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

Beginner friendly Everything

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124 open issues indexed

Proposal: Allow Views to subscribe to server resource updates via resources/subscribe Open

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

modelcontextprotocol/ext-apps#659 · 2 comments · 1 reaction · Opened May 9, 2026
McpUiHostCapabilities missing tools field — widget-declared tools unimplementable by hosts Open

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

modelcontextprotocol/ext-apps#655 · Opened May 6, 2026
Support for non-HTML View mimetypes Open

enhancement

modelcontextprotocol/ext-apps#654 · 1 assignee · Opened May 6, 2026
unsafe-eval warning is thrown from AJV via @modelcontextprotocol/sdk dependency Open

bug

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

modelcontextprotocol/ext-apps#652 · Opened May 6, 2026
app-bridge pulls in entire Zod library (~1.4MB pre-minified) - most of it unused Open

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

modelcontextprotocol/ext-apps#649 · 5 reactions · Opened May 1, 2026
`tools/call` requests no longer echo `Mcp-Session-Id` (violates Streamable HTTP spec) Open

bug

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

modelcontextprotocol/ext-apps#647 · 1 comment · Opened Apr 30, 2026
basic-host does not forward toolResult _meta to the ui. Open

bug

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

modelcontextprotocol/ext-apps#646 · Opened Apr 28, 2026
v1.7.0 refreshRoots() clears allowedLocalDirs when host advertises roots capability but returns empty list — wipes CLI-arg directories Open

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

modelcontextprotocol/ext-apps#644 · Opened Apr 27, 2026
pdf-server: make tombstone-persistence e2e runnable (basic-host iframe-reload replay or URL-keyed storage) Open

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

modelcontextprotocol/ext-apps#642 · Opened Apr 27, 2026
Feature: Add Angular basic example Open

enhancement

Difficulty 4/5 3-5 days Newbie friendliness 64/100

modelcontextprotocol/ext-apps#635 · 3 comments · Opened Apr 22, 2026
Spec 2026-01-26: misleading "View initialize" example uses `initialize` + `clientInfo` instead of `ui/initialize` + `appInfo` Open

bug

Difficulty 1/5 Under an hour Newbie friendliness 88/100

modelcontextprotocol/ext-apps#634 · Opened Apr 22, 2026
bug: Safari/WebKit event.source identity mismatch in sandbox.ts relay breaks PostMessageTransport Open

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

modelcontextprotocol/ext-apps#633 · Opened Apr 21, 2026
server-pdf: get_viewer_state always returns pageCount: 1 and get_text returns empty in VS Code Open

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

modelcontextprotocol/ext-apps#617 · Opened Apr 19, 2026
Version negotiation mechanism exists but HOST behavior doesn't change based on negotiated version Open

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

modelcontextprotocol/ext-apps#611 · 1 reaction · Opened Apr 13, 2026
Support `wasm-unsafe-eval` CSP directive to enable WebAssembly in MCP Apps Open

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

modelcontextprotocol/ext-apps#605 · 6 comments · 6 reactions · Opened Apr 7, 2026
Proposal: Stream HTML resources for MCP Apps Open

enhancement

modelcontextprotocol/ext-apps#603 · 4 comments · 1 reaction · 1 assignee · Opened Apr 6, 2026
💡 Idea: Growth strategy for MCP extension ecosystem Open

Difficulty 5/5 Over a week Newbie friendliness 20/100

modelcontextprotocol/ext-apps#599 · 2 reactions · Opened Apr 4, 2026
Feature Request: Contextual Inline Citations with Modal/Dialog Popups for MCP Apps Open

enhancement

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

modelcontextprotocol/ext-apps#598 · Opened Apr 3, 2026
`downloadFile` not implemented on Claude iOS (error -32601) Open

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

modelcontextprotocol/ext-apps#574 · 1 comment · Opened Mar 29, 2026
[Proposal] Support web workers (`worker-src`) via `workerDomains` on `McpUiResourceCsp` Open

enhancement

Difficulty 3/5 1-2 days Newbie friendliness 64/100

modelcontextprotocol/ext-apps#566 · 3 reactions · Opened Mar 25, 2026
ui/update-model-context: How should hosts handle multiple instances of the same app resource? Open

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

modelcontextprotocol/ext-apps#558 · 1 comment · Opened Mar 20, 2026
PostMessageTransport: Race condition with srcdoc iframes — host misses ui/initialize Open

Difficulty 4/5 3-5 days Newbie friendliness 25/100

modelcontextprotocol/ext-apps#542 · 2 comments · 1 reaction · Opened Mar 8, 2026
CSP: Clarify/Allow '*' and scheme-based policies Open

enhancement

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

modelcontextprotocol/ext-apps#515 · 1 comment · 1 reaction · Opened Mar 2, 2026
[Proposal] Features for speeding up slow Python/ Pyodide based apps Open

enhancement

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

modelcontextprotocol/ext-apps#513 · 1 comment · Opened Mar 1, 2026
[Proposal] Rich UI elicitation — attach an MCP App to an elicitation/create request Open

enhancement

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

modelcontextprotocol/ext-apps#511 · 5 comments · 11 reactions · Opened Feb 27, 2026
autoResize: true default causes layout bugs — need height management guidance Open

