Claude Code "advisor tool is unavailable" with Fable 5: workaround
The Fable 5 advisor fails on the first call in every session. Here is why it happens and the only workaround in v2.1.198.
TL;DR: Claude Code's "The advisor tool is unavailable" error with Fable 5 as advisor is an open bug (#73365) in v2.1.198; skip /advisor and run Fable 5 as a separate session.
The error lands on the first advisor() call of every session, fresh or long, the moment Fable 5 is set as advisor with Opus 4.8 as the main model. Switching the advisor back to Opus works in the same setup, which is the clue that separates this from the large-transcript advisor failures most existing write-ups describe. The bug is tracked but unresolved, and Claude Code gives no actionable reason for the refusal.
Why does the advisor tool say it is unavailable?
With Fable 5 set as advisor, /advisor accepts the choice and prints "Advisor set to Fable 5" with no error. The failure surfaces only when Claude calls the advisor mid-task, which returns the generic refusal "The advisor tool is unavailable. Do not try to use it again." The bug is tracked in GitHub issue #73365, filed 2026-07-02 against Claude Code v2.1.198 on Windows 11 with Opus 4.8 (claude-opus-4-8) as the main model, and it is still open with no maintainer response.
Two details make this distinct from the advisor failures you may already have read about. First, it is deterministic and does not depend on transcript size: it reproduces in a brand-new short session, not only in long transcripts. That separates it from issue #67609, which is specific to transcripts over 100K tokens. Second, /advisor accepts Fable 5 at setup, so the later refusal reads as a session or context issue. The cause is the advisor role paired with the Fable 5 model. The same generic "unavailable" surface also appears in issues #67306 and #67411, which is why the report is labeled a duplicate even though the Fable 5 trigger is its own case.
The reporter's open question, whether the account is missing a Fable 5 entitlement for the advisor role or whether this is a genuine bug, is unresolved. The account in the report has confirmed Fable 5 access as a main model, and the docs list "Opus-4.8 main + Fable advisor" as a valid pairing with v2.1.198 above the required v2.1.170. Claude Code does not distinguish the two causes in its error, which is the actual usability problem: a generic refusal with no next step.
How do you work around it?
There is no fix yet. The workaround is to stop routing Fable 5 through the /advisor handoff and run it as a standalone session instead, so the advisor role is never invoked. /advisor is one of several Claude Code slash commands, and the failure comes from the advisor tool's model pairing, not Fable 5 itself.
- Open a separate Fable 5 session. Start a new Claude Code session with Fable 5 as the main model and paste the question or context you wanted the advisor to weigh in on. This sidesteps
/advisorentirely. - Keep Opus 4.8 as your working model. In the main session, leave the main model on Opus 4.8 and the advisor unset, or set the advisor to Opus. The advisor works normally when it is Opus-on-Opus; only the Fable 5 pairing fails.
- Copy the advisor's answer back manually. Paste the Fable 5 session's output into your working session. It is less convenient than
/advisorbut it is the only path that returns Fable 5 output in v2.1.198.
If you have not yet updated, install or update Claude Code to at least v2.1.170, the floor that introduced the advisor feature. v2.1.198 is the version the bug is confirmed on, so a newer build is your only hope for a real fix. Watch issue #73365 for a maintainer reply or a "last working version" note.
How do you confirm the workaround works?
Run the advisor path and the workaround path in parallel. In session A, set /advisor fable (or pick Fable 5 from the /advisor menu) and ask Claude to consult the advisor; expect the generic refusal on the first call. In session B, start a fresh session on Fable 5 directly and ask the same question; expect a real answer. If session B returns Fable 5 output and session A refuses, you have confirmed the advisor pairing is the fault, not your account or your transcript.
What if the workaround is not enough?
Two fallbacks, in order. Switch the advisor to Opus with /advisor opus if you need the in-session advisor workflow more than you need Fable 5 specifically; it works in the same setup where Fable 5 fails. If you need Fable 5's output inside a long-running Opus session and the copy-back is too lossy, the honest answer is that there is no supported path in v2.1.198. File your own repro on #73365 or subscribe to it for a fix. This is one of several Claude Code tool-call failures where the tool refuses or desyncs mid-session, and it is cataloged in the Automation Error Index alongside other Claude Code errors.
FAQ
Why does Claude Code say "The advisor tool is unavailable. Do not try to use it again."?
It is the generic refusal Claude Code emits when the advisor tool cannot run. With Fable 5 as advisor and Opus 4.8 as main, it fires on the first advisor() call of every session in v2.1.198, regardless of transcript size. The message gives no reason, which is the core usability bug in issue #73365.
Does the Fable 5 advisor error only happen on large transcripts?
No. Unlike issue #67609, which is tied to transcripts over 100K tokens, the Fable 5 advisor failure reproduces in a brand-new short session. That independence from transcript size is what marks it as a pairing bug rather than a context-length problem.
How do I work around the Fable 5 advisor bug?
Skip /advisor and run Fable 5 as a separate session with Fable 5 as the main model, then copy the answer back. Or set the advisor to Opus, which works in the same setup. There is no real fix in v2.1.198.
Is the Fable 5 advisor error an entitlement problem or a bug?
Undetermined. The reporter's account has confirmed Fable 5 access as a main model, and the docs list Opus-4.8 main plus Fable advisor as a valid pairing. Claude Code does not distinguish a missing entitlement from a genuine bug in its error, so the root cause is still disputed in #73365.
Which Claude Code version introduced the advisor feature?
The advisor feature requires v2.1.170 or later. The Fable 5 advisor bug is confirmed on v2.1.198, which is above that floor, so updating past v2.1.170 alone does not fix it.
Does switching the advisor to Opus fix it?
Yes, as a workaround. Setting the advisor to Opus with /advisor opus works normally in the same setup where Fable 5 fails. You lose Fable 5's advisory input, but the advisor tool itself runs.