There were 7 head coaching hires this offseason. Someday, all but one of them will have been fired (or moved on from). This market is for which NFL coach will last the longest in the league 

. A coach who immediately signs with another team or is traded will be eliminated.  If a team changes cities, the coach will not be eliminated. If a team folds, that coach will be eliminated. If there is a surprise firing/hiring before the 2025/26 season starts, that coach won't count.

Temporary leaves of absence (for a game or two, i.e. McVay has a baby) 

will not count. Other, more complicated cases (i.e. Pagano having cancer) can be adjudicated in the spirit of the market (and will mostly likely not impact the outcome so will probably lean towards leniency).

Market could resolve by based on the exact date or even time if the survivors are fired the same offseason.

If, somehow multiple coaches are still around with their same team through the end of the 2059 season, then this market will resolve with them as joint winners.

If the NFL folds (or inherently changes in an extreme way where all the coaches are removed/change at the same time), then all coaches at that conclusion will resolve as joint winners (and split the winning probability).