What is the --system-prompt-file Flag in Claude Code
The --system-prompt-file flag overrides Claude Code's default system prompt with custom instructions from a file, enabling specialized workflows and consistent prompting behavior.
How to Use It
Use --system-prompt-file with a file path containing your custom prompt instructions. This flag only works in print mode, not interactive mode.
claude --system-prompt-file path/to/prompt.txt "Review this code"
claude --system-prompt-file prompts/reviewer.txt --model opus "Analyze security"
Creating Custom Prompt Files
File Format - Plain text files with clear instructions:
You are a Python code reviewer. Focus on:
- Performance optimizations
- Security vulnerabilities
- PEP 8 compliance
Be concise and provide specific suggestions.
Benefits:
- Complete Control: Replaces default Claude Code behavior entirely
- Specialized Workflows: Tailored prompts for code review, documentation, testing
- Team Consistency: Share standardized prompts across development teams
- Print Mode Only: Works exclusively with non-interactive Claude Code usage
Relationship to --append-system-prompt
Key Differences - Two distinct approaches to prompt customization:
- --system-prompt-file: Completely replaces the default system prompt
- --append-system-prompt: Adds instructions to the existing default prompt
See Also: --print Flag|--append-system-prompt