Escalate hard decisions with the advisor tool Anthropic released an experimental advisor tool for Claude Code that lets users designate a separate model to consult on hard decisions during long, multi-step tasks, with the advisor model set via the /advisor command, the advisorModel setting, or the --advisor flag. The tool requires the Anthropic API and is unavailable on Amazon Bedrock, Claude Platform on AWS, Google Cloud's Agent Platform, and Microsoft Foundry, and it requires Claude Code v2.1.260 or later for non-interactive mode, the Agent SDK, the desktop app, and Remote Control. Anthropic warns that behavior, pricing, and availability may change, and on some plans using Fable as the advisor requires one-time consent to bill Fable usage to usage credits. The advisor tool is experimental and requires the Anthropic API. It is not available on Amazon Bedrock, Claude Platform on AWS, Google Cloud’s Agent Platform, or Microsoft Foundry. Behavior, pricing, and availability may change. server tool https://platform.claude.com/docs/en/agents-and-tools/tool-use/advisor-tool , available to both subscription and API-billed accounts. You choose which model acts as the advisor, and Claude decides when to call it. This page covers how to enable the advisor, which model pairings are accepted, what Claude shows during a consultation, and how advisor usage is billed. When to use the advisor The 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. It 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 https://code.claude.com/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. Enable the advisor You can set the advisor model in three ways: - /advisor command : set or change the advisor mid-session and save it as your default - advisorModel setting : configure a persistent default in your settings file https://code.claude.com/docs/en/settings - --advisor flag : set the advisor for a single session at launch 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 . On some plans, Fable as the advisor also needs your one-time consent to bill Fable usage to usage credits https://code.claude.com/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 . Use the /advisor command Run /advisor without arguments to open a picker listing the available advisor models, or pass the model directly: 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 lists as applying to the current session only. The command also works where there is no terminal picker: in https://code.claude.com/docs/en/settings-reference advisormodel advisorModel entry non-interactive mode https://code.claude.com/docs/en/headless with -p , in the Agent SDK, in the desktop app, and over Remote Control https://code.claude.com/docs/en/remote-control . This requires Claude Code v2.1.260 or later. On those surfaces: - Run /advisor with no argument to print the current advisor model and the aliases it accepts. - Run /advisor with a model, such as /advisor opus , to set it. - Run /advisor off to turn it off. allowlist excludes. To use the advisor, pick an allowed model with https://code.claude.com/docs/en/model-config restrict-model-selection availableModels /advisor . Claude 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 . If the API already refused the saved advisor in the current conversation, it stays off until https://code.claude.com/docs/en/model-config setting-your-model /model /clear or /compact , even after you switch models. On some plans, Fable as the advisor also needs your one-time consent to bill Fable usage to usage credits https://code.claude.com/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 . Set advisorModel in settings To configure the advisor as a default without opening a session, set it in your settings file: Use the --advisor flag To set the advisor for a single session without changing your saved setting, launch with the flag: advisorModel setting for that session. It doesn’t list --advisor in claude --help . Claude Code exits with an error at launch if: - The session’s main model doesn’t support the advisor - The requested model, such as Haiku, can’t act as an advisor - Your organization’s availableModels https://code.claude.com/docs/en/model-config restrict-model-selection allowlist excludes the requested model - You requested Fable and your account still requires the usage-credits consent fable-advisor-and-usage-credits background session https://code.claude.com/docs/en/agent-view with --advisor and one of these applies, Claude Code starts the session without the advisor instead of exiting. Choose an advisor model The advisor must be at least as capable as the main model. The accepted advisors for each main model are: Fable 5.1 requires Claude Code v2.1.257 or later. Both Fable models require Fable access https://code.claude.com/docs/en/model-config work-with-fable . Set the advisor as fable , opus , or sonnet . These aliases resolve to Claude Code’s built-in default version 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 . Subagents inherit the configured advisor and apply the same pairing check against their own model. Claude Code validates the pairing before sending a request, and the API validates it again: - For an advisor the table lists as rejected, Claude Code doesn’t attach it to the main model’s requests. The /advisor command output and a notification show this. Subagents whose own model satisfies the pairing may still use the advisor. - For an advisor the table lists as refused by the API, Claude Code attaches it and the API refuses it. Claude Code then resends that request without the advisor, and the rest of the conversation runs without one, so you see no error and get no advisor calls. Pick an accepted advisor with /advisor ; the change takes effect after /clear or /compact and in new sessions. - If the main model or the advisor is a model Claude Code does not recognize, the advisor is not attached. Fable advisor and usage credits On 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 https://code.claude.com/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. Before 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 . To accept the consent, run /model fable and choose to continue on Fable. Claude Code records the consent and saves Fable as your selected model https://code.claude.com/docs/en/model-config default-model-setting . Then select Fable as the advisor. Common model pairings Any accepted pairing works. These combinations balance cost against capability in different ways: When Claude consults the advisor Claude decides when to call the advisor. It tends to consult before committing to an approach, when an error keeps recurring, and before declaring a task done, but the timing is model-driven rather than rule-based. You can ask for a consultation in your prompt the same way you would request any tool, for example consult the advisor before you continue . There is no setting to cap or force advisor calls; if you want Claude to consult more or less often during a task, say so in your instructions. What you see during a session When Claude calls the advisor, the transcript shows an Advising line with the advisor model name while the call is in progress. When the result returns, the line reports whether the advisor gave guidance: - Reviewed : the line confirms that the advisor has reviewed the conversation. When the advisor returned readable guidance, press Ctrl+O to read it. - Declined : the line reads Advisor declined to advise on this request . If the advisor gave a reason, press Ctrl+O to read it. - Unavailable : the advisor call failed, and the line reads Advisor unavailable