Stop Handing Engineers Your Vibe-Coded Prototype. Hand Them the Spec.
The prototype was never the asset. The thinking behind it was. Most teams are shipping the wrong artifact to their engineers.
There is a workflow taking over product teams right now and it looks like progress. A PM or designer vibe-codes a working prototype in a weekend, demos it, everyone is thrilled, and then it gets tossed over the wall to an AI engineer to "make it real."
I do this myself. I also think the handoff, as most people run it, quietly destroys the most valuable thing that got created.
The prototype is a side effect
When you build something with Claude or Cursor over a weekend, the running app is not the output. It is the residue. The actual output is the sequence of decisions you made getting there: why this data model and not that one, which edge cases you chose to ignore for now, where the regulatory landmines are, what "done" actually means.
That reasoning lives in your head and in a messy chat history. The prototype captured almost none of it. So when you hand the engineer the repo, you are handing them the answer with the work erased. They reverse-engineer your intent from code that an AI generated to satisfy a prompt you have already forgotten.
Specs are the source of truth, code is a cache
The model I keep coming back to: the specification is the durable asset, and the code is a disposable cache you can regenerate. If the spec is good enough, the implementation is almost incidental — you can regenerate it when the framework changes, when requirements shift, when the model gets better.
This is not a new idea dressed up. It is the old idea finally becoming practical. We never wrote rigorous specs before because writing the spec cost almost as much as writing the code, so why bother. Now the code is cheap and the spec is the leverage point. The economics flipped, and most teams have not noticed.
What the better handoff looks like
When I move a prototype to an engineer now, the prototype is the appendix, not the deliverable. The deliverable is: here is the spec, here are the invariants that must hold, here are the three places I know are load-bearing and dangerous, here is the verification harness that proves the regenerated code actually does what the spec says.
In a regulated domain this is not optional. "It worked in the demo" is not a defense in an audit. The spec is what you can point to and say, this is the intended behavior, and here is the test that proves the system matches it.
The teams winning with these tools are not the ones generating the most code the fastest. They are the ones who figured out that when code becomes cheap, the thinking that was always the real product finally has to be written down.