🤖 feat: add -m flag to /new, forward start message to modal on error

- Support /new -m <model> to set initial model (like /compact)
- Forward start message and model to modal when errors occur
- Add textarea in NewWorkspaceModal for start message display
- Model selector defaults to provided model or workspace default
- Send start message with specified model after workspace creation

Fixes three bugs:
1. Missing -m flag support for model selection
2. Lost start message on errors (now preserved in modal)
3. No way to see/edit start message in error modal

All tests pass (16 /new command tests + 54 other slash command tests).

Author: ammar-agent

src/App.tsx

@@ -54,6 +54,10 @@ function AppInner() {
     undefined
   );
   const [workspaceModalLoadError, setWorkspaceModalLoadError] = useState<string | null>(null);
+  const [workspaceModalStartMessage, setWorkspaceModalStartMessage] = useState<string | undefined>(
+    undefined
+  );
+  const [workspaceModalModel, setWorkspaceModalModel] = useState<string | undefined>(undefined);
   const workspaceModalProjectRef = useRef<string | null>(null);
 
   // Auto-collapse sidebar on mobile by default
@@ -175,46 +179,55 @@ function AppInner() {
     [removeProject, selectedWorkspace, setSelectedWorkspace]
   );
 
-  const handleAddWorkspace = useCallback(async (projectPath: string) => {
-    const projectName = projectPath.split("/").pop() ?? projectPath.split("\\").pop() ?? "project";
+  const handleAddWorkspace = useCallback(
+    async (
+      projectPath: string,
+      initialData?: { startMessage?: string; model?: string; error?: string }
+    ) => {
+      const projectName =
+        projectPath.split("/").pop() ?? projectPath.split("\\").pop() ?? "project";
+
+      workspaceModalProjectRef.current = projectPath;
+      setWorkspaceModalProject(projectPath);
+      setWorkspaceModalProjectName(projectName);
+      setWorkspaceModalBranches([]);
+      setWorkspaceModalDefaultTrunk(undefined);
+      setWorkspaceModalLoadError(initialData?.error ?? null);
+      setWorkspaceModalStartMessage(initialData?.startMessage);
+      setWorkspaceModalModel(initialData?.model);
+      setWorkspaceModalOpen(true);
 
-    workspaceModalProjectRef.current = projectPath;
-    setWorkspaceModalProject(projectPath);
-    setWorkspaceModalProjectName(projectName);
-    setWorkspaceModalBranches([]);
-    setWorkspaceModalDefaultTrunk(undefined);
-    setWorkspaceModalLoadError(null);
-    setWorkspaceModalOpen(true);
+      try {
+        const branchResult = await window.api.projects.listBranches(projectPath);
 
-    try {
-      const branchResult = await window.api.projects.listBranches(projectPath);
+        // Guard against race condition: only update state if this is still the active project
+        if (workspaceModalProjectRef.current !== projectPath) {
+          return;
+        }
 
-      // Guard against race condition: only update state if this is still the active project
-      if (workspaceModalProjectRef.current !== projectPath) {
-        return;
-      }
+        const sanitizedBranches = Array.isArray(branchResult?.branches)
+          ? branchResult.branches.filter((branch): branch is string => typeof branch === "string")
+          : [];
 
-      const sanitizedBranches = Array.isArray(branchResult?.branches)
-        ? branchResult.branches.filter((branch): branch is string => typeof branch === "string")
-        : [];
+        const recommended =
+          typeof branchResult?.recommendedTrunk === "string" &&
+          sanitizedBranches.includes(branchResult.recommendedTrunk)
+            ? branchResult.recommendedTrunk
+            : sanitizedBranches[0];
 
