Google's SynthID (which is built specifically for Google-generated images) seems to work even for the final edit. Try sending it to Gemini with the query "Is this image ai generated?"
See here for more info: blog[dot]google/innovation-and-ai/products/ai-image-verification-gemini-app/
Can software save us from deepfakes? We put six detection tools to the test with a 'Nano Banana Pro' image. The results show that current tech is easily outsmarted. Simple edits using standard software were enough to drop detection rates to almost zero.