Escalate hard decisions with the advisor tool changedadvisor
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1717The advisor fits long, multi-step tasks where most turns are routine but plan quality determines the outcome. Examples include large refactors, debugging sessions where an error keeps recurring, and tasks you want independently checked before Claude declares them done.
1818
19It adds less value on short tasks where there is little to plan, or on work where every turn needs the strongest model. For those, [switch the main model](/docs/en/model-config#setting-your-model) instead, or see [how the advisor compares with opusplan and subagents](#compare-with-related-features) for other ways to get a second opinion.
19It adds less value on short tasks where there is little to plan, or on work where every turn needs the strongest model. For those, [switch the main model](/docs/en/model-config.md#setting-your-model) instead, or see [how the advisor compares with opusplan and subagents](#compare-with-related-features) for other ways to get a second opinion.
2020
2121## Enable the advisor
2222
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2323You can set the advisor model in three ways:
2424
2525* **`/advisor` command**: set or change the advisor mid-session and save it as your default
26* **`advisorModel` setting**: configure a persistent default in your [settings file](/docs/en/settings)
26* **`advisorModel` setting**: configure a persistent default in your [settings file](/docs/en/settings.md)
2727* **`--advisor` flag**: set the advisor for a single session at launch
2828
2929Each of these enables the advisor for sessions whose main model [supports it](#choose-an-advisor-model). After the session starts, Claude Code shows an `Advisor Tool (experimental) is on and may use more tokens · /advisor` notification. To stop using the advisor, see [Turn the advisor off](#turn-the-advisor-off).
3030
31On some plans, Fable as the advisor also needs your one-time [consent to bill Fable usage to usage credits](/docs/en/model-config#fable-and-usage-credits). For what happens before you have given that consent, see [Fable advisor and usage credits](#fable-advisor-and-usage-credits).
31On some plans, Fable as the advisor also needs your one-time [consent to bill Fable usage to usage credits](/docs/en/model-config.md#fable-and-usage-credits). For what happens before you have given that consent, see [Fable advisor and usage credits](#fable-advisor-and-usage-credits).
3232
3333### Use the `/advisor` command
3434
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4040
4141The command confirms with `Advisor set to` followed by the advisor model name. Your selection is saved to `advisorModel` in your user settings and persists across sessions, except in the cases the [`advisorModel` entry](/docs/en/settings-reference#advisormodel) lists as applying to the current session only.
4242
43The command also works where there is no terminal picker: in [non-interactive mode](/docs/en/headless) with `-p`, in the Agent SDK, in the desktop app, and over [Remote Control](/docs/en/remote-control). This requires Claude Code v2.1.260 or later. On those surfaces:
43The command also works where there is no terminal picker: in [non-interactive mode](/docs/en/headless.md) with `-p`, in the Agent SDK, in the desktop app, and over [Remote Control](/docs/en/remote-control.md). This requires Claude Code v2.1.260 or later. On those surfaces:
4444
4545* Run `/advisor` with no argument to print the current advisor model and the aliases it accepts.
4646* Run `/advisor` with a model, such as `/advisor opus`, to set it.
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5050
5151Claude Code still saves an advisor that your current main model doesn't support. That advisor activates after you switch to a [compatible main model](#choose-an-advisor-model) with [`/model`](/docs/en/model-config#setting-your-model). If the API already refused the saved advisor in the current conversation, it stays off until `/clear` or `/compact`, even after you switch models.
5252
53On some plans, Fable as the advisor also needs your one-time [consent to bill Fable usage to usage credits](/docs/en/model-config#fable-and-usage-credits). For what `/advisor fable` does before you have given that consent, see [Fable advisor and usage credits](#fable-advisor-and-usage-credits).
53On some plans, Fable as the advisor also needs your one-time [consent to bill Fable usage to usage credits](/docs/en/model-config.md#fable-and-usage-credits). For what `/advisor fable` does before you have given that consent, see [Fable advisor and usage credits](#fable-advisor-and-usage-credits).
5454
5555### Set `advisorModel` in settings
5656
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7777* Your organization's [`availableModels`](/docs/en/model-config#restrict-model-selection) allowlist excludes the requested model
7878* You requested Fable and your account still requires the [usage-credits consent](#fable-advisor-and-usage-credits)
7979
80If you start a [background session](/docs/en/agent-view) with `--advisor` and one of these applies, Claude Code starts the session without the advisor instead of exiting.
80If you start a [background session](/docs/en/agent-view.md) with `--advisor` and one of these applies, Claude Code starts the session without the advisor instead of exiting.
8181
8282If the model you pass can act as an advisor but [ranks below your main model](#choose-an-advisor-model), the session starts whether or not it's a background session. Your main model then runs without the advisor.
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9797| Fable 5 | Fable 5.1 or Fable 5 |
9898| Fable 5.1 | Fable 5.1 |
9999
100Fable 5.1 requires Claude Code v2.1.257 or later. Fable models require [Fable access](/docs/en/model-config#work-with-fable). Sonnet 5.5 as the advisor for an Opus 4.7 or Opus 4.8 main model requires Claude Code v2.1.287 or later. Haiku 5.5 as the main model or as the advisor requires Claude Code v2.1.293 or later.
