Baby Eve, an experience lab on eve.dev

A prototype with a contract

A prototype that ships nothing drifts toward becoming a second product. Baby Eve had a written contract instead: it answers one question at a time about how Eve should feel and behave, uses just enough real Slack, model, and state to make the answer credible, and stops before it becomes a production system.

The rule for what belongs where is one sentence. If a change needs production credentials, writes customer data, adds a real integration, creates a second source of truth, or has to be operated for customers, it does not belong in the lab. What leaves the lab is a behaviour contract and its evidence, never a copy of the code.

One question at a time

Every experiment was a small vertical story, not a subsystem. It named one uncertainty, stated what should become more legible or trustworthy, changed only the surfaces that scenario needed, and replayed the golden path plus at least one failure.

An experiment was done only with evidence: the transcript, the renders, a check that fails when the behaviour breaks, and a written decision to graduate, iterate, reject, or archive. No more than two ran at once.

A design doc the build fails on

Baby Eve invented conversation patterns that had no spec anywhere: reactions as the whole interaction, a message that redraws instead of a feed that grows, silence as a designed state. I named 22 of them as a system. Each is a choreography, a copy contract for the strings it posts, and anchors that point at the code that implements it.

The anchors are checked. A script parses every one and fails the build when a cited file is gone or its symbol no longer appears in it, so renaming the code forces the doc to change in the same commit. A pattern without a test is labelled "not yet", and five of them still are. An honest label is the invitation to write the test.

Rebuilt on eve

By August the prototype's custom runtime was spending its effort on generic agent problems: sessions, resuming, approvals, retries, schedules, tracing. None of that was what the lab existed to learn.

So I rebuilt Baby Eve on Vercel's eve framework, one vertical slice at a time. eve owns the durable machinery. Baby Eve keeps everything that is Eve: her judgment, the seeded world, the information hierarchy, the Slack presentation, the artifacts, the personality. Dependencies are pinned exactly, and every framework upgrade has to pass the build, the evals, a restart, an approval, and a Slack replay. The decision covered the lab only; EVE's production architecture is its engineers' call.

Planning at AI speed

I built Baby Eve with AI coding agents as pairs, and that changed how the lab planned. Calendar estimates meant little when a focused pass could take an idea from question to replayed evidence. The unit of planning became the pass.

Anything bigger than three passes was not accepted; it had to be split into independent experiments first. Things outside the lab, such as a Slack reinstall, a production change, or a research session, were gates, not estimates.

What a lab is for

The lab's value was never its code. It was a place where "how should Eve behave here" could be answered with a replay and a check instead of an opinion, and then handed to the production team as a contract they could hold me to.

Rebuilding it on eve made that sharper. Once the framework owned the plumbing, every remaining line in the lab was about the experience, which is the only thing a designer's prototype should be about.