Compatibility

The protocol target is MCP 2026-07-28, using the official TypeScript SDK v2. Compatibility with MCP 2025-11-25 is tested separately.

Version negotiation

protocol: 'auto' probes server/discover and selects the current era when supported. protocol: 'current' pins 2026-07-28 and fails if it is unavailable. protocol: 'legacy' explicitly uses the older initialization handshake.

The current era carries protocol version and capabilities on each request. It uses subscriptions/listen for change streams and input_required for additional input. The SDK manages these wire details and aggregates paginated capability lists.

A failed network request is not evidence that an endpoint uses an older protocol. Interrupted tool calls are not retried automatically by this UI. A cancelled request does not prove that remote work was rolled back.

Supported capabilities

• Tools, JSON Schema arguments, progress and cancellation.
• Resources, resource templates, prompts and catalog change subscriptions.
• Form and URL elicitation through the SDK's shared handler model.
• Browser Streamable HTTP with anonymous, bearer or OAuth authentication.
• Optional authenticated Node connector with operator-controlled destinations.

Tasks, Skills and MCP Apps are separate extensions. This release does not advertise them, launch stdio processes, or render remote MCP Apps iframes. Sampling, Roots and the legacy HTTP+SSE transport are not added to new applications.

WebMCP compatibility

WebMCP is a browser proposal with a separate release lifecycle. The adapter distinguishes the current document API from the older navigator API. The simulator is always labeled and does not count as evidence of native browser support.

Source of truth: MCP versioning, MCP changes, and WebMCP implementation status.