modelcontextprotocol/ext-apps

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Official repo for spec & SDK of MCP Apps protocol - standard for UIs embedded AI chatbots, served by MCP servers

Stars: 2.9k
Forks: 387
Open beginner issues: 0
Indexed issues: 124
Avg merge: 3h 21m
Merged PRs (30d): 6

Dominant language: TypeScript
License: No license data
Last GitHub push: Sep 9, 2026
Latest indexed: Sep 20, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: No beginner labels indexed

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124 issues indexed so far

Chat composer is displaced upward after interacting with a fullscreen MCP App and sending a message Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

modelcontextprotocol/ext-apps#776 · Opened Sep 14, 2026
Míne Open

Difficulty 5/5 Over a week Newbie friendliness 15/100

modelcontextprotocol/ext-apps#774 · Opened Sep 10, 2026
Reference host renders tool.name in the app header; base spec display precedence is title → annotations.title → name Open

bug

Difficulty 2/5 1-3 hours Newbie friendliness 84/100

modelcontextprotocol/ext-apps#767 · Opened Sep 3, 2026
Example proposal: review and select web sources Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/ext-apps#764 · Opened Sep 1, 2026
Sandbox proxy does not apply _meta.ui.csp from the UI resource, so resourceDomains has no effect Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

modelcontextprotocol/ext-apps#761 · Opened Aug 28, 2026
Extend permission-policy negotiation for media/video widgets (fullscreen, presentation/Cast, remote-playback, PiP, encrypted-media) Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/ext-apps#757 · 1 reaction · Opened Aug 25, 2026
MCP spec conformance: 5 requirements violated (via @hasmcp/mcp-spec-test) — spec 2025-11-25 Open

Difficulty 3/5 1-2 days Newbie friendliness 52/100

modelcontextprotocol/ext-apps#756 · Opened Aug 24, 2026
MCP spec conformance: 10 requirements violated (via @hasmcp/mcp-spec-test) — spec 2026-07-28 Open

Difficulty 3/5 1-2 days Newbie friendliness 38/100

modelcontextprotocol/ext-apps#755 · Opened Aug 24, 2026
Host support for persistent (pip/pinned) app views: clinical use case where inline rendering breaks the core loop Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/ext-apps#754 · 2 comments · Opened Aug 24, 2026
Widget callServerTool calls hardcode bare tool names, breaking under multi-server MCP hosts Open

Difficulty 4/5 3-5 days Newbie friendliness 68/100

modelcontextprotocol/ext-apps#753 · Opened Aug 23, 2026
server-pdf: read_pdf_bytes hides the byte payload in structuredContent only — text content is a bare size summary, so CLI clients can't read the PDF Open

Difficulty 3/5 1-2 days Newbie friendliness 65/100

modelcontextprotocol/ext-apps#762 · 1 comment · Opened Aug 20, 2026
Grok host: MCP Apps iframe rendering unstable for Paybox connector (custom BYO MCP) Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

modelcontextprotocol/ext-apps#750 · 1 comment · Opened Aug 19, 2026
No way to distinguish an app-initiated tools/call from a model-initiated one Open

Difficulty 5/5 Over a week Newbie friendliness 28/100

modelcontextprotocol/ext-apps#746 · Opened Aug 15, 2026
Apps cannot call their server's tools through a namespacing aggregator Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/ext-apps#745 · Opened Aug 15, 2026
Add UI "preload" Control and "ui/close" Signal for MCP Apps Tool-Driven Widgets Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/ext-apps#744 · 2 comments · 1 reaction · Opened Aug 14, 2026
MCP Apps Conformance Test - Host Interface Requirements Open

Difficulty 5/5 Over a week Newbie friendliness 38/100

modelcontextprotocol/ext-apps#743 · 5 reactions · Opened Aug 13, 2026
Documentation for MCP Apps does not match 2026-07-28 specification Open

bug

Difficulty 2/5 1-3 hours Newbie friendliness 68/100

modelcontextprotocol/ext-apps#742 · 1 comment · Opened Aug 12, 2026
App view frame is labeled with the tool `name`, not its `title` — no `_meta.ui` field to name a view Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

modelcontextprotocol/ext-apps#740 · Opened Aug 5, 2026
Standardize provenance for app-initiated server tool calls Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/ext-apps#738 · 1 comment · Opened Aug 4, 2026
[RFC] Session Resilience & Lifecycle Management for Heavy Server-Side Rendered UIs (WebRTC/CAD) Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 30/100

modelcontextprotocol/ext-apps#737 · Opened Aug 3, 2026
Claude iOS: template renders but host delivers no lifecycle notifications to MCP App iframes (tool-input, tool-result, size-changed all absent) Open

Difficulty 4/5 3-5 days Newbie friendliness 42/100

modelcontextprotocol/ext-apps#734 · Opened Jul 30, 2026
No way to mark a secondary tool as visible only to app Open

bug

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/ext-apps#732 · Opened Jul 29, 2026
Proposal: Guidelines for hosts to implement API for collapsible MCP Apps Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 30/100

modelcontextprotocol/ext-apps#731 · 1 reaction · Opened Jul 29, 2026
spec: decouple rendering requirements from the double-sandboxed iframe architecture Open

enhancement

modelcontextprotocol/ext-apps#716 · 1 assignee · Opened Jul 16, 2026
Add your HVTrust badge to the README? Open

