitals,
+  ...nextTypeScript,
+  globalIgnores([".next/**", "next-env.d.ts"]),
+]);
diff --git a/services/cross-runtime-queues/frontend/package.json b/services/cross-runtime-queues/frontend/package.json
new file mode 100644
index 0000000000..59692f67d5
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/package.json
@@ -0,0 +1,26 @@
+{
+  "name": "frontend",
+  "version": "1.0.0",
+  "private": true,
+  "scripts": {
+    "dev": "next dev",
+    "build": "next build",
+    "start": "next start",
+    "lint": "eslint .",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@vercel/queue": "^0.4.0",
+    "next": "^16.3.1",
+    "react": "^19.2.8",
+    "react-dom": "^19.2.8"
+  },
+  "devDependencies": {
+    "@types/node": "^26.2.0",
+    "@types/react": "^19.2.18",
+    "@types/react-dom": "^19.2.4",
+    "eslint": "^9.39.5",
+    "eslint-config-next": "^16.3.1",
+    "typescript": "^5.9.3"
+  }
+}
diff --git a/services/cross-runtime-queues/frontend/public/nextjs.svg b/services/cross-runtime-queues/frontend/public/nextjs.svg
new file mode 100644
index 0000000000..06a2bd6eed
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/public/nextjs.svg
@@ -0,0 +1 @@
+<svg role="img" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Next.js</title><path d="M18.665 21.978C16.758 23.255 14.465 24 12 24 5.377 24 0 18.623 0 12S5.377 0 12 0s12 5.377 12 12c0 3.583-1.574 6.801-4.067 9.001L9.219 7.2H7.2v9.596h1.615V9.251l9.85 12.727Zm-3.332-8.533 1.6 2.061V7.2h-1.6v6.245Z"/></svg>
\ No newline at end of file
diff --git a/services/cross-runtime-queues/frontend/public/python.svg b/services/cross-runtime-queues/frontend/public/python.svg
new file mode 100644
index 0000000000..30587d8164
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/public/python.svg
@@ -0,0 +1 @@
+<svg role="img" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Python</title><path d="M14.25.18l.9.2.73.26.59.3.45.32.34.34.25.34.16.33.1.3.04.26.02.2-.01.13V8.5l-.05.63-.13.55-.21.46-.26.38-.3.31-.33.25-.35.19-.35.14-.33.1-.3.07-.26.04-.21.02H8.77l-.69.05-.59.14-.5.22-.41.27-.33.32-.27.35-.2.36-.15.37-.1.35-.07.32-.04.27-.02.21v3.06H3.17l-.21-.03-.28-.07-.32-.12-.35-.18-.36-.26-.36-.36-.35-.46-.32-.59-.28-.73-.21-.88-.14-1.05-.05-1.23.06-1.22.16-1.04.24-.87.32-.71.36-.57.4-.44.42-.33.42-.24.4-.16.36-.1.32-.05.24-.01h.16l.06.01h8.16v-.83H6.18l-.01-2.75-.02-.37.05-.34.11-.31.17-.28.25-.26.31-.23.38-.2.44-.18.51-.15.58-.12.64-.1.71-.06.77-.04.84-.02 1.27.05zm-6.3 1.98l-.23.33-.08.41.08.41.23.34.33.22.41.09.41-.09.33-.22.23-.34.08-.41-.08-.41-.23-.33-.33-.22-.41-.09-.41.09zm13.09 3.95l.28.06.32.12.35.18.36.27.36.35.35.47.32.59.28.73.21.88.14 1.04.05 1.23-.06 1.23-.16 1.04-.24.86-.32.71-.36.57-.4.45-.42.33-.42.24-.4.16-.36.09-.32.05-.24.02-.16-.01h-8.22v.82h5.84l.01 2.76.02.36-.05.34-.11.31-.17.29-.25.25-.31.24-.38.2-.44.17-.51.15-.58.13-.64.09-.71.07-.77.04-.84.01-1.27-.04-1.07-.14-.9-.2-.73-.25-.59-.3-.45-.33-.34-.34-.25-.34-.16-.33-.1-.3-.04-.25-.02-.2.01-.13v-5.34l.05-.64.13-.54.21-.46.26-.38.3-.32.33-.24.35-.2.35-.14.33-.1.3-.06.26-.04.21-.02.13-.01h5.84l.69-.05.59-.14.5-.21.41-.28.33-.32.27-.35.2-.36.15-.36.1-.35.07-.32.04-.28.02-.21V6.07h2.09l.14.01zm-6.47 14.25l-.23.33-.08.41.08.41.23.33.33.23.41.08.41-.08.33-.23.23-.33.08-.41-.08-.41-.23-.33-.33-.23-.41-.08-.41.08z"/></svg>
\ No newline at end of file
diff --git a/services/cross-runtime-queues/frontend/src/app/api/next/fanout/route.ts b/services/cross-runtime-queues/frontend/src/app/api/next/fanout/route.ts
new file mode 100644
index 0000000000..4bcd951a78
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/src/app/api/next/fanout/route.ts
@@ -0,0 +1,27 @@
+import { send } from '@vercel/queue'
+import { deleteTask, putTask, type TaskRecord } from '@/lib/task-store'
+
+export async function POST(request: Request) {
+  const payload = await request.json()
+  const taskId = crypto.randomUUID()
+  const task: TaskRecord = {
+    taskId,
+    expectedConsumers: ['nextjs', 'python'],
