Introduction

When a realtime avatar disappears in the middle of a call, the failure mode is usually not “the model stopped talking.” It’s almost always a transport problem: the WebSocket that carries session state drops, the WebRTC connection that carries media stalls, or your browser-side app gets into a reconnection state that looks healthy but is no longer synchronized.

This post walks through how to debug those failures in a SvelteKit banking avatar: how to distinguish signaling issues from media issues, how to inspect browser and server logs without chasing ghosts, and how to make reconnect behavior predictable. By the end, you should be able to isolate whether the problem is session setup, TURN/NAT traversal, auth expiry, or a frontend lifecycle bug in SvelteKit.

Start by separating the control plane from the media plane

Most developers lump “WebRTC” and “WebSocket” together because they show up in the same feature. In practice, they fail differently:

• WebSocket is usually the control plane: session creation, metadata, presence, and agent state.

• WebRTC is the media plane: audio, video, and sometimes data channels.

That distinction matters. If the WebSocket dies but WebRTC stays up, the avatar may keep rendering video briefly while the app loses sync with the session. If WebRTC fails but the WebSocket stays connected, your UI may still think the session is active even though there is no audio/video flowing.

For a banking avatar, the symptom is often “the face froze” or “the call is connected but silent.” Those are different bugs. First question: which transport broke?

What to inspect in the browser

Use the browser devtools Network tab and separate the two channels explicitly.

1. Look at the WebSocket entry and confirm whether it closes cleanly. A normal close code and reason are useful; a 1006 or abrupt disconnect usually means network interruption, proxy reset, or server termination.

2. Open the WebRTC internals in your browser if available, or at least inspect the RTCPeerConnection state from your app logs: connectionState, iceConnectionState, and signalingState.

3. Check whether the media tracks are still live. A connected peer connection with zero inbound bytes is usually a path issue, not a rendering issue.

Good logging is the difference between “the avatar vanished” and “the ICE state went to disconnected after the TURN allocation expired.” Add state transitions to your client logs early, before the bug is intermittent.

pc.onconnectionstatechange = () => {

};

pc.onconnectionstatechange = () => {

};

pc.onconnectionstatechange = () => {

};

WebRTC failure modes that look like “random disconnects”

Most WebRTC disconnects in production boil down to network path issues or lifecycle bugs:

• ICE candidate gathering succeeded, but connectivity failed. This is usually NAT, firewall, or UDP blocking. If your users sit behind aggressive enterprise proxies, the connection may need TURN relay and still be fragile.

• ICE goes to disconnected and never recovers. Short interruptions can recover automatically; prolonged loss usually means the peer is gone or consent freshness failed.

• The browser tab got suspended. Mobile browsers and background tabs can throttle timers and media processing enough to trigger disconnect logic.

• You recreated the peer connection on a Svelte re-render. In SvelteKit, this happens when connection state lives inside component initialization instead of a durable store or module singleton.

One subtle bug in SvelteKit is tearing down the connection during navigation or hot reload. If your avatar component is mounted/unmounted frequently, you can accidentally close the peer connection while the rest of the app still believes the session is active. Keep the connection manager outside transient component state, and make teardown explicit.

WebSocket disconnects: authentication, proxies, and idle timeouts

WebSocket problems are easier to miss because the socket often appears healthy until it suddenly isn’t. Common causes:

• Expired or rotated auth tokens. If your browser-side code is indirectly relying on a session token, a reconnect may fail even though the original socket worked.

• Idle proxies or load balancers. Some infrastructure closes long-lived connections unless keepalives are active.

• Server-side session cleanup. If the backend decides the avatar session is over, the client will see a close that looks “unexpected” unless you log the reason.

• Browser lifecycle events. Route changes, page visibility changes, or unhandled exceptions can kill the socket without obviously touching the media path.

For debugging, always capture the close code and the last few protocol messages before disconnect. If your app uses a heartbeat, log both the heartbeat send time and the last acknowledged message. That lets you distinguish “the socket is dead” from “the server is alive but stopped processing my messages.”

ws.addEventListener("message", (event) => {

});

ws.addEventListener("message", (event) => {

});

ws.addEventListener("message", (event) => {

});

SvelteKit-specific traps

SvelteKit makes it easy to create subtle realtime bugs because its rendering and navigation model is not the same as a single-page app with one immortal root component.

