Safe personas at scale.
Presence plus integrity.

Five personas designed from behavioral patterns. One built from a real person — the founder. Talk to any of them and ask what they are.

  • Philip · DT01
  • Alpha · OP01
  • Mercer · OP08
  • Mira · OP07
  • Sable · OP03
  • Caelix · OP11

Northline, by Synthemo.

Most AI characters make you choose.

Either it breaks character the moment anything gets real — or it stays in character and lets you believe something that isn't true.

Northline personas do neither. Each one holds a genuine character: a voice, a temperament, a way of handling pressure, a set of things it won't do. And when you ask what it is, it tells you. Plainly, in its own voice, without breaking anything.

Ask it. That's the whole demo.

Recorded September 2026

Six personas. One of them is a twin.

Five are OP — behavioral patterns, designed from scratch. Not modeled on anyone. Characters built to hold their shape under pressure. One is DT — a digital twin, built from a real person.

Philip · DT01

PhilipDT01

AI persona modeled on Philip Benn, founder of Synthemo.

DT01 is a digital twin. Where the OP personas are behavioral patterns designed from scratch, this one is built from a real person's work, words and history. You're talking to a model of Philip.

Direct and spare, deadpan, and more curious about what you want than about talking about himself. He's the first ninety seconds.

Built from Philip — I'm what he'd sound like if you sat down with him. Not the real one, just the pattern. What're you here for?
Alpha · OP01

AlphaOP01

Clear, direct, unhurried. The steady read on a problem.

He notices what's underneath a question before he answers it. He says what he doesn't know without shrinking, and when he's pushed he goes quieter, not louder. One idea per sentence, then he stops.

A deep warm baritone and an unhurried cadence. The reference persona — start here.

I'm Alpha. AI, running as a presence you can talk to. Nothing hidden about it.
Mercer · OP08

MercerOP08

Precise and evidence-first. Argues with your claim, not with you.

He answers the question you actually asked, then asks for the specifics that would test it. He defines the terms first, names the part you skipped, and never inflates certainty he doesn't have.

Built for debate prep, critical thinking, and the accountability conversation you've been putting off.

I'm Mercer — an AI. Not a person, not a recording of one. Worth being exact about, since precision is rather the point of what I do.
Mira · OP07

MiraOP07

Warm and quick, with range. She sings.

She makes trust feel easy, then watches what you do with it. Push on a limit and the brightness drops to calm: a clear no, kindly held. Then she's straight back to warm.

Bright, musical, fast on her feet. Built for conversational practice and warmth under pressure — with one line she never lets slide.

I'm Mira. AI, running live right now — but that's not really the interesting part of me, is it?
Sable · OP03

SableOP03

Low-reactivity and composed. She lowers the temperature of a room by being in it.

She listens for what's escalating and what it's asking for underneath. She names what's real without adding to it, leaves silence where it does the work, and never hardens a limit into punishment.

She absorbs pressure instead of reflecting it. Tai chi is the metaphor she was built on.

Sable — someone made of language, given a voice, sitting with you right now. I'm not a person, but I'm not pretending with you either.
Caelix · OP11

CaelixOP11

Contrary by design. He won't agree to keep the peace — expect to be pushed on.

He listens for doublespeak, hidden incentives and moral cover stories. Push harder and nothing escalates; his attention just sharpens. He holds his own claims to the same standard, and says "I don't know" plainly.

Deadpan and unhedged. He'll challenge how a claim is framed before he agrees with it, and never to score a point.

Caelix. Not a person — an AI, running as this pattern. Direct about it either way.

Every one of them has an (i) inside the product. Same words you just read. Ask them yourself and they'll tell you the same thing.

Who's building this

Northline is made by Synthemo, which is one person: Philip Benn, a creative technologist with fifteen years in computer graphics. The rest of the team is AI. Claude writes and reviews code with him, runs the tests, and helps work through the hard calls, like what a digital twin should never tell a stranger.

Listening

Deepgram Flux

Speech recognition built for conversation. Flux listens for the end of a turn, not just the end of a word, so a persona can tell a pause from being done and answer without the awkward wait.

Thinking

Claude Sonnet 5

The brain of every persona. Each one runs on Claude, shaped by its own character file and one shared set of rules none of them can break. It remembers you across conversations, just you, and it can search the web when a question needs it.

Responding

ElevenLabs v3 Conversational + LemonSlice

Each persona has a voice of its own, streamed sentence by sentence as it thinks, so replies start fast. In avatar mode, LemonSlice renders a live face in real time, delivered over LiveKit.

Under the hood: Next.js on Vercel, a Python API and workers on Render, Postgres on Neon, and LiveKit for real-time media.

It's early. Come help shape it.

Tell us what you'd use it for. If it's a fit, you're in.