Add verbose diagnostics for /mcp (#18610)

Fixes #18539.

## Summary
The recent `/mcp` performance work kept the default command fast by
avoiding resource and resource-template inventory probes, but it also
removed useful diagnostics for users trying to confirm MCP server state.

This keeps bare `/mcp` on the fast tools/auth path and adds `/mcp
verbose` for the slower diagnostic view. Verbose mode requests full MCP
server status from the app-server and restores status, resources, and
resource templates in the TUI output.

## Testing
In addition to running automation, I manually tested the feature to
confirm that it works.

codex-rs/tui/src/app.rs

@@ -2055,14 +2055,18 @@ impl App {
     /// tradeoff because the effect is limited to stale inventory output in history,
     /// while request-token invalidation would add cross-cutting async state for a
     /// low-severity path.
-    fn fetch_mcp_inventory(&mut self, app_server: &AppServerSession) {
+    fn fetch_mcp_inventory(
+        &mut self,
+        app_server: &AppServerSession,
+        detail: McpServerStatusDetail,
+    ) {
         let request_handle = app_server.request_handle();
         let app_event_tx = self.app_event_tx.clone();
         tokio::spawn(async move {
-            let result = fetch_all_mcp_server_statuses(request_handle)
+            let result = fetch_all_mcp_server_statuses(request_handle, detail)
                 .await
                 .map_err(|err| err.to_string());
-            app_event_tx.send(AppEvent::McpInventoryLoaded { result });
+            app_event_tx.send(AppEvent::McpInventoryLoaded { result, detail });
         });
     }
 
@@ -2387,7 +2391,11 @@ impl App {
     ///
     /// When both the local config and the app-server report zero servers, a special
     /// "empty" cell is shown instead of the full table.
-    fn handle_mcp_inventory_result(&mut self, result: Result<Vec<McpServerStatus>, String>) {
+    fn handle_mcp_inventory_result(
+        &mut self,
+        result: Result<Vec<McpServerStatus>, String>,
+        detail: McpServerStatusDetail,
+    ) {
         let config = self.chat_widget.config_ref().clone();
         self.chat_widget.clear_mcp_inventory_loading();
         self.clear_committed_mcp_inventory_loading();
@@ -2409,9 +2417,7 @@ impl App {
 
         self.chat_widget
             .add_to_history(history_cell::new_mcp_tools_output_from_statuses(
-                &config,
-                &statuses,
-                McpServerStatusDetail::ToolsAndAuthOnly,
+                &config, &statuses, detail,
             ));
     }
 
@@ -4969,11 +4975,11 @@ impl App {
                         .on_plugin_enabled_set(cwd, plugin_id, enabled, result);
                 }
             }
-            AppEvent::FetchMcpInventory => {
-                self.fetch_mcp_inventory(app_server);
+            AppEvent::FetchMcpInventory { detail } => {
+                self.fetch_mcp_inventory(app_server, detail);
             }
-            AppEvent::McpInventoryLoaded { result } => {
-                self.handle_mcp_inventory_result(result);
+            AppEvent::McpInventoryLoaded { result, detail } => {
+                self.handle_mcp_inventory_result(result, detail);
             }
             AppEvent::SkillsListLoaded { result } => {
                 self.handle_skills_list_result(
@@ -6671,6 +6677,7 @@ fn side_return_shortcut_matches(key_event: KeyEvent) -> bool {
 /// the inventory atomically. Each page requests up to 100 entries.
 async fn fetch_all_mcp_server_statuses(
     request_handle: AppServerRequestHandle,
+    detail: McpServerStatusDetail,
 ) -> Result<Vec<McpServerStatus>> {
     let mut cursor = None;
     let mut statuses = Vec::new();
@@ -6683,7 +6690,7 @@ async fn fetch_all_mcp_server_statuses(
                 params: ListMcpServerStatusParams {
                     cursor: cursor.clone(),
                     limit: Some(100),
-                    detail: Some(McpServerStatusDetail::ToolsAndAuthOnly),
+                    detail: Some(detail),
                 },
             })
             .await
@@ -7142,13 +7149,16 @@ mod tests {
                 /*animations_enabled*/ false,
             )));
 
