mcp: remove codex/sandbox-state custom request support (#17957)

## Why

#17763 moved sandbox-state delivery for MCP tool calls to request
`_meta` via the `codex/sandbox-state-meta` experimental capability.
Keeping the older `codex/sandbox-state` capability meant Codex still
maintained a second transport that pushed updates with the custom
`codex/sandbox-state/update` request at server startup and when the
session sandbox policy changed.

That duplicate MCP path is redundant with the per-tool-call metadata
path and makes the sandbox-state contract larger than needed. The
existing managed network proxy refresh on sandbox-policy changes is
still needed, so this keeps that behavior separate from the removed MCP
notification.

## What Changed

- Removed the exported `MCP_SANDBOX_STATE_CAPABILITY` and
`MCP_SANDBOX_STATE_METHOD` constants.
- Removed detection of `codex/sandbox-state` during MCP initialization
and stopped sending `codex/sandbox-state/update` at server startup.
- Removed the `McpConnectionManager::notify_sandbox_state_change`
plumbing while preserving the managed network proxy refresh when a user
turn changes sandbox policy.
- Slimmed `McpConnectionManager::new` so startup paths pass only the
initial `SandboxPolicy` needed for MCP elicitation state.
- Kept `codex/sandbox-state-meta` support intact; servers that opt in
still receive the current `SandboxState` on tool-call request `_meta`
([remaining call
path](ff2d3c1e72/codex-rs/core/src/mcp_tool_call.rs (L487-L526))).
- Added regression coverage for refreshing the live managed network
proxy on a per-turn sandbox-policy change.

## Verification

- `cargo test -p codex-core
new_turn_refreshes_managed_network_proxy_for_sandbox_change`
- `cargo test -p codex-mcp`

codex-rs/codex-mcp/src/lib.rs

@@ -36,9 +36,7 @@ pub use mcp::tool_plugin_provenance;
 pub use mcp::with_codex_apps_mcp;
 pub use mcp_connection_manager::CodexAppsToolsCacheKey;
 pub use mcp_connection_manager::DEFAULT_STARTUP_TIMEOUT;
-pub use mcp_connection_manager::MCP_SANDBOX_STATE_CAPABILITY;
 pub use mcp_connection_manager::MCP_SANDBOX_STATE_META_CAPABILITY;
-pub use mcp_connection_manager::MCP_SANDBOX_STATE_METHOD;
 pub use mcp_connection_manager::McpConnectionManager;
 pub use mcp_connection_manager::SandboxState;
 pub use mcp_connection_manager::ToolInfo;

codex-rs/codex-mcp/src/mcp/mod.rs

@@ -35,7 +35,6 @@ use codex_protocol::protocol::SandboxPolicy;
 use serde_json::Value;
 
 use crate::mcp_connection_manager::McpConnectionManager;
-use crate::mcp_connection_manager::SandboxState;
 use crate::mcp_connection_manager::codex_apps_tools_cache_key;
 pub type McpManager = McpConnectionManager;
 
@@ -347,14 +346,6 @@ pub async fn collect_mcp_snapshot_with_detail(
     let (tx_event, rx_event) = unbounded();
     drop(rx_event);
 
-    // Use ReadOnly sandbox policy for MCP snapshot collection (safest default)
-    let sandbox_state = SandboxState {
-        sandbox_policy: SandboxPolicy::new_read_only_policy(),
-        codex_linux_sandbox_exe: config.codex_linux_sandbox_exe.clone(),
-        sandbox_cwd: env::current_dir().unwrap_or_else(|_| PathBuf::from("/")),
-        use_legacy_landlock: config.use_legacy_landlock,
-    };
-
     let (mcp_connection_manager, cancel_token) = McpConnectionManager::new(
         &mcp_servers,
         config.mcp_oauth_credentials_store_mode,
@@ -362,7 +353,7 @@ pub async fn collect_mcp_snapshot_with_detail(
         &config.approval_policy,
         submit_id,
         tx_event,
-        sandbox_state,
+        SandboxPolicy::new_read_only_policy(),
         config.codex_home.clone(),
         codex_apps_tools_cache_key(auth),
         tool_plugin_provenance,
@@ -421,13 +412,6 @@ pub async fn collect_mcp_server_status_snapshot_with_detail(
     let (tx_event, rx_event) = unbounded();
     drop(rx_event);
 
-    let sandbox_state = SandboxState {
-        sandbox_policy: SandboxPolicy::new_read_only_policy(),
-        codex_linux_sandbox_exe: config.codex_linux_sandbox_exe.clone(),
-        sandbox_cwd: env::current_dir().unwrap_or_else(|_| PathBuf::from("/")),
-        use_legacy_landlock: config.use_legacy_landlock,
-    };
-
     let (mcp_connection_manager, cancel_token) = McpConnectionManager::new(
         &mcp_servers,
         config.mcp_oauth_credentials_store_mode,
@@ -435,7 +419,7 @@ pub async fn collect_mcp_server_status_snapshot_with_detail(
         &config.approval_policy,
         submit_id,
         tx_event,
-        sandbox_state,
+        SandboxPolicy::new_read_only_policy(),
         config.codex_home.clone(),
         codex_apps_tools_cache_key(auth),
         tool_plugin_provenance,

