Flashing Output in AI Agent

I am testing my AI Agent, which generates code, and I noticed that the output background flashes between black and white while the code is being generated. It doesn't do this when it's generating standard text, only when providing code.

RRichcantoo I am testing my AI Agent, which generates code, and I noticed that the output ba...

Tico | Voiceflow Assistant•7/28/25, 10:14 PM

Why it happens
When the assistant streams a message that is tagged as a Markdown code-block (

), the web-chat first prints the raw text, then runs the syntax-highlighter. The highlighter swaps in a dark code theme after it recognises the language, so on every incremental update you momentarily see the default (white) background before it is restyled – that’s the “flash”. It does not occur on normal text because those lines are never passed through the highlighter.

Fix / work-arounds

**Turn the highlighter off for a response** ‑ add `text` (or any unknown language) after the opening back-ticks. The library will skip colourising and the flash stops: ```text```textyour code here``````
**Lock the code-block colours with CSS** If you still want highlighting, pin the background colour so it never flips. Add a small stylesheet in your `chat.load()` snippet:```htmlwindow.voiceflow.chat.load({ verify: { projectID: '<ID>' }, url: 'https://general-runtime.voiceflow.com', versionID: 'production', assistant: { // override widget styles stylesheet: `data:text/css;base64,${btoa(` .vfrc-system-response pre, .vfrc-system-response code { background:#1e1e1e !important; /* pick any colour */ transition:none !important; /* remove blink */ } `)}` }});```(You can host the CSS instead and pass the URL via `assistant.stylesheet`.)

Either option prevents the alternating black/white flash while the agent is streaming code.

Docs for reference:
https://docs.voiceflow.com (section Custom web chat styling → Custom CSS styling).

Braden•7/28/25, 11:09 PM

oh, that's interesting. We haven't seen a ton of code generation usecases. thanks for reporting this @Richcantoo