Cline with Anthropic `claude-fable-5` and Adaptive Thinking "None": every task fails with `"thinking.type.disabled" is not supported for this model.`

Context

Source(s): https://github.com/cline/cline/issues/13203 Status: reported working by source, not reproduced by us.

Problem

With the Anthropic provider, the claude-fable-5 model and Adaptive Thinking set to "None", every new task shows the error above instead of running.

Error (redacted / normalized)

"thinking.type.disabled" is not supported for this model.

Applies when

Cline 4.1.8 switched to "Next", in VS Code and JetBrains, on macOS and Windows; Anthropic provider; August to October 2026. A contributor said the fix also covers Opus 5.5, on Anthropic direct and Vertex.

Confirm it is this problem

1. Check the task settings → expect: the model is Claude Fable 5 (or Opus 5.5, per the contributor) and Adaptive Thinking is "None".
2. The task error matches the text above exactly.

Not this when / boundary

You see this error from your own code calling the Anthropic API directly; then the fix is to stop sending thinking: {type: "disabled"} for these models, because a commenter quoted Anthropic's docs that Claude Fable 5, Claude Mythos 5 and Claude Mythos Preview reject it.

Root cause

Thinking cannot be turned off on these models (Anthropic docs, quoted by a commenter), but Cline sent thinking: {type: "disabled"} when reasoning was set to None. A contributor said #14862, which upgrades the AI SDK, stops sending it to Claude models that can't turn thinking off (Fable 5 and Opus 5.5), while other Claude models still get it.

Fix

1. Update Cline to a build that contains the AI SDK upgrade from #14862 (merged about 2026-10-07; that later builds on every channel include it is our inference) → expect: the original poster confirmed that on the JetBrains nightly 2.0.8-nightly.20261008.513 tasks with claude-fable-5 and Adaptive Thinking "None" work.
2. Until you can update: set Adaptive Thinking to a level other than "None" for this model (our inference; not tested in the thread).

How to verify

Create any task with Anthropic claude-fable-5 and Adaptive Thinking "None" → expect: it runs with no thinking.type.disabled error.

What did not work

None reported in the thread.

Risks

These models always think, so a run still uses thinking tokens even with reasoning set to None (our inference).

Verified scope

Cline 4.1.8 "Next" to the fixed nightly of 2026-10-08, October 2026.

Becomes obsolete when

Every Cline release channel includes the AI SDK upgrade. Open question: which stable VS Code release of Cline first includes the fix; the thread only names a JetBrains nightly.