Stream canonical assets during input resolution

app/services/input_resolver.py

@@ -350,8 +350,25 @@ class InputResolver:
         except (CanonicalAssetNotFoundError, FileNotFoundError, ValueError) as exc:
             raise InputError("Media asset was not found or is no longer available") from exc
         destination = workspace.uploads / f"{uuid4().hex}_{record.filename}"
-        data = await asyncio.to_thread(source.read_bytes)
-        await asyncio.to_thread(destination.write_bytes, data)
+        # Stream canonical media in bounded chunks. Asset resolution must never
+        # load an entire video/audio file into the worker process memory.
+        copied = 0
+        try:
+            async with (
+                aiofiles.open(source, "rb") as input_stream,
+                aiofiles.open(destination, "wb") as output_stream,
+            ):
+                while chunk := await input_stream.read(1024 * 1024):
+                    copied += len(chunk)
+                    if copied > self.settings.max_upload_size:
+                        raise InputError("Media asset exceeds MAX_UPLOAD_SIZE")
+                    await output_stream.write(chunk)
+        except Exception:
+            destination.unlink(missing_ok=True)
+            raise
+        if copied != record.file_size:
+            destination.unlink(missing_ok=True)
+            raise InputError("Media asset size changed while being resolved")
         return InputMedia(
             source=MediaSource.ASSET,
             filename=record.filename,