## Lecture Videos
### New Features
* Introducing a state machine for Lecture Video mode with support for
playback checkpoints, in-video question prompts, answer follow-ups, and
guided resume points.
* Session state management allows one browser tab to actively control
playback at a time, with automatic lease expiry and renewal support. All
interaction submissions support idempotency keys, preventing duplicate
events if a request is retried.
* Lecture Video interactions are stored. Thread viewers can review key
session events such as questions shown, answers submitted, pauses,
seeks, resumes, and completions.
* The server supports streaming lecture-specific narration audio during
guided video interactions. Narration access is gated on thread state, so
a user can't fetch post-answer audio before answering.