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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
    • Bedrock: an inference profile ARN
    • Foundry: a deployment name
    • Vertex: a version name

    ANTHROPIC_BASE_URL changes where requests are sent, not which model answers them. To route Claude through an LLM gateway, see LLM gateway configuration.

Model aliases

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

Model alias Behavior
default Special value that clears any model override and reverts to the recommended model for your account type. Not itself a model alias
best Uses the most capable available model, currently equivalent to opus
sonnet Uses the latest Sonnet model for daily coding tasks
opus Uses the latest Opus model 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 for long sessions
opus[1m] Uses Opus with a 1 million token context window for long sessions
opusplan Special mode that uses opus during plan mode, then switches to sonnet for execution

On the Anthropic API and Claude Platform on AWS, opus resolves to Opus 4.7 and sonnet resolves to Sonnet 4.6. On Bedrock, Vertex, and Foundry, opus resolves to Opus 4.6 and sonnet resolves to Sonnet 4.5; newer models are available on those providers by selecting the full model name explicitly or setting ANTHROPIC_DEFAULT_OPUS_MODEL or ANTHROPIC_DEFAULT_SONNET_MODEL.

Aliases point to the recommended version for your provider and update over time. To pin to a specific version, use the full model name (for example, claude-opus-4-7) or set the corresponding environment variable like ANTHROPIC_DEFAULT_OPUS_MODEL.

Opus 4.7 requires Claude Code v2.1.111 or later. Run claude update to upgrade.

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 immediately, or run /model with no argument to open the picker. The picker asks for confirmation when the conversation has prior output, since the next response re-reads the full history without cached context
  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.

As of v2.1.144, /model applies to the current session only and is not written to settings. To save your choice as the default for new sessions, press d on the highlighted row in the picker, which writes the model field in your user settings. Managed settings take precedence and reapply on the next launch.

The --model flag and ANTHROPIC_MODEL environment variable also apply only to the session you launch with them. To run different models in different terminals at the same time, launch each one with its own --model flag rather than switching with /model.

Resumed sessions started with claude --resume, --continue, or the /resume picker keep the model they were using when the transcript was saved, regardless of the current model setting. If that model has been retired, the session falls through to the normal precedence order. This prevents another session's /model choice from changing the model on resume.

When the active model at startup comes from project or managed settings rather than your own selection, the startup header shows which settings file set it. Run /model to override for the current session.

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, 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

The model setting is an initial selection, not enforcement. It sets which model is active when a session starts, but users can still open /model and pick Default, which resolves to the system default for their tier regardless of what model is set to.

To fully control the model experience, combine three settings:

  • availableModels: restricts which named models users can switch to
  • model: sets the initial model selection when a session starts
  • ANTHROPIC_DEFAULT_SONNET_MODEL / ANTHROPIC_DEFAULT_OPUS_MODEL / ANTHROPIC_DEFAULT_HAIKU_MODEL: control what the Default option and the sonnet, opus, and haiku aliases resolve to

This example starts users on Sonnet 4.5, limits the picker to Sonnet and Haiku, and pins Default to resolve to Sonnet 4.5 rather than the latest release:

{
  "model": "claude-sonnet-4-5",
  "availableModels": ["claude-sonnet-4-5", "haiku"],
  "env": {
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "claude-sonnet-4-5"
  }
}

Without the env block, a user who selects Default in the picker would get the latest Sonnet release, bypassing the version pin in model and availableModels.

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.

Mantle model IDs

When the Bedrock Mantle endpoint is enabled, entries in availableModels that start with anthropic. are added to the /model picker as custom options and routed to the Mantle endpoint. This is an exception to the alias-only matching described in Pin models for third-party deployments. The setting still restricts the picker to listed entries, so include the standard aliases alongside any Mantle IDs.

Special model behavior

default model setting

The behavior of default depends on your account type:

  • Max and Team Premium: defaults to Opus 4.7
  • Pro, Team Standard, Enterprise, and Anthropic API: defaults to Sonnet 4.6
  • Bedrock, Vertex, and Foundry: defaults to Sonnet 4.5

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

On April 23, 2026, the default model for Enterprise pay-as-you-go and Anthropic API users will change to Opus 4.7. To keep a different default, set ANTHROPIC_MODEL or the model field in server-managed settings.

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.

The plan-mode Opus phase runs with the standard 200K context window. The automatic 1M upgrade described in Extended context applies to the opus model setting and does not extend to opusplan.

Adjust effort level

Effort levels control adaptive reasoning, which lets the model decide whether and how much to think on each step based on task complexity. Lower effort is faster and cheaper for straightforward tasks, while higher effort provides deeper reasoning for complex problems.

Effort is supported on Opus 4.7, Opus 4.6, and Sonnet 4.6. The available levels depend on the model:

Model Levels
Opus 4.7 low, medium, high, xhigh, max
Opus 4.6 and Sonnet 4.6 low, medium, high, max

If you set a level the active model does not support, Claude Code falls back to the highest supported level at or below the one you set. For example, xhigh runs as high on Opus 4.6.

