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---
title: "Database persistence for chat"
sidebarTitle: "Database persistence"
description: "Split conversation state and live session metadata across hooks — preload, turn start, turn complete — without tying the pattern to a specific ORM or schema."
---
Durable chat runs can span **hours** and **many turns**. You usually want:
1. **Conversation state** — full **`UIMessage[]`** (or equivalent) keyed by **`chatId`**, so reloads and history views work.
2. **Live session state** — a **scoped access token** for the session and optionally **`lastEventId`** for stream resume.
This page describes a **hook mapping** that works with any database. Adapt table and column names to your stack.
## Conceptual data model
You can use one table or two; the important split is **semantic**:
| Concept | Purpose | Typical fields |
| ------- | ------- | -------------- |
| **Conversation** | Durable transcript + display metadata | Stable id (same as **`chatId`**), serialized **`uiMessages`**, title, model choice, owner/user id, timestamps |
| **Active session** | Hydrate the transport on page reload | Same **`chatId`** as key (or FK), **`publicAccessToken`**, optional **`lastEventId`** |
The **conversation** row is what your UI lists as "chats." The **session** row is what the **transport** needs after a refresh: a session-scoped PAT (so the transport doesn't have to re-mint on first paint) and the SSE resume cursor.
Storing the current **`runId`** is optional — useful for telemetry / dashboard linking ("View this run") but not required for resume. The Session row owns its current run server-side; the transport reads from `session.out` keyed on `chatId`, so a run swap (continuation, upgrade) is invisible to your DB schema.
<Note>
Store **`UIMessage[]`** in a JSON-compatible column, or normalize to a messages table — the pattern is *when* you read/write, not *how* you encode rows.
</Note>
## Where each hook writes
This pattern covers **durable DB rows** (the conversation and the active session). Per-process in-memory state ([`chat.local`](/ai-chat/chat-local), [DB connection pools](/database-connections), sandboxes, etc.) belongs in [`onBoot`](/ai-chat/lifecycle-hooks#onboot) — it fires on every fresh worker including continuation runs, where `onPreload` and `onChatStart` do not.
### `onPreload` (optional)
When the user triggers [preload](/ai-chat/fast-starts#preload), the run starts **before** the first user message.
- Ensure the **conversation** row exists (create or no-op).
- **Upsert session**: **`chatAccessToken`** from the event (a session-scoped PAT covering both `read:sessions:{chatId}` and `write:sessions:{chatId}`).
- Load any **user / tenant context** you need for prompts (`clientData`).
If you skip preload, do the equivalent in **`onChatStart`** when **`preloaded`** is false.
### `onChatStart` (chat's first message, non-preloaded path)
- Fires **once per chat**, on the very first user message. Does NOT fire on continuation runs (post-`endRun`, post-waitpoint-timeout, post-`chat.requestUpgrade`) or on OOM-retry attempts.
- If **`preloaded`** is true, return early — **`onPreload`** already ran.
- Otherwise mirror preload: user/context, conversation create, session upsert.
- No need to gate the conversation create on `continuation` — it's always a brand-new chat at this point.
- For continuation runs that need to refresh per-run state (new PAT, new `lastEventId`), do it in **`onTurnStart`** / **`onTurnComplete`** — both fire on every turn including the first turn of a continuation run.
### `onTurnStart`
- **`await`** persist **`uiMessages`** (full accumulated history including the new user turn) **before** the hook returns — `chat.agent` does not begin streaming until `onTurnStart` resolves, so this is what bounds "user message is durable before the stream".
<Warning>
**Don't use [`chat.defer()`](/ai-chat/background-injection#chat-defer-standalone) for the message write here.** `chat.defer` is fire-and-forget — the hook resolves before the write lands and the stream starts immediately. If the user refreshes mid-stream, the next page load reads `[]` from your DB, the resumed SSE stream pushes the assistant into an empty array, and the user's message disappears from the rendered conversation forever.
```ts
// ❌ Bad — non-blocking write, mid-stream refresh drops the user message.
onTurnStart: async ({ chatId, uiMessages }) => {
chat.defer(db.chat.update({ where: { id: chatId }, data: { messages: uiMessages } }));
},
// ✅ Good — awaited, durable before the model starts.
onTurnStart: async ({ chatId, uiMessages }) => {
await db.chat.update({ where: { id: chatId }, data: { messages: uiMessages } });
},
```
`chat.defer` is for writes whose timing doesn't matter for resume — analytics, audit logs, search-index updates, etc. Anything the next page load reads needs to land before the stream begins.
</Warning>
### `onTurnComplete`
- Persist **`uiMessages`** again with the **assistant** reply finalized.