100Fable 5.1 requires Claude Code v2.1.257 or later. Fable models require [Fable access](/docs/en/model-config.md#work-with-fable). Sonnet 5.5 as the advisor for an Opus 4.7 or Opus 4.8 main model requires Claude Code v2.1.287 or later. Haiku 5.5 as the main model or as the advisor requires Claude Code v2.1.293 or later.
101101
102Set the advisor as `fable`, `opus`, or `sonnet`. These aliases resolve to Claude Code's [built-in default version](/docs/en/model-config#model-aliases) for each model family, which advances with new Claude Code releases. You can also pass a full model ID such as `claude-opus-5-5` or `claude-haiku-5-5`. Haiku 4.5 can call the advisor but can't act as one.
102Set the advisor as `fable`, `opus`, or `sonnet`. These aliases resolve to Claude Code's [built-in default version](/docs/en/model-config.md#model-aliases) for each model family, which advances with new Claude Code releases. You can also pass a full model ID such as `claude-opus-5-5` or `claude-haiku-5-5`. Haiku 4.5 can call the advisor but can't act as one.
103103
104104Subagents inherit the configured advisor and apply the same pairing check against their own model.
105105
106106Claude Code validates the pairing before sending a request, and the API validates it again:
107107
108* For an advisor that ranks below the main model, Claude Code doesn't attach it to the main model's requests. The `/advisor` command output and a notification show this; see [Advisor is less capable than the current main model](/docs/en/errors#advisor-is-less-capable-than-the-current-main-model). Subagents whose own model satisfies the pairing may still use the advisor.
108* For an advisor that ranks below the main model, Claude Code doesn't attach it to the main model's requests. The `/advisor` command output and a notification show this; see [Advisor is less capable than the current main model](/docs/en/errors.md#advisor-is-less-capable-than-the-current-main-model). Subagents whose own model satisfies the pairing may still use the advisor.
109109* If the API refuses the pairing of an advisor that Claude Code attached, Claude Code resends that request without the advisor. The conversation continues without one, so you see no error and get no advisor calls. If you then pick a different advisor with `/advisor`, it takes effect after `/clear` or `/compact` and in new sessions.
110110* If the main model or the advisor is a model Claude Code does not recognize, the advisor is not attached.
111111
112112### Fable advisor and usage credits
113113
114On some plans, Fable usage bills to usage credits, and Fable as the advisor bills the same way. If your account requires the [one-time consent to bill Fable usage to usage credits](/docs/en/model-config#fable-and-usage-credits), Claude Code asks for it when you select a Fable model with `/model` and doesn't apply Fable as the advisor until you have accepted that consent.
114On some plans, Fable usage bills to usage credits, and Fable as the advisor bills the same way. If your account requires the [one-time consent to bill Fable usage to usage credits](/docs/en/model-config.md#fable-and-usage-credits), Claude Code asks for it when you select a Fable model with `/model` and doesn't apply Fable as the advisor until you have accepted that consent.
115115
116116Before you have accepted it, Claude Code doesn't save Fable as the advisor when you type `/advisor fable` or pick Fable in the `/advisor` picker. It points you to `/model fable` instead. With `claude --advisor fable`, Claude Code exits at launch with a message that points to `/model fable`. In a [background session](#use-the-advisor-flag), it starts the session without the advisor instead of exiting. With Fable already saved as your `advisorModel`, Claude Code sends requests without the advisor. In an interactive session whose main model supports the advisor, it also shows a notification that points to `/model fable`.
117117
118To accept the consent, run `/model fable` and choose to continue on Fable. Claude Code records the consent and [saves Fable as your selected model](/docs/en/model-config#default-model-setting). Then select Fable as the advisor.
118To accept the consent, run `/model fable` and choose to continue on Fable. Claude Code records the consent and [saves Fable as your selected model](/docs/en/model-config.md#default-model-setting). Then select Fable as the advisor.
119119
120120### Common model pairings
121121
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153153When Claude calls the advisor, the advisor model reads the conversation, so each call consumes tokens at the advisor model's rates in addition to your main model's usage. How those advisor tokens are billed depends on how you pay:
154154
155155* **API billing**: you pay the advisor model's input and output rates for advisor tokens
156* **Subscription plans**: advisor usage counts toward your plan's usage limits, except that a Fable advisor bills to [usage credits](/docs/en/model-config#fable-and-usage-credits) on plans where Fable usage does
156* **Subscription plans**: advisor usage counts toward your plan's usage limits, except that a Fable advisor bills to [usage credits](/docs/en/model-config.md#fable-and-usage-credits) on plans where Fable usage does
157157
158158If your account requires the usage-credits consent, a Fable advisor bills nothing before you give it, because Claude Code [doesn't apply the selection](#fable-advisor-and-usage-credits) until then.