+    messageId: null,
+  }
+
+  await putTask(task)
+  try {
+    const { messageId } = await send('demo-fanout', {
+      ...payload,
+      taskId,
+    })
+    task.messageId = messageId
+    await putTask(task)
+
+    return Response.json(task)
+  } catch (error) {
+    await deleteTask(taskId)
+    throw error
+  }
+}
diff --git a/services/cross-runtime-queues/frontend/src/app/api/next/next-to-python/route.ts b/services/cross-runtime-queues/frontend/src/app/api/next/next-to-python/route.ts
new file mode 100644
index 0000000000..332b281a84
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/src/app/api/next/next-to-python/route.ts
@@ -0,0 +1,27 @@
+import { send } from '@vercel/queue'
+import { deleteTask, putTask, type TaskRecord } from '@/lib/task-store'
+
+export async function POST(request: Request) {
+  const payload = await request.json()
+  const taskId = crypto.randomUUID()
+  const task: TaskRecord = {
+    taskId,
+    expectedConsumers: ['python'],
+    messageId: null,
+  }
+
+  await putTask(task)
+  try {
+    const { messageId } = await send('demo-next-to-python', {
+      ...payload,
+      taskId,
+    })
+    task.messageId = messageId
+    await putTask(task)
+
+    return Response.json(task)
+  } catch (error) {
+    await deleteTask(taskId)
+    throw error
+  }
+}
diff --git a/services/cross-runtime-queues/frontend/src/app/api/queues/fanout/route.ts b/services/cross-runtime-queues/frontend/src/app/api/queues/fanout/route.ts
new file mode 100644
index 0000000000..ce84fd87b4
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/src/app/api/queues/fanout/route.ts
@@ -0,0 +1,22 @@
+import { handleCallback } from '@vercel/queue'
+import { completeTask } from '@/lib/task-store'
+
+type DemoMessage = {
+  taskId: string
+  text: string
+  sentAt: string
+}
+
+export const POST = handleCallback<DemoMessage>(async (message, metadata) => {
+  await completeTask(message.taskId, 'nextjs', {
+    messageId: metadata.messageId,
+    deliveryCount: metadata.deliveryCount,
+    received: message,
+  })
+  console.log('[nextjs fanout consumer] received a copy', {
+    message,
+    messageId: metadata.messageId,
+    consumerGroup: metadata.consumerGroup,
+    deliveryCount: metadata.deliveryCount,
+  })
+})
diff --git a/services/cross-runtime-queues/frontend/src/app/api/queues/from-python/route.ts b/services/cross-runtime-queues/frontend/src/app/api/queues/from-python/route.ts
new file mode 100644
index 0000000000..4f65b02027
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/src/app/api/queues/from-python/route.ts
@@ -0,0 +1,22 @@
+import { handleCallback } from '@vercel/queue'
+import { completeTask } from '@/lib/task-store'
+
+type DemoMessage = {
+  taskId: string
+  text: string
+  sentAt: string
+}
+
+export const POST = handleCallback<DemoMessage>(async (message, metadata) => {
+  await completeTask(message.taskId, 'nextjs', {
+    messageId: metadata.messageId,
+    deliveryCount: metadata.deliveryCount,
+    received: message,
+  })
+  console.log('[nextjs consumer] received from Python', {
+    message,
+    messageId: metadata.messageId,
+    deliveryCount: metadata.deliveryCount,
+    topic: metadata.topicName,
+  })
+})
diff --git a/services/cross-runtime-queues/frontend/src/app/layout.tsx b/services/cross-runtime-queues/frontend/src/app/layout.tsx
new file mode 100644
index 0000000000..5e928a37ed
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/src/app/layout.tsx
@@ -0,0 +1,16 @@
+import type { Metadata } from 'next'
+import type { ReactNode } from 'react'
+import './styles.css'
+
+export const metadata: Metadata = {
+  title: 'Cross-runtime Queues',
+  description: 'Vercel Queues with Next.js and Python',
+}
+
+export default function RootLayout({ children }: { children: ReactNode }) {
+  return (
+    <html lang="en">
+      <body>{children}</body>
+    </html>
+  )
+}
