StartupENGINEERING
Loop 2 of 5 · The Five Loops

The Solution Loop

North star: “This solution creates the value.

At hand
Prototype

A prototype — a hypothesis made clickable.

What you hold is the tool of discovery — every loop's input, never its output. The name tells you what you're hunting; your hands tell you where you're standing.

North star

This solution creates the value.

Entering assumption

The problem validated — Loop 1's bar behind you.

Engineering bar
Disposable Prototype

A disposable prototype — real on the one risky thing, fake everywhere else, fate pre-committed in writing. Disposable is what buys this loop its speed: you iterate fearlessly on a thing you've already agreed to throw away.

  1. 1 · Problem LoopManual Delivery
  2. 2 · Solution LoopDisposable Prototype
  3. 3 · Product LoopLaunchable MVP
  4. 4 · Market LoopObservable Product
  5. 5 · Fit LoopRepeatable System
The engineering bar rises only when the evidence earns it.Beyond 1: Scalable Platform — off this ladder, by design.
Exit bar
Observable evidence to leave. None of it is a feeling.
  1. 1Capability leg — we can solve it: the question you named before anyone saw the demo, answered; real data through the prototype at least once.
  2. 2Value leg — it solves their problem: a commitment to buy when handed over, costing them something today — a prepayment, a signed pilot, a scheduled slot. Never a compliment.
  3. 3The prototype's fate decided in writing: spec for the build, harden into the product, or delete with the learning kept.

Earns: Solution validated. All five exit bars →

First principles
  • A demo is software performing under supervision; a product is software you can safely abandon to strangers.

    Everything in this loop follows from that line.

  • The invisible 80%.

    What separates the two is, by design, the boring part — accounts and access, data that survives, safety against accident and malice, graceful handling of inputs nobody imagined, and the machinery that reports failure. A demo needs none of it; a product is all of it.

  • Fidelity is a dial, not a virtue.

    A prototype should be exactly as real as its question requires: a clickable mock answers understanding questions, a working prototype answers workflow questions, and only a naked test answers capability questions. More fidelity than the question needs is buying furniture for a stage set.

This loop in the AI era
Revision surface — rewritten when the wave changes. The framework beneath it doesn't move.
What changed

This loop's cost collapsed — what took a freelancer a month now takes a founder a weekend. That made prototyping-by-founder the default, and made the loop's exit question (“what is this thing, really?”) the most misjudged decision of the decade.

What didn't change

The invisible 80%. AI tools build stage sets at miraculous speed; they do not make stage sets livable.

Embrace

Build it yourself — budgeted, disposable.

Ignore

Anyone — tool vendor or agency — telling you the weekend demo is, or can never be, a product. Both answers are for sale.

Decisions in this loop
Browse Solution Loop decisions in the catalogue →
Not Yet

Decisions explicitly deferred while you're in this loop. Not wrong questions — early ones. Written down, and set down.

  • Scalability
  • “Will this handle 10,000 users”
  • Technology stack permanence
  • Hiring
  • Infrastructure choices
  • Security beyond not-being-careless
  • Code quality

Stamp your own worries with the Loop Check →

Decision skills

Free, ungated plain-text files you hand to Claude or ChatGPT. All skills →