Model configuration

Learn about the Claude Code model configuration, including model aliases like opusplan

Available models

For the model setting in Claude Code, you can configure either:

• A model alias
• A model name
  • Anthropic API: A full model name
  • Bedrock: an inference profile ARN
  • Foundry: a deployment name
  • Vertex: a version name

Model aliases

Model aliases provide a convenient way to select model settings without remembering exact version numbers:

Aliases always point to the latest version. To pin to a specific version, use the full model name (for example, claude-opus-4-6) or set the corresponding environment variable like ANTHROPIC_DEFAULT_OPUS_MODEL.

Setting your model

You can configure your model in several ways, listed in order of priority:

1. During session - Use /model <alias|name> to switch models mid-session
2. At startup - Launch with claude --model <alias|name>
3. Environment variable - Set ANTHROPIC_MODEL=<alias|name>
4. Settings - Configure permanently in your settings file using the model field.

Example usage:

# Start with Opus
claude --model opus

# Switch to Sonnet during session
/model sonnet

Example settings file:

{
    "permissions": {
        ...
    },
    "model": "opus"
}

Restrict model selection

Enterprise administrators can use availableModels in managed or policy settings to restrict which models users can select.

When availableModels is set, users cannot switch to models not in the list via /model, --model flag, Config tool, or ANTHROPIC_MODEL environment variable.

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

Default model behavior

The Default option in the model picker is not affected by availableModels. It always remains available and represents the system's runtime default based on the user's subscription tier:

Even with availableModels: [], users can still use Claude Code with the Default model for their tier.

Control the model users run on

To fully control the model experience, use availableModels together with the model setting:

• availableModels: restricts what users can switch to
• model: sets the explicit model override, taking precedence over the Default

This example ensures all users run Sonnet 4.5 and can only choose between Sonnet and Haiku:

{
  "model": "sonnet",
  "availableModels": ["sonnet", "haiku"]
}

Merge behavior

When availableModels is set at multiple levels, such as user settings and project settings, arrays are merged and deduplicated. To enforce a strict allowlist, set availableModels in managed or policy settings which take highest priority.

Special model behavior

default model setting

The behavior of default depends on your account type:

• Max and Teams: defaults to Opus 4.6
• Pro: defaults to Opus 4.6 in Claude Code
• Enterprise: Opus 4.6 is available but not the default

Claude Code may automatically fall back to Sonnet if you hit a usage threshold with Opus.

opusplan model setting

The opusplan model alias provides an automated hybrid approach:

• In plan mode - Uses opus for complex reasoning and architecture decisions
• In execution mode - Automatically switches to sonnet for code generation and implementation

This gives you the best of both worlds: Opus's superior reasoning for planning, and Sonnet's efficiency for execution.

Adjust effort level

Effort levels control Opus 4.6's adaptive reasoning, which dynamically allocates thinking based on task complexity. Lower effort is faster and cheaper for straightforward tasks, while higher effort provides deeper reasoning for complex problems.

Three levels are available: low, medium, and high (default).

Setting effort:

• In /model: use left/right arrow keys to adjust the effort slider when selecting a model
• Environment variable: set CLAUDE_CODE_EFFORT_LEVEL=low|medium|high
• Settings: set effortLevel in your settings file

Effort is currently supported on Opus 4.6. The effort slider appears in /model when a supported model is selected.

Extended context with [1m]

The [1m] suffix enables a 1 million token context window for long sessions.

You can use the [1m] suffix with model aliases or full model names:

# Use the sonnet[1m] alias
/model sonnet[1m]

# Or append [1m] to a full model name
/model claude-sonnet-4-5-20250929[1m]

Note: Extended context models have different pricing.

Checking your current model

You can see which model you're currently using in several ways:

1. In status line (if configured)
2. In /status, which also displays your account information.

Environment variables

You can use the following environment variables, which must be full model names (or equivalent for your API provider), to control the model names that the aliases map to.

Note: ANTHROPIC_SMALL_FAST_MODEL is deprecated in favor of ANTHROPIC_DEFAULT_HAIKU_MODEL.

Prompt caching configuration

Claude Code automatically uses prompt caching to optimize performance and reduce costs. You can disable prompt caching globally or for specific model tiers:

These environment variables give you fine-grained control over prompt caching behavior. The global DISABLE_PROMPT_CACHING setting takes precedence over the model-specific settings, allowing you to quickly disable all caching when needed. The per-model settings are useful for selective control, such as when debugging specific models or working with cloud providers that may have different caching implementations.