[Feature]: Upgrade MCP support to protocol 2026-07-28

[loveRhythm1990]

Is there an existing issue for the same feature?

• I have checked the existing issues.

Is your feature request related to a problem?

Memoria currently implements MCP manually and always advertises protocol version 2024-11-05. Its stdio and HTTP paths duplicate RPC dispatch logic, and the HTTP endpoint does not implement the stateless request envelope and routing headers introduced by MCP 2026-07-28.

Changing only the protocolVersion string would produce a non-conformant server because the 2026-07-28 revision contains breaking lifecycle, transport, request, and response changes.

Describe the feature you would like

Add MCP 2026-07-28 support while retaining compatibility with existing handshake-era clients during a migration period.

Recommended behavior:

• Legacy clients using 2024-11-05 continue to use initialize and notifications/initialized.
• Modern clients use the stateless 2026-07-28 request model.
• Protocol selection is explicit and shared across stdio and Streamable HTTP transports.
• Business tool implementations remain independent of the wire protocol version.

Implementation / design notes

Protocol lifecycle

• Implement the required server/discover method.
• Do not require initialize or notifications/initialized for 2026-07-28 requests.
• Parse and validate per-request metadata, including protocol version and client capabilities.
• Continue the legacy handshake only for supported pre-2026 protocol versions.

Streamable HTTP

• Validate MCP-Protocol-Version, Mcp-Method, and Mcp-Name headers.
• Reject missing or mismatched headers according to the 2026-07-28 specification.
• Preserve the existing authentication and group write-guard behavior.
• Plan removal of the deprecated legacy HTTP+SSE transport separately or as a documented migration step.

Responses and discovery

• Add resultType to all successful modern-protocol results.
• Add ttlMs and cacheScope to tools/list responses.
• Return supported versions, capabilities, server information, and caching fields from server/discover.
• Keep legacy response shapes unchanged for legacy clients.

Architecture

• Consolidate the duplicated dispatch logic in memoria/crates/memoria-mcp/src/server.rs before or during the migration.
• Separate protocol decoding/encoding from tool execution.
• Evaluate using an official MCP SDK versus maintaining the handwritten protocol layer.

Testing

Add conformance-focused tests for:

• modern server/discover
• direct modern tools/list and tools/call without initialize
• required request metadata
• HTTP header/body mismatch errors
• resultType and cache fields
• legacy 2024-11-05 compatibility
• stdio and HTTP protocol selection
• authentication and notification behavior

Additional information

MCP 2026-07-28 release overview:
https://blog.modelcontextprotocol.io/posts/2026-07-28/

MCP 2026-07-28 schema:
https://modelcontextprotocol.io/specification/2026-07-28/schema

Related legacy compatibility issue:
#235

Acceptance criteria

• Memoria passes the agreed 2026-07-28 protocol conformance tests for tools over supported transports.
• Existing supported legacy clients continue to function during the documented migration window.
• Protocol-version-specific behavior is tested and is not duplicated across transport dispatchers.
• Documentation states supported protocol versions and transport deprecations.