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

modelcontextprotocol/ext-apps#502 · 1 comment · 1 reaction · Opened Feb 24, 2026
Proposal: Direct AI processing channel (sendMessage immediate mode) Open

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

modelcontextprotocol/ext-apps#501 · 2 comments · Opened Feb 24, 2026
Proposal: Slot-based updateModelContext() for independent context channels Open

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

modelcontextprotocol/ext-apps#500 · Opened Feb 24, 2026
Provide a consistent way for MCP Apps to know which tool invoked them Open

enhancement

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

modelcontextprotocol/ext-apps#492 · 5 comments · Opened Feb 23, 2026
ontoolinput is not consistently called Open

bug

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

modelcontextprotocol/ext-apps#476 · 4 comments · 1 reaction · Opened Feb 20, 2026
Constraining UI variability, or enforcing a restricted UI/component set? Open

enhancement

Difficulty 5/5 Over a week Newbie friendliness 20/100

modelcontextprotocol/ext-apps#467 · 3 comments · Opened Feb 17, 2026
Feature parity with Apps SDK setWidgetState Open

enhancement

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

modelcontextprotocol/ext-apps#465 · 2 reactions · Opened Feb 17, 2026
Multiple `initialize` calls per conversation breaks `Mcp-Session-Id` linking Open

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

modelcontextprotocol/ext-apps#458 · 2 comments · Opened Feb 15, 2026
MCP-Apps UI Widget Host Runtime Not Starting After Successful `resources/read` Open

bug upstream-host

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

modelcontextprotocol/ext-apps#482 · 5 comments · Opened Feb 14, 2026
MCP Apps: No shared session identity between AppBridge and Model sub-connections Open

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

modelcontextprotocol/ext-apps#481 · 1 comment · 1 reaction · Opened Feb 14, 2026
Accessibility Open

enhancement protocol

modelcontextprotocol/ext-apps#431 · 7 comments · 6 reactions · 2 assignees · Opened Feb 5, 2026
Re-usable views Open

enhancement protocol v2

modelcontextprotocol/ext-apps#430 · 5 comments · 8 reactions · 1 assignee · Opened Feb 3, 2026
Angular based MCP apps example Open

enhancement

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

modelcontextprotocol/ext-apps#423 · 1 comment · 1 reaction · Opened Feb 2, 2026
MCP Apps - start server issue Open

bug

modelcontextprotocol/ext-apps#420 · 7 comments · 1 assignee · Opened Feb 2, 2026
[research] MCP Apps support for TUIs Open

enhancement

modelcontextprotocol/ext-apps#419 · 3 reactions · 1 assignee · Opened Jan 31, 2026
View state persistence Open

enhancement protocol

modelcontextprotocol/ext-apps#417 · 2 comments · 8 reactions · 1 assignee · Opened Jan 31, 2026
Mechanism to defer `UIResource` rendering for intermediate tool calls Open

modelcontextprotocol/ext-apps#402 · 4 comments · 1 assignee · Opened Jan 29, 2026
Support `frameDomains` → `frame-src` CSP Mapping for External Iframe Embeds Open

enhancement

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

modelcontextprotocol/ext-apps#387 · 8 comments · 3 reactions · Opened Jan 28, 2026
Getting errors when using server-map mcp app. Open

bug

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

modelcontextprotocol/ext-apps#383 · 2 comments · 1 reaction · Opened Jan 28, 2026
Standardizing Host CSS Variables Open

documentation

modelcontextprotocol/ext-apps#382 · 2 comments · 1 assignee · Opened Jan 27, 2026
Properly clarify content model visibility - content vs structuredContent vs _meta Open

documentation

modelcontextprotocol/ext-apps#380 · 5 comments · 9 reactions · 1 assignee · Opened Jan 27, 2026
Side Panels For Interactive Documents Open

enhancement

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

modelcontextprotocol/ext-apps#412 · 1 reaction · Opened Jan 27, 2026
MCP Apps portability issue: widgets render in ChatGPT but not Claude due to host-specific globals and asset assumptions Open

Difficulty 3/5 1-2 days Newbie friendliness 42/100

modelcontextprotocol/ext-apps#413 · 1 comment · Opened Jan 27, 2026
Add official CLI scaffolding tool for MCP Apps Open

enhancement

modelcontextprotocol/ext-apps#354 · 1 comment · 1 assignee · Opened Jan 25, 2026
E2E tests fail on snapshots mismatch Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 35/100

modelcontextprotocol/ext-apps#327 · 1 comment · Opened Jan 22, 2026

modelcontextprotocol/ext-apps

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