diff --git a/services/cross-runtime-queues/frontend/src/app/page.tsx b/services/cross-runtime-queues/frontend/src/app/page.tsx
new file mode 100644
index 0000000000..38330ac201
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/src/app/page.tsx
@@ -0,0 +1,372 @@
+'use client'
+
+import Image from 'next/image'
+import { useRef, useState } from 'react'
+
+type Consumer = 'nextjs' | 'python'
+
+type Demo = {
+  title: string
+  description: string
+  producer: 'Next.js' | 'Python'
+  topic: string
+  expectedConsumers: Consumer[]
+  endpoint: string
+}
+
+type Completion = {
+  result: {
+    received: { text?: string }
+  }
+}
+
+type TaskResult = {
+  taskId: string
+  messageId: string | null
+  status: 'pending' | 'completed' | 'error'
+  expectedConsumers: Consumer[]
+  completions: Record<string, Completion>
+  detail?: string
+}
+
+type ActiveRun = {
+  title: string
+  expectedConsumers: Consumer[]
+  taskId?: string
+  messageId?: string | null
+}
+
+const demos: Demo[] = [
+  {
+    title: 'Next.js → Python',
+    description: 'Send in Next.js, consume in Python.',
+    producer: 'Next.js',
+    topic: 'demo-next-to-python',
+    expectedConsumers: ['python'],
+    endpoint: '/api/next/next-to-python',
+  },
+  {
+    title: 'Python → Next.js',
+    description: 'Send in Python, consume in Next.js.',
+    producer: 'Python',
+    topic: 'demo-python-to-next',
+    expectedConsumers: ['nextjs'],
+    endpoint: '/api/python/messages/python-to-next',
+  },
+  {
+    title: 'Fan out',
+    description: 'Send once, consume in both runtimes.',
+    producer: 'Next.js',
+    topic: 'demo-fanout',
+    expectedConsumers: ['nextjs', 'python'],
+    endpoint: '/api/next/fanout',
+  },
+]
+
+export default function Home() {
+  const [pending, setPending] = useState<string>()
+  const [activeRun, setActiveRun] = useState<ActiveRun>()
+  const [results, setResults] = useState<Record<string, TaskResult>>({})
+  const runIds = useRef<Record<string, string>>({})
+
+  async function pollTask(
+    title: string,
+    taskId: string,
+    runId: string,
+    attempt = 0
+  ) {
+    if (runIds.current[title] !== runId) return
+
+    try {
+      const response = await fetch(
+        `/api/python/tasks/${encodeURIComponent(taskId)}`,
+        { cache: 'no-store' }
+      )
+      if (!response.ok) {
+        throw new Error(`Result lookup failed (${response.status})`)
+      }
+
+      const task = (await response.json()) as TaskResult
+      if (runIds.current[title] !== runId) return
+      setResults((current) => ({ ...current, [title]: task }))
+
+      if (task.status !== 'completed' && attempt < 120) {
+        window.setTimeout(
+          () => pollTask(title, taskId, runId, attempt + 1),
+          1000
+        )
+      }
+    } catch (error) {
+      if (runIds.current[title] !== runId) return
+      setResults((current) => ({
+        ...current,
+        [title]: {
+          ...current[title],
+          taskId,
+          status: 'error',
+          expectedConsumers: current[title]?.expectedConsumers ?? [],
+          completions: current[title]?.completions ?? {},
+          messageId: current[title]?.messageId ?? null,
+          detail:
+            error instanceof Error ? error.message : 'Unable to read result',
+        },
+      }))
+    }
+  }
+
+  async function enqueue(demo: Demo) {
+    const runId = crypto.randomUUID()
+    runIds.current[demo.title] = runId
+    setPending(demo.title)
+    setActiveRun({
+      title: demo.title,
+      expectedConsumers: demo.expectedConsumers,
+    })
+    setResults((current) => {
+      const next = { ...current }
+      delete next[demo.title]
+      return next
+    })
+
+    try {
+      const response = await fetch(demo.endpoint, {
+        method: 'POST',
+        headers: { 'content-type': 'application/json' },
+        body: JSON.stringify({
+          text: `Hello from ${demo.producer}`,
+          sentAt: new Date().toISOString(),
+        }),
+      })
