OpenAI Realtime API Voice Agent

\n\n

\n\n \n \n",[],[154,173],[154],{"_102":183,"_95":184,"_155":185,"_157":-5,"_158":136,"_159":160,"_161":162,"_104":186,"_99":32,"_164":165,"_166":-5,"_167":22,"_168":-5,"_169":187,"_98":224},"011d77b4-8a98-11f0-81eb-0224a6c84d84","routes","01991b98-4f4e-720c-95f8-8f127958eebf",["D",1757104590583],[188,198,207,215],{"_102":189,"_95":190,"_155":191,"_157":185,"_158":136,"_159":135,"_161":162,"_104":192,"_99":193,"_164":194,"_166":195,"_167":22,"_168":-5,"_169":196,"_98":197},"0febbdec-8ab5-11f0-b988-0224a6c84d84","observer.ts","01991b98-4f4e-720c-95f8-7c81debf2d78",["D",1757117070918],52,"script","import { Hono } from \"npm:hono\";\nimport WebSocket from \"npm:ws\";\nimport { getErrorText, makeHeaders, makeUrl } from \"./utils.ts\";\n\nconst observer = new Hono();\n\n// POST /observer/:callId : self-connect to establish a web socket\nobserver.post(\"/:callId\", async (c) => {\n const callId = c.req.param(\"callId\");\n const url = makeUrl(callId);\n const ws = new WebSocket(url, { headers: makeHeaders() });\n ws.on(\"open\", () => handleOpen(ws, callId));\n ws.on(\"message\", (data) => handleMessage(ws, callId, JSON.parse(data)));\n ws.on(\"error\", (err) => handleError(ws, callId, err));\n\n // Block forever to keep the socket alive.\n await new Promise(() => {});\n return c.newResponse(null);\n});\n\nfunction handleOpen(ws: WebSocket, _callId: string) {\n console.log(\"✅ websocket connected\");\n const message = { type: \"response.create\" };\n setTimeout(() => ws.send(JSON.stringify(message)), 250);\n}\n\nasync function handleMessage(_ws: WebSocket, callId: string, message: any) {\n if (message.type !== \"response.output_audio_transcript.delta\") {\n console.log(message);\n }\n if (message.type == \"response.function_call_arguments.done\") {\n if (message.name == \"end_call\") {\n doHangup(callId);\n }\n }\n}\n\nasync function doHangup(callId: string) {\n const url = makeUrl(callId, \"hangup\");\n console.log(`? hangup: ${url}`);\n const resp = await fetch(url, { method: \"POST\", headers: makeHeaders() });\n if (!resp.ok) {\n console.error(`🔴 end call failed: ${await getErrorText(resp)}`);\n return;\n }\n\n console.log(\"✅ call ended\");\n}\n\nfunction handleError(_ws: WebSocket, _callId: string, err: Error) {\n console.error(`🔴 websocket failed: ${err.message}`);\n}\n\nexport default observer;",[],[184,190],{"_102":199,"_95":200,"_155":201,"_157":185,"_158":136,"_159":135,"_161":162,"_104":202,"_99":203,"_164":194,"_166":204,"_167":22,"_168":-5,"_169":205,"_98":206},"0febbfcc-8ab5-11f0-b988-0224a6c84d84","rtc.ts","01991b98-4f4e-720c-95f8-82f112734664",["D",1757117070918],12,"import { Hono } from \"npm:hono\";\nimport { getErrorText, makeHeaders, makeSession, makeUrl } from \"./utils.ts\";\n\nconst rtc = new Hono();\n\n// POST /rtc : create a new call\nrtc.post(\"/\", async (c) => {\n // Create the call.\n const headers = makeHeaders();\n const fd = new FormData();\n fd.set(\"sdp\", await c.req.text());\n fd.set(\"session\", JSON.stringify(makeSession()));\n const opts = { method: \"POST\", headers: makeHeaders(), body: fd };\n const resp = await fetch(makeUrl(), opts);\n if (!resp.ok) {\n console.error(`🔴 start call failed: ${await getErrorText(resp)}`);\n return c.text(\"Internal error\", 500);\n }\n\n const contentType = resp.headers.get(\"Content-Type\");\n const location = resp.headers.get(\"Location\");\n const callId = location?.split(\"/\").pop();\n console.log(\"✅ call created:\", callId);\n\n // Kick off observer in the background (fire-and-forget).