-        app.handle_mcp_inventory_result(Ok(vec![McpServerStatus {
-            name: "docs".to_string(),
-            tools: HashMap::new(),
-            resources: Vec::new(),
-            resource_templates: Vec::new(),
-            auth_status: codex_app_server_protocol::McpAuthStatus::Unsupported,
-        }]));
+        app.handle_mcp_inventory_result(
+            Ok(vec![McpServerStatus {
+                name: "docs".to_string(),
+                tools: HashMap::new(),
+                resources: Vec::new(),
+                resource_templates: Vec::new(),
+                auth_status: codex_app_server_protocol::McpAuthStatus::Unsupported,
+            }]),
+            McpServerStatusDetail::ToolsAndAuthOnly,
+        );
 
         assert_eq!(app.transcript_cells.len(), 0);
     }

codex-rs/tui/src/app_event.rs

@@ -14,6 +14,7 @@ use codex_app_server_protocol::AddCreditsNudgeCreditType;
 use codex_app_server_protocol::AddCreditsNudgeEmailStatus;
 use codex_app_server_protocol::AppInfo;
 use codex_app_server_protocol::McpServerStatus;
+use codex_app_server_protocol::McpServerStatusDetail;
 use codex_app_server_protocol::PluginInstallResponse;
 use codex_app_server_protocol::PluginListResponse;
 use codex_app_server_protocol::PluginReadParams;
@@ -334,11 +335,14 @@ pub(crate) enum AppEvent {
     PluginInstallAuthAbandon,
 
     /// Fetch MCP inventory via app-server RPCs and render it into history.
-    FetchMcpInventory,
+    FetchMcpInventory {
+        detail: McpServerStatusDetail,
+    },
 
     /// Result of fetching MCP inventory via app-server RPCs.
     McpInventoryLoaded {
         result: Result<Vec<McpServerStatus>, String>,
+        detail: McpServerStatusDetail,
     },
 
     /// Result of the startup skills refresh that runs after the first frame is scheduled.

codex-rs/tui/src/chatwidget.rs

@@ -95,6 +95,7 @@ use codex_app_server_protocol::GuardianApprovalReviewAction;
 use codex_app_server_protocol::ItemCompletedNotification;
 use codex_app_server_protocol::ItemStartedNotification;
 use codex_app_server_protocol::McpServerStartupState;
+use codex_app_server_protocol::McpServerStatusDetail;
 use codex_app_server_protocol::McpServerStatusUpdatedNotification;
 use codex_app_server_protocol::ServerNotification;
 use codex_app_server_protocol::ServerRequest;
@@ -10212,7 +10213,7 @@ impl ChatWidget {
     ///
     /// The spinner lives in `active_cell` and is cleared by
     /// [`clear_mcp_inventory_loading`] once the result arrives.
-    pub(crate) fn add_mcp_output(&mut self) {
+    pub(crate) fn add_mcp_output(&mut self, detail: McpServerStatusDetail) {
         self.flush_answer_stream_with_separator();
         self.flush_active_cell();
         self.active_cell = Some(Box::new(history_cell::new_mcp_inventory_loading(
@@ -10220,7 +10221,8 @@ impl ChatWidget {
         )));
         self.bump_active_cell_revision();
         self.request_redraw();
-        self.app_event_tx.send(AppEvent::FetchMcpInventory);
+        self.app_event_tx
+            .send(AppEvent::FetchMcpInventory { detail });
     }
 
     /// Remove the MCP loading spinner if it is still the active cell.

