diff --git a/app/webrtc/lifecycle.go b/app/webrtc/lifecycle.go
index 2583d09..bf1c7d8 100644
--- a/app/webrtc/lifecycle.go
+++ b/app/webrtc/lifecycle.go
@@ -141,6 +141,11 @@ func (s *Subsystem) allocAdjacentPair(id string) (int, *corewebrtc.Source, *core
 			lastErr = err
 			continue
 		}
+		// Activate IDR keyframe caching on the video source so that
+		// late-joining WHEP peers receive a reference frame immediately
+		// instead of waiting up to one full keyframe interval.
+		videoSrc.EnableKeyFrameCache()
+
 		audioSrc, err := corewebrtc.NewSourceOn(id+":audio", "127.0.0.1", port+1)
 		if err != nil {
 			_ = videoSrc.Close()