Multiline commit messages

The Shell tool sends commands as a single string. Heredoc syntax (<<'EOF') inside $(cat ...) is fragile and fails silently — the literal $(cat <<'EOF' ... ends up as the commit message instead of the intended text.

Rule

Never use $(cat <<'EOF' ...) or $(cat <<EOF ...) for commit messages.

Use single-quoted strings with embedded newlines:

git commit -m 'short summary line

Longer body paragraph explaining why the change exists.
Additional context if needed.'

Why heredocs fail

The Shell tool passes the command as a single string argument. When you write:

git commit -m "$(cat <<'EOF'
message
EOF
)"

The shell may not parse the heredoc correctly in this context — the EOF delimiter, newlines, and nested quoting interact unpredictably. The result is the raw $(cat <<'EOF' ... text appearing as the commit message.

Single-quoted strings with literal newlines are simple, portable, and always work.