codex-rs/tui/src/chatwidget/slash_dispatch.rs

@@ -359,7 +359,7 @@ impl ChatWidget {
                 self.add_app_server_stub_message("Memory maintenance");
             }
             SlashCommand::Mcp => {
-                self.add_mcp_output();
+                self.add_mcp_output(McpServerStatusDetail::ToolsAndAuthOnly);
             }
             SlashCommand::Apps => {
                 self.add_connectors_output();
@@ -543,6 +543,10 @@ impl ChatWidget {
                     }
                 }
             }
+            SlashCommand::Mcp => match trimmed.to_ascii_lowercase().as_str() {
+                "verbose" => self.add_mcp_output(McpServerStatusDetail::Full),
+                _ => self.add_error_message("Usage: /mcp [verbose]".to_string()),
+            },
             SlashCommand::Rename if !trimmed.is_empty() => {
                 if !self.ensure_thread_rename_allowed() {
                     return;

codex-rs/tui/src/chatwidget/tests.rs

@@ -73,6 +73,7 @@ pub(super) use codex_app_server_protocol::ItemGuardianApprovalReviewStartedNotif
 pub(super) use codex_app_server_protocol::ItemStartedNotification;
 pub(super) use codex_app_server_protocol::MarketplaceInterface;
 pub(super) use codex_app_server_protocol::McpServerStartupState;
+pub(super) use codex_app_server_protocol::McpServerStatusDetail;
 pub(super) use codex_app_server_protocol::McpServerStatusUpdatedNotification;
 pub(super) use codex_app_server_protocol::PatchApplyStatus as AppServerPatchApplyStatus;
 pub(super) use codex_app_server_protocol::PatchChangeKind;

codex-rs/tui/src/chatwidget/tests/slash_commands.rs

@@ -1111,7 +1111,48 @@ async fn slash_mcp_requests_inventory_via_app_server() {
     chat.dispatch_command(SlashCommand::Mcp);
 
     assert!(active_blob(&chat).contains("Loading MCP inventory"));
-    assert_matches!(rx.try_recv(), Ok(AppEvent::FetchMcpInventory));
+    assert_matches!(
+        rx.try_recv(),
+        Ok(AppEvent::FetchMcpInventory {
+            detail: McpServerStatusDetail::ToolsAndAuthOnly
+        })
+    );
+    assert!(op_rx.try_recv().is_err(), "expected no core op to be sent");
+}
+
+#[tokio::test]
+async fn slash_mcp_verbose_requests_full_inventory_via_app_server() {
+    let (mut chat, mut rx, mut op_rx) = make_chatwidget_manual(/*model_override*/ None).await;
+
+    submit_composer_text(&mut chat, "/mcp verbose");
+
+    assert!(active_blob(&chat).contains("Loading MCP inventory"));
+    assert_matches!(
+        rx.try_recv(),
+        Ok(AppEvent::FetchMcpInventory {
+            detail: McpServerStatusDetail::Full
+        })
+    );
+    assert!(op_rx.try_recv().is_err(), "expected no core op to be sent");
+}
+
+#[tokio::test]
+async fn slash_mcp_invalid_args_show_usage() {
+    let (mut chat, mut rx, mut op_rx) = make_chatwidget_manual(/*model_override*/ None).await;
+
+    submit_composer_text(&mut chat, "/mcp full");
+
+    let cells = drain_insert_history(&mut rx);
+    let rendered = cells
+        .iter()
+        .map(|cell| lines_to_single_string(cell))
+        .collect::<Vec<_>>()
+        .join("\n");
+    assert!(
+        rendered.contains("Usage: /mcp [verbose]"),
+        "expected usage message, got: {rendered:?}"
+    );
+    assert_eq!(recall_latest_after_clearing(&mut chat), "/mcp full");
     assert!(op_rx.try_recv().is_err(), "expected no core op to be sent");
 }
 

codex-rs/tui/src/history_cell.rs

@@ -2097,6 +2097,18 @@ pub(crate) fn new_mcp_tools_output_from_statuses(
         let header: Vec<Span<'static>> = vec!["  • ".into(), server.clone().into()];
 
