From 532461599b7518f4609002cdb314ff2ce9f3a70f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miguel=20=C3=81ngel?= <miguel.sierra@heygen.com>
Date: Sat, 18 Jul 2026 19:25:24 +0000
Subject: [PATCH] fix(producer): preserve normalized audio mux duration

---
 .../src/services/distributed/assemble.ts      | 24 ++++++++++++-------
 .../render/stages/assembleStage.test.ts       |  2 +-
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/packages/producer/src/services/distributed/assemble.ts b/packages/producer/src/services/distributed/assemble.ts
index 91f56ed90..2f98ccef9 100644
--- a/packages/producer/src/services/distributed/assemble.ts
+++ b/packages/producer/src/services/distributed/assemble.ts
@@ -289,8 +289,11 @@ export async function assemble(
     }
 
     // ── 3. Audio: pad-or-trim then mux ────────────────────────────────────
-    let audioForMux: string | null = null;
-    let preserveAudioPrimingEditList = false;
+    let normalizedAudio: {
+      path: string;
+      preserveAudioPrimingEditList: boolean;
+      durationSeconds: number;
+    } | null = null;
     if (audioPath !== null && existsSync(audioPath)) {
       const paddedAudioPath = join(workDir, "audio-padded.m4a");
       const padTrimResult = await padOrTrimAudioToVideoFrameCount({
@@ -302,8 +305,11 @@ export async function assemble(
       if (!padTrimResult.success) {
         throw new Error(`[assemble] audio pad/trim failed: ${padTrimResult.error}`);
       }
-      audioForMux = paddedAudioPath;
-      preserveAudioPrimingEditList = padTrimResult.operation === "trim";
+      normalizedAudio = {
+        path: paddedAudioPath,
+        preserveAudioPrimingEditList: padTrimResult.operation === "trim",
+        durationSeconds: padTrimResult.targetDurationSeconds,
+      };
       log.info("[assemble] audio normalized for mux", {
         operation: padTrimResult.operation,
         targetDurationSeconds: padTrimResult.targetDurationSeconds,
@@ -316,17 +322,17 @@ export async function assemble(
     // because it operates on a `RenderJob` and emits `updateJobStatus`
     // payloads — the distributed activity has no job to thread through.
     const muxOutputPath =
-      audioForMux !== null ? join(workDir, `mux.${plan.dimensions.format}`) : postConcatPath;
-    if (audioForMux !== null) {
+      normalizedAudio !== null ? join(workDir, `mux.${plan.dimensions.format}`) : postConcatPath;
+    if (normalizedAudio !== null) {
       const muxResult = await muxVideoWithAudio(
         postConcatPath,
-        audioForMux,
+        normalizedAudio.path,
         muxOutputPath,
         abortSignal,
         {
           audioCodec: "aac",
-          preserveAudioPrimingEditList,
-          durationSeconds: padTrimResult.targetDurationSeconds,
+          preserveAudioPrimingEditList: normalizedAudio.preserveAudioPrimingEditList,
+          durationSeconds: normalizedAudio.durationSeconds,
         },
         { num: plan.dimensions.fpsNum, den: plan.dimensions.fpsDen },
       );
diff --git a/packages/producer/src/services/render/stages/assembleStage.test.ts b/packages/producer/src/services/render/stages/assembleStage.test.ts
index ae0696202..a6d392bac 100644
--- a/packages/producer/src/services/render/stages/assembleStage.test.ts
+++ b/packages/producer/src/services/render/stages/assembleStage.test.ts
@@ -69,7 +69,7 @@ describe("runAssembleStage audio duration parity", () => {
       "/tmp/audio.duration-normalized.m4a",
       "/tmp/output.mp4",
       undefined,
-      { audioCodec: "aac", preserveAudioPrimingEditList: true },
+      { audioCodec: "aac", preserveAudioPrimingEditList: true, durationSeconds: 1 },
       { num: 30, den: 1 },
     );
   });