Difficulty 1/5 Under an hour Newbie friendliness 72/100

modelcontextprotocol/ext-apps#711 · Opened Jul 15, 2026
Align MCP Apps capability negotiation with SEP-2133 Open

Difficulty 3/5 1-2 days Newbie friendliness 48/100

modelcontextprotocol/ext-apps#708 · Opened Jul 13, 2026
Help Open

bug

Difficulty 5/5 Over a week Newbie friendliness 10/100

modelcontextprotocol/ext-apps#707 · Opened Jul 13, 2026
Spec: Deprecate Sampling Open

Difficulty 2/5 1-3 hours Newbie friendliness 65/100

modelcontextprotocol/ext-apps#706 · Opened Jul 13, 2026
Add ui.homepage field for redirecting to the app's homepage Open

Difficulty 2/5 1-3 hours Newbie friendliness 72/100

modelcontextprotocol/ext-apps#703 · 1 reaction · Opened Jul 10, 2026
Bug: file_manager widget renders content then infinite re-render loop (oncalltool handler replaced storm) in Claude Desktop Open

Difficulty 4/5 3-5 days Newbie friendliness 46/100

modelcontextprotocol/ext-apps#701 · 4 comments · Opened Jul 8, 2026
Claude Desktop strips structuredContent from ui/notifications/tool-result — views built per SDK examples render blank Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

modelcontextprotocol/ext-apps#696 · 2 comments · 6 reactions · Opened Jul 7, 2026
Clarify host behavior for rendering an MCP App view when the tool result is an error (isError: true) Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/ext-apps#694 · 2 comments · 2 reactions · Opened Jul 1, 2026
Guidelines for hosts to support Command Line (CLI) MCP Apps Open

enhancement

modelcontextprotocol/ext-apps#689 · 3 reactions · 1 assignee · Opened Jun 15, 2026
Minimal preferred size Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/ext-apps#688 · 2 comments · 1 reaction · Opened Jun 11, 2026
fresh install of basic-host example fails Open

bug

Difficulty 2/5 1-3 hours Newbie friendliness 78/100

modelcontextprotocol/ext-apps#687 · Opened Jun 11, 2026
autoResize misses absolutely-positioned portal growth (popover opens → no size-changed) Open

Difficulty 4/5 3-5 days Newbie friendliness 56/100

modelcontextprotocol/ext-apps#686 · Opened Jun 10, 2026
Pinned or Split Screen MCP Apps Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 30/100

modelcontextprotocol/ext-apps#684 · 3 comments · 6 reactions · Opened Jun 3, 2026
د Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 10/100

modelcontextprotocol/ext-apps#682 · Opened Jun 2, 2026
Support configuring approved redirect domains for ui/open-link Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 52/100

modelcontextprotocol/ext-apps#678 · 4 comments · 4 reactions · Opened May 29, 2026
Should hostCapabilities.appTools exist? Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/ext-apps#676 · 2 comments · Opened May 28, 2026
Set up public MCP Apps platform tests Open

enhancement

modelcontextprotocol/ext-apps#674 · 14 comments · 8 reactions · 1 assignee · Opened May 27, 2026
Adding an official MCP App validator Open

enhancement

modelcontextprotocol/ext-apps#673 · 1 comment · 6 reactions · 1 assignee · Opened May 27, 2026
Explore UI views that are not tied to specific tool calls Open

enhancement

modelcontextprotocol/ext-apps#672 · 4 comments · 3 reactions · 1 assignee · Opened May 27, 2026
Bug Report: MCP Apps UI Resource Not Rendering in Claude Desktop / claude.ai Open

bug

Difficulty 5/5 Over a week Newbie friendliness 32/100

modelcontextprotocol/ext-apps#671 · 23 comments · 9 reactions · Opened May 27, 2026
Explore MCP App discovery mechanisms Open

enhancement protocol

Difficulty 5/5 Over a week Newbie friendliness 25/100

modelcontextprotocol/ext-apps#670 · 1 comment · Opened May 26, 2026
Define a breaking-change process for Apps security and CSP behavior Open

protocol

Difficulty 5/5 Over a week Newbie friendliness 30/100

modelcontextprotocol/ext-apps#669 · Opened May 26, 2026
Clarify MCP Apps behavior with code mode Open

needs spec change protocol

Difficulty 5/5 Over a week Newbie friendliness 35/100

modelcontextprotocol/ext-apps#668 · 2 reactions · Opened May 26, 2026
@modelcontextprotocol/ext-apps consumers ship ~140K of unused zod v4 locale files in browser bundles Open

Difficulty 3/5 1-2 days Newbie friendliness 52/100

modelcontextprotocol/ext-apps#665 · 1 comment · Opened May 23, 2026
Clarification Request: Standardized Guidance for Detecting Malicious Patterns in Widget HTML Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

modelcontextprotocol/ext-apps#664 · Opened May 22, 2026
,. Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 10/100

modelcontextprotocol/ext-apps#661 · 1 comment · Opened May 18, 2026

modelcontextprotocol/ext-apps

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