diff --git a/tools/lazy_deps.py b/tools/lazy_deps.py
index 5b5878eb451..02e3038d4d3 100644
--- a/tools/lazy_deps.py
+++ b/tools/lazy_deps.py
@@ -456,7 +456,23 @@ def ensure(feature: str, *, prompt: bool = True) -> None:
             "lazy installs disabled (security.allow_lazy_installs=false)"
         )
 
-    if prompt and sys.stdin.isatty() and sys.stdout.isatty():
+    # Only show the interactive confirmation when we own a TTY and
+    # prompt_toolkit isn't running.  A bare input() deadlocks when a
+    # prompt_toolkit app owns the terminal because keystrokes route to
+    # its event loop rather than stdin, so the prompt blocks forever.
+    # Under the TUI we skip the prompt and proceed — lazy installs are
+    # gated by security.allow_lazy_installs, so reaching here is
+    # already user opt-in.
+    _pt_active = False
+    if "prompt_toolkit.application.current" in sys.modules:
+        try:
+            from prompt_toolkit.application.current import get_app_or_none
+            _app = get_app_or_none()
+            _pt_active = _app is not None and getattr(_app, "is_running", False)
+        except Exception:
+            _pt_active = False
+
+    if prompt and not _pt_active and sys.stdin.isatty() and sys.stdout.isatty():
         spec_list = ", ".join(missing)
         try:
             answer = input(