We spent WEEKS getting the permission system right for this project.

This monday 11.30 they tell me we need to change it, preferably by this morning

Now I have 4 branches to merge, I can't remember where the features are, we have regressions all around, the client aren't happy, people can't work, everything explode.

We started this projects 6 months ago, you had all the time to think about it.

Are there any tests? Or is your company one of those bureaucracy first, engineering second' kind of shops?

Always push back. Tell people the risks. Never work overtime, especially if it's their fault things were missed or wrong in planning.

@djsumdog worst, start up. I'm trying to implement tests but i can't write tests if requirement change every 5 minutes, I have actual work to do

In my experience it's always OK to admit that a requirement is overwhelming and will take much longer than a stakeholder imagines.

They will not be upset if you just honestly say you're in the middle of working on 4 other features and this is a big change.

(but they might be short sighted and just say "screw the other 4 features" without realising that'll delay the entire project)

But my advice is: don't say anything in spite like "I told you so" or "We started this projects 6 months ago, you had all the time to think about it." type thing - if you're gonna mention that - talk it over with your PM and mention it a few days later in a retro when you cool off.

Stakeholders are dumb and they hate being reminded of it in snarky ways. But if you can phrase it in a certain nice way they may understand.