codex-rs/codex-mcp/src/mcp_connection_manager.rs

@@ -439,7 +439,6 @@ struct ManagedClient {
     tool_filter: ToolFilter,
     tool_timeout: Option<Duration>,
     server_instructions: Option<String>,
-    server_supports_sandbox_state_capability: bool,
     server_supports_sandbox_state_meta_capability: bool,
     codex_apps_tools_cache_context: Option<CodexAppsToolsCacheContext>,
 }
@@ -469,22 +468,6 @@ impl ManagedClient {
 
         self.tools.clone()
     }
-
-    /// Returns once the server has ack'd the sandbox state update.
-    async fn notify_sandbox_state_change(&self, sandbox_state: &SandboxState) -> Result<()> {
-        if !self.server_supports_sandbox_state_capability {
-            return Ok(());
-        }
-
-        let _response = self
-            .client
-            .send_custom_request(
-                MCP_SANDBOX_STATE_METHOD,
-                Some(serde_json::to_value(sandbox_state)?),
-            )
-            .await?;
-        Ok(())
-    }
 }
 
 #[derive(Clone)]
@@ -642,19 +625,8 @@ impl AsyncManagedClient {
         };
         tools.map(annotate_tools)
     }
-
-    async fn notify_sandbox_state_change(&self, sandbox_state: &SandboxState) -> Result<()> {
-        let managed = self.client().await?;
-        managed.notify_sandbox_state_change(sandbox_state).await
-    }
 }
 
-pub const MCP_SANDBOX_STATE_CAPABILITY: &str = "codex/sandbox-state";
-
-/// Custom MCP request to push sandbox state updates.
-/// When used, the `params` field of the notification is [`SandboxState`].
-pub const MCP_SANDBOX_STATE_METHOD: &str = "codex/sandbox-state/update";
-
 /// MCP server capability indicating that Codex should include [`SandboxState`]
 /// in tool-call request `_meta` under this key.
 pub const MCP_SANDBOX_STATE_META_CAPABILITY: &str = "codex/sandbox-state-meta";
@@ -735,7 +707,7 @@ impl McpConnectionManager {
         approval_policy: &Constrained<AskForApproval>,
         submit_id: String,
         tx_event: Sender<Event>,
-        initial_sandbox_state: SandboxState,
+        initial_sandbox_policy: SandboxPolicy,
         codex_home: PathBuf,
         codex_apps_tools_cache_key: CodexAppsToolsCacheKey,
         tool_plugin_provenance: ToolPluginProvenance,
@@ -744,10 +716,8 @@ impl McpConnectionManager {
         let mut clients = HashMap::new();
         let mut server_origins = HashMap::new();
         let mut join_set = JoinSet::new();
-        let elicitation_requests = ElicitationRequestManager::new(
-            approval_policy.value(),
-            initial_sandbox_state.sandbox_policy.clone(),
-        );
+        let elicitation_requests =
+            ElicitationRequestManager::new(approval_policy.value(), initial_sandbox_policy);
         let tool_plugin_provenance = Arc::new(tool_plugin_provenance);
         let startup_submit_id = submit_id.clone();
         let mcp_servers = mcp_servers.clone();
@@ -787,25 +757,13 @@ impl McpConnectionManager {
             let tx_event = tx_event.clone();
             let submit_id = startup_submit_id.clone();
             let auth_entry = auth_entries.get(&server_name).cloned();
-            let sandbox_state = initial_sandbox_state.clone();
             join_set.spawn(async move {
                 let outcome = async_managed_client.client().await;
                 if cancel_token.is_cancelled() {
                     return (server_name, Err(StartupOutcomeError::Cancelled));
                 }
                 let status = match &outcome {
-                    Ok(_) => {
-                        // Send sandbox state notification immediately after Ready
-                        if let Err(e) = async_managed_client
-                            .notify_sandbox_state_change(&sandbox_state)
-                            .await
-                        {
-                            warn!(
-                                "Failed to notify sandbox state to MCP server {server_name}: {e:#}",
-                            );
-                        }
-                        McpStartupStatus::Ready
-                    }
+                    Ok(_) => McpStartupStatus::Ready,
                     Err(error) => {
                         let error_str = mcp_init_error_display(
                             server_name.as_str(),
@@ -1219,34 +1177,6 @@ impl McpConnectionManager {
             .into_values()
             .find(|tool| tool.canonical_tool_name() == *tool_name)
     }
-
-    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(
@@ -1492,12 +1422,6 @@ async fn start_server_task(
         .await
         .map_err(StartupOutcomeError::from)?;
 
-    let server_supports_sandbox_state_capability = initialize_result
-        .capabilities
-        .experimental
-        .as_ref()
-        .and_then(|exp| exp.get(MCP_SANDBOX_STATE_CAPABILITY))
-        .is_some();
     let server_supports_sandbox_state_meta_capability = initialize_result
         .capabilities
         .experimental
@@ -1539,7 +1463,6 @@ async fn start_server_task(
         tool_timeout: Some(tool_timeout),
         tool_filter,
         server_instructions: initialize_result.instructions,
-        server_supports_sandbox_state_capability,
         server_supports_sandbox_state_meta_capability,
         codex_apps_tools_cache_context,
     };