Some founders don't need a one-off project. They need one senior engineer in their corner, month after month, who already knows their product inside out. That's what I do on retainer: itemized scope so you always know what you're paying for, no surprise scope creep, clear communication, and someone who treats your product like their own. I've run year-long retainers as a client's lead engineer, shipping all the way to the App Store and Google Play. A real technical partner, not a revolving door of contractors.