Launch Claude Code with a Specific Model Using the --model Flag
Different tasks need different models. Instead of launching Claude Code and then switching with /model, pick the right one upfront.
claude --model opus
This starts a session with Opus regardless of your default setting. Perfect for when you know the task ahead needs a specific model's strengths.
# Heavy architecture work — use the most capable model
claude --model opus -p "plan a migration from monolith to microservices"
# Everyday coding — balanced speed and quality
claude --model sonnet
# Quick lookups and simple tasks — fastest responses
claude --model haiku -p "what's the syntax for a Laravel migration rollback?"
Combine with other flags for powerful one-liners:
# Fast, cheap code review
claude --model haiku -p "review this diff for obvious issues" --max-turns 5
# Deep security audit with the strongest model
claude --model opus -p "audit src/ for security vulnerabilities"
# Quick formatting fix
claude --model haiku -p "fix the indentation in config/app.php"
This is especially useful in scripts and automation where you want to control cost and quality:
# CI pipeline — use haiku for fast, cheap PR checks
claude --model haiku -p "review this PR" --output-format json --max-turns 10
# Nightly deep analysis — use opus for thorough work
claude --model opus -p "find performance issues across the codebase" --max-turns 30
The --model flag overrides your default for just that session. Your configured default stays the same for the next time you launch without the flag.
Match the model to the task — opus for thinking, sonnet for building, haiku for checking.
via Claude Code
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When Claude starts referencing files you've since deleted, remembering old code you've already changed, or getting confused by contradictory instructions from a long session — type /clear to wipe the slate clean. Unlike /compact which preserves context, /clear gives you a true fresh start without restarting the CLI.
Not every task needs deep reasoning. Type /fast to switch Claude Code into fast mode — same model, faster output — for quick edits, simple questions, and routine changes. Toggle it off when you need Claude to think harder on complex problems.
Long sessions eat through your context window as conversation history piles up. Type /compact to summarize the conversation so far and reclaim space — keeping Claude's understanding of what you're working on while freeing up room for more work.