From c26144403c78d54b28f605ea8421229ac51b2a0e Mon Sep 17 00:00:00 2001
From: Andres Perez <1676612+andresperezl@users.noreply.github.com>
Date: Wed, 11 Jun 2025 19:56:42 -0400
Subject: [PATCH] api/stream: add Transfer-Encoding header to tunnel responses

For HTTP/1.1 when the length of the content isn't known, you must send
the header `Transfer-Encoding: chunked`, so the client knows that it
needs to process the response in parts (chunks). This header is
deprecated in HTTP/2, and maybe not neccessary when using a proxy
(nginx, haproxy, etc), but neccesary when accesing cobalt directly.
https://en.wikipedia.org/wiki/Chunked_transfer_encoding
---
 api/src/core/api.js     | 3 ++-
 api/src/stream/types.js | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/api/src/core/api.js b/api/src/core/api.js
index eb5cf4ff..09d80ecc 100644
--- a/api/src/core/api.js
+++ b/api/src/core/api.js
@@ -276,7 +276,8 @@ export const runAPI = async (express, app, __dirname, isPrimary = true) => {
         methods: ['GET'],
         exposedHeaders: [
             'Estimated-Content-Length',
-            'Content-Disposition'
+            'Content-Disposition',
+            'Transfer-Encoding'
         ],
         ...corsConfig,
     }));
diff --git a/api/src/stream/types.js b/api/src/stream/types.js
index 6b493efa..ac1e564a 100644
--- a/api/src/stream/types.js
+++ b/api/src/stream/types.js
@@ -156,6 +156,7 @@ const merge = async (streamInfo, res) => {
         res.setHeader('Connection', 'keep-alive');
         res.setHeader('Content-Disposition', contentDisposition(streamInfo.filename));
         res.setHeader('Estimated-Content-Length', await estimateTunnelLength(streamInfo));
+        res.setHeader('Transfer-Encoding', 'chunked');
 
         pipe(muxOutput, res, shutdown);
 
@@ -220,6 +221,7 @@ const remux = async (streamInfo, res) => {
         res.setHeader('Connection', 'keep-alive');
         res.setHeader('Content-Disposition', contentDisposition(streamInfo.filename));
         res.setHeader('Estimated-Content-Length', await estimateTunnelLength(streamInfo));
+        res.setHeader('Transfer-Encoding', 'chunked');
 
         pipe(muxOutput, res, shutdown);
 
@@ -296,6 +298,7 @@ const convertAudio = async (streamInfo, res) => {
                 estimateAudioMultiplier(streamInfo) * 1.1
             )
         );
+        res.setHeader('Transfer-Encoding', 'chunked');
 
         pipe(muxOutput, res, shutdown);
         res.on('finish', shutdown);
@@ -334,6 +337,7 @@ const convertGif = async (streamInfo, res) => {
         res.setHeader('Connection', 'keep-alive');
         res.setHeader('Content-Disposition', contentDisposition(streamInfo.filename));
         res.setHeader('Estimated-Content-Length', await estimateTunnelLength(streamInfo, 60));
+        res.setHeader('Transfer-Encoding', 'chunked');
 
         pipe(muxOutput, res, shutdown);