diff --git a/scripts/test_gui_contracts.mjs b/scripts/test_gui_contracts.mjs
index 4c7c322..14e1353 100644
--- a/scripts/test_gui_contracts.mjs
+++ b/scripts/test_gui_contracts.mjs
@@ -19,9 +19,15 @@ assert(/renderRequestGeneration\s*===\s*renderGeneration\)\s*renderDirty\s*=\s*f
   'an in-flight render must not clear a newer render request');
 assert(/const frameDue\s*=\s*audioOk\s*\|\|\s*elapsed\s*>=\s*target/.test(main),
   'live displays must use requestAnimationFrame directly instead of a second 60 Hz gate');
+assert(/await flushPendingPhoenixData\(env, CONFIG\);[^]*?const currentMetricsSeq/.test(main),
+  'the render loop must publish buffered Phoenix data before reading frame sequences');
 assert(/await updateActiveMeters\(env, d, CONFIG\);\s*[^]*?env\.requestRender\?\.\('audio'\)/.test(audio),
   'audio rendering must be requested after active meters finish updating');
-assert(!/phoenixPacketRaf\s*=\s*requestAnimationFrame/.test(audio),
-  'metrics packets must not wait for a competing requestAnimationFrame pump');
+assert(/export async function flushPendingPhoenixData\(env, CONFIG\)/.test(audio),
+  'Phoenix data paths must expose one display-synchronized presentation pump');
+assert(!/requestAnimationFrame/.test(audio),
+  'audio transport must not create requestAnimationFrame loops that compete with the canvas loop');
+assert(!/while\s*\(pendingPhoenixFrame\)/.test(audio),
+  'metrics transport must coalesce bursts instead of draining every queued state');
 
 console.log('GUI contract regression tests passed');
diff --git a/www/core/audio.js b/www/core/audio.js
index 1bfb66a..9f82243 100644
--- a/www/core/audio.js
+++ b/www/core/audio.js
@@ -16,17 +16,14 @@ let phoenixSpectroSocket = null;
 let phoenixSpectroRetryTimer = null;
 let phoenixSpectroDemanded = false;
 let pendingSpectroBuffer = null;
-let phoenixSpectroRaf = 0;
 let phoenixVisualsSocket = null;
 let phoenixVisualsRetryTimer = null;
 let pendingVisualsBuffer = null;
-let phoenixVisualsRaf = 0;
 let envRef = null;
 let lifecycleHandlersBound = false;
 let recoverTimer = null;
 let lastHardRecoverAt = 0;
 let pendingPhoenixFrame = null;
-let phoenixPacketBusy = false;
 
 const RMS_RING = { L: new Float32Array(512), R: new Float32Array(512), i: 0, n: 0 };
 const WAVEFORM_RING_SECONDS = 20;
@@ -106,8 +103,6 @@ function closePhoenixSocket() {
   phoenixSpectroSocket = null;
   phoenixSpectroDemanded = false;
   pendingSpectroBuffer = null;
-  if (phoenixSpectroRaf) cancelAnimationFrame(phoenixSpectroRaf);
-  phoenixSpectroRaf = 0;
   if (phoenixVisualsRetryTimer) clearTimeout(phoenixVisualsRetryTimer);
   phoenixVisualsRetryTimer = null;
   if (phoenixVisualsSocket) {
@@ -121,10 +116,7 @@ function closePhoenixSocket() {
   }
   phoenixVisualsSocket = null;
   pendingVisualsBuffer = null;
-  if (phoenixVisualsRaf) cancelAnimationFrame(phoenixVisualsRaf);
-  phoenixVisualsRaf = 0;
   pendingPhoenixFrame = null;
-  phoenixPacketBusy = false;
 }
 
 async function requestPhoenixRtaConfig(baseUrl, config) {
@@ -269,7 +261,6 @@ function openPhoenixSpectroSocket(baseUrl, env) {
   socket.onmessage = (event) => {
     if (!(event.data instanceof ArrayBuffer)) return;
     pendingSpectroBuffer = event.data;
-    scheduleSpectroBufferPump(env);
   };
 
   const retry = () => {
@@ -306,27 +297,6 @@ function setPhoenixSpectroDemand(baseUrl, env, demanded) {
     } catch (_) {}
   }
   pendingSpectroBuffer = null;
-  if (phoenixSpectroRaf) cancelAnimationFrame(phoenixSpectroRaf);
-  phoenixSpectroRaf = 0;
-}
-
-function scheduleSpectroBufferPump(env) {
-  if (phoenixSpectroRaf || !pendingSpectroBuffer) return;
-  phoenixSpectroRaf = requestAnimationFrame(() => {
-    phoenixSpectroRaf = 0;
-    const buffer = pendingSpectroBuffer;
-    pendingSpectroBuffer = null;
-    try {
-      const decoded = decodePhoenixSpectroBuffer(buffer);
-      if (!decoded) return;
-      if (!copyPhoenixSpectroBins(env.audio, decoded)) return;
-      env.requestRender?.('spectro');
-    } catch (err) {
-      console.warn('Phoenix spectrogram packet error:', err);
-    } finally {
-      if (pendingSpectroBuffer) scheduleSpectroBufferPump(env);
-    }
-  });
 }
 
 function openPhoenixVisualsSocket(baseUrl, env) {
@@ -340,7 +310,6 @@ function openPhoenixVisualsSocket(baseUrl, env) {
   socket.onmessage = (event) => {
     if (!(event.data instanceof ArrayBuffer)) return;
     pendingVisualsBuffer = event.data;
-    scheduleVisualsBufferPump(env);
   };
   const retry = () => {
     if (phoenixVisualsSocket === socket) phoenixVisualsSocket = null;
@@ -355,22 +324,6 @@ function openPhoenixVisualsSocket(baseUrl, env) {
   socket.onclose = retry;
 }
 