+      const result = (await response.json()) as {
+        taskId?: string
+        messageId?: string | null
+        detail?: string
+        expectedConsumers?: Consumer[]
+      }
+
+      if (!response.ok) {
+        throw new Error(result.detail ?? `Request failed (${response.status})`)
+      }
+      if (!result.taskId) {
+        throw new Error('Producer did not return a task ID')
+      }
+      if (!result.expectedConsumers) {
+        throw new Error('Producer did not return expected consumers')
+      }
+      const taskId = result.taskId
+      const expectedConsumers = result.expectedConsumers
+      setActiveRun((current) =>
+        current?.title === demo.title
+          ? {
+              ...current,
+              taskId,
+              messageId: result.messageId ?? null,
+            }
+          : current
+      )
+
+      setResults((current) => ({
+        ...current,
+        [demo.title]: {
+          taskId,
+          messageId: result.messageId ?? null,
+          status: 'pending',
+          expectedConsumers,
+          completions: {},
+        },
+      }))
+      void pollTask(demo.title, taskId, runId)
+    } catch (error) {
+      setResults((current) => ({
+        ...current,
+        [demo.title]: {
+          taskId: '',
+          messageId: null,
+          status: 'error',
+          expectedConsumers: demo.expectedConsumers,
+          completions: {},
+          detail:
+            error instanceof Error
+              ? error.message
+              : 'Unable to enqueue message',
+        },
+      }))
+    } finally {
+      setPending(undefined)
+    }
+  }
+
+  const activeTask = activeRun ? results[activeRun.title] : undefined
+
+  function runtimeState(runtime: Consumer) {
+    if (!activeRun?.expectedConsumers.includes(runtime)) return 'idle'
+    if (!activeTask) return 'processing'
+    if (activeTask.completions[runtime]) return 'completed'
+    if (activeTask.status === 'error') return 'error'
+    return 'processing'
+  }
+
+  return (
+    <main>
+      <header className="hero">
+        <h1>Next.js + Python queues</h1>
+        <p>Send a message and watch each consumer run.</p>
+      </header>
+
+      <section className="demo-grid" aria-label="Queue demos">
+        {demos.map((demo, index) => (
+          <article
+            className={`demo-card ${
+              activeRun?.title === demo.title ? 'selected' : ''
+            }`}
+            key={demo.title}
+          >
+            <div className="card-topline">
+              <span>0{index + 1}</span>
+              <span>{demo.producer}</span>
+            </div>
+            <div className="card-copy">
+              <h2>{demo.title}</h2>
+              <p>{demo.description}</p>
+            </div>
+            <div className="mini-code">
+              <div className="code-chrome">
+                <span>
+                  {demo.producer === 'Python' ? 'main.py' : 'route.ts'}
+                </span>
+                <span>{demo.topic}</span>
+              </div>
+              <pre>
+                <code>
+                  <span className="syntax-keyword">await</span>{' '}
+                  <span className="syntax-fn">send</span>
+                  (&quot;{demo.topic}&quot;, payload)
+                </code>
+              </pre>
+            </div>
+            <button
+              disabled={pending !== undefined}
+              onClick={() => enqueue(demo)}
+              type="button"
+            >
+              <span>
+                {pending === demo.title ? 'Sending…' : 'Send message'}
+              </span>
+              <span aria-hidden="true">→</span>
+            </button>
+            <output aria-live="polite" className="task-output">
+              {results[demo.title] && (
+                <>
+                  <div className="task-state">
+                    <span
+                      className={`status-dot ${results[demo.title].status}`}
