Claude Code Model Selection: Choosing the Right Claude for Each Task

Why Model Selection Matters in Claude Code

Claude Code does not lock you into a single model. You can switch between Opus, Sonnet, and Haiku depending on what the task requires. Getting that choice right is where most developers leave money on the table — and where using the wrong model causes frustrating failures on tasks it should handle easily.

Opus vs Sonnet vs Haiku

Opus 4.7 is the reasoning flagship. Use it when you need multi-step architectural decisions, complex debugging across many files, or tasks where missing something is expensive. It is slower and more costly, but for hard problems it finishes faster because it gets things right the first time.

Sonnet 4.6 is the daily driver. Most development tasks — writing functions, tests, API integrations, refactoring — run fine on Sonnet at roughly half the cost of Opus. If you default to Sonnet for everything except the genuinely hard stuff, you will be right most of the time.

Haiku is the fast and cheap option for straightforward tasks where you need correctness but not deep reasoning: summarizing logs, formatting data, simple transformations. Do not use it for anything involving complex logic.

Context Window Considerations

All Claude models support large context windows, but they behave differently at high usage levels. Opus handles long documents more reliably. Sonnet degrades more noticeably approaching context limits. If you are feeding it large codebases, Opus is worth the premium.

How to Switch Models

Use the --model flag when starting a session:

claude --model opus-4.7
claude --model sonnet-4-6
claude --model haiku

Or set a default in claude_settings.json:

{ "defaultModel": "sonnet-4-6" }

You can also switch mid-session with /model.