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MCP Stateless Check

MCP016 — Deprecated HTTP+SSE transport detected
Severity warning
Fixed by Upgrading your MCP SDK to a release targeting 2026-07-28
Transports http
Specification 2026-07-28
Changelog entry Deprecated 2 (SEP-2596)

Why this changed

The original HTTP+SSE transport — a GET stream that opens with an endpoint event naming a separate POST URL — has been deprecated since 2025-03-26 and was reclassified under the formal lifecycle policy in 2026-07-28.

Distinct from MCP010, which flags a leftover GET stream on a Streamable HTTP endpoint. This rule looks for the two-endpoint handshake specifically.

Running just this check

Terminal window
npx mcp-stateless --http https://mcp.example.com/mcp --only MCP016

Suppressing it

If this check does not apply to your server, skip it:

Terminal window
npx mcp-stateless --http https://mcp.example.com/mcp --skip MCP016

Rule ids are permanent and are never reissued, so a suppression cannot start silently matching a different check later.

Generated from src/rules/MCP016.ts by scripts/gen-rule-docs.mjs. Edit the rule source, not this page.