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163163
164164## Impact on prompt caching
165165
166Enabling or disabling the advisor mid-session does not invalidate your main model's [prompt cache](/docs/en/prompt-caching). Unlike [switching models](/docs/en/prompt-caching#switching-models), toggling `/advisor` keeps the cached prefix intact, and the advisor's returned guidance is cached as part of the transcript on later turns.
166Enabling or disabling the advisor mid-session does not invalidate your main model's [prompt cache](/docs/en/prompt-caching.md). Unlike [switching models](/docs/en/prompt-caching.md#switching-models), toggling `/advisor` keeps the cached prefix intact, and the advisor's returned guidance is cached as part of the transcript on later turns.
167167
168168The advisor model's own read of the conversation is not cached. Each advisor call processes the full transcript anew, with no reuse between calls.
169169
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171171
172172The advisor tool requires all of the following:
173173
174* **Anthropic API only**: the advisor is a server-executed tool. It is not available on Amazon Bedrock, Claude Platform on AWS, Google Cloud's Agent Platform, or Microsoft Foundry. Through an [LLM gateway](/docs/en/llm-gateway) configured with `ANTHROPIC_BASE_URL`, availability depends on whether the gateway forwards the request intact to the Anthropic API. If the gateway or its upstream doesn't recognize the advisor tool, see [Automatic retry and error forwarding](/docs/en/llm-gateway-protocol#automatic-retry-and-error-forwarding) for how Claude Code responds.
174* **Anthropic API only**: the advisor is a server-executed tool. It is not available on Amazon Bedrock, Claude Platform on AWS, Google Cloud's Agent Platform, or Microsoft Foundry. Through an [LLM gateway](/docs/en/llm-gateway) configured with `ANTHROPIC_BASE_URL`, availability depends on whether the gateway forwards the request intact to the Anthropic API. If the gateway or its upstream doesn't recognize the advisor tool, see [Automatic retry and error forwarding](/docs/en/llm-gateway-protocol.md#automatic-retry-and-error-forwarding) for how Claude Code responds.
175175* **Supported main model**: Fable, Opus 4.6 or later, Sonnet 4.6 or later, Haiku 4.5, or Haiku 5.5. See [Choose an advisor model](#choose-an-advisor-model) for which advisors each accepts.
176* **Feature-flag fetching**: Claude Code turns the advisor on through a feature flag it fetches from Anthropic. In a session where a variable that turns flag fetching off is set, such as `DISABLE_TELEMETRY`, the advisor stays off. See [Features that need feature-flag fetching](/docs/en/env-vars#features-that-need-feature-flag-fetching).
176* **Feature-flag fetching**: Claude Code turns the advisor on through a feature flag it fetches from Anthropic. In a session where a variable that turns flag fetching off is set, such as `DISABLE_TELEMETRY`, the advisor stays off. See [Features that need feature-flag fetching](/docs/en/env-vars.md#features-that-need-feature-flag-fetching).
177177
178178## Turn the advisor off
179179
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183183/advisor off
184184```
185185
186To disable the advisor tool entirely, set `CLAUDE_CODE_DISABLE_ADVISOR_TOOL=1`. The `/advisor` command becomes unavailable and any configured `advisorModel` is ignored. The `--advisor` flag is accepted but has no effect. See [Environment variables](/docs/en/env-vars).
186To disable the advisor tool entirely, set `CLAUDE_CODE_DISABLE_ADVISOR_TOOL=1`. The `/advisor` command becomes unavailable and any configured `advisorModel` is ignored. The `--advisor` flag is accepted but has no effect. See [Environment variables](/docs/en/env-vars.md).
187187
188188## Compare with related features
189189
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193193| - | - | - |
194194| Advisor tool | At decision points mid-task | Claude calls it when it needs guidance |
195195| [`opusplan`](/docs/en/model-config#opusplan-model-setting) | During plan mode when [allowed by `availableModels`](/docs/en/model-config#restrict-model-selection), then switches to Sonnet for execution | You enter plan mode |
196| [Subagents](/docs/en/sub-agents#choose-a-model) with `model` set | For the entire delegated subtask | Claude delegates, or you invoke the subagent |
196| [Subagents](/docs/en/sub-agents.md#choose-a-model) with `model` set | For the entire delegated subtask | Claude delegates, or you invoke the subagent |
197197| [`/model`](/docs/en/model-config#setting-your-model) | From the next request onward | You switch models |
198198
199199## See also
200200
201* [Model configuration](/docs/en/model-config): switch models, set effort levels, and use `opusplan`
202* [Manage costs effectively](/docs/en/costs): track token usage across models
201* [Model configuration](/docs/en/model-config.md): switch models, set effort levels, and use `opusplan`
202* [Manage costs effectively](/docs/en/costs.md): track token usage across models
203203* [Advisor tool in the Claude API](https://platform.claude.com/docs/en/agents-and-tools/tool-use/advisor-tool): understand the underlying server tool, or use it directly from the Messages API
204204* [The advisor strategy](https://claude.com/blog/the-advisor-strategy): why pairing a fast main model with a stronger advisor works
205205
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