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8181
8282The advisor must be at least as capable as the main model. The accepted advisors for each main model are:
8383
84| Main model | Accepted advisors | Notes |
85| -------------------- | ---------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
86| Haiku 4.5 | Fable, Opus, Sonnet | Haiku can call the advisor but cannot act as one |
87| Sonnet 4.6 | Fable, Opus, Sonnet | |
88| Sonnet 5 | Fable, Opus, Sonnet 5 | A Sonnet 4.6 advisor is rejected |
89| Opus 4.6 | Fable, Opus, Sonnet 5 | Sonnet 5 and Opus 4.6 are ranked as equally capable, so an Opus 4.6 main accepts a Sonnet 5 advisor |
90| Opus 4.7 or later | Fable, and Opus 4.7 or later | Opus 4.7 and later Opus models are ranked as equally capable, so any of them accepts another as an advisor. An Opus 4.7 main with an Opus 4.6 or Sonnet 5 advisor is rejected |
91| Fable 5.1 or Fable 5 | Fable 5.1 or Fable 5 | An Opus or Sonnet advisor is rejected |
84| Main model | Accepted advisors | Notes |
85| -------------------- | ---------------------------------- | ------------------------------------------------------------------------------------------------------------------- |
86| Haiku 4.5 | Fable, Opus, Sonnet | Haiku can call the advisor but cannot act as one |
87| Sonnet 4.6 | Fable, Opus, Sonnet | |
88| Sonnet 5 | Fable, Opus 4.7 or later, Sonnet 5 | A Sonnet 4.6 advisor is rejected, and requests with an Opus 4.6 advisor fail with an API error |
89| Opus 4.6 | Fable, Opus, Sonnet 5 | A Sonnet 4.6 advisor is rejected |
90| Opus 4.7 or Opus 4.8 | Fable, and Opus 4.7 or later | An Opus 4.6 or Sonnet advisor is rejected |
91| Opus 5 | Fable, Opus 5 | An Opus 4.6 or Sonnet advisor is rejected, and requests with an Opus 4.7 or Opus 4.8 advisor fail with an API error |
92| Fable 5 | Fable 5.1 or Fable 5 | An Opus or Sonnet advisor is rejected |
93| Fable 5.1 | Fable 5.1 | An Opus or Sonnet advisor is rejected, and requests with a Fable 5 advisor fail with an API error |
9294
9395Fable 5.1 requires Claude Code v2.1.257 or later. Both Fable models require [Fable access](/docs/en/model-config#work-with-fable).
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9698
9799Subagents inherit the configured advisor and apply the same pairing check against their own model.
98100
99Claude Code validates the pairing before sending a request:
101Claude Code validates the pairing before sending a request, and the API validates it again:
100102
101* If the advisor is less capable than the main model, the advisor is not attached 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.
103* 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.
104* For an advisor the table lists as failing with an API error, Claude Code attaches it and the API refuses it. Every request fails with `'<advisor model>' cannot be used as an advisor when the request model is '<main model>'` until you change the advisor with `/advisor` or turn it off.
102105* If the main model or the advisor is a model Claude Code does not recognize, the advisor is not attached.
103106
104107### Fable advisor and usage credits