Wymcp.
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Modern-lane enforcement of the protocol fields (docs/glossary.md,
protocol fields). On a modern-classified request, params._meta
must carry io.modelcontextprotocol/protocolVersion as a string and
io.modelcontextprotocol/clientCapabilities as an object — a missing or
wrong-typed field answers -32602 + 400 — and the version must be a
modern revision wymcp serves — anything else answers -32022 + 400 with
data.supported naming every version either era serves (so a
legacy-capable client sees its initialize fall-back in the same
answer) and data.requested echoing the offer.
Notifications are exempt: JSON-RPC forbids error responses to
notifications, and the modern core defines no client→server
notifications over HTTP — Wymcp.Plugs.Dispatch answers them 202 and
drops them. Legacy-classified messages pass through untouched.
The MCP-Protocol-Version header is deliberately not read: the
protocol fields are authoritative, and the whole header-binding family
(-32020, Mcp-Method, Mcp-Name) is one coherent design, planned to
land as a single future change. Until it lands, wymcp under-enforces
headers but never rejects a compliant client.