-function scheduleVisualsBufferPump(env) {
-  if (phoenixVisualsRaf || !pendingVisualsBuffer) return;
-  phoenixVisualsRaf = requestAnimationFrame(() => {
-    phoenixVisualsRaf = 0;
-    const buffer = pendingVisualsBuffer;
-    pendingVisualsBuffer = null;
-    try {
-      applyVisualsBuffer(env, buffer);
-    } catch (err) {
-      console.warn('Phoenix visual packet error:', err);
-    } finally {
-      if (pendingVisualsBuffer) scheduleVisualsBufferPump(env);
-    }
-  });
-}
-
 function applyVisualsBuffer(env, buffer) {
   const decoded = decodePhoenixVisualsBuffer(buffer);
   if (!decoded) return;
@@ -626,32 +579,49 @@ function mergePendingPhoenixFrame(previous, next) {
   return merged;
 }
 
-function schedulePhoenixPacketPump(env, CONFIG) {
-  if (phoenixPacketBusy || !pendingPhoenixFrame) return;
-  phoenixPacketBusy = true;
-  void (async () => {
-    try {
-      // Consume the newest packet immediately. Incoming packets are still
-      // coalesced while an asynchronous meter/config update is in progress,
-      // but they no longer wait for a second requestAnimationFrame loop.
-      while (pendingPhoenixFrame) {
-        const frame = pendingPhoenixFrame;
-        pendingPhoenixFrame = null;
-        const packet = buildPhoenixMeterPacket(frame);
-        await applyIncomingAudioPacket(env, packet, CONFIG, performance.now());
-      }
-    } catch (err) {
-      console.warn('Phoenix packet error:', err);
-    } finally {
-      phoenixPacketBusy = false;
-      if (pendingPhoenixFrame) schedulePhoenixPacketPump(env, CONFIG);
-    }
-  })();
+function enqueuePhoenixFrame(frame) {
+  pendingPhoenixFrame = mergePendingPhoenixFrame(pendingPhoenixFrame, frame);
 }
 
-function enqueuePhoenixFrame(env, CONFIG, frame) {
-  pendingPhoenixFrame = mergePendingPhoenixFrame(pendingPhoenixFrame, frame);
-  schedulePhoenixPacketPump(env, CONFIG);
+// WebSocket delivery and the display's VSync are independent clocks. Keep the
+// callbacks allocation-light and publish one coherent newest-state snapshot at
+// the beginning of the single canvas render loop. This prevents metrics,
+// visuals and spectrogram updates from being applied in bursts between frames.
+export async function flushPendingPhoenixData(env, CONFIG) {
+  const metricsFrame = pendingPhoenixFrame;
+  const visualsBuffer = pendingVisualsBuffer;
+  const spectroBuffer = pendingSpectroBuffer;
+  pendingPhoenixFrame = null;
+  pendingVisualsBuffer = null;
+  pendingSpectroBuffer = null;
+
+  if (metricsFrame) {
+    try {
+      const packet = buildPhoenixMeterPacket(metricsFrame);
+      await applyIncomingAudioPacket(env, packet, CONFIG, performance.now());
+    } catch (err) {
+      console.warn('Phoenix packet error:', err);
+    }
+  }
+
+  if (visualsBuffer) {
+    try {
+      applyVisualsBuffer(env, visualsBuffer);
+    } catch (err) {
+      console.warn('Phoenix visual packet error:', err);
+    }
+  }
+
+  if (spectroBuffer) {
+    try {
+      const decoded = decodePhoenixSpectroBuffer(spectroBuffer);
+      if (decoded && copyPhoenixSpectroBins(env.audio, decoded)) {
+        env.requestRender?.('spectro');
+      }
+    } catch (err) {
+      console.warn('Phoenix spectrogram packet error:', err);
+    }
+  }
 }
 
 function bindLifecycleHandlers() {
@@ -1174,7 +1144,7 @@ async function initPhoenixAudio(env) {
     socket.onmessage = (event) => {
       try {
         const frame = JSON.parse(event.data);
-        enqueuePhoenixFrame(env, CONFIG, frame);
+        enqueuePhoenixFrame(frame);
       } catch (err) {
         console.warn('Phoenix metrics parse error:', err);
       }
diff --git a/www/main.js b/www/main.js
index 8a2d5d7..4badc77 100644
--- a/www/main.js
+++ b/www/main.js
@@ -23,7 +23,7 @@ try {
 import { CONFIG, applyRtaBpoSelection, loadConfig, saveConfig, loadLayoutPreset } from './core/config.js';
 import * as utils from './core/utils.js';
 import { meterFacade, registerMeter } from './core/registry.js';
-import { initAudio, audioLost, reloadAudio } from './core/audio.js';
+import { initAudio, audioLost, reloadAudio, flushPendingPhoenixData } from './core/audio.js';
 import { createScreensaver } from './core/screensaver.js';
 
 // Views
@@ -2675,6 +2675,10 @@ async function maybeRecoverAudio(reason) {
 
 async function loop(now){
   const elapsed = now - lastFrameTime;
+  // Apply all newest transport states once, immediately before this display
+  // frame reads them. WebSocket callbacks only buffer; this is the sole
+  // presentation pump for metrics, visuals and spectrogram data.
+  await flushPendingPhoenixData(env, CONFIG);
   const audioOk = env.audio.alive && !audioLost(env);
   const renderStyle = getRenderableStyle();
   if (processingProfileDirty || appliedProcessingProfileView !== renderStyle) {