ralph-loop: setup-ralph-loop.sh crashes with unbound variable when called without arguments

[faramarz]

Bug

/ralph-loop:ralph-loop called without arguments crashes with:

setup-ralph-loop.sh: line 113: PROMPT_PARTS[*]: unbound variable

Root Cause

Line 6 sets set -euo pipefail. The -u (nounset) flag treats empty bash arrays as unbound variables.

Line 9 initializes PROMPT_PARTS=() as empty, and line 113 references ${PROMPT_PARTS[*]} which fails under set -u when no arguments were provided.

The script never reaches the helpful "No prompt provided" error message at line 116-128.

Fix

Line 113 — change:

PROMPT="${PROMPT_PARTS[*]}"

to:

PROMPT="${PROMPT_PARTS[*]:-}"

The :- provides a default empty string when the array is empty/unbound, allowing execution to reach the proper error handling block.

Reproduction

bash scripts/setup-ralph-loop.sh
# Expected: "No prompt provided" error with usage examples
# Actual: "PROMPT_PARTS[*]: unbound variable" crash

Environment

• macOS (Darwin 25.3.0)
• bash 3.2.57 (Apple default)
• Claude Code 2.1.32