[alexpotato]

> But, for many tasks, ultra mode is possibly worse and certainly more expensive.

Went through something similar. Fable would just spends minutes thinking, processing, confabulating etc.

I dropped down to Haiku and got an answer in >30 seconds.

[Huppie]

Simon Willison recently had a useful tip instructing Claude to use its judgement to pick an appropriate model for tasks.

After a short discussion about the idea with Claude mostly on how it fits in my workflow and what models / effort I would like for certain tasks it placed a paragraph in my global Claude.md and it has worked wonders. Ultra became a lot better (faster, cheaper for the same output) and the amount of time Fable gets stuck overthinking things are reduced to the places where I think that model makes sense, for the rest it started fanning out a lot to Opus, Sonnet and even Haiku.

[kingkongjaffa]

How does it change model mid conversation?

Does it spawn sub agents with different models or is it the same single conversation dynamically switching models?

[Huppie]

Subagents indeed. This [0] was the post I was referencing, and here's the original suggested prompt:

> For all coding tasks use your judgement to decide an appropriate lower power model and run that in a subagent

As said, I tweaked it a little bit to my preference (mostly because it started delegating a bit too much) and had it placed in my global claude.md but that's the gist.

[0] https://simonwillison.net/2026/Jul/3/judgement/

[theptip]

Yes, sub-agents I believe. You need to pay to reload context if you switch the main conversation model effort.