I see both sides of this reply. I get it violated a technicality of a verbal agreement. Personally though I see that a one word reply may deescalated the situation. Not replying at all sends a strong message that there is bad blood and they are enemies. And while that's not far off, to send an 'OK' reply to me means 'we're not enemies, but I'm not able to continue dialogue with you'. It would've been a lot different if he started suggesting potential hires, meeting for lunh to discuss, etc.
I sense that you are very insecure with your H's past behavior and he level of his recommitment. I know there is a balance between standing up for yourself vs becoming crazy and controlling. Has he done other things that make you feel he is violating your boundaries? That might be important context here.
Bottom line, I think the text isn't a big deal. I think if its part of a pattern then you address the pattern and why that is important to you. At the same time I'd make sure you have done what you can to have recognized what he HAS done. If I had been trying to recommit to a M and was doing my best but felt I couldn't win and my W would never forgive me and be suspicious and hyper critical forever because of it that would make it a pretty miserable M in my book. Any gets have advice?
Me:38 XW:38 T:11 years M:8 years Kids: S14, D11, D7 BD/Move out day: 6/17/14, D final Dec 15