Well, it is trespass and they should not have access to the house unless there was an agreement to deliver possession to you much later, obviously not the case here.

If nothing was damaged in the house, just give the builder a good talking to and ask him to change all the locks at his expense.

Safest thing to do is call a locksmith to re-key your locks. Edit to add: I wouldn't trust the builder/project manager to change the locks and not make a spare for themselves.

I don't know what action can be taken against them without video proof. It's going to be a he said/she said with no one taking responsibility and a huge headache. But you can call your local police and see if you can make an official report, just so you have documentation if anything else weird happens. Also, unless you have the change of locks agreement in writing, I don't think they'll pay for anything at this point.

Swap out your keyed locks for electronic deadbolts and you can rekey the house anytime you want. If you do that, be sure to change the keyed doorknobs to regular knobs so no one can accidently lock you out.

All works in progress have concealed keys on the property for trade access to a single door at times convenient to them. All of the rest of the doors should be keyed to homeowner access, with no spares anywhere but with the builder. It’s not surprising to have punch items still being done late in the game. And it’s not surprising that many of the trades have zero idea of when the closing date is, so they come in at times after other jobs to finish up yours.

What is surprising is a builder who doesn’t rekey the trade door and remove the key from its hiding place at closing.

No respectable builder hides a key under a rock. What an insane idea. One door has a lockbox that the trades can access. That lock then gets changed.

We put coded keypads in from the beginning then just changed the code as the project was wrapping. Now that we are on the tail end of things, we have the family code and the contractor code. Contractor code will be deleted as soon as we get the last few items taken care of.

I suggest programming one or two single use only emergency codes in case you need future assistance. It is really nice to be able to remotely give access to a property and not have to worry someone might make a copy of the key.

At one property I had a lockbox with a key but I knew one of the guys was rather absentminded. I put a chain on the key, just long enough to comfortably reach the lock, drilled a hole in the box and secured the key so it couldn't be removed. No chance of careless or intentional removal of the key.

We've been in our new house for 1.5 years and still have a lock box outside and a key in it. I would be horrified if anyone came in obviously but I love the ease of the key and box being there when we need it.

In your case, for me the issue would be, that you didn't know someone still had access and was coming in. Yes it is great they want to finish the job. But that shouldn't make it okay for them to come in unannounced. They should want to finish the job AND be respectful that it is your home and space. Not one over the other.

At this point, if you are nervous, get the locks redone yourself, not via the builder.