Reliable Live Replies: Reconnects and Partial Messages

§1 Live replies arrive in pieces, not finished messages

A streaming chat interface shows an answer while the AI is still generating it. Instead of waiting for a complete paragraph, readers see small pieces appear as they arrive. This makes the interface feel responsive, but it also creates a practical challenge: the connection can break before the answer is finished.

Reliable streaming means handling both ordinary fragments and unexpected interruptions. Your application needs to know what it has received, what it has displayed, and whether the reply actually finished.

§2 Network chunks are not complete streaming events

Many AI APIs deliver replies through Server-Sent Events, or SSE. Each event carries a small update, often inside a JSON payload. However, the network does not promise to deliver one complete event at a time. A single read might contain half an event, several events, or part of a multibyte character.

Keep a buffer between the network reader and the message parser. Decode bytes with a streaming text decoder, then accumulate text until the parser recognizes a complete SSE event. Use an SSE-aware parser rather than treating every line or network chunk as a standalone JSON object.

Only parse JSON after the full event has been assembled. Then extract the text update according to the API's event format. Not every event contains visible text; some carry metadata, completion information, or errors.

§3 Partial replies need an explicit status

Keep the accumulated answer separate from its status. Useful states include connecting, streaming, completed, interrupted, and canceled. A reply containing readable text is not necessarily a completed reply.

• – Show incoming text while the reply is streaming.
• – Mark the reply complete only after receiving the API's documented completion signal.
• – Keep unfinished text visible when a connection fails, but label it as interrupted.
• – Treat a deliberate user cancellation differently from a network failure.

If the connection closes without a completion signal, do not silently present the partial answer as final. An unfinished instruction or code sample can look convincing while missing its most important step.

§4 Reconnecting does not automatically resume generation

Reopening a connection and resuming the same answer are different operations. Some services support resumable streams with stored events and event identifiers. Others require a new generation request. Check the endpoint's documented behavior before implementing automatic recovery.

SSE event identifiers can help only when the server supports replaying missed events. A browser's automatic SSE reconnection does not make an arbitrary AI request resumable. Many AI clients use streamed HTTP requests through fetch or an SDK rather than the browser's EventSource interface.

Never assume a retry will return the missing continuation. A repeated request may produce a different answer and incur additional token charges. If true resume is unavailable, offer a clearly labeled retry that creates a fresh attempt rather than appending it to the broken reply.

§5 Safe retries preserve context without duplicating text

Give each generation attempt its own identifier. Ignore late updates from an older attempt after a retry begins. If the service provides stable event identifiers and replay support, use those identifiers to discard duplicate events.

Retry temporary failures with a short, increasing delay and some randomness, while respecting server retry guidance. Limit the number of attempts. Authentication failures and invalid requests usually need correction, not repeated network calls.

Preserve the user's original message and completed conversation history. Do not silently add an interrupted assistant reply to that history as though it were finished. If you offer a continuation request, make clear that the model is generating a continuation, not recovering an identical lost stream.

§6 Test interrupted streams before shipping live chat

Test split events, slow connections, dropped connections, cancellation, and retries after partial output. Verify that the interface never duplicates text or confuses an interrupted reply with a completed one.

Fluxio is a useful option for building this experience: it is a streaming-first, pay-per-token AI API relay that works with OpenAI SDK clients. You can use one key to access models such as Claude Haiku 4.5 and Gemini 2.5 Flash. Keep buffering and recovery logic in your application, and verify the chosen endpoint's resume behavior rather than assuming it.

Sign up for Fluxio to build your streaming interface.