From 47f0478ef56d5ede9e06f22b95a20ab46c019ad4 Mon Sep 17 00:00:00 2001
From: Kent Dong <ch3cho@qq.com>
Date: Tue, 19 Aug 2025 15:53:49 +0800
Subject: [PATCH] fix: Remove "accept-encoding" header for mcp-sse upstreams
 (#2786)

---
 plugins/golang-filter/mcp-session/filter.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/plugins/golang-filter/mcp-session/filter.go b/plugins/golang-filter/mcp-session/filter.go
index 9a42770d6..9d9a27605 100644
--- a/plugins/golang-filter/mcp-session/filter.go
+++ b/plugins/golang-filter/mcp-session/filter.go
@@ -149,6 +149,9 @@ func (f *filter) processMcpRequestHeadersForRestUpstream(header api.RequestHeade
 func (f *filter) processMcpRequestHeadersForSSEUpstream(header api.RequestHeaderMap, endStream bool) api.StatusType {
 	// We don't need to process the request body for SSE upstream.
 	f.skipRequestBody = true
+	// Remove Accept-Encoding header to avoid gzip encoding,
+	// which our response body handling logic doesn't support.
+	header.Del("Accept-Encoding")
 	return api.Continue
 }