As of v2.1.117, the default effort is xhigh on Opus 4.7 and high on Opus 4.6 and Sonnet 4.6.

When you first run Opus 4.7, Claude Code applies xhigh even if you previously set a different effort level for Opus 4.6 or Sonnet 4.6. Run /effort again to choose a different level after switching.

low, medium, high, and xhigh persist across sessions. max provides the deepest reasoning with no constraint on token spending and applies to the current session only, except when set through the CLAUDE_CODE_EFFORT_LEVEL environment variable.

Choose an effort level

Each level trades token spend against capability. The default suits most coding tasks; adjust when you want a different balance.

Level When to use it
low Reserve for short, scoped, latency-sensitive tasks that are not intelligence-sensitive
medium Reduces token usage for cost-sensitive work that can trade off some intelligence
high Balances token usage and intelligence. Use as a minimum for intelligence-sensitive work, or to reduce token spend relative to xhigh
xhigh Best results for most coding and agentic tasks. Recommended default on Opus 4.7
max Can improve performance on demanding tasks but may show diminishing returns and is prone to overthinking. Test before adopting broadly

The effort scale is calibrated per model, so the same level name does not represent the same underlying value across models.

Use ultrathink for one-off deep reasoning

Include ultrathink anywhere in your prompt to request deeper reasoning on that turn without changing your session effort setting. Claude Code recognizes the keyword and adds an in-context instruction. The effort level sent to the API is unchanged. Other phrases such as "think", "think hard", and "think more" are passed through as ordinary prompt text and are not recognized as keywords.

Set the effort level

You can change effort through any of the following:

  • /effort: run /effort with no arguments to open an interactive slider, /effort followed by a level name to set it directly, 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 a level name to set it for a single session when launching Claude Code
  • Environment variable: set CLAUDE_CODE_EFFORT_LEVEL to a level name or auto
  • Settings: set effortLevel to low, medium, high, or xhigh in your settings file. max is session-only and is not accepted here
  • Skill and subagent frontmatter: set effort in a skill or subagent markdown file to override the effort level when that skill or subagent runs

The environment variable takes precedence over all other methods, then your configured level, then the model default. Frontmatter effort applies when that skill or subagent is active, overriding the session level but not the environment variable.

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.

Adaptive reasoning and fixed thinking budgets

Adaptive reasoning makes thinking optional on each step, so Claude can respond faster to routine prompts and reserve deeper thinking for steps that benefit from it. If you want Claude to think more or less often than the current level produces, you can say so directly in your prompt or in CLAUDE.md; the model responds to that guidance within its effort setting.

Opus 4.7 always uses adaptive reasoning. The fixed thinking budget mode and CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING do not apply to it.

On Opus 4.6 and Sonnet 4.6, you can set CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING=1 to revert to the previous fixed thinking budget controlled by MAX_THINKING_TOKENS. See environment variables.

Extended thinking

Extended thinking is the reasoning Claude emits before responding. On models that support adaptive reasoning, the effort level is the primary control for how much thinking happens; the settings below turn thinking on or off and control how it displays.

Control How to set it
Toggle for the current session Press Option+T on macOS or Alt+T on Windows and Linux
Set the global default Run /config and toggle thinking mode. Saved as alwaysThinkingEnabled in ~/.claude/settings.json
Disable regardless of effort Set MAX_THINKING_TOKENS=0. Other values apply only with a fixed thinking budget

Thinking output is collapsed by default. Press Ctrl+O to toggle verbose mode and see the reasoning as gray italic text. Interactive sessions on the Anthropic API receive redacted thinking blocks by default, so set showThinkingSummaries: true in settings if you want the full summaries available when you expand. You are charged for all thinking tokens generated, even when collapsed or redacted.

Extended context

Opus 4.7, Opus 4.6, and Sonnet 4.6 support a 1 million 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. Sonnet with 1M context is not part of the automatic upgrade and requires usage credits on every subscription plan, including Max.

Plan Opus with 1M context Sonnet with 1M context
Max, Team, and Enterprise Included with subscription Requires usage credits
Pro Requires usage credits Requires usage credits
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.

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 usage credits, tokens are billed to usage credits.

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:

# 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-4-7[1m]

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.

Add a custom model option

Use ANTHROPIC_CUSTOM_MODEL_OPTION to add a single custom entry to the /model picker without replacing the built-in aliases. This is useful for testing model IDs that Claude Code does not list by default. For LLM gateway deployments, Claude Code can populate the picker from the gateway's /v1/models endpoint when CLAUDE_CODE_ENABLE_GATEWAY_MODEL_DISCOVERY=1 is set, so this variable is needed only when discovery is disabled or does not return the model you want. See LLM gateway model selection.

This example sets all three variables to make a gateway-routed Opus deployment selectable:

export ANTHROPIC_CUSTOM_MODEL_OPTION="my-gateway/claude-opus-4-7"
export ANTHROPIC_CUSTOM_MODEL_OPTION_NAME="Opus via Gateway"
export ANTHROPIC_CUSTOM_MODEL_OPTION_DESCRIPTION="Custom deployment routed through the internal LLM gateway"

The custom entry appears at the bottom of the /model picker. ANTHROPIC_CUSTOM_MODEL_OPTION_NAME and ANTHROPIC_CUSTOM_MODEL_OPTION_DESCRIPTION are optional. If omitted, the model ID is used as the name and the description defaults to Custom model (<model-id>).

