diff --git a/apps/media-worker/src/producer/assemble-builder.ts b/apps/media-worker/src/producer/assemble-builder.ts
index 8fb990c..41f2baf 100644
--- a/apps/media-worker/src/producer/assemble-builder.ts
+++ b/apps/media-worker/src/producer/assemble-builder.ts
@@ -143,7 +143,12 @@ export function clipVideoChain(rotate: EdlRotate, fit: "cover" | "contain", aspe
 
 function clipAudioChain(volumeDb: number, hasAudio: boolean, inputIndex: number, trimSpanSec: string): string {
   const aformat = `aformat=sample_fmts=fltp:sample_rates=${ASSEMBLE_PRESET.sampleRate}:channel_layouts=stereo`;
-  if (!hasAudio) return `anullsrc=r=${ASSEMBLE_PRESET.sampleRate}:cl=stereo,aformat=sample_fmts=fltp:sample_rates=${ASSEMBLE_PRESET.sampleRate}:channel_layouts=stereo`;
+  if (!hasAudio) {
+    // anullsrc is an INFINITE source — unbounded, concat never finishes the
+    // segment and the encode deadlocks (2026-10-16 production hang). atrim pins
+    // the bed to the clip's trim span; asetpts restarts timestamps.
+    return `anullsrc=r=${ASSEMBLE_PRESET.sampleRate}:cl=stereo,atrim=0:${trimSpanSec},asetpts=PTS-STARTPTS,aformat=sample_fmts=fltp:sample_rates=${ASSEMBLE_PRESET.sampleRate}:channel_layouts=stereo`;
+  }
   return `[${inputIndex}:a]${aformat}${volumeDb === 0 ? "" : `,volume=${volumeDb}dB`}`;
 }