Your pytest configuration is lying to you. Not loudly but just quietly running different things in different places.

Picture this. A test starts failing in CI. You pull the branch locally, run the suite, and it passes. You dig in for twenty minutes before realising the CI run has --capture-screenshots=failed and yours doesn't, so the screenshot that would have told you exactly what broke exists in CI, but you never thought to check because your local run gave you nothing. Or the reverse: you add --plus-email to your CI command to get the report delivered after each run, forget to strip it out of the local conf