Feature Request: Easy Way to Add/Remove Files for Context And Specify Maximum Context Length

Apologies if this feature already exists, but I’ve been searching for it over the past few days without success.
I’m testing out codex -p ollama with DevStral, and the good news is that Codex is successfully communicating with the model.
However, I haven’t found a straightforward way to add or remove specific files from the context.
Running codex -f seems to include everything even assets and binary files.
Also, how can I configure the maximum context size? The default appears to be set at 2,000,000, which is too large for a local model.
There must be simple ways for these tasks in order to make local models more usable.
Thanks!