SHELL001: Unescaped backticks in strings

Error

Command substitution (backticks or $()) detected in double-quoted strings, which can cause unexpected behavior when the shell interprets them.

Why this matters

Backticks inside double quotes trigger command substitution. In commit messages like fix bug in parser module, the shell tries to execute parser as a command. This produces garbled output or errors.

How to fix

Use HEREDOC (recommended)

git commit -sS -m "$(cat <<'EOF'
Fix bug in `parser` module
EOF
)"

Use file-based input

echo "Fix bug in \`parser\` module" > commit-msg.txt
git commit -sS -F commit-msg.txt

Escape backticks

git commit -sS -m "Fix bug in \`parser\` module"

Modes

Legacy mode (default)

Validates backticks only in specific commands: git commit -m, gh pr create --body/--title, gh issue create --body/--title.

Comprehensive mode (opt-in)

Validates all Bash commands for backtick issues. Detects unquoted backticks, backticks in double quotes, and suggests single quotes when no variables are present.

Configuration

[validators.shell.backtick]
enabled = true
check_all_commands = false      # enable comprehensive mode
check_unquoted = false          # check unquoted backticks (comprehensive mode)
suggest_single_quotes = true    # suggest single quotes when no vars present

Hook output

When this error is triggered, klaudiush writes JSON to stdout:

permissionDecisionReason (shown to Claude): [SHELL001] Command substitution detected in double-quoted strings. Use HEREDOC syntax or file-based input (git commit -F file.txt)

systemMessage (shown to user): Formatted error with fix hint and reference URL.

additionalContext (behavioral guidance): Automated klaudiush validation check. Fix the reported errors and retry the same command.

GIT004 - commit title issues

SHELL001