\n const selfUrl = new URL(c.req.url);\n fetch(`${selfUrl.origin}/observer/${callId}`, { method: \"POST\" })\n .catch((e) => console.error(\"observer start failed:\", e));\n\n const responseHeaders = {\n \"Content-Type\": contentType,\n \"Location\": location,\n };\n return c.newResponse(resp.body, { headers: responseHeaders });\n});\n\nexport default rtc;",[],[184,200],{"_102":208,"_95":209,"_155":210,"_157":185,"_158":136,"_159":135,"_161":162,"_104":211,"_99":176,"_164":194,"_166":212,"_167":22,"_168":-5,"_169":213,"_98":214},"0febc152-8ab5-11f0-b988-0224a6c84d84","sip.ts","01991b98-4f4e-720c-95f8-8596df6f7a6a",["D",1757117070918],"import { Hono } from \"npm:hono\";\nimport { Webhook } from \"npm:svix\";\nimport { getErrorText, makeHeaders, makeSession, makeUrl } from \"./utils.ts\";\n\nconst sip = new Hono();\n\n// POST /sip : webhook endpoint\nsip.post(\"/\", async (c) => {\n // Verify the webhook.\n const OPENAI_SIGNING_SECRET = Deno.env.get(\"OPENAI_SIGNING_SECRET\");\n if (!OPENAI_SIGNING_SECRET) {\n console.error(\"🔴 webhook secret not configured\");\n return c.text(\"Internal error\", 500);\n }\n const webhook = new Webhook(OPENAI_SIGNING_SECRET);\n const bodyStr = await c.req.text();\n let callId: string | undefined;\n try {\n const headers = Object.fromEntries(c.req.raw.headers.entries());\n const payload: any = webhook.verify(bodyStr, headers);\n callId = payload.data.call_id;\n console.log(\"✅ verified webhook:\", callId);\n } catch (error) {\n console.error(`🔴 verify failed: ${error}`);\n return c.text(\"Invalid signature\", 401);\n }\n\n // Accept the call.\n const url = makeUrl(callId, \"accept\");\n const headers = makeHeaders(\"application/json\");\n const body = JSON.stringify(makeSession());\n const opts = { method: \"POST\", headers, body };\n const resp = await fetch(url, opts);\n if (!resp.ok) {\n console.error(`🔴 accept failed: ${await getErrorText(resp)}`);\n return c.text(\"Internal error\", 500);\n }\n console.log(\"✅ call accepted:\", callId);\n\n // Kick off observer in the background (fire-and-forget).\n const selfUrl = new URL(c.req.url);\n fetch(`${selfUrl.origin}/observer/${callId}`, { method: \"POST\" })\n .catch((e) => console.error(\"observer start failed:\", e));\n\n return c.newResponse(null);\n});\n\nexport default sip;",[],[184,209],{"_102":216,"_95":217,"_155":218,"_157":185,"_158":136,"_159":135,"_161":162,"_104":219,"_99":220,"_164":194,"_166":221,"_167":22,"_168":-5,"_169":222,"_98":223},"0febc2ec-8ab5-11f0-b988-0224a6c84d84","utils.ts","01991b98-4f4e-720c-95f8-8aaa21f3ce2d",["D",1757117070918],25,"const REALTIME_BASE_URL = \"https://api.openai.com/v1/realtime\";\nconst MODEL = \"gpt-realtime\";\nconst INSTRUCTIONS = `\n Greet the user in English, and thank them for trying the new OpenAI Realtime API.\n Give them a brief summary based on the list below, and then ask if they have any questions.\n Answer questions using the information below. For questions outside this scope,\n apologize and say you can't help with that.\n ---\n Short summary:\n - The Realtime API is now generally available, and has improved instruction following, voice naturalness, and audio quality.\n There are two new voices and it's easier to develop for. There's also a new telephony integration for phone scenarios.\n Full list of improvements:\n - generally available (no longer in beta)\n - two new voices (Cedar and Marin)\n - improved instruction following\n - enhanced voice naturalness\n - higher audio quality\n - improved handling of alphanumerics (eg, properly understanding credit card and phone numbers)\n - support for the OpenAI Prompts API\n - support for MCP-based tools\n - auto-truncation to reduce context size\n - native telephony support, making it simple to connect voice calls to existing Realtime API applications\n - when using WebRTC, you can connect without needing an ephemeral token\n - when using WebRTC, you can now control sessions (including tool calls) from the server\n - when using WebRTC, you can now send video to the model, and it can respond based on what it sees\n - many helpful bugfixes!