+                    />
+                    {results[demo.title].status}
+                  </div>
+                  {results[demo.title].detail && (
+                    <span>{results[demo.title].detail}</span>
+                  )}
+                </>
+              )}
+            </output>
+          </article>
+        ))}
+      </section>
+
+      <section className="consumers-section" aria-labelledby="consumers-title">
+        <div className="section-heading">
+          <h2 id="consumers-title">Consumers</h2>
+        </div>
+
+        <div className="handler-grid">
+          <article className="handler-card" data-state={runtimeState('nextjs')}>
+            <div className="handler-header">
+              <div>
+                <span className="runtime-icon">
+                  <Image alt="" height={22} src="/nextjs.svg" width={22} />
+                </span>
+                <div>
+                  <strong>Next.js callback</strong>
+                  <small>route.ts</small>
+                </div>
+              </div>
+              <span className="handler-state">
+                <i />
+                {runtimeState('nextjs')}
+              </span>
+            </div>
+            <pre className="handler-code">
+              <code>
+                <span className="syntax-keyword">export const</span> POST ={' '}
+                <span className="syntax-fn">handleCallback</span>(
+                <span className="syntax-keyword">async</span> (message) =&gt;{' '}
+                {'{'}
+                {'\n  '}
+                <span className="syntax-keyword">await</span>{' '}
+                <span className="syntax-fn">completeTask</span>(message)
+                {'\n'}
+                {'}'})
+              </code>
+            </pre>
+            <div className="handler-result">
+              <span>Latest result</span>
+              <code>
+                {activeTask?.completions.nextjs?.result.received.text ??
+                  'Waiting for a delivery…'}
+              </code>
+            </div>
+          </article>
+
+          <article className="handler-card" data-state={runtimeState('python')}>
+            <div className="handler-header">
+              <div>
+                <span className="runtime-icon">
+                  <Image alt="" height={22} src="/python.svg" width={22} />
+                </span>
+                <div>
+                  <strong>Python subscriber</strong>
+                  <small>subscribers.py</small>
+                </div>
+              </div>
+              <span className="handler-state">
+                <i />
+                {runtimeState('python')}
+              </span>
+            </div>
+            <pre className="handler-code">
+              <code>
+                <span className="syntax-decorator">@subscribe</span>
+                (topic=<span className="syntax-string">&quot;demo-*&quot;</span>
+                ){'\n'}
+                <span className="syntax-keyword">async def</span>{' '}
+                <span className="syntax-fn">handle</span>(message):
+                {'\n  '}
+                <span className="syntax-keyword">await</span>{' '}
+                <span className="syntax-fn">complete_task</span>(message)
+              </code>
+            </pre>
+            <div className="handler-result">
+              <span>Latest result</span>
+              <code>
+                {activeTask?.completions.python?.result.received.text ??
+                  'Waiting for a delivery…'}
+              </code>
+            </div>
+          </article>
+        </div>
+
+        {activeRun && (
+          <div className="run-meta">
+            <span>Current task</span>
+            <code>{activeRun.taskId ?? 'Creating task…'}</code>
+            <span>
+              {activeRun.taskId
+                ? activeRun.messageId ?? 'ingestion deferred'
+                : ' '}
+            </span>
