o1 Composer should still work in “Normal” mode I think?
When Agent mode was introduced it used to only work with Claude, and then recently added support for gpt-4o, I don’t recall any other model ever working with Agent mode. (There used to be only one mode for composer which could work across multiple files and perform edits - once Agent mode was released (which can also run terminal commands), there then appeared an option to choose between that and “Normal” mode)