-      const recommended =
-        typeof branchResult?.recommendedTrunk === "string" &&
-        sanitizedBranches.includes(branchResult.recommendedTrunk)
-          ? branchResult.recommendedTrunk
-          : sanitizedBranches[0];
-
-      setWorkspaceModalBranches(sanitizedBranches);
-      setWorkspaceModalDefaultTrunk(recommended);
-      setWorkspaceModalLoadError(null);
-    } catch (err) {
-      console.error("Failed to load branches for modal:", err);
-      const message = err instanceof Error ? err.message : "Unknown error";
-      setWorkspaceModalLoadError(
-        `Unable to load branches automatically: ${message}. You can still enter the trunk branch manually.`
-      );
-    }
-  }, []);
+        setWorkspaceModalBranches(sanitizedBranches);
+        setWorkspaceModalDefaultTrunk(recommended);
+        setWorkspaceModalLoadError(null);
+      } catch (err) {
+        console.error("Failed to load branches for modal:", err);
+        const message = err instanceof Error ? err.message : "Unknown error";
+        setWorkspaceModalLoadError(
+          `Unable to load branches automatically: ${message}. You can still enter the trunk branch manually.`
+        );
+      }
+    },
+    []
+  );
 
   // Memoize callbacks to prevent LeftSidebar/ProjectSidebar re-renders
   const handleAddProjectCallback = useCallback(() => {
@@ -238,7 +251,9 @@ function AppInner() {
   const handleCreateWorkspace = async (
     branchName: string,
     trunkBranch: string,
-    runtime?: string
+    runtime?: string,
+    startMessage?: string,
+    model?: string
   ) => {
     if (!workspaceModalProject) return;
 
@@ -274,6 +289,26 @@ function AppInner() {
         const runtimeKey = getRuntimeKey(workspaceModalProject);
         localStorage.setItem(runtimeKey, runtime);
       }
+
+      // Send start message if provided
+      if (startMessage) {
+        // Build send message options - use provided model or default
+        const { buildSendMessageOptions } = await import("@/hooks/useSendMessageOptions");
+        const sendOptions = buildSendMessageOptions(newWorkspace.workspaceId);
+
+        if (model) {
+          sendOptions.model = model;
+        }
+
+        // Defer until React finishes rendering and WorkspaceStore subscribes
+        requestAnimationFrame(() => {
+          void window.api.workspace.sendMessage(
+            newWorkspace.workspaceId,
+            startMessage,
+            sendOptions
+          );
+        });
+      }
     }
   };
 
@@ -615,6 +650,30 @@ function AppInner() {
       );
   }, [projects, setSelectedWorkspace, setWorkspaceMetadata]);
 
+  // Handle open new workspace modal event
+  useEffect(() => {
+    const handleOpenNewWorkspaceModal = (e: Event) => {
+      const customEvent = e as CustomEvent<{
+        projectPath: string;
+        startMessage?: string;
+        model?: string;
+        error?: string;
+      }>;
+      const { projectPath, startMessage, model, error } = customEvent.detail;
+      void handleAddWorkspace(projectPath, { startMessage, model, error });
+    };
+
+    window.addEventListener(
+      CUSTOM_EVENTS.OPEN_NEW_WORKSPACE_MODAL,
+      handleOpenNewWorkspaceModal as EventListener
+    );
+    return () =>
+      window.removeEventListener(
+        CUSTOM_EVENTS.OPEN_NEW_WORKSPACE_MODAL,
+        handleOpenNewWorkspaceModal as EventListener
+      );
+  }, [handleAddWorkspace]);
+
   return (
     <>
       <div className="bg-bg-dark flex h-screen overflow-hidden [@media(max-width:768px)]:flex-col">
@@ -682,6 +741,8 @@ function AppInner() {
             branches={workspaceModalBranches}
             defaultTrunkBranch={workspaceModalDefaultTrunk}
             loadErrorMessage={workspaceModalLoadError}
+            initialStartMessage={workspaceModalStartMessage}
+            initialModel={workspaceModalModel}
             onClose={() => {
               workspaceModalProjectRef.current = null;
               setWorkspaceModalOpen(false);
@@ -690,6 +751,8 @@ function AppInner() {
               setWorkspaceModalBranches([]);
               setWorkspaceModalDefaultTrunk(undefined);
               setWorkspaceModalLoadError(null);
+              setWorkspaceModalStartMessage(undefined);
+              setWorkspaceModalModel(undefined);
             }}
             onAdd={handleCreateWorkspace}
           />

src/components/NewWorkspaceModal.tsx

@@ -12,8 +12,16 @@ interface NewWorkspaceModalProps {
   branches: string[];
   defaultTrunkBranch?: string;
   loadErrorMessage?: string | null;
+  initialStartMessage?: string;
+  initialModel?: string;
   onClose: () => void;
-  onAdd: (branchName: string, trunkBranch: string, runtime?: string) => Promise<void>;
+  onAdd: (
+    branchName: string,
+    trunkBranch: string,
+    runtime?: string,
+    startMessage?: string,
+    model?: string
+  ) => Promise<void>;
 }
 
