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michaelneale wants to merge 2 commits into from
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implementing SEP-2164 #890

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2863526
feat: implement SEP-2164 resource not found errors
michaelneale Jun 5, 2026
9074050
test: update protocol version utility expectations
michaelneale Jun 7, 2026
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42 changes: 42 additions & 0 deletions crates/rmcp/src/model.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -152,6 +152,7 @@ impl std::fmt::Display for ProtocolVersion {
}

impl ProtocolVersion {
pub const V_2026_07_28: Self = Self(Cow::Borrowed("2026-07-28"));
pub const V_2025_11_25: Self = Self(Cow::Borrowed("2025-11-25"));
pub const V_2025_06_18: Self = Self(Cow::Borrowed("2025-06-18"));
pub const V_2025_03_26: Self = Self(Cow::Borrowed("2025-03-26"));
Expand All @@ -164,6 +165,7 @@ impl ProtocolVersion {
Self::V_2025_03_26,
Self::V_2025_06_18,
Self::V_2025_11_25,
Self::V_2026_07_28,
];

/// Returns the string representation of this protocol version.
Expand Down Expand Up @@ -193,6 +195,7 @@ impl<'de> Deserialize<'de> for ProtocolVersion {
"2025-03-26" => return Ok(ProtocolVersion::V_2025_03_26),
"2025-06-18" => return Ok(ProtocolVersion::V_2025_06_18),
"2025-11-25" => return Ok(ProtocolVersion::V_2025_11_25),
"2026-07-28" => return Ok(ProtocolVersion::V_2026_07_28),
_ => {}
}
Ok(ProtocolVersion(Cow::Owned(s)))
Expand Down Expand Up @@ -544,6 +547,25 @@ impl ErrorData {
pub fn resource_not_found(message: impl Into<Cow<'static, str>>, data: Option<Value>) -> Self {
Self::new(ErrorCode::RESOURCE_NOT_FOUND, message, data)
}

/// Create a resource-not-found error using the code required by the negotiated protocol version.
///
/// SEP-2164 standardizes resource-not-found as JSON-RPC `INVALID_PARAMS` (`-32602`)
/// starting with protocol version `2026-07-28`. Older protocol versions continue to use
/// the legacy MCP-specific `RESOURCE_NOT_FOUND` code (`-32002`).
pub fn resource_not_found_for(
protocol_version: &ProtocolVersion,
message: impl Into<Cow<'static, str>>,
data: Option<Value>,
) -> Self {
let code = if protocol_version.as_str() >= ProtocolVersion::V_2026_07_28.as_str() {
ErrorCode::INVALID_PARAMS
} else {
ErrorCode::RESOURCE_NOT_FOUND
};
Self::new(code, message, data)
}

pub fn parse_error(message: impl Into<Cow<'static, str>>, data: Option<Value>) -> Self {
Self::new(ErrorCode::PARSE_ERROR, message, data)
}
Expand Down Expand Up @@ -4021,6 +4043,26 @@ mod tests {
assert_eq!(json_url, expected_url_json);
}

#[test]
fn resource_not_found_for_uses_legacy_code_for_older_protocol_versions() {
let error = ErrorData::resource_not_found_for(
&ProtocolVersion::V_2025_11_25,
"resource not found",
None,
);
assert_eq!(error.code, ErrorCode::RESOURCE_NOT_FOUND);
}

#[test]
fn resource_not_found_for_uses_invalid_params_for_sep_2164_protocol_versions() {
let error = ErrorData::resource_not_found_for(
&ProtocolVersion::V_2026_07_28,
"resource not found",
None,
);
assert_eq!(error.code, ErrorCode::INVALID_PARAMS);
}

#[test]
fn notification_without_params_should_deserialize_as_bare_jsonrpc_message() {
let payload = b"{\"method\":\"notifications/initialized\",\"jsonrpc\":\"2.0\"}";
Expand Down
4 changes: 3 additions & 1 deletion crates/rmcp/tests/test_custom_headers.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -866,16 +866,18 @@ async fn test_server_rejects_unsupported_protocol_version() {
fn test_protocol_version_utilities() {
use rmcp::model::ProtocolVersion;

assert_eq!(ProtocolVersion::V_2026_07_28.as_str(), "2026-07-28");
assert_eq!(ProtocolVersion::V_2025_11_25.as_str(), "2025-11-25");
assert_eq!(ProtocolVersion::V_2025_06_18.as_str(), "2025-06-18");
assert_eq!(ProtocolVersion::V_2025_03_26.as_str(), "2025-03-26");
assert_eq!(ProtocolVersion::V_2024_11_05.as_str(), "2024-11-05");

assert_eq!(ProtocolVersion::KNOWN_VERSIONS.len(), 4);
assert_eq!(ProtocolVersion::KNOWN_VERSIONS.len(), 5);
assert!(ProtocolVersion::KNOWN_VERSIONS.contains(&ProtocolVersion::V_2024_11_05));
assert!(ProtocolVersion::KNOWN_VERSIONS.contains(&ProtocolVersion::V_2025_03_26));
assert!(ProtocolVersion::KNOWN_VERSIONS.contains(&ProtocolVersion::V_2025_06_18));
assert!(ProtocolVersion::KNOWN_VERSIONS.contains(&ProtocolVersion::V_2025_11_25));
assert!(ProtocolVersion::KNOWN_VERSIONS.contains(&ProtocolVersion::V_2026_07_28));
}

/// Integration test: Verify server validates only the Host header for DNS rebinding protection
Expand Down