fix: RFC 5987 encoding for Unicode filenames in Content-Disposition header (#257)

* fix: RFC 5987 encoding for Unicode filenames in Content-Disposition header

Fixes download failures for songs with non-ASCII characters (Vietnamese,
Japanese, Korean, etc.) by properly encoding the Content-Disposition header.

The issue occurred when downloading separated audio files with Unicode
filenames like "Việt Nhân - Sầu Thương_(Vocals).flac" - the HTTP header
encoding failed with "'latin-1' codec can't encode character".

Solution:
- Add ASCII fallback filename for older clients
- Add RFC 5987 filename*=UTF-8'' parameter for modern clients
- Both parameters in the header ensure broad compatibility

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* chore: bump version to 0.41.1

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: beveradb

audio_separator/remote/deploy_modal.py

@@ -31,6 +31,7 @@
 from importlib.metadata import version
 import typing
 from typing import Optional
+from urllib.parse import quote
 
 # Third-party imports
 from fastapi import FastAPI, File, Form, HTTPException, Response, UploadFile
@@ -712,7 +713,13 @@ async def download_file(task_id: str, file_hash: str) -> Response:
             print(f"WARNING: Could not detect MIME type for {actual_filename}, using generic type")
             content_type = "application/octet-stream"
 
-        return Response(content=file_data, media_type=content_type, headers={"Content-Disposition": f"attachment; filename={actual_filename}"})
+        # RFC 5987 encoding for Unicode filenames in Content-Disposition header
+        # Provide ASCII fallback for older clients, and UTF-8 encoded filename for modern clients
+        ascii_filename = "".join(c if ord(c) < 128 else "_" for c in actual_filename)
+        encoded_filename = quote(actual_filename, safe="")
+        content_disposition = f"attachment; filename=\"{ascii_filename}\"; filename*=UTF-8''{encoded_filename}"
+
+        return Response(content=file_data, media_type=content_type, headers={"Content-Disposition": content_disposition})
 
     except FileNotFoundError as exc:
         raise HTTPException(status_code=404, detail="File not found") from exc

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "poetry.core.masonry.api"
 
 [tool.poetry]
 name = "audio-separator"
-version = "0.41.0"
+version = "0.41.1"
 description = "Easy to use audio stem separation, using various models from UVR trained primarily by @Anjok07"
 authors = ["Andrew Beveridge <andrew@beveridge.uk>"]
 license = "MIT"