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model-config.md

Changed on 2026-03-14 00:06:33 EST

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> ## Documentation Index¶
> Fetch the complete documentation index at: https://code.claude.com/docs/llms.txt¶
> Use this file to discover all available pages before exploring further.¶

# 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](https://platform.claude.com/docs/en/about-claude/models/overview)**¶
* 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:¶

| Model alias | Behavior |¶
| ---------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------- |¶
| **`default`** | Recommended model setting, depending on your account type |¶
| **`sonnet`** | Uses the latest Sonnet model (currently Sonnet 4.6) for daily coding tasks |¶
| **`opus`** | Uses the latest Opus model (currently Opus 4.6) for complex reasoning tasks |¶
| **`haiku`** | Uses the fast and efficient Haiku model for simple tasks |¶
| **`sonnet[1m]`** | Uses Sonnet with a [1 million token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows#1m-token-context-window) for long sessions |¶
| **`opus[1m]`** | Uses Opus with a [1 million token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows#1m-token-context-window) for long sessions |¶
| **`opusplan`** | Special mode that uses `opus` during plan mode, then switches to `sonnet` for execution |¶

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:¶

```bash theme={null}¶
# Start with Opus¶
claude --model opus¶

# Switch to Sonnet during session¶
/model sonnet¶
```¶

Example settings file:¶

```json theme={null}¶
{¶
"permissions": {¶
...¶
},¶
"model": "opus"¶
}¶
```¶

## Restrict model selection¶

Enterprise administrators can use `availableModels` in [managed or policy settings](/en/settings#settings-files) 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.¶

```json theme={null}¶
{¶
"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](#default-model-setting).¶

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 4.6 and can only choose between Sonnet and Haiku:¶

```json theme={null}¶
{¶
"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 Team Premium**: defaults to Opus 4.6¶
* **Pro and Team Standard**: defaults to Sonnet 4.6¶
* **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](https://platform.claude.com/docs/en/build-with-claude/effort) control 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 availablepersist across sessions: **low**, **medium**, and **high**. Opus 4.6 defaults to medium effort for Max and Team subscribers.¶

**Setting effort:**¶

* **In `/model`**: use left/right arrow keys to adjust the effort slider when selecting a modelA fourth level, **max**, provides the deepest reasoning with no constraint on token spending, so responses are slower and cost more than at `high`. `max` is available on Opus 4.6 only and applies to the current session without persisting. Opus 4.6 defaults to medium effort for Max and Team subscribers.¶

**Setting effort:**¶

* **`/effort`**: run `/effort low`, `/effort medium`, `/effort high`, or `/effort max` to change the level, or `/effort auto` to reset to the model default¶
* **In `/model`**: use left/right arrow keys to adjust the effort slider when selecting a model¶
* **`--effort` flag**: pass `low`, `medium`, `high`, or `max` to set the level for a single session when launching Claude Code
* **Environment variable**: set `CLAUDE_CODE_EFFORT_LEVEL=low|medium|high` to `low`, `medium`, `high`, `max`, or `auto`¶
* **Settings**: set `effortLevel` in your settings file to `"low"`, `"medium"`, or `"high"`¶

The environment variable takes precedence, then your configured level, then the model default.

Effort is supported on Opus 4.6 and Sonnet 4.6. The effort slider appears in `/model` when a supported model is selected. The current effort level is also displayed next to the logo and spinner, (for example, "with low effort"), so you can confirm which setting is active without opening `/model`.¶

To disable adaptive reasoning on Opus 4.6 and Sonnet 4.6 and revert to the previous fixed thinking budget, set `CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING=1`. When disabled, these models use the fixed budget controlled by `MAX_THINKING_TOKENS`. See [environment variables](/en/env-vars).¶

### Extended context¶

Opus 4.6 and Sonnet 4.6 support a [1 million token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows#1m-token-context-window) for long sessions with large codebases.¶

Availability varies by model and plan. On Max, Team, and Enterprise plans, Opus is automatically upgraded to 1M context with no additional configuration. This applies to both Team Standard and Team Premium seats.¶

| Plan | Opus 4.6 with 1M context | Sonnet 4.6 with 1M context |¶
| ------------------------- | --------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------- |¶
| Max, Team, and Enterprise | Included with subscription | Requires [extra usage](https://support.claude.com/en/articles/12429409-extra-usage-for-paid-claude-plans) |¶
| Pro | Requires [extra usage](https://support.claude.com/en/articles/12429409-extra-usage-for-paid-claude-plans) | Requires [extra usage](https://support.claude.com/en/articles/12429409-extra-usage-for-paid-claude-plans) |¶
| API and pay-as-you-go | Full access | Full access |¶

