ralph-loop: setup script crashes with 'unbound variable' when PROMPT_PARTS is empty

[cha1mers]

Bug

The ralph-loop plugin's scripts/setup-ralph-loop.sh crashes on line 113 with:

PROMPT_PARTS[*]: unbound variable

Root Cause

The script uses set -euo pipefail (line 6), which includes set -u (nounset). On line 9, PROMPT_PARTS=() initializes an empty array, but on line 113:

PROMPT="${PROMPT_PARTS[*]}"

In bash, expanding an empty array with set -u triggers unbound variable. This happens both when no arguments are passed AND when all arguments are flags (e.g., --max-iterations 5).

Fix

Change line 113 from:

PROMPT="${PROMPT_PARTS[*]}"

to:

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

The :- default operator provides an empty string fallback, allowing the script to reach the proper empty-prompt validation on line 116.

Repro

1. Install the ralph-loop plugin
2. Run /ralph-loop (no arguments)
3. Script crashes instead of showing the usage help

Environment

• macOS (bash 3.2 — Apple default)
• Claude Code with official plugins marketplace