         lines.push(header.into());
+        if matches!(detail, McpServerStatusDetail::Full) {
+            let enabled = cfg.map(|cfg| cfg.enabled).unwrap_or(true);
+            let status_text = if enabled {
+                "enabled".green()
+            } else {
+                "disabled".red()
+            };
+            lines.push(vec!["    • Status: ".into(), status_text].into());
+            if let Some(reason) = cfg.and_then(|cfg| cfg.disabled_reason.as_ref()) {
+                lines.push(vec!["    • Reason: ".into(), reason.to_string().dim()].into());
+            }
+        }
         let auth_status = status
             .map(|status| match status.auth_status {
                 codex_app_server_protocol::McpAuthStatus::Unsupported => McpAuthStatus::Unsupported,
@@ -3446,6 +3458,61 @@ mod tests {
         insta::assert_snapshot!(rendered);
     }
 
+    #[tokio::test]
+    async fn mcp_tools_output_from_statuses_renders_verbose_inventory() {
+        let mut config = test_config().await;
+        let plugin_docs =
+            stdio_server_config("docs-server", vec!["--stdio"], /*env*/ None, vec![]);
+        let servers = HashMap::from([("plugin_docs".to_string(), plugin_docs)]);
+        config
+            .mcp_servers
+            .set(servers)
+            .expect("test mcp servers should accept any configuration");
+
+        let statuses = vec![McpServerStatus {
+            name: "plugin_docs".to_string(),
+            tools: HashMap::from([(
+                "lookup".to_string(),
+                Tool {
+                    description: None,
+                    name: "lookup".to_string(),
+                    title: None,
+                    input_schema: serde_json::json!({"type": "object", "properties": {}}),
+                    output_schema: None,
+                    annotations: None,
+                    icons: None,
+                    meta: None,
+                },
+            )]),
+            resources: vec![Resource {
+                annotations: None,
+                description: None,
+                mime_type: None,
+                name: "docs".to_string(),
+                size: None,
+                title: Some("Docs".to_string()),
+                uri: "file:///docs".to_string(),
+                icons: None,
+                meta: None,
+            }],
+            resource_templates: vec![ResourceTemplate {
+                annotations: None,
+                uri_template: "file:///docs/{id}".to_string(),
+                name: "doc-template".to_string(),
+                title: Some("Doc Template".to_string()),
+                description: None,
+                mime_type: None,
+            }],
+            auth_status: codex_app_server_protocol::McpAuthStatus::Unsupported,
+        }];
+
+        let cell =
+            new_mcp_tools_output_from_statuses(&config, &statuses, McpServerStatusDetail::Full);
+        let rendered = render_lines(&cell.display_lines(/*width*/ 120)).join("\n");
+
+        insta::assert_snapshot!(rendered);
+    }
+
     #[test]
     fn empty_agent_message_cell_transcript() {
         let cell = AgentMessageCell::new(vec![Line::default()], /*is_first_line*/ false);

codex-rs/tui/src/slash_command.rs

@@ -115,7 +115,7 @@ impl SlashCommand {
             }
             SlashCommand::Experimental => "toggle experimental features",
             SlashCommand::Memories => "configure memory use and generation",
-            SlashCommand::Mcp => "list configured MCP tools",
+            SlashCommand::Mcp => "list configured MCP tools; use /mcp verbose for details",
             SlashCommand::Apps => "manage apps",
             SlashCommand::Plugins => "browse plugins",
             SlashCommand::Logout => "log out of Codex",
@@ -138,6 +138,7 @@ impl SlashCommand {
                 | SlashCommand::Rename
                 | SlashCommand::Plan
                 | SlashCommand::Fast
+                | SlashCommand::Mcp
                 | SlashCommand::Side
                 | SlashCommand::Resume
                 | SlashCommand::SandboxReadRoot

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

@@ -0,0 +1,15 @@
+---
+source: tui/src/history_cell.rs
+expression: rendered
+---
+/mcp
+
+🔌  MCP Tools
+
+  • plugin_docs
+    • Status: enabled
+    • Auth: Unsupported
+    • Command: docs-server --stdio
+    • Tools: lookup
+    • Resources: Docs (file:///docs)
+    • Resource templates: Doc Template (file:///docs/{id})