feat(task): add task support (SEP-1686)

crates/rmcp/Cargo.toml

@@ -23,7 +23,7 @@ tracing = { version = "0.1" }
 tokio-util = { version = "0.7" }
 pin-project-lite = "0.2"
 paste = { version = "1", optional = true }
-
+async-trait = "0.1"
 # oauth2 support
 oauth2 = { version = "5.0", optional = true }
 

crates/rmcp/src/error.rs

@@ -41,6 +41,10 @@ pub enum RmcpError {
         error: Box<dyn std::error::Error + Send + Sync>,
     },
     // and cancellation shouldn't be an error?
+
+    // TODO: add more error variants as needed
+    #[error("Task error: {0}")]
+    TaskError(String),
 }
 
 impl RmcpError {

crates/rmcp/src/handler/server.rs

@@ -10,12 +10,21 @@ mod resource;
 pub mod router;
 pub mod tool;
 pub mod wrapper;
+
 impl<H: ServerHandler> Service<RoleServer> for H {
     async fn handle_request(
         &self,
         request: <RoleServer as ServiceRole>::PeerReq,
         context: RequestContext<RoleServer>,
     ) -> Result<<RoleServer as ServiceRole>::Resp, McpError> {
+        // Pre-dispatch: check task meta and optionally enqueue as task
+        if context.meta.get_task().is_some() {
+            // Allow handler to decide whether and how to enqueue task
+            if let Some(result) = self.enqueue_task(&request, context.clone()).await? {
+                return Ok(result);
+            }
+        }
+
         match request {
             ClientRequest::InitializeRequest(request) => self
                 .initialize(request.params, context)
@@ -68,6 +77,14 @@ impl<H: ServerHandler> Service<RoleServer> for H {
                 .list_tools(request.params, context)
                 .await
                 .map(ServerResult::ListToolsResult),
+            ClientRequest::ListTasksRequest(request) => self
+                .list_tasks(request.params, context)
+                .await
+                .map(ServerResult::ListTasksResult),
+            ClientRequest::GetTaskInfoRequest(request) => self
+                .get_task_info(request.params, context)
+                .await
+                .map(ServerResult::GetTaskInfoResult),
         }
     }
 
@@ -100,6 +117,19 @@ impl<H: ServerHandler> Service<RoleServer> for H {
 
 #[allow(unused_variables)]
 pub trait ServerHandler: Sized + Send + Sync + 'static {
+    /// Optional pre-dispatch hook to enqueue incoming request as a background task.
+    /// Default: do nothing and return None.
+    /// Implementors that also act as an OperationHandler may override this to:
+    /// - Inspect `context.meta` (e.g., key "modelcontextprotocol.io/task")
+    /// - Build an operation and submit to a task manager
+    /// - Return an immediate ServerResult (e.g., EmptyResult or a Task ack)
+    fn enqueue_task(
+        &self,
+        _request: &ClientRequest,
+        _context: RequestContext<RoleServer>,
+    ) -> impl Future<Output = Result<Option<ServerResult>, McpError>> + Send + '_ {
+        std::future::ready(Ok(None))
+    }
     fn ping(
         &self,
         context: RequestContext<RoleServer>,
@@ -228,4 +258,20 @@ pub trait ServerHandler: Sized + Send + Sync + 'static {
     fn get_info(&self) -> ServerInfo {
         ServerInfo::default()
     }
+
+    fn list_tasks(
+        &self,
+        request: Option<PaginatedRequestParam>,
+        context: RequestContext<RoleServer>,
+    ) -> impl Future<Output = Result<ListTasksResult, McpError>> + Send + '_ {
+        std::future::ready(Err(McpError::method_not_found::<ListTasksMethod>()))
+    }
+
+    fn get_task_info(
+        &self,
+        request: GetTaskInfoParam,
+        context: RequestContext<RoleServer>,
+    ) -> impl Future<Output = Result<GetTaskInfoResult, McpError>> + Send + '_ {
+        std::future::ready(Err(McpError::method_not_found::<GetTaskInfoMethod>()))
+    }
 }

crates/rmcp/src/lib.rs

@@ -162,6 +162,7 @@ pub use service::{RoleClient, serve_client};
 pub use service::{RoleServer, serve_server};
 
 pub mod handler;
+pub mod task_manager;
 pub mod transport;
 