+          </div>
+        )}
+      </section>
+    </main>
+  )
+}
diff --git a/services/cross-runtime-queues/frontend/src/app/styles.css b/services/cross-runtime-queues/frontend/src/app/styles.css
new file mode 100644
index 0000000000..8f695dbd4b
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/src/app/styles.css
@@ -0,0 +1,439 @@
+:root {
+  color-scheme: dark;
+  --background: #000;
+  --panel: #0a0a0a;
+  --border: #262626;
+  --muted: #888;
+  --foreground: #ededed;
+  --green: #50e3c2;
+}
+
+* {
+  box-sizing: border-box;
+}
+
+body {
+  margin: 0;
+  background: var(--background);
+  color: var(--foreground);
+  font-family: 'Geist Sans', 'Helvetica Neue', Arial, sans-serif;
+  -webkit-font-smoothing: antialiased;
+}
+
+main {
+  width: min(1200px, calc(100% - 48px));
+  margin: 0 auto;
+}
+
+.hero {
+  padding: 72px 0 48px;
+}
+
+.hero h1 {
+  margin: 0 0 12px;
+  font-size: clamp(38px, 5vw, 56px);
+  font-weight: 600;
+  letter-spacing: -0.055em;
+  line-height: 1;
+}
+
+.hero p {
+  margin: 0;
+  color: var(--muted);
+  font-size: 15px;
+  line-height: 1.6;
+}
+
+.demo-grid {
+  display: grid;
+  grid-template-columns: repeat(3, minmax(0, 1fr));
+  gap: 1px;
+  overflow: hidden;
+  border: 1px solid var(--border);
+  border-radius: 14px;
+  background: var(--border);
+}
+
+.demo-card {
+  display: flex;
+  min-height: 440px;
+  flex-direction: column;
+  background: var(--panel);
+  transition: background 180ms ease;
+}
+
+.demo-card.selected {
+  background: #0e0e0e;
+  box-shadow: inset 0 2px 0 #fff;
+}
+
+.card-topline {
+  display: flex;
+  justify-content: space-between;
+  padding: 18px 20px;
+  border-bottom: 1px solid var(--border);
+  color: #777;
+  font-family: monospace;
+  font-size: 11px;
+  text-transform: uppercase;
+}
+
+.card-copy {
+  min-height: 150px;
+  padding: 26px 24px 22px;
+}
+
+.card-copy h2 {
+  margin: 0 0 10px;
+  font-size: 22px;
+  font-weight: 550;
+  letter-spacing: -0.035em;
+}
+
+.card-copy p {
+  margin: 0;
+  color: var(--muted);
+  font-size: 14px;
+  line-height: 1.55;
+}
+
+.mini-code {
+  margin: 0 16px 16px;
+  overflow: hidden;
+  border: 1px solid var(--border);
+  border-radius: 8px;
+  background: #050505;
+}
+
+.code-chrome {
+  display: flex;
+  justify-content: space-between;
+  padding: 8px 11px;
+  border-bottom: 1px solid #1c1c1c;
+  color: #666;
+  font-family: monospace;
+  font-size: 9px;
+}
+
+.mini-code pre {
+  margin: 0;
+  padding: 18px 14px;
+  overflow-x: auto;
+  color: #d4d4d4;
+  font-size: 13px;
+  line-height: 1.5;
+}
+
+.syntax-keyword {
+  color: #c586c0;
+}
+
+.syntax-fn {
+  color: #dcdcaa;
+}
+
+.syntax-decorator {
+  color: #4ec9b0;
+}
+
+.syntax-string {
+  color: #ce9178;
+}
+
+.demo-card > button {
+  display: flex;
+  width: auto;
+  min-height: 42px;
+  align-items: center;
+  justify-content: space-between;
+  margin: auto 16px 16px;
+  padding: 0 14px;
+  border: 1px solid #fff;
+  border-radius: 7px;
+  background: #fff;
+  color: #000;
+  cursor: pointer;
+  font-size: 13px;
+  font-weight: 550;
+  transition: background 150ms ease, color 150ms ease;
+}
+
+.demo-card > button:hover:not(:disabled) {
+  background: #000;
+  color: #fff;
+}
+
+.demo-card > button:disabled {
+  cursor: wait;
+  opacity: 0.55;
+}
+
+.task-output {
+  display: block;
+  min-height: 16px;
+  margin: -8px 16px 16px;
+  color: var(--muted);
+  font-family: monospace;
+  font-size: 10px;
+  overflow-wrap: anywhere;
+}
+
+.task-state {
+  display: flex;
+  align-items: center;
+  gap: 7px;
+  text-transform: capitalize;
+}
+
+.status-dot {
+  width: 6px;
+  height: 6px;
+  border-radius: 50%;
+  background: #666;
+}
+
+.status-dot.pending {
+  background: #f5a623;
+  box-shadow: 0 0 8px #f5a623;
+  animation: pulse 1.2s ease-in-out infinite;
+}
+
+.status-dot.completed {
+  background: var(--green);
+}
+
+.status-dot.error {
+  background: #e00;
+}
+
+.consumers-section {
+  margin-top: 72px;