To disable 1M context entirely, set `CLAUDE_CODE_DISABLE_1M_CONTEXT=1`. This removes 1M model variants from the model picker. See [environment variables](/en/env-vars).¶

The 1M context window uses standard model pricing with no premium for tokens beyond 200K. For plans where extended context is included with your subscription, usage remains covered by your subscription. For plans that access extended context through extra usage, tokens are billed to extra usage.¶

If your account supports 1M context, the option appears in the model picker (`/model`) in the latest versions of Claude Code. If you don't see it, try restarting your session.¶

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

```bash theme={null}¶
# Use the opus[1m] or sonnet[1m] alias¶
/model opus[1m]¶
/model sonnet[1m]¶

# Or append [1m] to a full model name¶
/model claude-opus-4-6[1m]¶
```¶

## Checking your current model¶

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

1. In [status line](/en/statusline) (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.¶

| Environment variable | Description |¶
| -------------------------------- | --------------------------------------------------------------------------------------------- |¶
| `ANTHROPIC_DEFAULT_OPUS_MODEL` | The model to use for `opus`, or for `opusplan` when Plan Mode is active. |¶
| `ANTHROPIC_DEFAULT_SONNET_MODEL` | The model to use for `sonnet`, or for `opusplan` when Plan Mode is not active. |¶
| `ANTHROPIC_DEFAULT_HAIKU_MODEL` | The model to use for `haiku`, or [background functionality](/en/costs#background-token-usage) |¶
| `CLAUDE_CODE_SUBAGENT_MODEL` | The model to use for [subagents](/en/sub-agents) |¶

Note: `ANTHROPIC_SMALL_FAST_MODEL` is deprecated in favor of¶
`ANTHROPIC_DEFAULT_HAIKU_MODEL`.¶

### Pin models for third-party deployments¶

When deploying Claude Code through [Bedrock](/en/amazon-bedrock), [Vertex AI](/en/google-vertex-ai), or [Foundry](/en/microsoft-foundry), pin model versions before rolling out to users.¶

Without pinning, Claude Code uses model aliases (`sonnet`, `opus`, `haiku`) that resolve to the latest version. When Anthropic releases a new model, users whose accounts don't have the new version enabled will break silently.¶

<Warning>¶
Set all three model environment variables to specific version IDs as part of your initial setup. Skipping this step means a Claude Code update can break your users without any action on your part.¶
</Warning>¶

Use the following environment variables with version-specific model IDs for your provider:¶

| Provider | Example |¶
| :-------- | :---------------------------------------------------------------------- |¶
| Bedrock | `export ANTHROPIC_DEFAULT_OPUS_MODEL='us.anthropic.claude-opus-4-6-v1'` |¶
| Vertex AI | `export ANTHROPIC_DEFAULT_OPUS_MODEL='claude-opus-4-6'` |¶
| Foundry | `export ANTHROPIC_DEFAULT_OPUS_MODEL='claude-opus-4-6'` |¶

Apply the same pattern for `ANTHROPIC_DEFAULT_SONNET_MODEL` and `ANTHROPIC_DEFAULT_HAIKU_MODEL`. For current and legacy model IDs across all providers, see [Models overview](https://platform.claude.com/docs/en/about-claude/models/overview). To upgrade users to a new model version, update these environment variables and redeploy.¶

To enable [extended context](#extended-context) for a pinned model, append `[1m]` to the model ID in `ANTHROPIC_DEFAULT_OPUS_MODEL` or `ANTHROPIC_DEFAULT_SONNET_MODEL`:¶

```bash theme={null}¶
export ANTHROPIC_DEFAULT_OPUS_MODEL='claude-opus-4-6[1m]'¶
```¶

The `[1m]` suffix applies the 1M context window to all usage of that alias, including `opusplan`. Claude Code strips the suffix before sending the model ID to your provider. Only append `[1m]` when the underlying model supports 1M context, such as Opus 4.6 or Sonnet 4.6.¶

<Note>¶
The `settings.availableModels` allowlist still applies when using third-party providers. Filtering matches on the model alias (`opus`, `sonnet`, `haiku`), not the provider-specific model ID.¶
</Note>¶

### Override model IDs per version¶

The family-level environment variables above configure one model ID per family alias. If you need to map several versions within the same family to distinct provider IDs, use the `modelOverrides` setting instead.¶

`modelOverrides` maps individual Anthropic model IDs to the provider-specific strings that Claude Code sends to your provider's API. When a user selects a mapped model in the `/model` picker, Claude Code uses your configured value instead of the built-in default.¶

