Haiku vs Sonnet vs Opus in Claude Code
Which Claude model to use in Claude Code for questions, everyday coding and hard reasoning, with the aliases, the defaults, and measured cost and pass rates.
Use Haiku for quick questions, Sonnet for most coding, and Opus for complex reasoning. That is Anthropic's own guidance. Our benchmark agrees: Haiku answered ten questions correctly for $0.08, against $0.50 on Opus. On 30 real coding tasks, plain Sonnet high passed 30 at $0.240 per passed task, and plain Opus passed 28 at $0.499.
The three models at a glance
| Model | Alias | Anthropic's description | Good for |
|---|---|---|---|
| Haiku 5.5 | haiku | Fast and efficient, for simple tasks | Questions, lookups, simple subagent work |
| Sonnet 5.5 | sonnet | For daily coding tasks | Features, fixes, refactors, tests |
| Opus 5.5 | opus | For complex reasoning tasks | Architecture, hard debugging, risky changes |
Aliases and descriptions from Anthropic's model configuration docs, read on 2026-11-05. On the Anthropic API, the aliases resolve to the 5.5 models. Other providers may resolve to earlier versions.
Which model does Claude Code use by default?
On Pro, Max, Team, Enterprise and the Anthropic API, the default is Opus 5.5. That is the strongest choice and the most expensive for routine work. Switch with /model sonnet, start with claude --model sonnet, or set model in your settings.
What did the models cost on real work?
| 30 real coding tasks | Passed | Cost per passed task |
|---|---|---|
| Plain Sonnet high | 30/30 | $0.240 |
| AutoMode | 29/30 | $0.275 |
| Plain Opus | 28/30 | $0.499 |
Opus did not pass more tasks here, and it cost about twice as much per passed task. On hard work, Haiku alone is a risk: a Haiku-first mode failed a task that Sonnet high passed. Read the benchmark.
What about opusplan and Fable?
opusplanuses Opus in plan mode and Sonnet for the edits.- Fable suits ambiguous work larger than one sitting, such as a root-cause investigation. It is not the default on any plan.
Can Claude Code pick the model for me?
Not by itself. A router can: AutoMode sends questions to Haiku and coding to Sonnet, moves risky work up to Opus, and checks the prompt cache cost before any switch. Estimate what it would save you.
Install AutoMode
Paste these into Claude Code, one at a time, then run /reload-plugins. It is free, needs no key and no server, and starts on its own.
/plugin marketplace add mralexivy/AutoMode
/plugin install automode@automodeLast updated on
Claude Code effort levels explained
What each Claude Code effort level does, low to max, the default for each model, how to set it with /effort, settings or env, and which level fits a task.
AutoMode vs effortless
AutoMode and effortless both route effort in Claude Code. In the same five sessions, AutoMode cost $2.01 and effortless $3.87, both passing 20 of 20.