Shell snapshot uses unguarded $ZSH_VERSION, breaks set -u (nounset)

Summary

Claude Code's shell snapshot scripts reference $ZSH_VERSION without a default-value guard, which causes set -u (nounset) to fail when running in bash.

Reproduction

1. In a Claude Code session, run any Bash tool call that starts with set -euo pipefail
2. If the shell snapshot's functions are invoked during initialization, the shell exits with:

/home/<user>/.claude/shell-snapshots/snapshot-bash-<id>.sh: line 129: ZSH_VERSION: unbound variable

1. This is intermittent — depends on whether the snapshot functions get triggered during shell init.

Root cause

The snapshot script contains three instances of:

if [[ -n $ZSH_VERSION ]]; then

(lines 93, 111, 129 in the generated snapshot)

In bash, $ZSH_VERSION is never defined. Under normal bash this evaluates to false silently, but under set -u (nounset) it's an error because the variable doesn't exist.

Fix

Replace all three instances with:

if [[ -n ${ZSH_VERSION:-} ]]; then

The :- default-value syntax returns empty string when the variable is unset, satisfying nounset.

Environment

• Claude Code CLI (npm package @anthropic-ai/claude-code)
• bash shell on Linux (WSL2 Ubuntu, kernel 6.6.87.2-microsoft-standard-WSL2)
• The snapshot file is auto-generated at ~/.claude/shell-snapshots/