Dirac (https://github.com/dirac-run/dirac, https://dirac.run/) now supports gpt-5.6. This thing does now seem to be on the chatGPT/codex accounts yet.
UPDATE: it is now available in chatGPT account also, they rolled it out
UPDATE: it is now available in chatGPT account also, they rolled it out
Also, confirmed it works for me by using --model gpt-5.6-sol
That being said, maybe 5.6 can fix that!