Speed up /mcp inventory listing (#16831)

Addresses #16244

This was a performance regression introduced when we moved the TUI on
top of the app server API.

Problem: `/mcp` rebuilt a full MCP inventory through
`mcpServerStatus/list`, including resources and resource templates that
made the TUI wait on slow inventory probes.

Solution: add a lightweight `detail` mode to `mcpServerStatus/list`,
have `/mcp` request tools-and-auth only, and cover the fast path with
app-server and TUI tests.

Testing: Confirmed slow (multi-second) response prior to change and
immediate response after change.

I considered two options:
1. Change the existing `mcpServerStatus/list` API to accept an optional
"details" parameter so callers can request only a subset of the
information.
2. Add a separate `mcpServer/list` API that returns only the servers,
tools, and auth but omits the resources.

I chose option 1, but option 2 is also a reasonable approach.

codex-rs/tui/src/app.rs

@@ -64,6 +64,7 @@ use codex_app_server_protocol::GetAccountRateLimitsResponse;
 use codex_app_server_protocol::ListMcpServerStatusParams;
 use codex_app_server_protocol::ListMcpServerStatusResponse;
 use codex_app_server_protocol::McpServerStatus;
+use codex_app_server_protocol::McpServerStatusDetail;
 use codex_app_server_protocol::PluginInstallParams;
 use codex_app_server_protocol::PluginInstallResponse;
 use codex_app_server_protocol::PluginListParams;
@@ -1871,8 +1872,8 @@ impl App {
         Ok(())
     }
 
-    /// Spawn a background task that fetches the full MCP server inventory from the
-    /// app-server via paginated RPCs, then delivers the result back through
+    /// Spawn a background task that fetches MCP server status from the app-server
+    /// via paginated RPCs, then delivers the result back through
     /// `AppEvent::McpInventoryLoaded`.
     ///
     /// The spawned task is fire-and-forget: no `JoinHandle` is stored, so a stale
@@ -2125,7 +2126,9 @@ impl App {
 
         self.chat_widget
             .add_to_history(history_cell::new_mcp_tools_output_from_statuses(
-                &config, &statuses,
+                &config,
+                &statuses,
+                McpServerStatusDetail::ToolsAndAuthOnly,
             ));
     }
 
@@ -6002,8 +6005,9 @@ impl App {
     }
 }
 
-/// Collect every MCP server status from the app-server by walking the paginated
-/// `mcpServerStatus/list` RPC until no `next_cursor` is returned.
+/// Collect every MCP server status needed for `/mcp` from the app-server by
+/// walking the paginated `mcpServerStatus/list` RPC until no `next_cursor` is
+/// returned.
 ///
 /// All pages are eagerly gathered into a single `Vec` so the caller can render
 /// the inventory atomically. Each page requests up to 100 entries.
@@ -6021,6 +6025,7 @@ async fn fetch_all_mcp_server_statuses(
                 params: ListMcpServerStatusParams {
                     cursor: cursor.clone(),
                     limit: Some(100),
+                    detail: Some(McpServerStatusDetail::ToolsAndAuthOnly),
                 },
             })
             .await

codex-rs/tui/src/history_cell.rs

@@ -40,6 +40,7 @@ use crate::wrapping::adaptive_wrap_line;
 use crate::wrapping::adaptive_wrap_lines;
 use base64::Engine;
 use codex_app_server_protocol::McpServerStatus;
+use codex_app_server_protocol::McpServerStatusDetail;
 use codex_config::types::McpServerTransportConfig;
 use codex_core::config::Config;
 #[cfg(test)]
@@ -1979,10 +1980,12 @@ pub(crate) fn new_mcp_tools_output(
 /// transport details such as command, URL, cwd, and environment display.
 ///
 /// This mirrors the layout of [`new_mcp_tools_output`] but sources data from
-/// the paginated RPC response rather than the in-process `McpManager`.
+/// the paginated RPC response rather than the in-process `McpManager`. The
+/// `detail` flag controls whether resources and resource templates are rendered.
 pub(crate) fn new_mcp_tools_output_from_statuses(
     config: &Config,
     statuses: &[McpServerStatus],
+    detail: McpServerStatusDetail,
 ) -> PlainHistoryCell {
     let mut lines: Vec<Line<'static>> = vec![
         "/mcp".magenta().into(),
@@ -2094,48 +2097,50 @@ pub(crate) fn new_mcp_tools_output_from_statuses(
             lines.push(vec!["    • Tools: ".into(), names.join(", ").into()].into());
         }
 
