diff --git a/README.md b/README.md
index 6e74d57..7503caa 100644
--- a/README.md
+++ b/README.md
@@ -70,8 +70,8 @@ Relay mode uses bounded per-worker input queues so one branch can briefly lag wi
 The UI intentionally hides these settings, but the backend still supports them through `POST /api/session`.
 
 - Frame rate defaults to `24fps`. Lower it if the client cannot keep up.
-- Max width defaults to `960px`. Lower it first if bandwidth or image decode is the bottleneck.
-- JPEG quality uses ffmpeg's `-q:v` scale, where lower is better. Set the default with `JPEG_QUALITY`; `7` is the fallback, `2` is high quality, and `18` is rough but lighter.
+- Max width defaults to `960px`, and the client now caps each session to its viewport width. Lower `DEFAULT_FRAME_WIDTH` first if bandwidth or image decode is the bottleneck.
+- JPEG quality uses ffmpeg's `-q:v` scale, where lower is better/larger. Set the default with `JPEG_QUALITY`; `7` is the fallback, `2` is high quality, and `18` is rough but much lighter.
 - Audio defaults to stereo MP3 at `160k`. Tune with `DEFAULT_AUDIO_BITRATE`, `DEFAULT_AUDIO_CHANNELS`, and `DEFAULT_AUDIO_SAMPLE_RATE`.
 
 ## Tradeoffs
diff --git a/public/app.js b/public/app.js
index 83cf552..94c2c65 100644
--- a/public/app.js
+++ b/public/app.js
@@ -95,7 +95,7 @@ elements.form.addEventListener('submit', async (event) => {
     const response = await fetch('/api/session', {
       method: 'POST',
       headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify({ url: elements.url.value }),
+      body: JSON.stringify({ url: elements.url.value, width: getViewportFrameWidth() }),
     });
 
     const payload = await response.json();
@@ -752,7 +752,7 @@ function trimPendingFrameQueue() {
   if (overflow > 0) {
     noteClientTelemetry('pendingQueueOverflowFrames', overflow);
     noteClientTelemetryMax('pendingQueuePeakFrames', state.pendingFrames.length);
-    state.pendingFrames.splice(0, overflow);
+    state.pendingFrames.splice(maxQueuedFrames, overflow);
   }
 }
 
@@ -766,7 +766,7 @@ function trimFrameQueue() {
     return;
   }
 
-  const removed = state.frames.splice(0, overflow);
+  const removed = state.frames.splice(maxQueuedFrames, overflow);
   noteClientTelemetry('decodedQueueOverflowFrames', overflow);
   noteClientTelemetryMax('decodedQueuePeakFrames', state.frames.length + overflow);
 
@@ -816,6 +816,15 @@ function getFrameQueueLimit(seconds, minimum) {
   return Math.max(minimum, Math.ceil(fps * seconds));
 }
 
+function getViewportFrameWidth() {
+  const width = Math.ceil(Math.max(
+    document.documentElement.clientWidth || 0,
+    window.innerWidth || 0,
+  ));
+
+  return clampNumber(width, 160, 1920);
+}
+
 function isLateFrame(timestamp) {
   if (!state.session || state.isSeeking || elements.audio.paused || elements.audio.readyState === 0) {
     return false;
diff --git a/server/index.js b/server/index.js
index 2b4577a..a87d39c 100644
--- a/server/index.js
+++ b/server/index.js
@@ -133,6 +133,8 @@ app.post('/api/session', async (request, response) => {
     lastUsedAt: Date.now(),
   });
 
+  logInfo(`session created id=${shortId(id)} mode=${getSessionPlaybackConnectionMode(sessions.get(id))} fps=${options.fps} width=${options.width} quality=${options.quality}`);
+
   if (METADATA_PROBE_ENABLED) {
     startSessionMetadataProbe(sessions.get(id));
   }