Always enable MCP Apps UI; remove remote_mcp_ui_apps flag gate - #3348
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SamMorrowDrums wants to merge 3 commits into
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SamMorrowDrums wants to merge 3 commits into
SamMorrowDrums wants to merge 3 commits into
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The remote_mcp_ui_apps flag is fully rolled out on the hosted server, but the OSS server still defaulted it off. Make MCP Apps unconditional: - _meta.ui is always emitted, stripped only when the client explicitly does not advertise the io.modelcontextprotocol/ui capability - ui_get is always registered - write tools defer to MCP App forms by default (still opt-out via mcp_apps_disable_form_deferral) - remove MCPAppsFeatureFlag and its AllowedFeatureFlags/InsidersFeatureFlags entries - update tests and regenerate docs Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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Copilot review overview
🟡 Changes recommended
HTTP capability detection is not connected to metadata stripping, and stripping exposes the app-only ui_get tool to models.
Review effort: Balanced
Findings: 1
Open (2)
What changed in this PR
Makes MCP Apps UI available by default by removing the legacy feature-flag gate.
Changes:
- Enables UI metadata,
ui_get, and form deferral by default. - Retains capability-based metadata stripping and deferral opt-out.
- Updates tests and generated documentation.
| File | Description |
|---|---|
README.md |
Documents UI-enabled tools. |
pkg/inventory/registry.go |
Removes the UI feature gate. |
pkg/inventory/registry_test.go |
Updates metadata behavior tests. |
pkg/inventory/builder.go |
Removes the inventory flag constant. |
pkg/http/server_test.go |
Updates feature-checker tests. |
pkg/http/handler_test.go |
Updates HTTP UI metadata tests. |
pkg/github/ui_tools.go |
Makes ui_get unconditional. |
pkg/github/ui_tools_test.go |
Verifies ui_get is ungated. |
pkg/github/ui_capability.go |
Defaults write tools to form deferral. |
pkg/github/ui_capability_test.go |
Updates deferral defaults. |
pkg/github/tools_validation_test.go |
Removes obsolete flag validation. |
pkg/github/server.go |
Updates UI resource documentation. |
pkg/github/pullrequests_test.go |
Updates PR form-routing tests. |
pkg/github/issues_test.go |
Updates issue form-routing tests. |
pkg/github/feature_flags.go |
Removes the legacy feature flag. |
pkg/github/feature_flags_test.go |
Updates flag resolution tests. |
pkg/github/feature_flags_benchmark_test.go |
Updates benchmark flag data. |
docs/server-configuration.md |
Documents always-on MCP Apps. |
docs/insiders-features.md |
Removes MCP Apps from insiders. |
docs/feature-flags.md |
Removes the retired flag. |
cmd/github-mcp-server/generate_docs.go |
Updates generated UI documentation logic. |
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Comment on lines
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| if shouldStripMCPAppsMetadata(ctx) { | ||
| tools = stripMCPAppsMetadata(tools) |
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| func shouldStripMCPAppsMetadata(ctx context.Context) bool { | ||
| supported, ok := ghcontext.HasUISupport(ctx) | ||
| return ok && !supported | ||
| } |
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
When a client does not advertise io.modelcontextprotocol/ui, stripping _meta.ui from ui_get turned it into an ordinary model-visible tool, violating its app-only contract. Now that ui_get is no longer feature gated, omit tools whose ui.visibility excludes "model" instead. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
tommaso-moro
approved these changes
Sep 29, 2026
tommaso-moro
self-requested a review
September 29, 2026 21:34
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Why
The
remote_mcp_ui_appsfeature flag is at 100% rollout on the hosted (remote) server, so MCP Apps is always on in production. In this repo it was still off by default unless enabled through--features/X-MCP-Featuresor insiders mode. This PR removes that difference so the OSS server matches the shipped remote behavior.What changed
_meta.uiis now always emitted. It's stripped only when the client explicitly doesn't advertise theio.modelcontextprotocol/uicapability, which is the spec-conformant check. The flag branch is gone fromToolsForRegistration,shouldStripMCPAppsMetadataandRequiredFeatures, andmcpAppsFeatureFlagis deleted.ui_get: no longer feature-gated. It is app-only (_meta.ui.visibility: ["app"]), so for clients without the UI capability, app-only tools are now left out entirely. Previously, stripping_meta.uiwould have exposed it as an ordinary model-visible tool.shouldDeferToFormno longer checksremote_mcp_ui_apps. Write tools hand off to their MCP App form by default for UI-capable clients.mcp_apps_disable_form_deferralis unchanged and remains the long-lived opt-out.MCPAppsFeatureFlagand its entries inAllowedFeatureFlagsandInsidersFeatureFlags.featureEnabledRule/featureDisabledRulestay because other flags use them.ui_get) are left out for clients without UI support and kept when support is present or unknown.script/generate-docs, so the README now lists the MCP App UI URIs andui_get, and theremote_mcp_ui_appssections are gone fromfeature-flags.md/insiders-features.md. The MCP Apps section inserver-configuration.mdnow says MCP Apps is always on.Follow-up for github/github-mcp-server-remote
After this merges, github/github-mcp-server-remote should:
github-mcp-serverdependency to pick this up;githubMcp.MCPAppsFeatureFlag(internal/featureflags/flags_test.go,pkg/mcp/inventory/inventory_test.go);remote_mcp_ui_appscomment ininternal/featureflags/flags.go.