+  padding-bottom: 72px;
+}
+
+.section-heading {
+  margin-bottom: 28px;
+}
+
+.section-heading h2 {
+  margin: 0;
+  font-size: 28px;
+  font-weight: 550;
+  letter-spacing: -0.045em;
+}
+
+.handler-grid {
+  display: grid;
+  grid-template-columns: repeat(2, minmax(0, 1fr));
+  gap: 16px;
+}
+
+.handler-card {
+  overflow: hidden;
+  border: 1px solid var(--border);
+  border-radius: 12px;
+  background: var(--panel);
+  transition: border-color 250ms ease, box-shadow 250ms ease,
+    transform 250ms ease;
+}
+
+.handler-card[data-state='processing'] {
+  border-color: #666;
+  box-shadow: 0 0 0 1px #444, 0 0 45px rgb(255 255 255 / 10%);
+  transform: translateY(-2px);
+}
+
+.handler-card[data-state='completed'] {
+  border-color: rgb(80 227 194 / 55%);
+  box-shadow: 0 0 40px rgb(80 227 194 / 8%);
+}
+
+.handler-card[data-state='error'] {
+  border-color: #8f2020;
+}
+
+.handler-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 16px;
+  border-bottom: 1px solid var(--border);
+}
+
+.handler-header > div {
+  display: flex;
+  align-items: center;
+  gap: 11px;
+}
+
+.runtime-icon {
+  display: grid;
+  width: 30px;
+  height: 30px;
+  place-items: center;
+  border: 1px solid #303030;
+  border-radius: 6px;
+  background: #111;
+}
+
+.runtime-icon img {
+  filter: invert(1);
+}
+
+.handler-header strong,
+.handler-header small {
+  display: block;
+}
+
+.handler-header strong {
+  margin-bottom: 3px;
+  font-size: 13px;
+  font-weight: 550;
+}
+
+.handler-header small {
+  color: #666;
+  font-family: monospace;
+  font-size: 10px;
+}
+
+.handler-state {
+  display: flex;
+  align-items: center;
+  gap: 7px;
+  color: #777;
+  font-family: monospace;
+  font-size: 9px;
+  text-transform: uppercase;
+}
+
+.handler-state i {
+  width: 6px;
+  height: 6px;
+  border-radius: 50%;
+  background: #444;
+}
+
+[data-state='processing'] .handler-state {
+  color: #fff;
+}
+
+[data-state='processing'] .handler-state i {
+  background: #fff;
+  box-shadow: 0 0 10px #fff;
+  animation: pulse 1s ease-in-out infinite;
+}
+
+[data-state='completed'] .handler-state {
+  color: var(--green);
+}
+
+[data-state='completed'] .handler-state i {
+  background: var(--green);
+  box-shadow: 0 0 8px var(--green);
+}
+
+.handler-code {
+  min-height: 155px;
+  margin: 0;
+  padding: 28px 24px;
+  overflow-x: auto;
+  background: linear-gradient(
+      90deg,
+      transparent 39px,
+      #161616 40px,
+      transparent 41px
+    ),
+    #070707;
+  color: #d4d4d4;
+  font-size: 13px;
+  line-height: 1.8;
+}
+
+.handler-result {
+  display: grid;
+  grid-template-columns: auto 1fr;
+  gap: 16px;
+  padding: 13px 16px;
+  border-top: 1px solid var(--border);
+  color: #666;
+  font-size: 10px;
+}
+
+.handler-result code {
+  overflow: hidden;
+  color: #aaa;
+  text-align: right;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.run-meta {
+  display: flex;
+  align-items: center;
+  gap: 14px;
+  margin-top: 14px;
+  padding: 12px 14px;
+  border: 1px solid var(--border);
+  border-radius: 8px;
+  color: #666;
+  font-family: monospace;
+  font-size: 9px;
+}
+
+.run-meta code {
+  color: #aaa;
+}
+
+.run-meta span:last-child {
+  margin-left: auto;
+}
+
+@keyframes pulse {
+  50% {
+    opacity: 0.4;
+  }
+}
+
+@media (max-width: 860px) {
+  main {
+    width: min(100% - 32px, 640px);
+  }
+
+  .hero {
+    padding: 56px 0 40px;
+  }
+
+  .demo-grid,
+  .handler-grid {
+    grid-template-columns: 1fr;
+  }
+
+  .demo-card {
+    min-height: 410px;
+  }
+
+  .consumers-section {
+    margin-top: 56px;
+  }
+}
+
+@media (max-width: 520px) {
+  .hero h1 {
+    font-size: 46px;
+  }
+
+  .handler-code {
+    padding: 22px 16px;
+    font-size: 11px;
+  }
+
+  .run-meta {
+    align-items: flex-start;
+    flex-direction: column;
+  }
+
+  .run-meta span:last-child {
+    margin-left: 0;
+  }
+}
diff --git a/services/cross-runtime-queues/frontend/src/lib/task-store.ts b/services/cross-runtime-queues/frontend/src/lib/task-store.ts
