feat(unstable): Add initial support for session config options

Cargo.toml

@@ -27,7 +27,7 @@ tokio = { version = "1.48", features = ["full"] }
 tokio-util = { version = "0.7", features = ["compat"] }
 
 # Protocol
-agent-client-protocol-schema = { version = "=0.10.4" }
+agent-client-protocol-schema = { version = "=0.10.5" }
 
 # Serialization
 serde = { version = "1.0", features = ["derive", "rc"] }

examples/agent.rs

@@ -142,6 +142,25 @@ impl acp::Agent for ExampleAgent {
         Ok(acp::SetSessionModelResponse::default())
     }
 
+    #[cfg(feature = "unstable_session_config_options")]
+    async fn set_session_config_option(
+        &self,
+        args: acp::SetSessionConfigOptionRequest,
+    ) -> Result<acp::SetSessionConfigOptionResponse, acp::Error> {
+        log::info!("Received set session config option request {args:?}");
+        Ok(acp::SetSessionConfigOptionResponse::new(vec![
+            acp::SessionConfigOption::select(
+                args.config_id,
+                "Example Option",
+                args.value,
+                vec![
+                    acp::SessionConfigSelectOption::new("option1", "Option 1"),
+                    acp::SessionConfigSelectOption::new("option2", "Option 2"),
+                ]),
+            ),
+        ]))
+    }
+
     async fn ext_method(&self, args: acp::ExtRequest) -> Result<acp::ExtResponse, acp::Error> {
         log::info!(
             "Received extension method call: method={}, params={:?}",

src/agent-client-protocol/src/agent.rs

@@ -12,6 +12,8 @@ use agent_client_protocol_schema::{ForkSessionRequest, ForkSessionResponse};
 use agent_client_protocol_schema::{ListSessionsRequest, ListSessionsResponse};
 #[cfg(feature = "unstable_session_resume")]
 use agent_client_protocol_schema::{ResumeSessionRequest, ResumeSessionResponse};
+#[cfg(feature = "unstable_session_config_options")]
+use agent_client_protocol_schema::{SetSessionConfigOptionRequest, SetSessionConfigOptionResponse};
 #[cfg(feature = "unstable_session_model")]
 use agent_client_protocol_schema::{SetSessionModelRequest, SetSessionModelResponse};
 use serde_json::value::RawValue;
@@ -132,6 +134,25 @@ pub trait Agent {
         Err(Error::method_not_found())
     }
 
+    /// **UNSTABLE**
+    ///
+    /// This capability is not part of the spec yet, and may be removed or changed at any point.
+    ///
+    /// Sets the current value for a session configuration option.
+    ///
+    /// Configuration options allow agents to expose arbitrary selectors (like model choice,
+    /// reasoning level, etc.) that clients can display and modify.
+    ///
+    /// The response returns the full list of configuration options with their current values,
+    /// as changing one option may affect others.
+    #[cfg(feature = "unstable_session_config_options")]
+    async fn set_session_config_option(
+        &self,
+        _args: SetSessionConfigOptionRequest,
+    ) -> Result<SetSessionConfigOptionResponse> {
+        Err(Error::method_not_found())
+    }
+
     /// **UNSTABLE**
     ///
     /// This capability is not part of the spec yet, and may be removed or changed at any point.
@@ -225,6 +246,13 @@ impl<T: Agent> Agent for Rc<T> {
     ) -> Result<SetSessionModelResponse> {
         self.as_ref().set_session_model(args).await
     }
+    #[cfg(feature = "unstable_session_config_options")]
+    async fn set_session_config_option(
+        &self,
+        args: SetSessionConfigOptionRequest,
+    ) -> Result<SetSessionConfigOptionResponse> {
+        self.as_ref().set_session_config_option(args).await
+    }
     #[cfg(feature = "unstable_session_list")]
     async fn list_sessions(&self, args: ListSessionsRequest) -> Result<ListSessionsResponse> {
         self.as_ref().list_sessions(args).await
@@ -278,6 +306,13 @@ impl<T: Agent> Agent for Arc<T> {
     ) -> Result<SetSessionModelResponse> {
         self.as_ref().set_session_model(args).await
     }
+    #[cfg(feature = "unstable_session_config_options")]
+    async fn set_session_config_option(
+        &self,
+        args: SetSessionConfigOptionRequest,
+    ) -> Result<SetSessionConfigOptionResponse> {
+        self.as_ref().set_session_config_option(args).await
+    }
     #[cfg(feature = "unstable_session_list")]
     async fn list_sessions(&self, args: ListSessionsRequest) -> Result<ListSessionsResponse> {
         self.as_ref().list_sessions(args).await

src/agent-client-protocol/src/lib.rs

@@ -185,6 +185,19 @@ impl Agent for ClientSideConnection {
             .await
     }
 
