Voldemort didn't break his promise to Lily - he intended to, presumably, but Lily broke her side first by trying to kill him instead of acting like a willing sacrifice.
First, I am certain that he completely anticipated her response. Desperate pleas aside, she wouldn't have trusted that he would have really left Harry alive. He gave her a few seconds to think, come to that conclusion, and then she tried to the only option she thought she had left.
Second, the wording was:
"Very well," said the voice of death, now sounding coldly amused, "I accept the bargain. Yourself to die, and the child to live. Now drop your wand so that I can murder you."
The only part of the bargain that she had to uphold was dying.
Though I'm not at all certain that the scene is what it looks like.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapters 91 & 92 . The previous thread has passed 500 comments.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18,19,20.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: