Most conversations stay short and never go anywhere. A few keep going, and those are the ones where output quality decides whether the User stays. **Auto-Switch to Pro** puts the Smart model on the first kind and the Pro model on the second, with nothing to manage on your side.

## How it works

A conversation starts on the **Smart** tier. It moves to the **Pro** tier the moment it outgrows its short-term memory window, today the [30 most recent messages](/content-creation/conversation-memory), and stays on Pro for the rest of its life.

| Conversation length | Tier used | Long-term Memory |
|---|---|---|
| Up to 30 messages | Smart | Not kept |
| From the 31st message on | Pro | Kept |

The message being processed counts, so the switch happens on the reply to the 31st message. The threshold follows the memory window: if that window moves, the switch point moves with it.

## The end user notices nothing

No interruption, no pause, no restart: same Persona, same personality, same history. Tone and continuity carry over unchanged. Which tier produced a reply is a routing decision on our side and is never exposed to the User.

## What it costs

Each reply is billed at the tier that produced it: Smart before the switch, Pro after. Smart and Pro usage appear as **separate lines on your invoice**, so you can see exactly what each part of a conversation cost. See [Choose Your Model](/getting-started/choose-your-model) for both rates, or the [rates in your dashboard](https://dash.dumgum.ai/pricing).

In practice you pay the Smart rate on the bulk of your volume, and the Pro rate only on the conversations that lasted long enough to deserve it.

## Turn it on

Point `replyParameters.chatModel` at the `-auto` variant of your model version when you enqueue a conversation, for example `chat-2.1-auto`. The choice is made per request: there is nothing to switch on in the dashboard. See the [API Reference](/api-reference/content-creation/endpoints/enqueue-conversation#body-reply-parameters-chat-model).

<Note>
  A request that names a fixed model (`chat-2.1-smart`, `chat-2.1-pro`, and so on) stays on that model whatever the conversation length.
</Note>

<Tip>
  If you are unsure which tier to send, the `-auto` variant is the safer default: you pay the Pro rate only on the conversations that get far enough to need it.
</Tip>

## What Pro adds past the switch

Beyond output quality, the Pro tier is what unlocks **Long-term Memory**: the facts the AI has learned about a User and a Persona, kept across their conversations. Recording starts at the switch, so a conversation that never reaches the threshold never produces memories. See [Conversation Memory](/content-creation/conversation-memory) for what the short-term window holds, and the [Memory Webhook](/content-creation/memory-webhook) to receive what is learned.