 // Shared form field styles
@@ -27,11 +35,14 @@ const NewWorkspaceModal: React.FC<NewWorkspaceModalProps> = ({
   branches,
   defaultTrunkBranch,
   loadErrorMessage,
+  initialStartMessage,
+  initialModel,
   onClose,
   onAdd,
 }) => {
   const [branchName, setBranchName] = useState("");
   const [trunkBranch, setTrunkBranch] = useState(defaultTrunkBranch ?? branches[0] ?? "");
+  const [startMessage, setStartMessage] = useState(initialStartMessage ?? "");
   const [isLoading, setIsLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
   const infoId = useId();
@@ -45,6 +56,10 @@ const NewWorkspaceModal: React.FC<NewWorkspaceModalProps> = ({
     setError(loadErrorMessage ?? null);
   }, [loadErrorMessage]);
 
+  useEffect(() => {
+    setStartMessage(initialStartMessage ?? "");
+  }, [initialStartMessage]);
+
   useEffect(() => {
     const fallbackTrunk = defaultTrunkBranch ?? branches[0] ?? "";
     setTrunkBranch((current) => {
@@ -66,6 +81,7 @@ const NewWorkspaceModal: React.FC<NewWorkspaceModalProps> = ({
     setBranchName("");
     setTrunkBranch(defaultTrunkBranch ?? branches[0] ?? "");
     setRuntimeOptions(RUNTIME_MODE.LOCAL, "");
+    setStartMessage("");
     setError(loadErrorMessage ?? null);
     onClose();
   };
@@ -104,11 +120,19 @@ const NewWorkspaceModal: React.FC<NewWorkspaceModalProps> = ({
     try {
       // Get runtime string from hook helper
       const runtime = getRuntimeString();
+      const trimmedStartMessage = startMessage.trim();
 
-      await onAdd(trimmedBranchName, normalizedTrunkBranch, runtime);
+      await onAdd(
+        trimmedBranchName,
+        normalizedTrunkBranch,
+        runtime,
+        trimmedStartMessage || undefined,
+        initialModel
+      );
       setBranchName("");
       setTrunkBranch(defaultTrunkBranch ?? branches[0] ?? "");
       setRuntimeOptions(RUNTIME_MODE.LOCAL, "");
+      setStartMessage("");
       onClose();
     } catch (err) {
       const message = err instanceof Error ? err.message : "Failed to create workspace";
@@ -202,6 +226,7 @@ const NewWorkspaceModal: React.FC<NewWorkspaceModalProps> = ({
           )}
         </div>
 
+<<<<<<< HEAD
         <div className={formFieldClasses}>
           <label htmlFor="runtimeMode">Runtime:</label>
           <select
@@ -243,6 +268,17 @@ const NewWorkspaceModal: React.FC<NewWorkspaceModalProps> = ({
           </div>
         )}
 
+        <div className="[&_label]:text-foreground [&_textarea]:bg-modal-bg [&_textarea]:border-border-medium [&_textarea]:focus:border-accent mb-5 [&_label]:mb-2 [&_label]:block [&_label]:text-sm [&_textarea]:w-full [&_textarea]:rounded [&_textarea]:border [&_textarea]:px-3 [&_textarea]:py-2 [&_textarea]:text-sm [&_textarea]:text-white [&_textarea]:focus:outline-none [&_textarea]:disabled:cursor-not-allowed [&_textarea]:disabled:opacity-60 [&_textarea]:resize-y [&_textarea]:min-h-[80px]">
+          <label htmlFor="startMessage">Start Message (optional):</label>
+          <textarea
+            id="startMessage"
+            value={startMessage}
+            onChange={(event) => setStartMessage(event.target.value)}
+            disabled={isLoading}
+            placeholder="Enter a message to send after creating the workspace..."
+          />
+        </div>
+
         <ModalInfo id={infoId}>
           <p>This will create a workspace at:</p>
           <code className="block break-all">
@@ -259,6 +295,7 @@ const NewWorkspaceModal: React.FC<NewWorkspaceModalProps> = ({
               {formatNewCommand(
                 branchName.trim(),
                 trunkBranch.trim() || undefined,
+                startMessage.trim() || undefined,
                 getRuntimeString()
               )}
             </div>

