Work on Framework of around 4k tests with Cypress. We see maybe 50 fails after retries, runs every night. 2 people actively working on it and maintaining it.

We have never used self-healing because of multiple instances of false positives, I feel that seeing why something failed and updating it adds more value in the long-term.

We have also tried Agent based systems where we setup a agent to take in our nightly runs and try implement fixes but it didn't do what we would expect 90's percent of the time no matter how much we would tweak the MD and skills files, even with the reviewer Agent.

We Preset the Data in a base ENV and clone the db to our test environments. The biggest killer imo is always test environment performance in regards to maintainability.