I accept code changes I do not understand
Set one gate for yourself: nothing gets kept until you can say, in one line, what the change does and why it is needed. If you cannot, do not accept it yet. Ask the AI to explain it, or ask for a smaller change. Your name is on the commit, so the understanding has to be yours too.
What is going on
The diff is forty lines. The tests pass. Reading it properly would take ten minutes, and accepting it takes one key. Do that a few hundred times and parts of your own project become code you have never read.
This is what the tools are designed to make easy, and nearly everyone who uses them does it sometimes. The risk is practical. When that code breaks at a bad moment, you are debugging a stranger's work with your name on it.
What to do this week
Predict before you look
Before reading the AI's change, say what you expect it to touch: which files, roughly what kind of edit. Surprises are where to read closely.
One line or no merge
For each change you keep, write one line: what it does and why. Put it in the commit message. No line, no commit.
Ask for smaller changes
"Make this change in steps of no more than about 20 lines, and stop after each one." Small diffs are ones you will really read.
Make the AI explain its own work
"Walk me through this change line by line. What could break?" Then run it and check one of its claims yourself.
What not to do
- Do not let passing tests stand in for understanding. Tests check what someone thought to test.
- Do not let the AI write the explanation line for you. The line is the check. If the AI writes it, nothing was checked.
- Do not aim for 100%. Generated boilerplate and config you have seen a hundred times can go through on a skim.
The honest limit
You will be slower, and some days the deadline wins. Choose where the gate is firm: anything touching money, security, user data or code you will have to maintain. Elsewhere, a skim is a fair trade. We are not citing a study on this page. This is ordinary code review discipline applied to yourself, and we have not measured it.
Questions
Is it realistic to understand everything an agent writes?
Not line by line, on a large change. It is realistic to understand what each part is for and to read the risky parts closely. If you cannot do even that, the change is too big.
Does retyping the code help?
Some developers do it for code they want to learn, and say it helps them notice what they skipped. We have no study to offer on it. Try it on one small change and judge for yourself.
What about code review by my team?
It helps, and it is not a substitute. Reviewers assume the author understands the change. If neither of you does, nobody does.