feat: declare sandbox state MCP capability

codex-rs/core/src/codex.rs

@@ -5,6 +5,7 @@ use std::sync::Arc;
 use std::sync::atomic::AtomicU64;
 
 use crate::AuthManager;
+use crate::SandboxState;
 use crate::client_common::REVIEW_PROMPT;
 use crate::compact;
 use crate::compact::run_inline_auto_compact_task;
@@ -612,6 +613,22 @@ impl Session {
             )
             .await;
 
+        let sandbox_state = SandboxState {
+            sandbox_policy: session_configuration.sandbox_policy.clone(),
+            codex_linux_sandbox_exe: config.codex_linux_sandbox_exe.clone(),
+            sandbox_cwd: session_configuration.cwd.clone(),
+        };
+        if let Err(e) = sess
+            .services
+            .mcp_connection_manager
+            .read()
+            .await
+            .notify_sandbox_state_change(&sandbox_state)
+            .await
+        {
+            tracing::error!("Failed to notify sandbox state change: {e}");
+        }
+
         // record_initial_history can emit events. We record only after the SessionConfiguredEvent is emitted.
         sess.record_initial_history(initial_history).await;
 

codex-rs/core/src/lib.rs

@@ -32,6 +32,9 @@ pub mod git_info;
 pub mod landlock;
 pub mod mcp;
 mod mcp_connection_manager;
+pub use mcp_connection_manager::MCP_SANDBOX_STATE_CAPABILITY;
+pub use mcp_connection_manager::MCP_SANDBOX_STATE_NOTIFICATION;
+pub use mcp_connection_manager::SandboxState;
 mod mcp_tool_call;
 mod message_history;
 mod model_provider_info;

codex-rs/core/src/mcp_connection_manager.rs

@@ -10,6 +10,7 @@ use std::collections::HashMap;
 use std::collections::HashSet;
 use std::env;
 use std::ffi::OsString;
+use std::path::PathBuf;
 use std::sync::Arc;
 use std::time::Duration;
 
@@ -26,6 +27,7 @@ use codex_protocol::protocol::McpStartupCompleteEvent;
 use codex_protocol::protocol::McpStartupFailure;
 use codex_protocol::protocol::McpStartupStatus;
 use codex_protocol::protocol::McpStartupUpdateEvent;
+use codex_protocol::protocol::SandboxPolicy;
 use codex_rmcp_client::OAuthCredentialsStoreMode;
 use codex_rmcp_client::RmcpClient;
 use futures::future::BoxFuture;
@@ -43,6 +45,8 @@ use mcp_types::Resource;
 use mcp_types::ResourceTemplate;
 use mcp_types::Tool;
 
+use serde::Deserialize;
+use serde::Serialize;
 use serde_json::json;
 use sha1::Digest;
 use sha1::Sha1;
@@ -116,6 +120,7 @@ struct ManagedClient {
     tools: Vec<ToolInfo>,
     tool_filter: ToolFilter,
     tool_timeout: Option<Duration>,
+    server_supports_sandbox_state_capability: bool,
 }
 
 #[derive(Clone)]
@@ -150,6 +155,35 @@ impl AsyncManagedClient {
     async fn client(&self) -> Result<ManagedClient, StartupOutcomeError> {
         self.client.clone().await
     }
+
+    async fn notify_sandbox_state_change(&self, sandbox_state: &SandboxState) -> Result<()> {
+        let managed = self.client().await?;
+        if !managed.server_supports_sandbox_state_capability {
+            return Ok(());
+        }
+
+        managed
+            .client
+            .send_custom_notification(
+                MCP_SANDBOX_STATE_NOTIFICATION,
+                Some(serde_json::to_value(sandbox_state)?),
+            )
+            .await
+    }
+}
+
+pub const MCP_SANDBOX_STATE_CAPABILITY: &str = "codex/sandbox-state";
+
+/// Custom MCP notification for sandbox state updates.
+/// When used, the `params` field of the notification is [`SandboxState`].
+pub const MCP_SANDBOX_STATE_NOTIFICATION: &str = "codex/sandbox-state/update";
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SandboxState {
+    pub sandbox_policy: SandboxPolicy,
+    pub codex_linux_sandbox_exe: Option<PathBuf>,
+    pub sandbox_cwd: PathBuf,
 }
 
 /// A thin wrapper around a set of running [`RmcpClient`] instances.
@@ -477,6 +511,34 @@ impl McpConnectionManager {
             .get(tool_name)
             .map(|tool| (tool.server_name.clone(), tool.tool_name.clone()))
     }
+
+    pub async fn notify_sandbox_state_change(&self, sandbox_state: &SandboxState) -> Result<()> {
+        let mut join_set = JoinSet::new();
+
+        for async_managed_client in self.clients.values() {
+            let sandbox_state = sandbox_state.clone();
+            let async_managed_client = async_managed_client.clone();
+            join_set.spawn(async move {
+                async_managed_client
+                    .notify_sandbox_state_change(&sandbox_state)
+                    .await
+            });
+        }
+
+        while let Some(join_res) = join_set.join_next().await {
+            match join_res {
+                Ok(Ok(())) => {}
+                Ok(Err(err)) => {
+                    warn!("Failed to notify sandbox state change to MCP server: {err:#}");
+                }
+                Err(err) => {
+                    warn!("Task panic when notifying sandbox state change to MCP server: {err:#}");
+                }
+            }
+        }
+
+        Ok(())
+    }
 }
 
 async fn emit_update(
@@ -639,7 +701,7 @@ async fn start_server_work(
         protocol_version: mcp_types::MCP_SCHEMA_VERSION.to_owned(),
     };
 
-    let client_result = match transport {
+    let (client, initialize_result) = match transport {
         McpServerTransportConfig::Stdio {
             command,
             args,
@@ -655,7 +717,7 @@ async fn start_server_work(
                     client
                         .initialize(params.clone(), Some(startup_timeout))
                         .await
-                        .map(|_| client)
+                        .map(|initialize_result| (client, initialize_result))
                 }
                 Err(err) => Err(err.into()),
             }
@@ -686,19 +748,12 @@ async fn start_server_work(
                     client
                         .initialize(params.clone(), Some(startup_timeout))
                         .await
-                        .map(|_| client)
+                        .map(|initialize_result| (client, initialize_result))
                 }
                 Err(err) => Err(err),
             }
         }
-    };
-
-    let client = match client_result {
-        Ok(client) => client,
-        Err(error) => {
-            return Err(error.into());
-        }
-    };
+    }?;
 
     let tools = match list_tools_for_client(&server_name, &client, startup_timeout).await {
         Ok(tools) => tools,
@@ -707,11 +762,19 @@ async fn start_server_work(
         }
     };
 
+    let server_supports_sandbox_state_capability = initialize_result
+        .capabilities
+        .experimental
+        .as_ref()
+        .and_then(|exp| exp.get(MCP_SANDBOX_STATE_CAPABILITY))
+        .is_some();
+
     let managed = ManagedClient {
         client: Arc::clone(&client),
         tools,
         tool_timeout: Some(tool_timeout),
         tool_filter,
+        server_supports_sandbox_state_capability,
     };
 
     Ok(managed)