fix(cli): treat unknown slash commands as regular input instead of showing error (#17393)

Co-authored-by: Tommaso Sciortino <sciortino@gmail.com>

packages/cli/src/ui/hooks/slashCommandProcessor.test.tsx

@@ -20,6 +20,7 @@ import {
   type GeminiClient,
   type UserFeedbackPayload,
   SlashCommandStatus,
+  MCPDiscoveryState,
   makeFakeConfig,
   coreEvents,
   CoreEvent,
@@ -389,21 +390,49 @@ describe('useSlashCommandProcessor', () => {
   });
 
   describe('Command Execution Logic', () => {
-    it('should display an error for an unknown command', async () => {
+    it('should treat unknown commands as regular input', async () => {
       const result = await setupProcessorHook();
       await waitFor(() => expect(result.current.slashCommands).toBeDefined());
 
+      let handled: Awaited<
+        ReturnType<typeof result.current.handleSlashCommand>
+      >;
       await act(async () => {
-        await result.current.handleSlashCommand('/nonexistent');
+        handled = await result.current.handleSlashCommand('/nonexistent');
       });
 
-      // Expect 2 calls: one for the user's input, one for the error message.
-      expect(mockAddItem).toHaveBeenCalledTimes(2);
-      expect(mockAddItem).toHaveBeenLastCalledWith(
-        {
+      // Unknown commands should return false so the input is sent to the model
+      expect(handled!).toBe(false);
+      // Should not add anything to history (the regular flow will handle it)
+      expect(mockAddItem).not.toHaveBeenCalled();
+    });
+
+    it('should show MCP loading warning for unknown commands when MCP is loading', async () => {
+      vi.spyOn(mockConfig, 'getMcpClientManager').mockReturnValue({
+        getDiscoveryState: () => MCPDiscoveryState.IN_PROGRESS,
+      } as ReturnType<typeof mockConfig.getMcpClientManager>);
+
+      const result = await setupProcessorHook();
+      await waitFor(() => expect(result.current.slashCommands).toBeDefined());
+
+      let handled: Awaited<
+        ReturnType<typeof result.current.handleSlashCommand>
+      >;
+      await act(async () => {
+        handled = await result.current.handleSlashCommand('/mcp-command');
+      });
+
+      // When MCP is loading, should handle the command (show warning)
+      expect(handled!).not.toBe(false);
+      // Should add user input and error message to history
+      expect(mockAddItem).toHaveBeenCalledWith(
+        { type: MessageType.USER, text: '/mcp-command' },
+        expect.any(Number),
+      );
+      expect(mockAddItem).toHaveBeenCalledWith(
+        expect.objectContaining({
           type: MessageType.ERROR,
-          text: 'Unknown command: /nonexistent',
-        },
+        }),
         expect.any(Number),
       );
     });
@@ -769,19 +798,17 @@ describe('useSlashCommandProcessor', () => {
       });
       await waitFor(() => expect(result.current.slashCommands).toHaveLength(1));
 
+      let handled: Awaited<
+        ReturnType<typeof result.current.handleSlashCommand>
+      >;
       await act(async () => {
         // Use uppercase when command is lowercase
-        await result.current.handleSlashCommand('/Test');
+        handled = await result.current.handleSlashCommand('/Test');
       });
 
-      // It should fail and call addItem with an error
-      expect(mockAddItem).toHaveBeenCalledWith(
-        {
-          type: MessageType.ERROR,
-          text: 'Unknown command: /Test',
-        },
-        expect.any(Number),
-      );
+      // Case mismatch means it's not a known command, so treat as regular input
+      expect(handled!).toBe(false);
+      expect(mockAddItem).not.toHaveBeenCalled();
     });
 
     it('should correctly match an altName', async () => {

packages/cli/src/ui/hooks/slashCommandProcessor.ts

@@ -362,6 +362,36 @@ export const useSlashCommandProcessor = (
         return false;
       }
 
+      const {
+        commandToExecute,
+        args,
+        canonicalPath: resolvedCommandPath,
+      } = parseSlashCommand(trimmed, commands);
+
+      // If the input doesn't match any known command, check if MCP servers
+      // are still loading (the command might come from an MCP server).
+      // Otherwise, treat it as regular text input (e.g. file paths like
+      // /home/user/file.txt) and let it be sent to the model.
+      if (!commandToExecute) {
+        const isMcpLoading =
+          config?.getMcpClientManager()?.getDiscoveryState() ===
+          MCPDiscoveryState.IN_PROGRESS;
+        if (isMcpLoading) {
+          setIsProcessing(true);
+          if (addToHistory) {
+            addItem({ type: MessageType.USER, text: trimmed }, Date.now());
+          }
+          addMessage({
+            type: MessageType.ERROR,
+            content: `Unknown command: ${trimmed}. Command might have been from an MCP server but MCP servers are not done loading.`,
+            timestamp: new Date(),
+          });
+          setIsProcessing(false);
+          return { type: 'handled' };
+        }
+        return false;
+      }
+
       setIsProcessing(true);
 
       if (addToHistory) {
@@ -373,11 +403,6 @@ export const useSlashCommandProcessor = (
       }
 
       let hasError = false;
-      const {
-        commandToExecute,
-        args,
-        canonicalPath: resolvedCommandPath,
-      } = parseSlashCommand(trimmed, commands);
 
       const subcommand =
         resolvedCommandPath.length > 1
@@ -654,19 +679,6 @@ export const useSlashCommandProcessor = (
           }
         }
 
-        const isMcpLoading =
-          config?.getMcpClientManager()?.getDiscoveryState() ===
-          MCPDiscoveryState.IN_PROGRESS;
-        const errorMessage = isMcpLoading
-          ? `Unknown command: ${trimmed}. Command might have been from an MCP server but MCP servers are not done loading.`
-          : `Unknown command: ${trimmed}`;
-
-        addMessage({
-          type: MessageType.ERROR,
-          content: errorMessage,
-          timestamp: new Date(),
-        });
-
         return { type: 'handled' };
       } catch (e: unknown) {
         hasError = true;