---
"@modelcontextprotocol/core-internal": minor
"@modelcontextprotocol/server": major
"@modelcontextprotocol/client": minor
---

`resources/read` for an unknown URI now answers with JSON-RPC error code `-32602`
(Invalid Params) on every protocol revision, with `error.data.uri` echoing the
requested URI. The 2026-07-28 specification requires `-32602`; the v1.x SDK already
emitted `-32602` on earlier revisions, so v1.x peers see no change.

This supersedes an interim `-32002` emission that shipped in earlier v2 alphas. The
era-aware encode seam (`WireCodec.encodeErrorCode`) maps any handler-thrown `-32002`
to `-32602` on the wire; note that a `-32002` thrown without `data.uri` is emitted as
a bare `-32602` and is no longer recognizable as resource-not-found — throw
`ResourceNotFoundError` (or include `data: { uri }`) to preserve the classification.

`ProtocolErrorCode.ResourceNotFound` (`-32002`) remains importable as receive-tolerated
vocabulary; clients should accept both `-32602` and `-32002` from peers (the
specification's backwards-compatibility clause). The new typed `ResourceNotFoundError`
class carries `data.uri`, and `ProtocolError.fromError` reconstructs it from a `-32602`
only when `error.data` is exactly `{ uri: string }` (and nothing else), and from a
legacy `-32002` whenever `data.uri` is a string; a bare `-32002` without `data.uri`
stays a generic `ProtocolError`.