Three patterns are worth checking:

1. Component-local connections. If the WebSocket or RTCPeerConnection is created inside a page component, navigation can destroy it even when you intended it to survive.

2. Reactive reinitialization. A $: block that reconstructs the session on any state change can trigger duplicate connections or race conditions.

3. SSR assumptions. Realtime objects should be initialized only in the browser. Guard all WebSocket/WebRTC setup behind client-only code such as onMount.

A practical pattern is to centralize session management in a store or service module, then let components subscribe to state rather than own the connection. That way route changes, hydration, and reactivity don’t accidentally become part of your network failure surface.

import { onMount } from "svelte";

});

import { onMount } from "svelte";

});

import { onMount } from "svelte";

});

How to debug from the backend side

If the browser logs are inconclusive, move up the stack and inspect the session lifecycle on the server. The key questions are simple:

• Did the session get created successfully?

• Did the media connection establish and remain active?

• Did the server intentionally terminate the session, or did it observe a transport failure?

If your backend is the source of truth for sessions, log the request ID, avatar/session ID, and any close reason when a connection ends. In practice, that gives you a join key across browser logs, server logs, and vendor logs.

When you need to reproduce a session setup problem, a direct API call is often the fastest way to rule out frontend issues. Keep the request minimal and confirm auth first.

curl -X POST https://api.protoface.com/<session-or-avatar-endpoint> \
-d '{"name":"debug-session"}'

curl -X POST https://api.protoface.com/<session-or-avatar-endpoint> \
-d '{"name":"debug-session"}'

curl -X POST https://api.protoface.com/<session-or-avatar-endpoint> \
-d '{"name":"debug-session"}'

The exact fields and endpoints depend on the object you are creating, so use the docs for the current schema. The point is to separate “API request failed” from “browser transport failed.”

Where Protoface fits in this workflow

Protoface is useful here because it lets you test the avatar/session layer independently of your application plumbing. If the banking avatar works through the developer surface but fails in your SvelteKit integration, the bug is almost certainly in your client lifecycle, proxying, or auth handling rather than in the avatar service itself.

For example, the REST API and Python SDK are a clean way to create or inspect sessions from a controlled environment, while the LiveKit plugin path is helpful when the avatar is embedded inside a voice agent and you want synchronized video without hand-rolling media orchestration. If you are integrating through LiveKit Agents, the plugin is a good place to verify that the avatar is stable before wiring it into a browser UI; see the repository at https://github.com/protoface-ai/protoface-quickstart-openai-realtime for a related realtime setup pattern, and the documentation at https://docs.protoface.com for the current API shape.

from protoface_sdk import ProtofaceClient

print(session)

from protoface_sdk import ProtofaceClient

print(session)

from protoface_sdk import ProtofaceClient

print(session)

If you are using a LiveKit-based voice agent, keep the avatar integration as close to the agent process as possible. That reduces the number of moving parts: one process owns the voice pipeline, the avatar plugin, and the session state. Fewer cross-process hops means fewer places for disconnect bugs to hide.

Practical recovery strategy

Once you can reproduce the issue, decide what should reconnect automatically and what should fail closed:

• Reconnect the WebSocket if it only carries session state and you have a reliable way to resync.

• Rebuild the RTCPeerConnection if ICE fails or media stops flowing after a network interruption.

• End the session explicitly if auth is invalid, the user navigated away, or the server has already cleaned up the avatar.

Do not retry indefinitely. In a banking context, a stuck reconnection loop is worse than a clean failure. Surface a deterministic error state, then let the user restart the session.

Conclusion

Debugging realtime avatar disconnects is mostly about disciplined separation: WebSocket versus WebRTC, control plane versus media plane, lifecycle bug versus network failure. In SvelteKit, pay close attention to component mounting, reactivity, and browser-only initialization so you do not accidentally create transient connections.

If you want to validate the avatar/session layer outside your app, use the developer docs and the API or SDK entry points to reproduce the problem in isolation. Then reintroduce the browser integration once the transport path is stable. For implementation details and current schemas, start with https://docs.protoface.com.