 // re-export

crates/rmcp/src/model.rs

@@ -8,6 +8,7 @@ mod meta;
 mod prompt;
 mod resource;
 mod serde_impl;
+mod task;
 mod tool;
 pub use annotated::*;
 pub use capabilities::*;
@@ -19,6 +20,7 @@ pub use prompt::*;
 pub use resource::*;
 use serde::{Deserialize, Serialize, de::DeserializeOwned};
 use serde_json::Value;
+pub use task::*;
 pub use tool::*;
 
 /// A JSON object type alias for convenient handling of JSON data.
@@ -1654,6 +1656,23 @@ pub struct GetPromptResult {
     pub messages: Vec<PromptMessage>,
 }
 
+// =============================================================================
+// TASK MANAGEMENT
+// =============================================================================
+
+const_string!(GetTaskInfoMethod = "tasks/get");
+pub type GetTaskInfoRequest = Request<GetTaskInfoMethod, GetTaskInfoParam>;
+
+#[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
+#[serde(rename_all = "camelCase")]
+#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
+pub struct GetTaskInfoParam {
+    pub task_id: String,
+}
+
+const_string!(ListTasksMethod = "tasks/list");
+pub type ListTasksRequest = RequestOptionalParam<ListTasksMethod, PaginatedRequestParam>;
+
 // =============================================================================
 // MESSAGE TYPE UNIONS
 // =============================================================================
@@ -1720,7 +1739,9 @@ ts_union!(
     | SubscribeRequest
     | UnsubscribeRequest
     | CallToolRequest
-    | ListToolsRequest;
+    | ListToolsRequest
+    | GetTaskInfoRequest
+    | ListTasksRequest;
 );
 
 impl ClientRequest {
@@ -1739,6 +1760,8 @@ impl ClientRequest {
             ClientRequest::UnsubscribeRequest(r) => r.method.as_str(),
             ClientRequest::CallToolRequest(r) => r.method.as_str(),
             ClientRequest::ListToolsRequest(r) => r.method.as_str(),
+            ClientRequest::GetTaskInfoRequest(r) => r.method.as_str(),
+            ClientRequest::ListTasksRequest(r) => r.method.as_str(),
         }
     }
 }
@@ -1794,6 +1817,8 @@ ts_union!(
     | CallToolResult
     | ListToolsResult
     | CreateElicitationResult
+    | GetTaskInfoResult
+    | ListTasksResult
     | EmptyResult
     ;
 );
@@ -1804,6 +1829,28 @@ impl ServerResult {
     }
 }
 
+// =============================================================================
+// TASK RESULT TYPES (Server responses for task queries)
+// =============================================================================
+#[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
+#[serde(rename_all = "camelCase")]
+#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
+pub struct GetTaskInfoResult {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub task: Option<crate::model::Task>,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Default)]
+#[serde(rename_all = "camelCase")]
+#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
+pub struct ListTasksResult {
+    pub tasks: Vec<crate::model::Task>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub next_cursor: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub total: Option<u64>,
+}
+
 pub type ServerJsonRpcMessage = JsonRpcMessage<ServerRequest, ServerResult, ServerNotification>;
 
 impl TryInto<CancelledNotification> for ServerNotification {

crates/rmcp/src/model/meta.rs

@@ -66,6 +66,8 @@ variant_extension! {
         UnsubscribeRequest
         CallToolRequest
         ListToolsRequest
+        GetTaskInfoRequest
+        ListTasksRequest
     }
 }
 
@@ -103,6 +105,7 @@ variant_extension! {
 #[serde(transparent)]
 pub struct Meta(pub JsonObject);
 const PROGRESS_TOKEN_FIELD: &str = "progressToken";
+const TASK_FIELD: &str = "modelcontextprotocol.io/task";
 impl Meta {
     pub fn new() -> Self {
         Self(JsonObject::new())
@@ -133,6 +136,12 @@ impl Meta {
         })
     }
 
+    pub fn get_task(&self) -> Option<String> {
+        self.0
+            .get(TASK_FIELD)
+            .and_then(|v| v.as_str().map(|s| s.to_string()))
+    }
+
     pub fn set_progress_token(&mut self, token: ProgressToken) {
         match token.0 {
             NumberOrString::String(ref s) => self.0.insert(