From f66a55b5f4eb7ce0f8b3885633bf9a7b1080e0b5 Mon Sep 17 00:00:00 2001
From: Matt <77928207+mattzcarey@users.noreply.github.com>
Date: Tue, 20 Jan 2026 11:56:17 +0100
Subject: [PATCH] Revert "fix(server): application/json header for
 notifictions" (#1388)

---
 .changeset/{strong-hairs-study.md => heavy-walls-swim.md} | 2 +-
 packages/middleware/node/test/streamableHttp.test.ts      | 1 -
 packages/server/src/server/streamableHttp.ts              | 7 +------
 3 files changed, 2 insertions(+), 8 deletions(-)
 rename .changeset/{strong-hairs-study.md => heavy-walls-swim.md} (50%)

diff --git a/.changeset/strong-hairs-study.md b/.changeset/heavy-walls-swim.md
similarity index 50%
rename from .changeset/strong-hairs-study.md
rename to .changeset/heavy-walls-swim.md
index 9addb05e..7a09cda0 100644
--- a/.changeset/strong-hairs-study.md
+++ b/.changeset/heavy-walls-swim.md
@@ -2,4 +2,4 @@
 '@modelcontextprotocol/server': patch
 ---
 
-add application/json header for notifications
+reverting application/json in notifications
diff --git a/packages/middleware/node/test/streamableHttp.test.ts b/packages/middleware/node/test/streamableHttp.test.ts
index 5f865ef4..3cc07e8c 100644
--- a/packages/middleware/node/test/streamableHttp.test.ts
+++ b/packages/middleware/node/test/streamableHttp.test.ts
@@ -657,7 +657,6 @@ describe.each(zodTestMatrix)('$zodVersionLabel', (entry: ZodMatrixEntry) => {
             const response = await sendPostRequest(baseUrl, batchNotifications, sessionId);
 
             expect(response.status).toBe(202);
-            expect(response.headers.get('content-type')).toBe('application/json');
         });
 
         it('should handle batch request messages with SSE stream for responses', async () => {
diff --git a/packages/server/src/server/streamableHttp.ts b/packages/server/src/server/streamableHttp.ts
index 19360310..decd862f 100644
--- a/packages/server/src/server/streamableHttp.ts
+++ b/packages/server/src/server/streamableHttp.ts
@@ -667,12 +667,7 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
                 for (const message of messages) {
                     this.onmessage?.(message, { authInfo: options?.authInfo, requestInfo });
                 }
-                return new Response(null, {
-                    status: 202,
-                    headers: {
-                        'Content-Type': 'application/json'
-                    }
-                });
+                return new Response(null, { status: 202 });
             }
 
             // The default behavior is to use SSE streaming