\n`;\nconst VOICE = \"marin\";\nconst HANGUP_TOOL = {\n type: \"function\",\n name: \"end_call\",\n description: `\n Use this function to hang up the call when the user says goodbye \n or otherwise indicates they are about to end the call.`,\n};\n\nconst OPENAI_API_KEY = Deno.env.get(\"OPENAI_API_KEY\");\nif (!OPENAI_API_KEY) {\n throw new Error(\"🔴 OpenAI API key not configured\");\n}\n\nexport function makeUrl(callId?: string, action?: string) {\n let url = REALTIME_BASE_URL;\n if (!callId) {\n // start call (POST)\n url += \"/calls\";\n } else if (action) {\n // accept, reject, hangup (POST)\n url += `/calls/${callId}/${action}`;\n } else {\n // observer (web socket)\n url += `?call_id=${callId}`;\n }\n return url;\n}\n\nexport function makeHeaders(contentType?: string) {\n const obj: Record = {\n Authorization: `Bearer ${OPENAI_API_KEY}`,\n };\n if (contentType) obj[\"Content-Type\"] = contentType;\n return obj;\n}\n\nexport function makeSession() {\n return {\n type: \"realtime\",\n model: MODEL,\n instructions: INSTRUCTIONS,\n audio: {\n input: { noise_reduction: { type: \"near_field\" } },\n output: { voice: VOICE },\n },\n tools: [HANGUP_TOOL],\n };\n}\n\nexport async function getErrorText(resp: Response) {\n const errBody = await resp.text().catch(() => \"\");\n return `${resp.status} ${resp.statusText}: ${errBody}`;\n}",[],[184,217],[184],{"_102":226,"_95":227,"_155":228,"_157":-5,"_158":136,"_159":160,"_161":162,"_104":229,"_99":32,"_164":177,"_166":230,"_167":22,"_168":-5,"_169":231,"_98":232},"011d79f8-8a98-11f0-81eb-0224a6c84d84","README.md","01991b98-4f4e-720c-95f8-9101b5f11ac5",["D",1757104590583],"# hello-realtime\n\n**Hello Realtime** is a OpenAI Realtime app that supports both WebRTC and SIP\n(telephone) users. You can access the app via WebRTC at\n[hello-realtime.val.run](https://hello-realtime.val.run), or via SIP by calling 425-800-0042.\n\nThis demo shows off the new SIP API, the new all-in-one WebRTC API, and the new\nserver-side websocket interface.\n\nIf you remix the app, you'll just need to pop in your own `OPENAI_API_KEY` (from\n[platform.openai.com](https://platform.openai.com)), and if you want SIP, the `OPENAI_SIGNING_SECRET`.\n\n## Architecture\n\n1. **WebRTC Flow**:\n - Browser connects to frontend\n - creates WebRTC offer\n - `/rtc` endpoint handles SDP negotiation with OpenAI\n - observer established to monitor session\n2. **SIP Flow**:\n - Phone calls triggers webhook\n - `/sip` endpoint verifies webhook and accepts call\n - observer established to monitor session\n\n## API Endpoints\n- `GET /` - serves the WebRTC-based app\n- `POST /rtc` - creates a new WebRTC-based Realtime API session\n- `POST /sip` - handles an incoming Realtime API SIP call\n- `POST /observer` - internal endpoint to establish a Realtime API websocket for session control\n\n## Project Structure\n```\n\n├── frontend/ \n│ └── index.html # HTML/JS application for WebRTC\n├── main.tsx # Main entrypoint for the val.town app\n└── routes/\n |── observer.ts # Server-side session control for SIP & WebRTC\n |── rtc.ts # WebRTC session setup\n |── sip.ts # SIP webhook handling and session setup\n └── utils.ts # Realtime API session configuration and