2026-07-27 21:55 UTCOriginal source2 min readUpdated: 2026-07-27 22:49 UTC

An opinionated guide to which AI to use to do stuff

Ethan Mollick's AI guide has evolved from focusing on chat models a year ago to now emphasizing agentic systems that can do hours of work in one go. Gemini is dropped due to lack of a mature product in the Codex/ChatGPT Work/Cowork category. The guide explains the confusing naming of ChatGPT and Claude's multiple agent modes, notably that switching to Work mode on ChatGPT mobile gives the code interpreter internet access.

SourceSimon Willison's Weblog

Simon Willison’s Weblog

27th July 2026 - Link Blog

An opinionated guide to which AI to use to do stuff. It's interesting watching the evolution of Ethan Mollick's guide over time.

A year ago it was still all about chat - ChatGPT, Claude, Gemini - with o3, Claude 4 Opus, and Gemini 2.5 Pro as the models and Deep Research as a useful alternative mode.

Today it's much more about agentic systems - "where the AI is capable of doing the equivalent of many hours of real human work in one go".

Gemini has fallen off Ethan's list, since Google still doesn’t have an established entry in the Codex/ChatGPT Work/Cowork category. Gemini Spark has yet to prove itself!

Ethan offers a useful explanation of the ways you can give ChatGPT or Claude a computer to use:

To use the computers provided by the AI companies, the mode you want is called ChatGPT Work in ChatGPT, and Cowork in Claude (the naming will not get less confusing, I am sorry to say). [...]

The most powerful way to use AI is to give it access to your computer. You do that by downloading the ChatGPT or Claude apps and picking a mode to use. ChatGPT's two agent modes are Work and Codex; Claude's are Cowork and Code. The names do not map onto each other in any way that will help you remember them. And yes, these use the same names as the Work and Cowork modes we discussed above, but operate differently, and have more features and capabilities because they can access your computer.

I think the difference between ChatGPT Work on a mobile device and ChatGPT Work inside the desktop app (where it's effectively a less intimidating skin on top of Codex) is spectacularly unintuitive.

Short version: if you flip ChatGPT mobile from "Chat" to "Work" mode you get a version where its Code Interpreter container is no longer restricted from accessing the internet!