Keep directory browsing usable without native pickers

Remote and server-hosted deployments cannot rely on the browser user's desktop tools being available inside the Node server process. Directory browsing now checks for native picker commands first and falls back to a configurable server-side workflows directory instead of surfacing command-not-found errors.

Constraint: The browse endpoint runs on the server, not on the Windows client browser

Constraint: Test servers may not have osascript, zenity, kdialog, PowerShell, or an interactive desktop session

Rejected: Keep propagating native picker failures to the modal | successful server deployments without desktop tools showed red command errors

Confidence: high

Scope-risk: narrow

Directive: For true client-local folder selection, use a separate File System Access API flow instead of this server filesystem endpoint

Tested: npx vitest run src/app/api/browse-directory/__tests__/route.test.ts src/components/__tests__/ProjectSetupModal.test.tsx

Tested: npm run build

Not-tested: Interactive Windows Server desktop picker session

src/app/api/browse-directory/route.ts

@@ -1,11 +1,47 @@
 import { NextResponse } from "next/server";
-import { exec } from "child_process";
+import { exec, execFile } from "child_process";
 import { promisify } from "util";
 import { writeFile, unlink } from "fs/promises";
-import { tmpdir } from "os";
+import { homedir, tmpdir } from "os";
 import { join } from "path";
 
 const execAsync = promisify(exec);
+const execFileAsync = promisify(execFile);
+
+async function commandExists(command: string): Promise<boolean> {
+  try {
+    await execFileAsync("sh", ["-lc", `command -v ${command}`]);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+async function findPowerShellCommand(): Promise<string | null> {
+  for (const command of ["powershell.exe", "powershell", "pwsh.exe", "pwsh"]) {
+    try {
+      await execFileAsync(command, ["-NoProfile", "-Command", "$PSVersionTable.PSVersion.ToString()"]);
+      return command;
+    } catch {
+      // Try the next PowerShell executable name.
+    }
+  }
+  return null;
+}
+
+function getFallbackDirectory(): string {
+  return process.env.POPIART_WORKFLOWS_DIR || join(homedir(), "Documents");
+}
+
+function fallbackDirectoryResponse(reason: string) {
+  return NextResponse.json({
+    success: true,
+    cancelled: false,
+    fallback: true,
+    path: getFallbackDirectory(),
+    warning: reason,
+  });
+}
 
 /**
  * Normalize a path returned by native directory pickers.
@@ -43,11 +79,20 @@ export async function GET() {
 
     if (platform === "darwin") {
       // macOS: Use osascript to open folder picker
+      if (!(await commandExists("osascript"))) {
+        return fallbackDirectoryResponse("Native folder picker is unavailable in this environment.");
+      }
+
       const { stdout } = await execAsync(
         `osascript -e 'set folderPath to POSIX path of (choose folder with prompt "Select a folder to save workflows")' -e 'return folderPath'`
       );
       selectedPath = stdout.trim();
     } else if (platform === "win32") {
+      const powershellCommand = await findPowerShellCommand();
+      if (!powershellCommand) {
+        return fallbackDirectoryResponse("Windows folder picker is unavailable in this environment.");
+      }
+
       // Windows: Use the modern IFileOpenDialog (Vista+) for a nice folder picker
       // Write script to temp file to avoid escaping issues
       const psScript = `
@@ -98,39 +143,39 @@ if ($result) { Write-Output $result }
       const tempFile = join(tmpdir(), `browse-folder-${Date.now()}.ps1`);
       try {
         await writeFile(tempFile, psScript, "utf-8");
-        const { stdout } = await execAsync(
-          `powershell -NoProfile -ExecutionPolicy Bypass -File "${tempFile}"`,
+        const { stdout } = await execFileAsync(
+          powershellCommand,
+          ["-NoProfile", "-ExecutionPolicy", "Bypass", "-File", tempFile],
           { timeout: 120000 }
         );
         selectedPath = stdout.trim();
+      } catch (error) {
+        if (
+          error instanceof Error &&
+          (error.message.includes("User canceled") || error.message.includes("-128"))
+        ) {
+          selectedPath = null;
+        } else {
+          return fallbackDirectoryResponse("Windows folder picker failed in this environment.");
+        }
       } finally {
         // Clean up temp file
         try { await unlink(tempFile); } catch { /* ignore */ }
       }
     } else if (platform === "linux") {
       // Linux: Try zenity (common on GNOME) or kdialog (KDE)
-      try {
+      if (await commandExists("zenity")) {
         const { stdout } = await execAsync(
           `zenity --file-selection --directory --title="Select a folder to save workflows" 2>/dev/null`
         );
         selectedPath = stdout.trim();
-      } catch {
-        // Try kdialog as fallback
-        try {
-          const { stdout } = await execAsync(
-            `kdialog --getexistingdirectory ~ --title "Select a folder to save workflows"`
-          );
-          selectedPath = stdout.trim();
-        } catch {
-          return NextResponse.json(
-            {
-              success: false,
-              error:
-                "No supported dialog tool found. Please install zenity or kdialog.",
-            },
-            { status: 500 }
-          );
-        }
+      } else if (await commandExists("kdialog")) {
+        const { stdout } = await execAsync(
+          `kdialog --getexistingdirectory ~ --title "Select a folder to save workflows"`
+        );
+        selectedPath = stdout.trim();
+      } else {
+        return fallbackDirectoryResponse("No supported folder picker was found. Using the default documents folder.");
       }
     } else {
       return NextResponse.json(
@@ -169,13 +214,6 @@ if ($result) { Write-Output $result }
       });
     }
 
-    return NextResponse.json(
-      {
-        success: false,
-        error:
-          error instanceof Error ? error.message : "Failed to open dialog",
-      },
-      { status: 500 }
-    );
+    return fallbackDirectoryResponse("Native folder picker failed in this environment.");
   }
 }