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Enhance client support checks for MCP Apps UI rendering#2051
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| Original file line number | Diff line number | Diff line change | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| @@ -1,27 +1,32 @@ | ||||||||||||||||||||
| package github | ||||||||||||||||||||
| import ( | ||||||||||||||||||||
| "context" | ||||||||||||||||||||
| ghcontext "github.com/github/github-mcp-server/pkg/context" | ||||||||||||||||||||
| "github.com/modelcontextprotocol/go-sdk/mcp" | ||||||||||||||||||||
| ) | ||||||||||||||||||||
| // mcpAppsExtensionKey is the capability extension key that clients use to | ||||||||||||||||||||
| // advertise MCP Apps UI support. | ||||||||||||||||||||
| const mcpAppsExtensionKey = "io.modelcontextprotocol/ui" | ||||||||||||||||||||
| // clientSupportsUI reports whether the MCP client that sent this request | ||||||||||||||||||||
| // supports MCP Apps UI rendering. | ||||||||||||||||||||
| // It checks the context first (set by HTTP/stateless servers from stored | ||||||||||||||||||||
| // session capabilities), then falls back to the go-sdk Session (for stdio). | ||||||||||||||||||||
| func clientSupportsUI(ctx context.Context, req *mcp.CallToolRequest) bool { | ||||||||||||||||||||
| // Check context first (works for HTTP/stateless servers) | ||||||||||||||||||||
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Member There was a problem hiding this comment. Is this a legit issue or not @mattdholloway? Will we only support this in remote and set the context on the request there, or should this also be supported in STDIO? | ||||||||||||||||||||
| if supported, ok := ghcontext.HasUISupport(ctx); ok { | ||||||||||||||||||||
| return supported | ||||||||||||||||||||
| } | ||||||||||||||||||||
| // Fall back to go-sdk session (works for stdio/stateful servers) | ||||||||||||||||||||
| if req != nil && req.Session != nil { | ||||||||||||||||||||
| params := req.Session.InitializeParams() | ||||||||||||||||||||
| if params != nil && params.Capabilities != nil { | ||||||||||||||||||||
| _, hasUI := params.Capabilities.Extensions[mcpAppsExtensionKey] | ||||||||||||||||||||
| return hasUI | ||||||||||||||||||||
| } | ||||||||||||||||||||
| } | ||||||||||||||||||||
| return false | ||||||||||||||||||||
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| } | ||||||||||||||||||||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -4,58 +4,84 @@ import ( | ||
| "context" | ||
| "testing" | ||
| ghcontext "github.com/github/github-mcp-server/pkg/context" | ||
| "github.com/modelcontextprotocol/go-sdk/mcp" | ||
| "github.com/stretchr/testify/assert" | ||
| "github.com/stretchr/testify/require" | ||
| ) | ||
| func createMCPRequestWithCapabilities(t *testing.T, caps *mcp.ClientCapabilities) mcp.CallToolRequest { | ||
| t.Helper() | ||
| srv := mcp.NewServer(&mcp.Implementation{Name: "test"}, nil) | ||
| st, _ := mcp.NewInMemoryTransports() | ||
| session, err := srv.Connect(context.Background(), st, &mcp.ServerSessionOptions{ | ||
| State: &mcp.ServerSessionState{ | ||
| InitializeParams: &mcp.InitializeParams{ | ||
| ClientInfo: &mcp.Implementation{Name: "test-client"}, | ||
| Capabilities: caps, | ||
| }, | ||
| }, | ||
| }) | ||
| require.NoError(t, err) | ||
| t.Cleanup(func() { _ = session.Close() }) | ||
| return mcp.CallToolRequest{Session: session} | ||
| } | ||
| func Test_clientSupportsUI(t *testing.T) { | ||
| t.Parallel() | ||
| ctx := context.Background() | ||
| t.Run("client with UI extension", func(t *testing.T) { | ||
| caps := &mcp.ClientCapabilities{} | ||
| caps.AddExtension("io.modelcontextprotocol/ui", map[string]any{ | ||
| "mimeTypes": []string{"text/html;profile=mcp-app"}, | ||
| }) | ||
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| req := createMCPRequestWithCapabilities(t, caps) | ||
| assert.True(t, clientSupportsUI(ctx, &req)) | ||
| }) | ||
| t.Run("client without UI extension", func(t *testing.T) { | ||
| req := createMCPRequestWithCapabilities(t, &mcp.ClientCapabilities{}) | ||
| assert.False(t, clientSupportsUI(ctx, &req)) | ||
| }) | ||
| t.Run("client with nil capabilities", func(t *testing.T) { | ||
| req := createMCPRequestWithCapabilities(t, nil) | ||
| assert.False(t, clientSupportsUI(ctx, &req)) | ||
| }) | ||
| t.Run("nil request", func(t *testing.T) { | ||
| assert.False(t, clientSupportsUI(ctx, nil)) | ||
| }) | ||
| t.Run("nil session", func(t *testing.T) { | ||
| req := createMCPRequest(nil) | ||
| assert.False(t, clientSupportsUI(ctx, &req)) | ||
| }) | ||
| } | ||
| func Test_clientSupportsUI_fromContext(t *testing.T) { | ||
| t.Parallel() | ||
| t.Run("UI supported in context", func(t *testing.T) { | ||
| ctx := ghcontext.WithUISupport(context.Background(), true) | ||
| assert.True(t, clientSupportsUI(ctx, nil)) | ||
| }) | ||
| t.Run("UI not supported in context", func(t *testing.T) { | ||
| ctx := ghcontext.WithUISupport(context.Background(), false) | ||
| assert.False(t, clientSupportsUI(ctx, nil)) | ||
| }) | ||
| t.Run("context takes precedence over session", func(t *testing.T) { | ||
| ctx := ghcontext.WithUISupport(context.Background(), false) | ||
| caps := &mcp.ClientCapabilities{} | ||
| caps.AddExtension("io.modelcontextprotocol/ui", map[string]any{}) | ||
| req := createMCPRequestWithCapabilities(t, caps) | ||
| assert.False(t, clientSupportsUI(ctx, &req)) | ||
| }) | ||
| t.Run("no context or session", func(t *testing.T) { | ||
| assert.False(t, clientSupportsUI(context.Background(), nil)) | ||
| }) | ||
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| } | ||
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CopilotAIFeb 24, 2026
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This helper now decides whether to add the UI extension by matching on
clientName(VS Code names). Since UI support detection has been refactored away from client-name matching, consider makingcreateMCPRequestWithSessionaccept an explicit*mcp.ClientCapabilities(or auiSupportedbool) so tests don’t implicitly rely on client-name heuristics and can set capabilities directly.