Track migration to MCP spec 2026-07-28 (stateless, MRTR, deprecated Sampling)

Start by reading the TypeScript SDK migration guide and changelog for support of the 2026-07-28 specification, then verify MRTR support in Claude Desktop, Claude Code, and VS Code Copilot. Audit this repository for uses of elicitInput and Sampling beyond PR #57. The work is complete when client support, SDK support, and all affected repository usage are documented well enough to define the migration.

Summary

The MCP spec released a new revision on 2026-07-28 (announced at https://blog.modelcontextprotocol.io/posts/2026-07-28/) that moves from the stateful bidirectional protocol to a stateless request/response model. Key changes relevant to us:

• The initialize/initialized handshake and session IDs are eliminated; each request is self-describing.
• Server-initiated elicitation is replaced by "Multi Round-Trip Requests" (MRTR).
• Sampling is deprecated.
• Roots and Logging are also deprecated.
• Header-based routing, cacheable list results, tasks moved to an official extensions framework.
• Security: RFC 9207 issuer validation required, shift from Dynamic Client Registration toward Client ID Metadata Documents (CIMD).
• Deprecations get a 12-month minimum window; legacy HTTP+SSE transport gets a year-long offramp. No fire drill, but not indefinite either.

As of this issue, @modelcontextprotocol/sdk on npm is still on the 1.x line (1.30.0 latest) — there is no separate 2.0.0 package. The new spec appears to be supported via 1.x releases, not a major SDK version bump.

Why this needs a dedicated pass, not an incidental bump

This repo is actively building on the mechanisms this spec revision replaces/deprecates — most concretely, the in-progress add-preview-token-elicitation work (PR #57) depends on server-initiated elicitation, the exact thing MRTR replaces. Migrating means redesigning against whatever MRTR's actual API surface turns out to be, not just bumping a dependency version.

What to check before starting

• Confirm real client support for MRTR (Claude Desktop, Claude Code, VS Code Copilot) — no point redesigning against a mechanism clients can't use yet.
• Read the SDK's actual migration guide/changelog for the TypeScript SDK version(s) that implement 2026-07-28 support.
• Audit this repo for every current use of elicitInput/Sampling beyond the in-progress PR #57 work.

Non-goals for now

• No urgency given the 12-month deprecation window.
• The routine SDK dependency bump (1.29.0 → 1.30.0) is handled separately and does not itself adopt the new spec — see the corresponding PR.

See also mapbox/mcp-server#245 for the equivalent tracking issue there.