-        let server_resources = status
-            .map(|status| status.resources.clone())
-            .unwrap_or_default();
-        if server_resources.is_empty() {
-            lines.push("    • Resources: (none)".into());
-        } else {
-            let mut spans: Vec<Span<'static>> = vec!["    • Resources: ".into()];
+        if matches!(detail, McpServerStatusDetail::Full) {
+            let server_resources = status
+                .map(|status| status.resources.clone())
+                .unwrap_or_default();
+            if server_resources.is_empty() {
+                lines.push("    • Resources: (none)".into());
+            } else {
+                let mut spans: Vec<Span<'static>> = vec!["    • Resources: ".into()];
 
-            for (idx, resource) in server_resources.iter().enumerate() {
-                if idx > 0 {
-                    spans.push(", ".into());
+                for (idx, resource) in server_resources.iter().enumerate() {
+                    if idx > 0 {
+                        spans.push(", ".into());
+                    }
+
+                    let label = resource.title.as_ref().unwrap_or(&resource.name);
+                    spans.push(label.clone().into());
+                    spans.push(" ".into());
+                    spans.push(format!("({})", resource.uri).dim());
                 }
 
-                let label = resource.title.as_ref().unwrap_or(&resource.name);
-                spans.push(label.clone().into());
-                spans.push(" ".into());
-                spans.push(format!("({})", resource.uri).dim());
+                lines.push(spans.into());
             }
 
-            lines.push(spans.into());
-        }
+            let server_templates = status
+                .map(|status| status.resource_templates.clone())
+                .unwrap_or_default();
+            if server_templates.is_empty() {
+                lines.push("    • Resource templates: (none)".into());
+            } else {
+                let mut spans: Vec<Span<'static>> = vec!["    • Resource templates: ".into()];
 
-        let server_templates = status
-            .map(|status| status.resource_templates.clone())
-            .unwrap_or_default();
-        if server_templates.is_empty() {
-            lines.push("    • Resource templates: (none)".into());
-        } else {
-            let mut spans: Vec<Span<'static>> = vec!["    • Resource templates: ".into()];
+                for (idx, template) in server_templates.iter().enumerate() {
+                    if idx > 0 {
+                        spans.push(", ".into());
+                    }
 
-            for (idx, template) in server_templates.iter().enumerate() {
-                if idx > 0 {
-                    spans.push(", ".into());
+                    let label = template.title.as_ref().unwrap_or(&template.name);
+                    spans.push(label.clone().into());
+                    spans.push(" ".into());
+                    spans.push(format!("({})", template.uri_template).dim());
                 }
 
-                let label = template.title.as_ref().unwrap_or(&template.name);
-                spans.push(label.clone().into());
-                spans.push(" ".into());
-                spans.push(format!("({})", template.uri_template).dim());
+                lines.push(spans.into());
             }
-
-            lines.push(spans.into());
         }
 
         lines.push(Line::from(""));
@@ -3340,7 +3345,11 @@ mod tests {
             auth_status: codex_app_server_protocol::McpAuthStatus::Unsupported,
         }];
 
-        let cell = new_mcp_tools_output_from_statuses(&config, &statuses);
+        let cell = new_mcp_tools_output_from_statuses(
+            &config,
+            &statuses,
+            McpServerStatusDetail::ToolsAndAuthOnly,
+        );
         let rendered = render_lines(&cell.display_lines(/*width*/ 120)).join("\n");
 
         insta::assert_snapshot!(rendered);

codex-rs/tui/src/snapshots/codex_tui__history_cell__tests__mcp_tools_output_from_statuses_renders_status_only_servers.snap

@@ -10,5 +10,3 @@ expression: rendered
     • Auth: Unsupported
     • Command: docs-server --stdio
     • Tools: lookup
-    • Resources: (none)
-    • Resource templates: (none)