- **Upsert session** with the fresh **`chatAccessToken`** and **`lastEventId`** from the event.
**`lastEventId`** lets the frontend [resume](/ai-chat/frontend) without replaying SSE events it already applied. Treat it as part of session state, not optional polish, if you care about duplicate chunks after refresh.
<Warning>
**Write the messages and `lastEventId` in a single transaction.** Both values are read in parallel on the next page load (one fetches the conversation, the other fetches the session). If a refresh races between the two writes, the page can see the assistant message persisted (full history) but a stale `lastEventId` from the previous turn. The transport then resumes from that stale cursor and replays this turn's chunks on top of the already-persisted assistant message, producing a duplicated render.
```ts
// ✅ Atomic — refresh on the next page load reads both writes consistently.
await db.$transaction([
db.chat.update({ where: { id: chatId }, data: { messages: uiMessages } }),
db.chatSession.upsert({
where: { id: chatId },
create: { id: chatId, publicAccessToken: chatAccessToken, lastEventId },
update: { publicAccessToken: chatAccessToken, lastEventId },
}),
]);
// ❌ Two awaits — narrow race window where messages are post-write but
// lastEventId is still pre-write. A page refresh that lands here will
// duplicate the assistant message on resume.
await db.chat.update({ where: { id: chatId }, data: { messages: uiMessages } });
await db.chatSession.upsert({ /* ... */ });
```
</Warning>
## Token renewal (app server)
The persisted PAT has a TTL (see **`chatAccessTokenTTL`** on **`chat.agent`**, default 1h). When the transport gets a **401** on a session-PAT-authed request, it calls your **`accessToken`** callback to mint a fresh PAT — no DB lookup required, since the session is keyed on `chatId` (which the transport already has).
Your `accessToken` callback typically just wraps `auth.createPublicToken`:
```ts
"use server";
import { auth } from "@trigger.dev/sdk";
export async function mintChatAccessToken(chatId: string) {
return auth.createPublicToken({
scopes: { read: { sessions: chatId }, write: { sessions: chatId } },
expirationTime: "1h",
});
}
```
If you want to keep your DB session row in sync, the transport's **`onSessionChange`** callback fires every time the cached PAT changes — persist the new value there.
No Trigger task code needs to run for renewal.
## Minimal pseudocode
```typescript
// Pseudocode — replace saveConversation / saveSession with your DB layer.
chat.agent({
id: "my-chat",
clientDataSchema: z.object({ userId: z.string() }),
onPreload: async ({ chatId, chatAccessToken, clientData }) => {
if (!clientData) return;
await ensureUser(clientData.userId);
await upsertConversation({ id: chatId, userId: clientData.userId /* ... */ });
await upsertSession({ chatId, publicAccessToken: chatAccessToken });
},
onChatStart: async ({ chatId, chatAccessToken, clientData, preloaded }) => {
if (preloaded) return;
// Fires once per chat — no continuation gate needed.
await ensureUser(clientData.userId);
await upsertConversation({ id: chatId, userId: clientData.userId /* ... */ });
await upsertSession({ chatId, publicAccessToken: chatAccessToken });
},
onTurnStart: async ({ chatId, uiMessages }) => {
// Awaited, not chat.defer — see the warning in `onTurnStart` above.
await saveConversationMessages(chatId, uiMessages);
},
onTurnComplete: async ({ chatId, uiMessages, chatAccessToken, lastEventId }) => {
// Atomic: messages + lastEventId must be readable consistently on resume.
// See the warning above for why a non-atomic write causes duplicate renders.
await db.$transaction([
saveConversationMessagesQuery(chatId, uiMessages),
upsertSessionQuery({ chatId, publicAccessToken: chatAccessToken, lastEventId }),
]);
},
run: async ({ messages, signal }) => {
/* streamText, etc. */
},
});
```
## Alternative: `hydrateMessages`
For apps that need the backend to be the single source of truth for message history — abuse prevention, branching conversations, or rollback support — use [`hydrateMessages`](/ai-chat/lifecycle-hooks#hydratemessages) instead of relying on the frontend's accumulated state.
