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feat: standardize resource-not-found error code (SEP-2164) (#899)

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* feat: implement SEP-2164 resource not found errors

* test: update protocol version utility expectations

* feat: gate not-found code at server boundary

---------

Co-authored-by: Michael Neale <michael.neale@gmail.com>
This commit is contained in:
Dale Seo 2026-06-16 21:55:25 -04:00 • committed by GitHub
commit 95a8e961e0
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1 changed files with 126 additions and 4 deletions
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17
crates/rmcp/src/handler/server.rs
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@ -22,7 +22,9 @@ impl<H: ServerHandler> Service<RoleServer> for H {
request: <RoleServer as ServiceRole>::PeerReq,
context: RequestContext<RoleServer>,
) -> Result<<RoleServer as ServiceRole>::Resp, McpError> {
match request {
// `context` is moved into the dispatch below, so read the negotiated version first.
let protocol_version = context.protocol_version();
let result = match request {
ClientRequest::InitializeRequest(request) => self
.initialize(request.params, context)
.await
@ -127,7 +129,18 @@ impl<H: ServerHandler> Service<RoleServer> for H {
.cancel_task(request.params, context)
.await
.map(ServerResult::CancelTaskResult),
}
};
// SEP-2164: peers negotiating 2026-07-28+ get the standard INVALID_PARAMS code for
// resource-not-found; older peers keep RESOURCE_NOT_FOUND. ISO `YYYY-MM-DD` versions
// compare lexically the same as chronologically.
let use_invalid_params =
protocol_version.is_some_and(|v| v.as_str() >= ProtocolVersion::V_2026_07_28.as_str());
result.map_err(|mut error| {
if use_invalid_params && error.code == ErrorCode::RESOURCE_NOT_FOUND {
error.code = ErrorCode::INVALID_PARAMS;
}
error
})
}
async fn handle_notification(