Wymcp.
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Modern-lane enforcement of the
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.
The fall-back clause is legacy-only: it points a rejected client at an
initialize handshake, and it goes at the legacy decommission.
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.
That pass-through is legacy-only: it exists only because a second era
does, and it goes at the legacy decommission.
The MCP-Protocol-Version header is deliberately not read here: the
protocol fields are authoritative, and comparing the mirrored headers
against the body they mirror is the
header-binding check's
(Wymcp.Plugs.HeaderBinding), which runs directly after this plug — with a
body value this one has just proven.