From 38aa70261ae9a012d9bb157deffcc2a0e9046d08 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Romuald=20Cz=C5=82onkowski?=
 <56956555+czlonkowski@users.noreply.github.com>
Date: Sat, 7 Feb 2026 15:18:50 +0100
Subject: [PATCH] fix: use text/html;profile=mcp-app MIME type for MCP Apps
 resources (#577)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The ext-apps spec requires RESOURCE_MIME_TYPE (text/html;profile=mcp-app)
for hosts to recognize resources as MCP Apps. Without the profile parameter,
Claude Desktop/web fails with "Failed to load MCP App: the resource may
exceed the 5 MB size limit."

Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
---
 CHANGELOG.md                          | 8 ++++++++
 package.json                          | 2 +-
 src/mcp/ui/app-configs.ts             | 4 ++--
 tests/unit/mcp/ui/app-configs.test.ts | 4 ++--
 4 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 689f0d5..24635df 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.34.3] - 2026-02-07
+
+### Fixed
+
+- **MCP Apps: Use correct MIME type for ext-apps spec**: Changed resource MIME type from `text/html` to `text/html;profile=mcp-app` (the `RESOURCE_MIME_TYPE` constant from `@modelcontextprotocol/ext-apps`). Without this profile parameter, Claude Desktop/web fails to recognize resources as MCP Apps and shows "Failed to load MCP App: the resource may exceed the 5 MB size limit."
+
+Conceived by Romuald Czlonkowski - https://www.aiadvisors.pl/en
+
 ## [2.34.2] - 2026-02-07
 
 ### Fixed
diff --git a/package.json b/package.json
index b708624..4dde40a 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "n8n-mcp",
-  "version": "2.34.2",
+  "version": "2.34.3",
   "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",
diff --git a/src/mcp/ui/app-configs.ts b/src/mcp/ui/app-configs.ts
index 71e11fd..37c704d 100644
--- a/src/mcp/ui/app-configs.ts
+++ b/src/mcp/ui/app-configs.ts
@@ -6,7 +6,7 @@ export const UI_APP_CONFIGS: UIAppConfig[] = [
     displayName: 'Operation Result',
     description: 'Visual summary of workflow operations (create, update, delete, test)',
     uri: 'ui://n8n-mcp/operation-result',
-    mimeType: 'text/html',
+    mimeType: 'text/html;profile=mcp-app',
     toolPatterns: [
       'n8n_create_workflow',
       'n8n_update_full_workflow',
@@ -22,7 +22,7 @@ export const UI_APP_CONFIGS: UIAppConfig[] = [
     displayName: 'Validation Summary',
     description: 'Visual summary of node and workflow validation results',
     uri: 'ui://n8n-mcp/validation-summary',
-    mimeType: 'text/html',
+    mimeType: 'text/html;profile=mcp-app',
     toolPatterns: [
       'validate_node',
       'validate_workflow',
diff --git a/tests/unit/mcp/ui/app-configs.test.ts b/tests/unit/mcp/ui/app-configs.test.ts
index e17a401..127bfaf 100644
--- a/tests/unit/mcp/ui/app-configs.test.ts
+++ b/tests/unit/mcp/ui/app-configs.test.ts
@@ -65,9 +65,9 @@ describe('UI_APP_CONFIGS', () => {
     }
   });
 
-  it('should have consistent mimeType of text/html', () => {
+  it('should have consistent mimeType of text/html;profile=mcp-app', () => {
     for (const config of UI_APP_CONFIGS) {
-      expect(config.mimeType).toBe('text/html');
+      expect(config.mimeType).toBe('text/html;profile=mcp-app');
     }
   });