src/constants/events.ts

@@ -46,6 +46,12 @@ export const CUSTOM_EVENTS = {
    * Detail: { commandId: string }
    */
   EXECUTE_COMMAND: "cmux:executeCommand",
+
+  /**
+   * Event to open the new workspace modal with initial data
+   * Detail: { projectPath: string, startMessage?: string, model?: string, error?: string }
+   */
+  OPEN_NEW_WORKSPACE_MODAL: "cmux:openNewWorkspaceModal",
 } as const;
 
 /**

src/utils/chatCommands.ts

@@ -302,11 +302,26 @@ export async function handleNewCommand(
 ): Promise<CommandHandlerResult> {
   const { workspaceId, sendMessageOptions, setInput, setIsSending, setToast } = context;
 
+  // Get workspace info to extract projectPath (needed for both cases)
+  const workspaceInfo = await window.api.workspace.getInfo(workspaceId);
+  if (!workspaceInfo) {
+    setToast({
+      id: Date.now().toString(),
+      type: "error",
+      message: "Failed to get workspace info",
+    });
+    return { clearInput: false, toastShown: true };
+  }
+
   // Open modal if no workspace name provided
   if (!parsed.workspaceName) {
     setInput("");
-    const event = new CustomEvent(CUSTOM_EVENTS.EXECUTE_COMMAND, {
-      detail: { commandId: "ws:new" },
+    const event = new CustomEvent(CUSTOM_EVENTS.OPEN_NEW_WORKSPACE_MODAL, {
+      detail: {
+        projectPath: workspaceInfo.projectPath,
+        startMessage: parsed.startMessage,
+        model: parsed.model,
+      },
     });
     window.dispatchEvent(event);
     return { clearInput: true, toastShown: false };
@@ -316,12 +331,6 @@ export async function handleNewCommand(
   setIsSending(true);
 
   try {
-    // Get workspace info to extract projectPath
-    const workspaceInfo = await window.api.workspace.getInfo(workspaceId);
-    if (!workspaceInfo) {
-      throw new Error("Failed to get workspace info");
-    }
-
     const createResult = await createNewWorkspace({
       projectPath: workspaceInfo.projectPath,
       workspaceName: parsed.workspaceName,
@@ -334,13 +343,17 @@ export async function handleNewCommand(
     if (!createResult.success) {
       const errorMsg = createResult.error ?? "Failed to create workspace";
       console.error("Failed to create workspace:", errorMsg);
-      setToast({
-        id: Date.now().toString(),
-        type: "error",
-        title: "Create Failed",
-        message: errorMsg,
+      // Open modal with error and preserve data
+      const event = new CustomEvent(CUSTOM_EVENTS.OPEN_NEW_WORKSPACE_MODAL, {
+        detail: {
+          projectPath: workspaceInfo.projectPath,
+          startMessage: parsed.startMessage,
+          model: parsed.model,
+          error: errorMsg,
+        },
       });
-      return { clearInput: false, toastShown: true };
+      window.dispatchEvent(event);
+      return { clearInput: true, toastShown: false };
     }
 
     setToast({
@@ -352,13 +365,17 @@ export async function handleNewCommand(
   } catch (error) {
     const errorMsg = error instanceof Error ? error.message : "Failed to create workspace";
     console.error("Create error:", error);
-    setToast({
-      id: Date.now().toString(),
-      type: "error",
-      title: "Create Failed",
-      message: errorMsg,
+    // Open modal with error and preserve data
+    const event = new CustomEvent(CUSTOM_EVENTS.OPEN_NEW_WORKSPACE_MODAL, {
+      detail: {
+        projectPath: workspaceInfo.projectPath,
+        startMessage: parsed.startMessage,
+        model: parsed.model,
+        error: errorMsg,
+      },
     });
-    return { clearInput: false, toastShown: true };
+    window.dispatchEvent(event);
+    return { clearInput: true, toastShown: false };
   } finally {
     setIsSending(false);
   }