diff --git a/packages/engine/src/services/audioMixer.ts b/packages/engine/src/services/audioMixer.ts
index 369562e328..8a2dff3135 100644
--- a/packages/engine/src/services/audioMixer.ts
+++ b/packages/engine/src/services/audioMixer.ts
@@ -765,6 +765,12 @@ export async function processCompositionAudio(
   // be able to abort the in-flight ffmpeg runs before the finally-block removes
   // workDir out from under them. Chained off the caller's signal so external
   // cancellation still behaves as before.
+  //
+  // Every child that can outlive a sibling's failure has to be given THIS
+  // signal, not the caller's: the trim, the video extract and the download all
+  // took `signal`, so `internalController.abort()` cancelled nothing and the
+  // `rmSync(workDir)` on the next line ran while their ffmpeg children were
+  // still writing into it.
   const internalController = new AbortController();
   const effectiveSignal = internalController.signal;
   if (signal) {
@@ -795,7 +801,7 @@ export async function processCompositionAudio(
 
         if (isHttpUrl(srcPath)) {
           try {
-            srcPath = await downloadToTemp(srcPath, workDir);
+            srcPath = await downloadToTemp(srcPath, workDir, undefined, effectiveSignal);
           } catch (err: unknown) {
             failures.push(
               downloadFailure(err instanceof Error ? err.message : String(err), element.id),
@@ -842,7 +848,7 @@ export async function processCompositionAudio(
               startTime: element.mediaStart,
               duration: element.end - element.start,
             },
-            signal,
+            effectiveSignal,
             config,
           );
           if (!extractResult.success) {
@@ -868,7 +874,7 @@ export async function processCompositionAudio(
             trimmedPath,
             element.mediaStart,
             element.end - element.start,
-            signal,
+            effectiveSignal,
             config,
           );
           if (!prepResult.success) {