From 722fd24cd72aa43d27dc07e3bc328b17d08cb487 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20N=C3=A9grier?= <d.negrier@thecodingmachine.com>
Date: Fri, 27 Feb 2026 18:13:59 +0100
Subject: [PATCH 1/2] fix(webrtc): reuse inactive publisher transceivers to
 avoid sender/transceiver churn

`RTCEngine.createSender`/`createSimulcastSender` always created new publisher transceivers via addTransceiver().
During repeated unpublish/publish cycles, this could accumulate inactive transceivers and increase memory usage.

Add a reuse path that:

- looks for an inactive publisher transceiver of matching media kind
- switches it back to sendonly
- replaces its sender track instead of creating a new transceiver
- applies to both primary sender creation and simulcast sender creation

This reduces transceiver churn and keeps memory growth bounded in restart-heavy flows (e.g. screenshare stop/start loops).
---
 src/room/RTCEngine.ts | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/src/room/RTCEngine.ts b/src/room/RTCEngine.ts
index b49c4f0894..e03492164e 100644
--- a/src/room/RTCEngine.ts
+++ b/src/room/RTCEngine.ts
@@ -910,6 +910,11 @@ export default class RTCEngine extends (EventEmitter as new () => TypedEventEmit
       track.codec = opts.videoCodec;
     }
 
+    const reusedSender = await this.reuseInactivePublisherSender(track.mediaStreamTrack, streams);
+    if (reusedSender) {
+      return reusedSender;
+    }
+
     const transceiverInit: RTCRtpTransceiverInit = { direction: 'sendonly', streams };
     if (encodings) {
       transceiverInit.sendEncodings = encodings;
@@ -932,6 +937,15 @@ export default class RTCEngine extends (EventEmitter as new () => TypedEventEmit
     if (!this.pcManager) {
       throw new UnexpectedConnectionState('publisher is closed');
     }
+    const reusedSender = await this.reuseInactivePublisherSender(simulcastTrack.mediaStreamTrack);
+    if (reusedSender) {
+      if (!opts.videoCodec) {
+        return;
+      }
+      track.setSimulcastTrackSender(opts.videoCodec, reusedSender);
+      return reusedSender;
+    }
+
     const transceiverInit: RTCRtpTransceiverInit = { direction: 'sendonly' };
     if (encodings) {
       transceiverInit.sendEncodings = encodings;
@@ -948,6 +962,34 @@ export default class RTCEngine extends (EventEmitter as new () => TypedEventEmit
     return transceiver.sender;
   }
 
+  private async reuseInactivePublisherSender(track: MediaStreamTrack, streams: MediaStream[] = []) {
+    if (!this.pcManager) {
+      return;
+    }
+
+    const transceiver = this.pcManager.publisher
+      .getTransceivers()
+      .find(
+        (candidate) =>
+          candidate.direction === 'inactive' &&
+          candidate.mid !== null &&
+          candidate.sender.track === null &&
+          candidate.receiver.track?.kind === track.kind &&
+          candidate.sender.transport?.state !== 'closed',
+      );
+
+    if (!transceiver) {
+      return;
+    }
+
+    transceiver.direction = 'sendonly';
+    if ('setStreams' in transceiver.sender && streams.length > 0) {
+      transceiver.sender.setStreams(...streams);
+    }
+    await transceiver.sender.replaceTrack(track);
+    return transceiver.sender;
+  }
+
   private async createRTCRtpSender(track: MediaStreamTrack) {
     if (!this.pcManager) {
       throw new UnexpectedConnectionState('publisher is closed');

From d3b394d51fed667d371251067d26698ecae56027 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20N=C3=A9grier?= <d.negrier@thecodingmachine.com>
Date: Sat, 28 Feb 2026 14:09:18 +0100
Subject: [PATCH 2/2] Adding changeset for reusing inactive publisher
 transceivers in RTCEngine to reduce memory growth on republish

---
 .changeset/sweet-planes-open.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/sweet-planes-open.md

diff --git a/.changeset/sweet-planes-open.md b/.changeset/sweet-planes-open.md
new file mode 100644
index 0000000000..115a97a450
--- /dev/null
+++ b/.changeset/sweet-planes-open.md
@@ -0,0 +1,5 @@
+---
+'livekit-client': patch
+---
+
+Reuse inactive publisher transceivers in RTCEngine to reduce memory growth on republish