01

Build: Your team writes, ships and owns the code

You design, implement, operate and maintain the software yourself. The logic is deterministic code in your repo, running on your infra, owned by your team forever.
Pros & cons
+Perfect fit
● same

Models your domain exactly. No bending your process around someone else's product.

✦Fit was always Build's strength. AI doesn't change it, but it does make getting there cheaper.

+Differentiation & moat
▲ stronger

What you build is what competitors can't buy. Customers experience the core of your product as your code.

✦Anyone can buy or prompt the commodity parts now, so the parts only you have are worth more.

+No lock-in, no seat tax
● same

No per-seat or per-transaction fees that grow with you. Adding a user costs close to nothing.

✦Unchanged. At high volume, owning the code is still the cheapest way to run.

+Deterministic & testable
▲ stronger

Same input, same output. You can unit test it, audit it, and explain it to a regulator.

✦LLM-driven parts are probabilistic, so a deterministic core you can verify is worth more than before.

+Data stays home
▲ stronger

Nothing leaves your perimeter. Security and privacy follow your rules.

✦Proprietary data is now the thing that makes AI useful. Keeping it in-house has strategic value.

−Slow to first value
▼ weaker

Months of design, implementation, hardening and edge cases before users see anything.

✦Coding agents compress weeks into days for well-specified software. This is the biggest shift.

−High upfront cost
▼ weaker

Engineer-months are expensive, and you pay them before you learn whether it works.

✦The same team ships 2–5× more. Upfront cost drops, but review and judgment don't compress.

−Maintenance forever
▼ weaker

60–80% of lifetime software cost comes after launch: upgrades, CVEs, migrations, on-call.

✦Agents handle dependency bumps, migrations and bug triage. Ownership and on-call are still yours.

−Opportunity cost
▼ weaker

Every engineer rebuilding commodity software isn't working on your core product.

✦With cheaper engineering hours, rebuilding a commodity tool steals less from your core roadmap.

−Key-person risk
▼ weaker

Tribal knowledge concentrates in a few people. When they leave, so does velocity.

✦Agents can read, explain and modify unfamiliar codebases, which softens the bus factor.

green = AI helps this optionred = AI hurts this option▲▼ = the point itself gets stronger / weaker
Score profile
Time to market1 → 3
Low upfront cost1 → 3
Low cost at scale5
Fit & control5
Differentiation5
Reliability & determinism5
Low maintenance burden1 → 3
Low lock-in5
Handles messy input1 → 3
Compliance & audit4
Grey = pre-AI (2022). Colour = AI era (2026). 5 = best.
Reach for Build when
  • →It is your core differentiation
  • →Rules are well understood and must be exact
  • →Volume is high and per-unit vendor fees would dominate
  • →Compliance requires you to explain every decision
Examples: Core ledger & payment orchestration · Pricing / risk engine · Internal admin tailored to your domain
  • why it mattersThe price of writing code fell, but the price of owning it didn't fall as much. Budget for review, on-call, security and upgrades, not only the first version.
  • why it mattersBuild is the only one of the three that produces an asset. Buy gets you a contract, and LLM gets you a dependency on a model provider.
  • why it mattersThe real cost to watch now is spec quality. Agents build exactly what you asked for, so a vague spec gets you the wrong thing quickly.