Client said: "And you promise there won't be any caterpillars in the app...",I gave him a strange look, he continued: "or how do you call that mistakes in apps".

He meant bugs...

Also, of course we can totally promise not to make bugs, you know, because we are mean people which implement malfunctioning code intentionally, just to troll the users. /s

I you find caterpillars it's time for new infrastructure.

No. I promise I'll try to reproduce bugs that you report. If I can, I promise to not make fun of you on the bug report you filed. If I can figure out the underlying issue, I promise I'll try to solve it without breaking any of the other working features. If I can do all that.. Well, still no. I promise that there will be some weird edge case that no one thought of, so there will always be bugs somewhere.

So, no. I can promise I won't lie to you about the product that we're making together, though.

ladybugs...