Use --append-system-prompt for Pipeline-Specific Rules

When running Claude Code in CI or automation, you often want to add extra constraints without fully replacing the default system prompt. --append-system-prompt lets you tack on additional instructions at the end.

claude --append-system-prompt \
  "Never modify migration files. If a schema change is needed, create a new migration." \
  "Fix the failing tests in the auth module"

This stacks on top of any existing CLAUDE.md context rather than replacing it — you get the project's standard instructions plus your pipeline-specific rules.

A few practical uses:

# Enforce output format for script parsing
claude -p \
  --append-system-prompt "Output only valid JSON. No markdown, no explanation." \
  "Audit the npm dependencies for known vulnerabilities"

# Add read-only mode guardrails to a review job
claude -p \
  --append-system-prompt "Do not write or modify any files. Analysis only." \
  "Review the changes in this PR for potential security issues"

# Restrict scope in a focused automation task
claude -p \
  --append-system-prompt "Only modify files in src/components/. Do not touch tests." \
  "Update all Button components to use the new design tokens"

Rules in --append-system-prompt take effect for that run only — they don't persist and don't pollute your CLAUDE.md.

--append-system-prompt is how you add guardrails without rebuilding the whole fence.