new file mode 100644
index 0000000000..6667b7a016
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/src/lib/task-store.ts
@@ -0,0 +1,55 @@
+type Consumer = 'nextjs' | 'python'
+
+export type TaskRecord = {
+  taskId: string
+  expectedConsumers: Consumer[]
+  messageId: string | null
+}
+
+function backendUrl(path: string) {
+  if (!process.env.BACKEND_URL) {
+    throw new Error('BACKEND_URL service binding is not configured')
+  }
+  return new URL(path, process.env.BACKEND_URL).toString()
+}
+
+async function assertSuccessful(response: Response) {
+  if (response.ok) return
+
+  const detail = await response.text()
+  throw new Error(`Result store request failed (${response.status}): ${detail}`)
+}
+
+export async function putTask(task: TaskRecord) {
+  const response = await fetch(backendUrl(`/api/python/tasks/${task.taskId}`), {
+    method: 'PUT',
+    headers: { 'content-type': 'application/json' },
+    body: JSON.stringify(task),
+  })
+  await assertSuccessful(response)
+}
+
+export async function deleteTask(taskId: string) {
+  const response = await fetch(backendUrl(`/api/python/tasks/${taskId}`), {
+    method: 'DELETE',
+  })
+  await assertSuccessful(response)
+}
+
+export async function completeTask(
+  taskId: string,
+  consumer: Consumer,
+  result: Record<string, unknown>
+) {
+  const response = await fetch(
+    backendUrl(`/api/python/tasks/${taskId}/completions/${consumer}`),
+    {
+      method: 'PUT',
+      headers: { 'content-type': 'application/json' },
+      body: JSON.stringify({
+        result,
+      }),
+    }
+  )
+  await assertSuccessful(response)
+}
diff --git a/services/cross-runtime-queues/frontend/tsconfig.json b/services/cross-runtime-queues/frontend/tsconfig.json
new file mode 100644
index 0000000000..4b89c2fedb
--- /dev/null
+++ b/services/cross-runtime-queues/frontend/tsconfig.json
@@ -0,0 +1,33 @@
+{
+  "compilerOptions": {
+    "target": "ES2017",
+    "lib": ["dom", "dom.iterable", "esnext"],
+    "skipLibCheck": true,
+    "strict": true,
+    "noEmit": true,
+    "esModuleInterop": true,
+    "module": "esnext",
+    "moduleResolution": "bundler",
+    "isolatedModules": true,
+    "jsx": "react-jsx",
+    "incremental": true,
+    "plugins": [
+      {
+        "name": "next"
+      }
+    ],
+    "paths": {
+      "@/*": ["./src/*"]
+    },
+    "allowJs": true,
+    "resolveJsonModule": true
+  },
+  "include": [
+    "next-env.d.ts",
+    ".next/types/**/*.ts",
+    "**/*.ts",
+    "**/*.tsx",
+    ".next/dev/types/**/*.ts"
+  ],
+  "exclude": ["node_modules"]
+}
diff --git a/services/cross-runtime-queues/vercel.json b/services/cross-runtime-queues/vercel.json
new file mode 100644
index 0000000000..6c727521c3
--- /dev/null
+++ b/services/cross-runtime-queues/vercel.json
@@ -0,0 +1,52 @@
+{
+  "$schema": "https://openapi.vercel.sh/vercel.json",
+  "services": {
+    "frontend": {
+      "root": "frontend/",
+      "bindings": [
+        {
+          "type": "service",
+          "service": "backend",
+          "format": "url",
+          "env": "BACKEND_URL"
+        }
+      ],
+      "functions": {
+        "src/app/api/queues/from-python/route.ts": {
+          "experimentalTriggers": [
+            {
+              "type": "queue/v2beta",
+              "topic": "demo-python-to-next"
+            }
+          ]
+        },
+        "src/app/api/queues/fanout/route.ts": {
+          "experimentalTriggers": [
+            {
+              "type": "queue/v2beta",
+              "topic": "demo-fanout"
+            }
+          ]
+        }
+      }
+    },
+    "backend": {
+      "root": "backend/",
+      "entrypoint": "pyproject.toml"
+    }
+  },
+  "rewrites": [
+    {
+      "source": "/api/python/(.*)",
+      "destination": {
+        "service": "backend"
+      }
+    },
+    {
+      "source": "/(.*)",
+      "destination": {
+        "service": "frontend"
+      }
+    }
+  ]
+}