[Bug] Advisor tool: Fable 5 returns "unavailable" error while Opus 4.8 works

Bug Description
Advisor tool: Fable 5 pairing fails with "unavailable" error, Opus 4.8 works fine (personal Claude Max 20x account)

Setup:

• Claude Code v2.1.207
• Account: personal Anthropic account, Claude Max 20x plan
• Main model: Sonnet 5
• CLAUDE_CODE_DISABLE_ADVISOR_TOOL is not set

Steps:

1. Ran /advisor and set Fable 5 as advisor → CLI confirms "Advisor set to Fable 5," but the advisor tool call still returns "The advisor tool is unavailable."
2. Ran /advisor and set Opus 4.8 as advisor instead (same session, same main model, no other config change) → advisor tool call succeeds and returns a normal response immediately.

Expected: Fable 5 should work as advisor for a Sonnet 5 main model per the docs (https://code.claude.com/docs/en/advisor).

Actual: Fable 5 pairing consistently fails as "unavailable," while Opus 4.8 pairing works with no other change.

Note: the docs mention Fable 5 access needing to be provisioned "for your organization," but this is a personal Max 20x account with no organization involved — so it's unclear whether/how Fable 5 access is supposed to be granted on individual subscription plans, or if this is a gap in provisioning/documentation for personal accounts.

Environment Info

• Platform: darwin
• Terminal: xterm-256color
• Version: 2.1.207
• Feedback ID: 80a17071-f088-4c99-8088-7d3c88894a0d

Errors

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