diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..bee8a64
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+__pycache__
diff --git a/workspaces.py b/workspaces.py
index 2a332b8..91da02c 100755
--- a/workspaces.py
+++ b/workspaces.py
@@ -524,6 +524,8 @@ def pick_workspace_with_iterfzf(workspaces: list[Path]) -> Path | None:
     """Use iterfzf (Python library) to pick a workspace from a list of paths.
     """
     names = [w.name for w in workspaces]
+    if not names:
+        return None
     choice = iterfzf(names, prompt="pick a workspace> ")
 
     if not choice:
@@ -1434,6 +1436,7 @@ def create_if_needed_and_attach(
         - If session doesn't exist: create_detached_session()
         - Then `tmux switch-client -t session_name`
     """
+    session_name = session_name.strip().replace(" ", "_").replace(':', '_').replace('.', '_').replace('/', '_')
     if not_in_tmux():
         r = run_tmux(
             ["new-session", "-As", session_name, "-c", str(path_name)],
@@ -1503,7 +1506,8 @@ def tmux_cli_attach(
         ),
     ),
 ):
-    """Attach or create a session for a repo in a workspace.
+    """
+    Attach or create a session for a repo in a workspace.
     """
     _settings, _repos_dir, workspaces_dir = get_ctx_paths(ctx)
     ws_dir = find_workspace_dir(workspaces_dir, workspace)
@@ -1608,6 +1612,13 @@ def attach(
         ),
     ),
 ):
+    _settings, _repos_dir, workspaces_dir = get_ctx_paths(ctx)
+    if len(list_workspaces(workspaces_dir)) == 0:
+        import sys
+        cmd = sys.executable
+        console.print("[red]No workspaces found. Exiting.[/red]")
+        console.print(f"Create a workspace with `[yellow]workspaces create[/yellow]` first.")
+        raise typer.Exit(1)
     if in_tmux():
         tmux_cli_attach(ctx, workspace)