helpers\n```\n\n- [`frontend/index.html`](./frontend/index.html)\n- [`main.tsx`](./main.tsx)\n- [`routes/observer.ts`](./routes/observer.ts)\n- [`routes/rtc.ts`](./routes/rtc.ts)\n- [`routes/sip.ts`](./routes/sip.ts)\n- [`routes/utils.ts`](./routes/utils.ts)",[],[227],{"_102":234,"_95":235,"_155":236,"_157":-5,"_158":136,"_159":160,"_161":162,"_104":237,"_99":32,"_164":238,"_166":239,"_167":22,"_168":-5,"_169":240,"_98":241},"011d7e08-8a98-11f0-81eb-0224a6c84d84","main.tsx","01991b98-4f4e-720c-95f8-96c65e5d475d",["D",1757104590583],"http","import { Hono } from \"npm:hono\";\nimport { parseVal, serveFile } from \"https://esm.town/v/std/utils/index.ts\";\n// import mcp from \"./routes/mcp.ts\";\nimport rtc from \"./routes/rtc.ts\";\nimport sip from \"./routes/sip.ts\";\nimport observer from \"./routes/observer.ts\";\n\nconst SOURCE_URL = parseVal(Deno.env.get(\"VALTOWN_ENTRYPOINT\")).links.self.val;\n\nconst app = new Hono();\napp.route(\"/rtc\", rtc);\napp.route(\"/sip\", sip);\napp.route(\"/observer\", observer);\n// app.route(\"/mcp\", mcp);\napp.get(\"/source\", (c) => c.redirect(SOURCE_URL));\n\napp.get(\"/\", () => serveFile(\"/frontend/index.html\"));\n\nexport default app.fetch;",[],[235],"files",[152,171,182,188,198,207,215,225,233],"counts",{"_246":32,"_247":248,"_249":32,"_250":248},"pulls","branches",2,"forks","envVars","contents",[253,256,259,262],{"_102":153,"_95":154,"_155":156,"_157":-5,"_158":136,"_159":160,"_161":162,"_104":254,"_99":32,"_164":165,"_166":-5,"_167":22,"_168":-5,"_98":255},["D",1757104590583],[154],{"_102":183,"_95":184,"_155":185,"_157":-5,"_158":136,"_159":160,"_161":162,"_104":257,"_99":32,"_164":165,"_166":-5,"_167":22,"_168":-5,"_98":258},["D",1757104590583],[184],{"_102":226,"_95":227,"_155":228,"_157":-5,"_158":136,"_159":160,"_161":162,"_104":260,"_99":32,"_164":177,"_166":230,"_167":22,"_168":-5,"_98":261},["D",1757104590583],[227],{"_102":234,"_95":235,"_155":236,"_157":-5,"_158":136,"_159":160,"_161":162,"_104":263,"_99":32,"_164":238,"_166":239,"_167":22,"_168":-5,"_98":264},["D",1757104590583],[235],"upstreamProject",{"_102":144,"_95":96,"_110":267,"_111":-5,"_108":109,"_23":268},"Sample app for the OpenAI Realtime API",{"_93":269,"_128":270},"jubertioai","https://img.clerk.com/eyJ0eXBlIjoicHJveHkiLCJzcmMiOiJodHRwczovL2ltYWdlcy5jbGVyay5kZXYvb2F1dGhfZ2l0aHViL2ltZ18yeTY4akpGdVF0NWxjckdtTndZMTBjWUJMTTAifQ","upstreamBranch",{"_102":139,"_104":273,"_274":275,"_95":43,"_137":144,"_99":141,"_138":276,"_140":277,"_278":279,"_106":-5,"_149":22,"_108":109,"_148":269,"_16":146,"_147":96},["D",1755188493466],"updatedAt",["D",1757117070866],"e004ac78-4230-11f0-834a-76b3cceeab13",47,"lockfileKey","1757117097496-esm.town_v_jubertioai_hello-realtime@211-main","emptyEnvVars","isNew","flags",[],"routes/_app.x.$handle.$name.environment-variables",{"_93":94,"_95":96,"_100":286,"_250":291},{"_102":103,"_95":96,"_104":287,"_106":-5,"_107":22,"_108":109,"_110":-5,"_111":-5,"_14":112,"_113":-5,"_114":22,"_115":-5,"_116":32,"_16":117,"_118":119,"_120":119,"_121":122,"_123":122,"_124":122,"_125":119,"_126":119,"_23":288,"_130":289,"_133":290,"_149":22},["D",1757104590583],{"_93":94,"_128":129},{"_93":94,"_132":129},{"_99":135,"_95":43,"_102":136,"_137":103,"_138":139,"_140":141,"_142":109,"_143":144,"_145":146,"_147":96,"_148":94},[292,298],{"_293":294,"_104":295,"_274":296,"_110":72,"_297":22},"key","OPENAI_API_KEY",["D",1757104590583],["D",1757104618088],"isEmpty",{"_293":299,"_104":300,"_274":-5,"_110":72,"_297":162},"OPENAI_SIGNING_SECRET",["D",1757104590583],"actionData","errors"]

Realtime Agent

Key	Description
OPENAI_API_KEY
OPENAI_SIGNING_SECRET

Environment variables