Your response doesn't answer OP's question all it does is punt the issue to a news agency. If a news agency reports it on the basis of a "mission accomplished type photo op", does that count? Or does it require a news agency to report it on the basis of a "prolonged stable holding"?
Just saying that the prediction market shall resolve because three reputable news agencies report something is completely devoid of any insight into the nature of issue. It's as logically absurd as claiming that you have cancer because a Doctor told you that you have cancer, or claiming that you killed Jack because a jury delivered a guilty verdict. No, you don't have cancer because a Doctor said so and no you didn't kill Jack because of a jury's verdict; you have cancer because of an actual condition involving the rapid and abnormal cell growth and you killed Jack because you took a knife and stabbed him.
You are certainly justified to believe you have cancer because a Doctor told you so, and I am justified to believe you killed Jack because a jury said so, but a justification is not the same thing as an actual cause.
So going back to the original question: what is the criteria that determines that Kyiv has actually fallen to Russian forces as opposed to what is the justification for believing that Kyiv has fallen.
Just saying that the prediction market shall resolve because three reputable news agencies report something is completely devoid of any insight into the nature of issue. It's as logically absurd as claiming that you have cancer because a Doctor told you that you have cancer, or claiming that you killed Jack because a jury delivered a guilty verdict. No, you don't have cancer because a Doctor said so and no you didn't kill Jack because of a jury's verdict; you have cancer because of an actual condition involving the rapid and abnormal cell growth and you killed Jack because you took a knife and stabbed him.
You are certainly justified to believe you have cancer because a Doctor told you so, and I am justified to believe you killed Jack because a jury said so, but a justification is not the same thing as an actual cause.
So going back to the original question: what is the criteria that determines that Kyiv has actually fallen to Russian forces as opposed to what is the justification for believing that Kyiv has fallen.