The chat app

The chat app is a public app your customers open in a browser and talk to. It answers as your business — with your knowledge, your tone, and your rules. It’s one of the ready-made apps in the catalog.

What your customers get

Your business’s name sits at the top of the sidebar, with New conversation under it and past chats listed below. Conversations are kept: each one is titled from the first thing the customer said, and it stays in the list for next time. Opening the app starts a fresh chat — a greeting, the composer, and starter prompts underneath showing what the app can do.

Customers sign in with just their email. They enter their address, Spark sends a one-time code, and entering the code signs them in. An account is created on their first visit; there are no passwords. A customer signed in on your chat app is signed in across your project’s public apps — customer accounts covers the details.

Preview and Configure

The chat app’s header carries a two-segment toggle, immediately left of the Edit button: Preview and Configure. Preview shows the app as your customers see it. Configure is where its behavior lives — the chat model row at the top, then Knowledge, then Instructions.

The app opens on Preview; whichever view you leave it on is remembered.

Configure moves at two speeds, and it helps to know which is which.

Immediate: the chat model and knowledge

The chat model row picks which model answers your customers. It offers the same models as the build agent’s picker — Claude Haiku 4.5 when speed matters in high-volume chats, Claude Sonnet 5 for everyday answers, Claude Opus 5 for high-value conversations — each with a one-line description of the job it suits. Same names, two different jobs: the build agent’s model writes your app, and this one talks to your customers. Picking a model saves on the spot. No agent turn, nothing to publish.

Knowledge skips the agent too: add or remove documents and the library updates directly. The knowledge library covers uploads, processing, and when new documents go live.

Through the agent: instructions

Instructions are shown read-only, section by section, straight from the app itself — a long section collapses behind Show all. To change one, use the Edit button beside it: it opens the agent chat with that section pinned to the composer, so you can say what should be different. The change lands in the preview, and you publish it like any other edit.

Instructions and knowledge

The two blocks sit next to each other in Configure and are easy to mix up. Instructions shape how the app responds: its tone, its boundaries, the things it should always mention. Knowledge is what it can look up: the documents and text it searches when a customer asks a question. “Always suggest booking a call for large orders” is an instruction. Your price list is knowledge.

Configure’s own labels are a good mnemonic — instructions are “How your chat app responds”, knowledge is “Documents and text your chat app can search”.

Test it as your customers

The preview’s browser frame carries a Preview as control, just right of the URL bar. It lets you use the app as a signed-out visitor, a free user, or a paying customer — no real account needed, and nothing you do there touches your live data. The Free user option switches on once your project sells something; until then there is nothing gated to preview. Preview as is available on the chat app and the online store.

One thing the preview leaves simulated is identity, since no real customer is signed in: the account button reads Preview account, and its Account settings and Sign out entries open the real screens with sample data — no code is sent, no session ends.

Styled to your brand

The agent styles the chat app to your brand — your colors, your type — so it reads as one business alongside your marketing site. Want it warmer, plainer, closer to your print materials? Ask the agent, watch the preview update, and publish when it looks right.