So, aside from Larabars...
 

...what's a good on-the-road snack that handles heat or cold well, is filling, and doesn't have the tree-bark-and-road-tar texture of most other bars?

Oatmeal raisin cookies.

Real food (including cookies). Like we ate before all this stuff was on the market.

Dates, fig newtons, PB&J, bananas

My main goal is not adding to the pre-ride routine; I'm looking for stuff that can survive in the seat bag or Camelbak pocket for at least several days, partly for those times when I forget to grab a banana or a handful of cookies. Clif bars are good at the surviving part, but after a few cycles of heating to 110+F and then cooling, it's like chewing on a tire.

I suspect that the suggestions of dates, fig newtons, PB&J, bananas, and my oatmeal raisin cookies are NOT part of the pre-ride routine ... they are the things we would take with us on rides, and eat during the rides. Well, I wouldn't eat PB&J, but I would eat the rest. I'd also add salted almonds into the collection.

Dried fruit, nuts, and cookies of various sorts survive quite well throughout a ride, and will survive if you leave them in your handlebar bag or bento bag for a few days.

I am perfectly happy with cliff bars.

Microwave blasted small red potatoes. Wash them well and microwave them the night before. I leave the skins on.