Flicker-Free Markdown for Live AI Replies

§1 Why token streams make Markdown jump

A live AI reply arrives in pieces, but Markdown formatting often needs context that has not arrived yet. An opening asterisk might become emphasis. Three backticks might start a code block. A line of ordinary text might become a table header when the next line appears.

If your interface rebuilds the entire message whenever another piece arrives, text can flash, code blocks can change shape, and the reader can lose their place. Smooth streaming is less about making text arrive faster and more about keeping the page steady while its meaning develops.

§2 Separate incoming text from visible updates

Start with two separate jobs: receiving the response and updating the screen. Store incoming text in a buffer, then let the interface display the latest buffered content on a controlled schedule.

For browser apps, scheduling updates with the browser’s animation cycle is a useful starting point. You can also batch updates over a short interval, such as 30 to 50 milliseconds, and adjust after testing. Neither approach guarantees smoothness if parsing is expensive, but both avoid unnecessary updates for every tiny fragment.

If you use server-sent events, or SSE, remember that network chunks are not necessarily complete events. Decode the stream correctly, assemble complete events, and extract their text before passing it to your Markdown buffer. Likewise, a text fragment is not guaranteed to contain a complete word or formatting marker.

§3 Keep finished blocks stable and unfinished text flexible

A useful rendering strategy divides the answer into a stable region and an active tail. The stable region contains content whose structure is settled. The active tail contains the part still being written.

Render the active tail with a streaming-aware Markdown parser, or show it as plain text until its structure becomes clearer. Update that region without repeatedly replacing every earlier paragraph.

A blank line is a clue, not a universal completion signal. Code fences, lists, and other structures can continue across multiple lines. Use parser state to decide what is safe to finalize. If your parser cannot track that state, reparsing the message while preserving stable interface elements is safer than inventing fragile block boundaries.

• – Keep an unfinished code fence inside a stable code container.
• – Delay expensive syntax highlighting until the code block closes, or run it less frequently.
• – Avoid turning incomplete link syntax into a clickable link prematurely.
• – Run a final parse when streaming ends so the completed reply has consistent formatting.

§4 Preserve message elements and the reader’s position

Even correct Markdown can flicker if the application destroys and recreates its interface elements. In a component framework, give each message a stable identifier. Avoid using the current text or its length as the message key, because either changes throughout the stream.

Keep the message container mounted and update its contents through normal framework rendering. Avoid repeatedly assigning the whole message as raw HTML. For custom renderers, preserve unchanged block elements where possible.

Scrolling needs the same care. Follow new text only when the reader is already near the bottom. If they scroll upward, stop pulling them back down. A small new-content indicator lets them return when ready.

§5 Use a streaming API without confusing transport and rendering

Fluxio is a practical option for the delivery layer: it is a streaming-first, pay-per-token AI API relay with an OpenAI-compatible interface. You can use one key to request supported models, such as Gemini 2.5 Flash, and receive replies incrementally.

The relay supplies the stream; your application still controls buffering, Markdown parsing, and screen updates. Keeping those responsibilities separate makes it easier to diagnose whether a pause comes from the network, the parser, or the interface.

§6 Test incomplete Markdown and interrupted replies

Test slow streams, unfinished emphasis, long code blocks, tables, and disconnections. Sanitize rendered output and restrict unsafe link destinations, including during intermediate updates. When a stream fails, preserve the text already received and clearly mark the reply as interrupted.

Sign up for Fluxio to try streaming replies.