+    #[cfg(feature = "unstable_session_config_options")]
+    async fn set_session_config_option(
+        &self,
+        args: SetSessionConfigOptionRequest,
+    ) -> Result<SetSessionConfigOptionResponse> {
+        self.conn
+            .request(
+                AGENT_METHOD_NAMES.session_set_config_option,
+                Some(ClientRequest::SetSessionConfigOptionRequest(args)),
+            )
+            .await
+    }
+
     async fn ext_method(&self, args: ExtRequest) -> Result<ExtResponse> {
         self.conn
             .request(
@@ -560,6 +573,12 @@ impl Side for AgentSide {
             m if m == AGENT_METHOD_NAMES.session_resume => serde_json::from_str(params.get())
                 .map(ClientRequest::ResumeSessionRequest)
                 .map_err(Into::into),
+            #[cfg(feature = "unstable_session_config_options")]
+            m if m == AGENT_METHOD_NAMES.session_set_config_option => {
+                serde_json::from_str(params.get())
+                    .map(ClientRequest::SetSessionConfigOptionRequest)
+                    .map_err(Into::into)
+            }
             m if m == AGENT_METHOD_NAMES.session_prompt => serde_json::from_str(params.get())
                 .map(ClientRequest::PromptRequest)
                 .map_err(Into::into),
@@ -644,6 +663,11 @@ impl<T: Agent> MessageHandler<AgentSide> for T {
                 let response = self.resume_session(args).await?;
                 Ok(AgentResponse::ResumeSessionResponse(response))
             }
+            #[cfg(feature = "unstable_session_config_options")]
+            ClientRequest::SetSessionConfigOptionRequest(args) => {
+                let response = self.set_session_config_option(args).await?;
+                Ok(AgentResponse::SetSessionConfigOptionResponse(response))
+            }
             ClientRequest::ExtMethodRequest(args) => {
                 let response = self.ext_method(args).await?;
                 Ok(AgentResponse::ExtMethodResponse(response))

src/agent-client-protocol/src/rpc_tests.rs

@@ -252,6 +252,30 @@ impl Agent for TestAgent {
         Ok(agent_client_protocol_schema::ResumeSessionResponse::new())
     }
 
+    #[cfg(feature = "unstable_session_config_options")]
+    async fn set_session_config_option(
+        &self,
+        args: agent_client_protocol_schema::SetSessionConfigOptionRequest,
+    ) -> Result<agent_client_protocol_schema::SetSessionConfigOptionResponse> {
+        Ok(
+            agent_client_protocol_schema::SetSessionConfigOptionResponse::new(vec![
+                agent_client_protocol_schema::SessionConfigOption::select(
+                    args.config_id,
+                    "Test Option",
+                    args.value,
+                    vec![
+                        agent_client_protocol_schema::SessionConfigSelectOption::new(
+                            "value1", "Value 1",
+                        ),
+                        agent_client_protocol_schema::SessionConfigSelectOption::new(
+                            "value2", "Value 2",
+                        ),
+                    ],
+                ),
+            ]),
+        )
+    }
+
     async fn ext_method(&self, args: ExtRequest) -> Result<ExtResponse> {
         dbg!();
         match dbg!(args.method.as_ref()) {
@@ -872,3 +896,36 @@ async fn test_session_info_update() {
         })
         .await;
 }
+
+#[cfg(feature = "unstable_session_config_options")]
+#[tokio::test]
+async fn test_set_session_config_option() {
+    let local_set = tokio::task::LocalSet::new();
+    local_set
+        .run_until(async {
+            let client = TestClient::new();
+            let agent = TestAgent::new();
+
+            let (agent_conn, _client_conn) = create_connection_pair(&client, &agent);
+
+            // Set a config option
+            let response = agent_conn
+                .set_session_config_option(
+                    agent_client_protocol_schema::SetSessionConfigOptionRequest::new(
+                        "test-session",
+                        "mode",
+                        "value2",
+                    ),
+                )
+                .await
+                .expect("set_session_config_option failed");
+
+            // Verify we got config options back
+            assert_eq!(response.config_options.len(), 1);
+            assert_eq!(
+                response.config_options[0].id,
+                agent_client_protocol_schema::SessionConfigId::new("mode")
+            );
+        })
+        .await;
+}