Compatibility: hosted /mcp rejects MCP 2026-07-28 server/discover

[MysticDakra]

Observation

On 2026-08-26 at 00:36 UTC I sent one read-only server/discover
request to the hosted endpoint. I did not request the tool list or call
any tool.

curl -i --max-time 10 \
  -X POST 'https://mcp.agenticterminal.ai/mcp' \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -H 'MCP-Protocol-Version: 2026-07-28' \
  -H 'Mcp-Method: server/discover' \
  --data '{
    "jsonrpc": "2.0",
    "id": "compat-20260826",
    "method": "server/discover",
    "params": {
      "_meta": {
        "io.modelcontextprotocol/protocolVersion": "2026-07-28",
        "io.modelcontextprotocol/clientCapabilities": {},
        "io.modelcontextprotocol/clientInfo": {
          "name": "compatibility-check",
          "version": "1.0.0"
        }
      }
    }
  }'

The endpoint returned HTTP 400:

{
  "jsonrpc": "2.0",
  "error": {
    "code": -32000,
    "message": "Bad Request: Unsupported protocol version: 2026-07-28 (supported versions: 2025-11-25, 2025-06-18, 2025-03-26, 2024-11-05, 2024-10-07)"
  },
  "id": null
}

This matches the repository state: the MCP package currently depends on
SDK v1, and the hosted handler constructs a v1
StreamableHTTPServerTransport per request.

This is not a report that existing 2025-era clients are broken. It only
means clients pinned to the 2026-07-28 era cannot currently complete
discovery. The official SDK migration guide describes additive dual-era
HTTP serving with explicit 2026 opt-in:
https://github.com/modelcontextprotocol/typescript-sdk/blob/main/docs/migration/support-2026-07-28.md

Would additive 2025 + 2026 HTTP support be within the AT Directory v1
scope? If so, I can prepare a focused proposal or PR after maintainer
confirmation, preserving the existing six-tool surface and legacy path,
with official conformance evidence, a legacy smoke test, and a rollback
path.