WIP: feat(mcp): advertise MCP Apps UI extension capability#6927
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WIP: feat(mcp): advertise MCP Apps UI extension capability#6927
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WIP: Depends on rmcp PR #643 being merged and released. This change updates the MCP client to advertise support for the io.modelcontextprotocol/ui extension during capability negotiation, as required by the MCP Apps specification. The client now advertises: { "capabilities": { "extensions": { "io.modelcontextprotocol/ui": { "mimeTypes": ["text/html;profile=mcp-app"] } } } } Blocked by: - modelcontextprotocol/rust-sdk#643 Related: - https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx
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note: Depending on timing, we might be able to leverage conditional declaration based off platform detection: #6931 |
Jazzcort
added a commit
to Jazzcort/goose
that referenced
this pull request
Feb 5, 2026
Introduces a GoosePlatform enum to distinguish between GooseCli and GooseDesktop environments.
This allows the MCP client to conditionally advertise capabilities based on the active
platform.
Changes:
- Core: Added GoosePlatform enum to crates/goose/src/agents/agent.rs and included it in
AgentConfig.
- MCP Integration: Updated GooseClient to include platform info. Now, the client
advertises its client name as "goose-desktop" while using Goose Desktop and "goose-cli"
for Goose Cli. Leave params.capabilities.extension part for
block#6927.
- Plumbing: Updated ExtensionManager, McpClient, and Agent constructors across the codebase
to propagate the platform type.
- Defaults:
- goose-acp and goose-cli default to GoosePlatform::GooseCli.
- AgentManager (used by the desktop execution flow) defaults to
GoosePlatform::GooseDesktop.
- Testing: Updated scenario runners and integration tests to explicitly pass a platform
variant (typically GooseCli).
Signed-off-by: Jazzcort <jason101011113@gmail.com>
Jazzcort
added a commit
to Jazzcort/goose
that referenced
this pull request
Feb 5, 2026
Introduces a GoosePlatform enum to distinguish between GooseCli and GooseDesktop environments.
This allows the MCP client to conditionally advertise capabilities based on the active
platform.
Changes:
- Core: Added GoosePlatform enum to crates/goose/src/agents/agent.rs and included it in
AgentConfig.
- MCP Integration: Updated GooseClient to include platform info. Now, the client
advertises its client name as "goose-desktop" while using Goose Desktop and "goose-cli"
for Goose Cli. Leave params.capabilities.extension part for block#6927
- Plumbing: Updated ExtensionManager, McpClient, and Agent constructors across the codebase
to propagate the platform type.
- Defaults:
- goose-acp and goose-cli default to GoosePlatform::GooseCli.
- AgentManager (used by the desktop execution flow) defaults to
GoosePlatform::GooseDesktop.
- Testing: Updated scenario runners and integration tests to explicitly pass a platform
variant (typically GooseCli).
Signed-off-by: Jazzcort <jason101011113@gmail.com>
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Summary
This PR updates the MCP client to advertise support for the
io.modelcontextprotocol/uiextension during capability negotiation, as required by the MCP Apps specification.Changes
ExtensionCapabilitiesfromrmcp::modelGooseClient::get_info()to build and advertise the UI extension capabilityCapability Advertised
{ "capabilities": { "extensions": { "io.modelcontextprotocol/ui": { "mimeTypes": ["text/html;profile=mcp-app"] } } } }Blocked By
extensionsfield toClientCapabilitiesinrmcpcrateOnce that PR is merged and a new version of
rmcpis released, we'll need to:rmcpversion inCargo.tomlRelated