## Lecture Videos (Preview)

> [!NOTE]
> This release adds new capabilities for Lecture Videos, which remain
under active development and are not yet officially supported in Groups.
APIs, features, and UI/UX may change before final release.
> 
> Lecture Video mode is currently visible only to institutional admins
when creating an assistant.

### New Features
* Lecture Video assistant instructions now use a unified speech/display
block format for math, symbols, Mermaid diagrams, SVG diagrams, and
follow-up suggestions.

### Updates & Improvements
* Improved Lecture Video response formatting so math, symbols, Mermaid
diagrams, and SVG diagrams can have separate spoken and visible
versions.
* Lecture Video responses can now include display-only content without
requiring silent speech text.
* Lecture Video text-to-speech now flushes spoken audio before long
visual-only diagram content and follow-up suggestions.

### Resolved Issues
* Fixed: Some Lecture Video responses with malformed, incomplete, or
split speech/display formatting may leak internal formatting markers or
drop later follow-up suggestions.
* Fixed: Spoken narration before Mermaid or SVG diagrams may be delayed
while the system waits for the full diagram content.
* Fixed: Lecture Video text-to-speech state may carry over incorrectly
after a mid-response flush.
* Fixed: Lecture Video responses with missing speech text in
display-only blocks may be treated as malformed.
* Fixed: Emoji and other characters represented by Unicode surrogate
pairs may not render correctly in Lecture Video speech/display
formatting.