Claude Code /model: switch models, aliases (opus, sonnet, haiku, opusplan), ANTHROPIC_MODEL and effort

• During a session: /model <alias|name>, or /model with no argument to open the picker
• At startup: claude --model <alias|name>
• Environment variable: ANTHROPIC_MODEL=<alias|name>
• Settings: the model field in your settings file
• Default for new sessions: ANTHROPIC_DEFAULT_MODEL=<alias|name> (v2.1.236 or later)

In the /model picker, Enter switches and saves the choice as your default. Press s on a row to switch for this session only.

claude --model opus

/model sonnet

{
  "model": "opus"
}

• default: clears any override and returns to your account's default
• sonnet: latest Sonnet, for daily coding
• opus: latest Opus, for complex reasoning
• haiku: fast and efficient, for simple tasks
• sonnet[1m], opus[1m]: 1 million token context window variants
• opusplan: Opus during plan mode, then Sonnet for execution
• fable: the Fable model for your provider, for your hardest and longest-running tasks
• best: the model fable resolves to where Fable is available to you, otherwise the same model as opus

On the Anthropic API, opus, sonnet and haiku currently resolve to Opus 5.5, Sonnet 5.5 and Haiku 5.5. Some other providers resolve them to earlier versions. To pin a version, use the full model name such as claude-opus-5-5.

Each value must be a full model name or your provider's identifier.

• ANTHROPIC_DEFAULT_OPUS_MODEL: model for opus, and for opusplan in plan mode
• ANTHROPIC_DEFAULT_SONNET_MODEL: model for sonnet, and for opusplan outside plan mode
• ANTHROPIC_DEFAULT_HAIKU_MODEL: model for haiku and background functionality
• CLAUDE_CODE_SUBAGENT_MODEL: default model for subagents that are not assigned one

export ANTHROPIC_DEFAULT_OPUS_MODEL=claude-opus-5-5

Opus 5.5, Sonnet 5.5 and Haiku 5.5 support low, medium, high, xhigh and max, and default to medium. Set it with /effort, --effort, CLAUDE_CODE_EFFORT_LEVEL, or the effortLevel settings key. /effort auto clears the saved level. max is session-only unless set through CLAUDE_CODE_EFFORT_LEVEL, and is not accepted by effortLevel.

/effort high

Admins can limit choices with availableModels in managed or policy settings. Add enforceAvailableModels to also restrict the Default option (v2.1.175 or later).

{
  "availableModels": ["sonnet", "haiku"],
  "enforceAvailableModels": true
}