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For browser voice sessions with OpenAI Realtime, we don’t relay the audio through a Vercel function. Our server mints a short-lived credential, and the browser connects straight to OpenAI over WebRTC. The old reason, that Vercel can’t host WebSockets, is no longer a safe thing to say. Vercel announced public-beta WebSocket support for Vercel Functions in a June 22, 2026 changelog. The case against relaying audio now rests on architecture, not on a platform ban.
The Vercel limitation is no longer categorical
Vercel’s changelog of June 22, 2026 says Vercel Functions can serve WebSocket connections in public beta. A Knowledge Base article updated the same day adds the details that matter for design. An established connection is pinned to one Function for that Function’s maximum duration. A later connection is not guaranteed to reach the same Function.
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Vercel’s general Limits page still says Functions do not support acting as a WebSocket server. The two official sources conflict. We give more weight to the newer, feature-specific beta announcement and KB. Check the beta’s status and your plan’s access before you depend on it, because beta features change.
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1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesShould the browser connect to OpenAI directly, or should the app server relay the audio?
The answer depends on where the Realtime client runs. OpenAI’s Realtime WebSockets documentation says WebSocket is a good fit for server-to-server applications. It also says: “if you are connecting from a client like a browser or mobile app, WebRTC will be a more robust solution in most cases.”
#1 Best Overall
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“More robust” is OpenAI’s qualitative wording. We found no official benchmark that puts a number on latency, reliability or cost for direct WebRTC versus a relay. Our reasoning that a relay adds a hop is an architectural inference, not a measured result.
What we do instead: ephemeral credentials and direct WebRTC
- The browser asks our server for a session credential, after we authenticate and authorize the user.
- The server uses its protected standard API key to request an ephemeral Realtime client secret from OpenAI.
- The server returns only the ephemeral secret. The standard key never leaves the server.
- The browser creates a WebRTC peer connection and starts its Realtime session directly with OpenAI.
Our server still handles authentication, authorization, session configuration and any business or tool logic. It just isn’t forwarding every audio frame. Protecting the API key doesn’t require that, which is the usual reason people build a relay.
Rank #2
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If you need the server in the setup path
OpenAI also documents a unified WebRTC setup. The browser sends its SDP offer to a server you control, and that server creates the Realtime call. This gives the backend control at session start. It is still not a continuous proxy of a live WebSocket audio stream.
What a Vercel relay would inherit
A relay would add its own constraints on top of the Realtime session:
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- Runtime model: per the changelog, WebSockets run on Fluid compute under the same Function limits and pricing model. Active CPU billing applies while messages are processed, not while the connection is idle.
- Bounded duration: Vercel’s Functions Limits page (last updated December 18, 2025) lists Fluid compute maximums of 300 seconds on Hobby and 800 seconds on Pro and Enterprise. Those figures are for the listed Node.js and Python runtimes. Actual values depend on plan, runtime and project configuration, and they change over time.
- Reconnects: because later connections may land on a different Function, clients must handle reconnection.
- State: instance memory isn’t durable shared state. Vercel’s KB recommends Redis for state that must persist across WebSocket connections.
The duration limits are deployment ceilings, not measurements of audio quality. A voice session that outlasts the ceiling needs a reconnect strategy in a relay design. The direct path avoids that dependency for the audio leg.
When a server-side WebSocket still makes sense
A relay is reasonable when a trusted server process is itself the Realtime client. It also fits when backend code must inspect or transform every event, or when policy requires the server to own the connection. That is the server-to-server case OpenAI documents for WebSocket. With Vercel’s beta, running it on Vercel is now technically possible. If you do, design for pinned-but-bounded connections, reconnects and external state.
Rank #4
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Choosing between the approaches
| Question | Direct WebRTC with ephemeral secret | Unified WebRTC via your server | Server-side WebSocket (including Vercel beta) |
|---|---|---|---|
| Where the client runs | Browser or mobile | Browser or mobile | Trusted server |
| Standard API key | Server only; client gets an ephemeral secret | Server only | Server only |
| Backend control | Credential minting and config | Also session setup (SDP exchange) | Every event can pass through your code |
| Platform limits to plan for | Only the token endpoint | Setup endpoint | Function duration, reconnects, external state, pricing |
Our default is the first column. We move to the second when the backend must be involved in call setup, and to the third only when the server has to be the Realtime client.
Quick Recap
Best Value
- SHARE IN-FLIGHT AUDIO — Connect two pairs of Bluetooth headphones or earbuds to one airplane entertainment screen, so you and a travel partner can listen together without wires.
- CLEAR, RELIABLE WIRELESS SOUND — Qualcomm audio technology with aptX Adaptive and aptX HD support delivers stable, detailed audio with compatible headphones.
- 25-HOUR BATTERY FOR LONG TRIPS — Built for long-haul flights with up to 25 hours of playtime, onboard volume controls, and a clear battery indicator.
- SIMPLE 3-STEP PAIRING — Plug Relay into the 3.5 mm audio jack, put your headphones in pairing mode, and connect. Includes a dual-prong airplane adapter.
- TRANSMITTER ONLY, CHECK BEFORE BUYING — Designed to send audio from 3.5 mm sources to Bluetooth headphones. It has no microphone and is not intended for phone calls, TVs, hearing aids, musical instruments, or receiving audio.
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