diff --git a/scripts/bootstrap.sh b/scripts/bootstrap.sh
index cee7251ad..4bd1ac7a5 100755
--- a/scripts/bootstrap.sh
+++ b/scripts/bootstrap.sh
@@ -423,11 +423,18 @@ string_to_bool() {
 }
 
 guided_input_stream() {
-  if [[ -t 0 ]]; then
+  # Some constrained Linux containers report interactive stdin but deny opening
+  # /dev/stdin directly. Probe readability before selecting it.
+  if [[ -t 0 ]] && (: </dev/stdin) 2>/dev/null; then
     echo "/dev/stdin"
     return 0
   fi
 
+  if [[ -t 0 ]] && (: </proc/self/fd/0) 2>/dev/null; then
+    echo "/proc/self/fd/0"
+    return 0
+  fi
+
   if (: </dev/tty) 2>/dev/null; then
     echo "/dev/tty"
     return 0