About Counterpart

Counterpart is a deliberate-practice environment for the conversations that decide outcomes — interviews, negotiations, hard feedback, medical talks, first dates, performance reviews. Pick a scenario, rehearse with an AI counterpart that holds a real position, and get an honest read on what happened.

This page is the map of the rest of the app. Read the theory if you want to know why these conversations are psychologically hard. Open a scenario if you want reps. If you build software and want to embed Counterpart in your own product, jump to the API documentation.

How it works

A scenario is the character brief: who the counterpart is, what they want, how trust and resistance shift in response to your moves. A session is a running instance of that scenario. The conversation itself runs in real time over voice or text.

• Real-time voice. Speech-to-speech with low latency. You can also type.
• A stateful counterpart. The character has trust, resistance, commitment, and emotion — and updates them deterministically after each turn. The AI generates prose consistent with the state, not the state itself.
• Optional coach. A second AI watches and can comment on what you just did, in voice.
• KSTAR report. After the session, Counterpart gives a structured read — what happened, where it moved, what to try next time.

Read the theory

Counterpart is built on a specific view of what conversation is. If you want the practice to feel legible, read the theory first.

Per-category guides

Each conversation type trains a distinct skill. Read the guide for the kind of conversation you want to get better at, then practice it.

Practice

Reading does not get you better at conversation. Reps do. There are two ways in.

• Browse scenarios — 30+ built-in scenarios across persuasion, coaching, interviews, sales, negotiation, customer support, medical, thesis defense, dating, and academic advising.
• Write your own scenario — describe a situation in plain language and the app drafts a full scenario you can rehearse immediately.

Integrate Counterpart in your own app

Counterpart is also a conversation-as-a-service API. If you are building a training product, a coaching tool, a hiring platform, or a health/education app, you can spin up a fully hosted practice conversation by POSTing a JSON config — and embed the result in your own UI with an iframe, a popup, or your own client driving turns over HTTP.

• API documentation — endpoints, schema, authentication, embedding, error model, and a full round-trip example.
• The OpenAPI-ish schema is also exported programmatically from lib/conversation/schema.ts if you want to validate configs in your own code.

Your account & history

Sessions you run are listed in your history, and you can manage your profile from account settings. Reports are generated at end of session — save them to your side if you need durable storage, since sessions themselves are ephemeral.