From 2546ed040aeee6e6492812e714f01ff23464e604 Mon Sep 17 00:00:00 2001
From: Miguel Angel Simon Sierra <miguel.sierra@heygen.com>
Date: Sun, 1 Nov 2026 15:19:47 -0500
Subject: [PATCH] fix(core): only the clips the start wait gave up on run on
 without data

---
 .../core/src/runtime/init.buffering.test.ts   | 17 ++++++++++++++
 packages/core/src/runtime/init.ts             | 22 ++++++++++---------
 2 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/packages/core/src/runtime/init.buffering.test.ts b/packages/core/src/runtime/init.buffering.test.ts
index e4d6c08295..870df4d661 100644
--- a/packages/core/src/runtime/init.buffering.test.ts
+++ b/packages/core/src/runtime/init.buffering.test.ts
@@ -148,6 +148,23 @@ it("after a start that ran on without data, the next clip without data holds aga
   expect(states.at(-1)).toEqual({ isPlaying: true, buffering: true });
 });
 
+it("a clip due while another catches up from the start still holds, then plays with the first one still cold", () => {
+  const { voiceReady, states, playFor } = playPodcast(0.5, "audio", 1);
+
+  playFor(0.45);
+  expect(states.at(-1)).toEqual({ isPlaying: true, buffering: false });
+  playFor(0.45);
+  expect(states.at(-1)).toEqual({ isPlaying: true, buffering: true });
+  const heldAt = window.__player!.getTime();
+  playFor(0.3);
+  expect(window.__player!.getTime()).toBe(heldAt);
+
+  voiceReady.value = 4;
+  playFor(0.3);
+  expect(states.at(-1)).toEqual({ isPlaying: true, buffering: false });
+  expect(window.__player!.getTime()).toBeGreaterThan(heldAt);
+});
+
 it("holds on the frame a slow tick skips into a clip with no data, after asking it to play", () => {
   const { voice, states, playFor, step } = playPodcast(0.5);
 
diff --git a/packages/core/src/runtime/init.ts b/packages/core/src/runtime/init.ts
index 7264883405..21c5bedf65 100644
--- a/packages/core/src/runtime/init.ts
+++ b/packages/core/src/runtime/init.ts
@@ -3447,7 +3447,7 @@ export function initSandboxRuntimeModular(): void {
   // Play waits this long for a clip with no data, then runs on and lets the clip catch up; mid-film it holds.
   const START_WAIT_MS = 300;
   let startWaitUntilMs: number | null = null;
-  let catchingUp = false;
+  let catchingUpFor: HTMLMediaElement[] = [];
   let resumingFromBuffering = false;
 
   // The one definition of "media the transport drives": timed itself, or hosted
@@ -4785,7 +4785,7 @@ export function initSandboxRuntimeModular(): void {
       bufferingFor = [];
       if (!resumingFromBuffering) {
         startWaitUntilMs = performance.now() + START_WAIT_MS;
-        catchingUp = false;
+        catchingUpFor = [];
       }
       const tl = state.capturedTimeline;
       if (clock.isPlaying()) return;
@@ -4822,7 +4822,7 @@ export function initSandboxRuntimeModular(): void {
       const wasBuffering = bufferingFor.length > 0;
       bufferingFor = [];
       startWaitUntilMs = null;
-      catchingUp = false;
+      catchingUpFor = [];
       if (clock.isPlaying()) haltPlayback();
       else if (wasBuffering) postState(true);
     },
@@ -5674,7 +5674,7 @@ export function initSandboxRuntimeModular(): void {
           if (clock.hasAudioSource()) clock.detachAudioSource();
         } else if (
           source &&
-          catchingUp &&
+          catchingUpFor.includes(source.el) &&
           source.el.readyState < HTMLMediaElement.HAVE_FUTURE_DATA
         ) {
           // Past the start wait the playhead runs on its own clock while this track catches up.
@@ -5908,16 +5908,18 @@ export function initSandboxRuntimeModular(): void {
       const notReady = mediaNotReadyAt(state.currentTime);
       if (startWaitUntilMs !== null && performance.now() >= startWaitUntilMs) {
         startWaitUntilMs = null;
-        catchingUp = notReady.length > 0;
+        catchingUpFor = notReady;
       }
-      if (notReady.length === 0) catchingUp = false;
-      if (clock.isPlaying() && notReady.length > 0 && !catchingUp) {
-        bufferingFor = notReady;
+      catchingUpFor = catchingUpFor.filter((el) => notReady.includes(el));
+      const mustWaitFor = notReady.filter((el) => !catchingUpFor.includes(el));
+      if (clock.isPlaying() && mustWaitFor.length > 0) {
+        bufferingFor = mustWaitFor;
         haltPlayback(true);
       } else if (
         bufferingFor.length > 0 &&
-        (catchingUp ||
-          !mediaNotReadyAt(state.currentTime, canResumeFrom).some((el) => bufferingFor.includes(el)))
+        !mediaNotReadyAt(state.currentTime, canResumeFrom)
+          .filter((el) => !catchingUpFor.includes(el))
+          .some((el) => bufferingFor.includes(el))
       ) {
         resumingFromBuffering = true;
         try {