Changelog

Source comments corrected. Nothing to rebuild or rewire.

OnMultimodalDismissed says when to take a card down. It fires when the visitor speaks again, on a restart or a reconnect, and when the session ends, but only if something was shown since the last time. Hide the widgets you showed for OnImageInteractionReceived or OnMultimodalInteraction there.

Subtitles clear when the session ends. OnSubtitleUpdated now also fires with an empty string when the session ends or its connection drops, so the last sentence never outlives its conversation.

Animate from the end of the voice, not the end of the turn. Speaking lasts until the backend closes the turn, and agents that save memories or plan their next step do that seconds after the voice stops. The new GetPerceivedState and OnPerceivedStateChanged give the state as the visitor perceives it: Speaking reads as Listening once the reply’s last audio has played out. See animate from the perceived state.

Two new events for turns with more than one reply. OnTTSResponseAudioComplete fires when each reply’s last audio has arrived, usually seconds before OnTurnAudioComplete. OnTTSReplyHeld fires when a later reply begins after the previous one has finished playing. With bExternalPlaybackControl, that reply is held and started through OnPrebufferReady, like a turn’s first reply.

An interruption now cuts cleanly. After a barge-in, the rest of the interrupted reply’s audio is dropped as it arrives instead of playing as a short leftover, and its subtitle text is not shown.

Short replies start sooner. A reply shorter than the buffering target used to wait for the turn to close. It now starts as soon as its last audio arrives.

?preview=true runs a session on the region’s preview platform — preview.eu.promethist.ai or preview.us.promethist.ai — for trying an agent before it goes live. The page also sends the browser’s time zone and a device identifier with each session.

AV1 video for viewers whose device decodes it in hardware. NVIDIA’s H.264 encoder leaks memory on every bitrate change, a driver bug, and its AV1 encoder does not. streamingDemo.bat now offers AV1 next to H.264, and the page asks for AV1 only in a Chromium browser with hardware AV1 decoding. Everyone else keeps H.264, and a GPU without an AV1 encoder never offers it. The page also asks for a fresh keyframe when the video stalls, instead of waiting out the browser’s timeout.

Web server fixes. Input, freeze-frame and connection fixes in Epic’s frontend library, which we have also offered upstream. The media proxy refuses SVG images and keeps phone photos upright.

SocketIOClient is updated to upstream 2.13.0, with our fixes on top. TLS certificate verification is new and stays off by default.

For C++ code. EPromethistState and the state delegates now live in PromethistLinkTypes.h, which PromethistLinkComponent.h includes, so existing code compiles unchanged. UPromethistLinkComponent::IsStreamingLaunch is no longer public. The module no longer depends on AudioMixer or JsonUtilities.

This release went out without an entry; this one was written afterwards.

These plugins are built for Unreal Engine 5.8. Moving up from 5.7 was a large change — both plugins in this package were reworked for it, and this is the first drop afterwards. Build your project against 5.8 and take the plugins whole rather than merging them into an older copy.

This is also where the changelog starts. Earlier drops went out without one, so nothing before this entry is written down here. From now on each release gets an entry at the top of this page.

Versions are dates, in the company’s scheme: YYYY.ww.index — the ISO week-year, the ISO week, and the build’s order within that week counting from zero. So this is the first build of week 38 of 2026, and the next one that week would be 2026.38.1. The git tag carries the same string with no v prefix.

PromethistLinkPixelStreaming carries that version. The bundled SocketIOClient keeps its own upstream number, 2.12.0, because tracking upstream is the only thing that version is for.