diff --git a/cli/pkg/installscript/installscript.go b/cli/pkg/installscript/installscript.go
index c7ca38210d3..a997405593f 100644
--- a/cli/pkg/installscript/installscript.go
+++ b/cli/pkg/installscript/installscript.go
@@ -26,6 +26,7 @@ func execScript(ctx context.Context, version string, args ...string) error {
 
 	scriptArgs := append([]string{script}, args...)
 	cmd := exec.CommandContext(ctx, "/bin/sh", scriptArgs...)
+	cmd.Stdin = os.Stdin
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 	return cmd.Run()
diff --git a/scripts/install.sh b/scripts/install.sh
index 2ae400d2d43..29720928ea5 100755
--- a/scripts/install.sh
+++ b/scripts/install.sh
@@ -303,8 +303,24 @@ set -e
 
 # Default values
 INSTALL_DIR_EXPLICIT=false
-if ! [ -t 0 ]; then # Detect non-interactive environments (e.g. piped input, CI, subprocesses)
-    NON_INTERACTIVE=${NON_INTERACTIVE:-true}
+
+# Default to non-interactive if STDIN is not a terminal (usually indicates e.g. agent, CI, subprocess).
+# Backwards compatibility: Old versions of `rill upgrade` didn't pass STDIN through, so we stay interactive if the parent process is named `rill`.
+if ! [ -t 0 ]; then
+    # Get parent process name
+    PARENT_NAME=""
+    if [ -n "$PPID" ]; then
+        if [ -f "/proc/$PPID/comm" ]; then
+            PARENT_NAME=$(basename "$(cat "/proc/$PPID/comm" 2>/dev/null)" 2>/dev/null)
+        elif command -v ps >/dev/null 2>&1; then
+            PARENT_NAME=$(basename "$(ps -o comm= -p "$PPID" 2>/dev/null)" 2>/dev/null)
+        fi
+    fi
+
+    # Apply the default
+    if [ "$PARENT_NAME" != "rill" ]; then
+        NON_INTERACTIVE=${NON_INTERACTIVE:-true}
+    fi
 fi
 NON_INTERACTIVE=${NON_INTERACTIVE:-false}