This lets enterprise administrators route each model version to a specific Bedrock inference profile ARN, Vertex AI version name, or Foundry deployment name for governance, cost allocation, or regional routing.¶

Set `modelOverrides` in your [settings file](/en/settings#settings-files):¶

```json theme={null}¶
{¶
"modelOverrides": {¶
"claude-opus-4-6": "arn:aws:bedrock:us-east-2:123456789012:application-inference-profile/opus-prod",¶
"claude-opus-4-5-20251101": "arn:aws:bedrock:us-east-2:123456789012:application-inference-profile/opus-45-prod",¶
"claude-sonnet-4-6": "arn:aws:bedrock:us-east-2:123456789012:application-inference-profile/sonnet-prod"¶
}¶
}¶
```¶

Keys must be Anthropic model IDs as listed in the [Models overview](https://platform.claude.com/docs/en/about-claude/models/overview). For dated model IDs, include the date suffix exactly as it appears there. Unknown keys are ignored.¶

Overrides replace the built-in model IDs that back each entry in the `/model` picker. On Bedrock, overrides take precedence over any inference profiles that Claude Code discovers automatically at startup. Values you supply directly through `ANTHROPIC_MODEL`, `--model`, or the `ANTHROPIC_DEFAULT_*_MODEL` environment variables are passed to the provider as-is and are not transformed by `modelOverrides`.¶

`modelOverrides` works alongside `availableModels`. The allowlist is evaluated against the Anthropic model ID, not the override value, so an entry like `"opus"` in `availableModels` continues to match even when Opus versions are mapped to ARNs.¶

### Prompt caching configuration¶

Claude Code automatically uses [prompt caching](https://platform.claude.com/docs/en/build-with-claude/prompt-caching) to optimize performance and reduce costs. You can disable prompt caching globally or for specific model tiers:¶

| Environment variable | Description |¶
| ------------------------------- | ---------------------------------------------------------------------------------------------- |¶
| `DISABLE_PROMPT_CACHING` | Set to `1` to disable prompt caching for all models (takes precedence over per-model settings) |¶
| `DISABLE_PROMPT_CACHING_HAIKU` | Set to `1` to disable prompt caching for Haiku models only |¶
| `DISABLE_PROMPT_CACHING_SONNET` | Set to `1` to disable prompt caching for Sonnet models only |¶
| `DISABLE_PROMPT_CACHING_OPUS` | Set to `1` to disable prompt caching for Opus models only |¶

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.¶

Unified Diff

--- a/model-config.md
+++ b/model-config.md
@@ -131,15 +131,19 @@
 
 [Effort levels](https://platform.claude.com/docs/en/build-with-claude/effort) control 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**. Opus 4.6 defaults to medium effort for Max and Team subscribers.
+Three levels persist across sessions: **low**, **medium**, and **high**. A fourth level, **max**, provides the deepest reasoning with no constraint on token spending, so responses are slower and cost more than at `high`. `max` is available on Opus 4.6 only and applies to the current session without persisting. Opus 4.6 defaults to medium effort for Max and Team subscribers.
 
 **Setting effort:**
 
+* **`/effort`**: run `/effort low`, `/effort medium`, `/effort high`, or `/effort max` to change the level, or `/effort auto` to reset to the model default
 * **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 supported on Opus 4.6 and Sonnet 4.6. The effort slider appears in `/model` when a supported model is selected. The current effort level is also displayed next to the logo and spinner (for example, "with low effort"), so you can confirm which setting is active without opening `/model`.
+* **`--effort` flag**: pass `low`, `medium`, `high`, or `max` to set the level for a single session when launching Claude Code
+* **Environment variable**: set `CLAUDE_CODE_EFFORT_LEVEL` to `low`, `medium`, `high`, `max`, or `auto`
+* **Settings**: set `effortLevel` in your settings file to `"low"`, `"medium"`, or `"high"`
+
+The environment variable takes precedence, then your configured level, then the model default.
+
+Effort is supported on Opus 4.6 and Sonnet 4.6. The effort slider appears in `/model` when a supported model is selected. The current effort level is also displayed next to the logo and spinner, for example "with low effort", so you can confirm which setting is active without opening `/model`.
 
 To disable adaptive reasoning on Opus 4.6 and Sonnet 4.6 and revert to the previous fixed thinking budget, set `CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING=1`. When disabled, these models use the fixed budget controlled by `MAX_THINKING_TOKENS`. See [environment variables](/en/env-vars).