feat(client): add SEP-2549 response caching

Author: starsaintf

README.md

@@ -74,6 +74,8 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 ```
 </details>
 
+For client-side TTL caching, configuration, and authorization partitioning, see [Client response caching](docs/CLIENT_CACHING.md).
+
 ### Build a Server
 
 <details>

crates/rmcp/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- add a configurable SEP-2549 client response cache with TTL, scope, pagination, and notification invalidation support
+
 ## [2.2.0](https://github.com/modelcontextprotocol/rust-sdk/compare/rmcp-v2.1.0...rmcp-v2.2.0) - 2026-07-08
 
 ### Added

crates/rmcp/src/handler/client.rs

@@ -55,15 +55,22 @@ impl<H: ClientHandler> Service<RoleClient> for H {
                 self.on_logging_message(notification.params, context).await
             }
             ServerNotification::ResourceUpdatedNotification(notification) => {
+                context
+                    .peer
+                    .invalidate_resource_read_cache(&notification.params.uri)
+                    .await;
                 self.on_resource_updated(notification.params, context).await
             }
             ServerNotification::ResourceListChangedNotification(_notification_no_param) => {
+                context.peer.invalidate_resource_list_cache().await;
                 self.on_resource_list_changed(context).await
             }
             ServerNotification::ToolListChangedNotification(_notification_no_param) => {
+                context.peer.invalidate_tool_cache().await;
                 self.on_tool_list_changed(context).await
             }
             ServerNotification::PromptListChangedNotification(_notification_no_param) => {
+                context.peer.invalidate_prompt_cache().await;
                 self.on_prompt_list_changed(context).await
             }
             ServerNotification::TaskStatusNotification(notification) => {

crates/rmcp/src/lib.rs

@@ -16,10 +16,10 @@ pub use handler::client::ClientHandler;
 pub use handler::server::ServerHandler;
 #[cfg(feature = "server")]
 pub use handler::server::wrapper::Json;
+#[cfg(feature = "client")]
+pub use service::{ClientCacheConfig, MAX_CLIENT_CACHE_TTL, RoleClient, serve_client};
 #[cfg(any(feature = "client", feature = "server"))]
 pub use service::{Peer, Service, ServiceError, ServiceExt};
-#[cfg(feature = "client")]
-pub use service::{RoleClient, serve_client};
 #[cfg(feature = "server")]
 pub use service::{RoleServer, serve_server};
 

crates/rmcp/src/service.rs

@@ -527,6 +527,8 @@ pub struct Peer<R: ServiceRole> {
     progress_token_provider: Arc<dyn ProgressTokenProvider>,
     progress_timeout_watchers: ProgressTimeoutWatchers,
     info: Arc<std::sync::RwLock<Option<Arc<R::PeerInfo>>>>,
+    #[cfg(feature = "client")]
+    response_cache: client::cache::PeerResponseCache<R>,
 }
 
 impl<R: ServiceRole> std::fmt::Debug for Peer<R> {
@@ -588,6 +590,8 @@ impl<R: ServiceRole> Peer<R> {
                 progress_token_provider: Arc::new(AtomicU32ProgressTokenProvider::default()),
                 progress_timeout_watchers: Default::default(),
                 info: Arc::new(std::sync::RwLock::new(peer_info.map(Arc::new))),
+                #[cfg(feature = "client")]
+                response_cache: Default::default(),
             },
             rx,
         )