Claude Code skips validation for the model ID set in ANTHROPIC_CUSTOM_MODEL_OPTION, so you can use any string your API endpoint accepts.

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
CLAUDE_CODE_SUBAGENT_MODEL The model to use for all subagents and agent teams. Overrides the per-invocation model parameter and the subagent definition's model frontmatter. Set to inherit to use normal model resolution instead

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, Vertex AI, Foundry, or Claude Platform on AWS, 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 that isn't yet enabled in a user's account, Bedrock and Vertex AI users see a notice and fall back to the previous version for that session, while Foundry users see errors because Foundry has no equivalent startup check.

Set all three model environment variables to specific version IDs as part of your initial setup. Pinning lets you control when your users move to a new model.

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-4-7'
Vertex AI export ANTHROPIC_DEFAULT_OPUS_MODEL='claude-opus-4-7'
Foundry export ANTHROPIC_DEFAULT_OPUS_MODEL='claude-opus-4-7'

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. To upgrade users to a new model version, update these environment variables and redeploy.

To enable extended context for a pinned model, append [1m] to the model ID in ANTHROPIC_DEFAULT_OPUS_MODEL or ANTHROPIC_DEFAULT_SONNET_MODEL:

export ANTHROPIC_DEFAULT_OPUS_MODEL='claude-opus-4-7[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.

  • The suffix is read per variable, not per model. On Bedrock, Vertex, and Foundry, a model ID without [1m] in one variable uses 200K context even if another variable sets the same model with the suffix.

    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.

Customize pinned model display and capabilities

When you pin a model on a third-party provider, the provider-specific ID appears as-is in the /model picker and Claude Code may not recognize which features the model supports. You can override the display name and declare capabilities with companion environment variables for each pinned model.

These variables take effect on third-party providers such as Bedrock, Vertex AI, and Foundry. The _NAME and _DESCRIPTION variables also take effect when ANTHROPIC_BASE_URL points to an LLM gateway. They have no effect when connecting directly to api.anthropic.com.

Environment variable Description
ANTHROPIC_DEFAULT_OPUS_MODEL_NAME Display name for the pinned Opus model in the /model picker. Defaults to the model ID when not set
ANTHROPIC_DEFAULT_OPUS_MODEL_DESCRIPTION Display description for the pinned Opus model in the /model picker. Defaults to Custom Opus model when not set
ANTHROPIC_DEFAULT_OPUS_MODEL_SUPPORTED_CAPABILITIES Comma-separated list of capabilities the pinned Opus model supports

The same _NAME, _DESCRIPTION, and _SUPPORTED_CAPABILITIES suffixes are available for ANTHROPIC_DEFAULT_SONNET_MODEL, ANTHROPIC_DEFAULT_HAIKU_MODEL, and ANTHROPIC_CUSTOM_MODEL_OPTION.

Claude Code enables features like effort levels and extended thinking by matching the model ID against known patterns. Provider-specific IDs such as Bedrock ARNs or custom deployment names often don't match these patterns, leaving supported features disabled. Set _SUPPORTED_CAPABILITIES to tell Claude Code which features the model actually supports:

Capability value Enables
effort Effort levels and the /effort command
xhigh_effort {/* min-version: 2.1.111 */}The xhigh effort level
max_effort The max effort level
thinking Extended thinking
adaptive_thinking Adaptive reasoning that dynamically allocates thinking based on task complexity
interleaved_thinking Thinking between tool calls

When _SUPPORTED_CAPABILITIES is set, listed capabilities are enabled and unlisted capabilities are disabled for the matching pinned model. When the variable is unset, Claude Code falls back to built-in detection based on the model ID.

This example pins Opus to a Bedrock custom model ARN, sets a friendly name, and declares its capabilities:

export ANTHROPIC_DEFAULT_OPUS_MODEL='arn:aws:bedrock:us-east-1:123456789012:custom-model/abc'
export ANTHROPIC_DEFAULT_OPUS_MODEL_NAME='Opus via Bedrock'
export ANTHROPIC_DEFAULT_OPUS_MODEL_DESCRIPTION='Opus 4.7 routed through a Bedrock custom endpoint'
export ANTHROPIC_DEFAULT_OPUS_MODEL_SUPPORTED_CAPABILITIES='effort,xhigh_effort,max_effort,thinking,adaptive_thinking,interleaved_thinking'

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:

{
  "modelOverrides": {
    "claude-opus-4-7": "arn:aws:bedrock:us-east-2:123456789012:application-inference-profile/opus-prod",
    "claude-opus-4-6": "arn:aws:bedrock:us-east-2:123456789012:application-inference-profile/opus-46-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. 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 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 the 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

To change the cache TTL or learn what triggers a cache miss, see How Claude Code uses prompt caching.