With hydration, the hook loads messages from your database on every turn. The frontend's messages are ignored (except for the new user message, which arrives in `incomingMessages`):
```ts
import { chat, upsertIncomingMessage } from "@trigger.dev/sdk/ai";
export const myChat = chat.agent({
id: "my-chat",
hydrateMessages: async ({ chatId, trigger, incomingMessages }) => {
const record = await db.chat.findUnique({ where: { id: chatId } });
const stored = record?.messages ?? [];
// `upsertIncomingMessage` pushes a fresh user message and no-ops
// on HITL continuations (the runtime overlays the new tool-state
// advance onto the existing entry). See lifecycle hooks for the
// full pattern: /ai-chat/lifecycle-hooks#hydratemessages
if (upsertIncomingMessage(stored, { trigger, incomingMessages })) {
// Upsert, not update: on a head-start first turn no preload ran,
// so the row may not exist yet when this hook fires.
await db.chat.upsert({
where: { id: chatId },
create: { id: chatId, messages: stored },
update: { messages: stored },
});
}
return stored;
},
onTurnComplete: async ({ chatId, uiMessages, chatAccessToken, lastEventId }) => {
// Persist the response and refresh session state atomically — see the
// warning in the previous section for why these two writes have to be
// in the same transaction.
await db.$transaction([
db.chat.update({ where: { id: chatId }, data: { messages: uiMessages } }),
db.chatSession.upsert({
where: { id: chatId },
create: { id: chatId, publicAccessToken: chatAccessToken, lastEventId },
update: { publicAccessToken: chatAccessToken, lastEventId },
}),
]);
},
run: async ({ messages, signal }) => {
return streamText({ model: anthropic("claude-sonnet-4-5"), messages, abortSignal: signal });
},
});
```
This replaces the `onTurnStart` persistence pattern — the hook handles both loading and persisting the new message in one place.
Hydration composes with [Head Start](/ai-chat/fast-starts#with-hydratemessages): on a head-start first turn the route handler's history arrives as `incomingMessages`, and the write path must be an upsert because no preload ran to create the row.
## Design notes
- **`chatId`** is stable for the life of a thread and is the only identifier the transport persists. Runs come and go (idle continuation, upgrade, cancel/restart) but the chat keeps its identity.
- **`continuation: true`** means "same logical chat, new run" — refresh the persisted PAT, don't assume an empty conversation.
- The current `runId` is available on every hook event for telemetry / dashboard linking ("View this run"), but you don't need to persist it for resume to work — the transport addresses by `chatId`.
- Keep **task modules** that perform writes **out of** browser bundles; the pattern assumes persistence runs **in the worker** (or your BFF that the task calls).
## Complete example
End-to-end implementation across the three files involved: agent task, server actions, and React component.
<Warning>
The example below trusts raw `chatId` and returns rows without filtering by user. In a real multi-user app, **scope every query by the authenticated user** — read the user from your auth/session in each server action and add `where: { userId }` to all `db.chat.*` and `db.chatSession.*` queries. Without that, one client could read or delete another user's chat state, and `getAllSessions()` would leak other users' `publicAccessToken`s. The snippet keeps auth out of the way to focus on the persistence shape.
</Warning>
<CodeGroup>
```ts trigger/chat.ts
import { chat } from "@trigger.dev/sdk/ai";
import { streamText, stepCountIs } from "ai";
import { anthropic } from "@ai-sdk/anthropic";
import { z } from "zod";
import { db } from "@/lib/db";
export const myChat = chat.agent({
id: "my-chat",
clientDataSchema: z.object({
userId: z.string(),
}),
onChatStart: async ({ chatId, clientData }) => {
await db.chat.create({
data: { id: chatId, userId: clientData.userId, title: "New chat", messages: [] },
});
},
onTurnStart: async ({ chatId, uiMessages, runId, chatAccessToken }) => {
// Persist messages + session before streaming
await db.chat.update({
where: { id: chatId },
data: { messages: uiMessages },
});
await db.chatSession.upsert({
where: { id: chatId },
create: { id: chatId, runId, publicAccessToken: chatAccessToken },
update: { runId, publicAccessToken: chatAccessToken },
});
},
onTurnComplete: async ({ chatId, uiMessages, runId, chatAccessToken, lastEventId }) => {
// Persist assistant response + stream position atomically — see the
// race-condition warning earlier on this page.
await db.$transaction([
db.chat.update({
where: { id: chatId },
data: { messages: uiMessages },
}),
db.chatSession.upsert({
where: { id: chatId },
create: { id: chatId, runId, publicAccessToken: chatAccessToken, lastEventId },
update: { runId, publicAccessToken: chatAccessToken, lastEventId },
}),
]);
},
run: async ({ messages, signal }) => {
return streamText({
model: anthropic("claude-sonnet-4-5"),
messages,
abortSignal: signal,
stopWhen: stepCountIs(15),
});
},
});
```
```ts app/actions.ts
"use server";
import { auth } from "@trigger.dev/sdk";
import { chat } from "@trigger.dev/sdk/ai";
import { db } from "@/lib/db";
export const startChatSession = chat.createStartSessionAction("my-chat");
export async function mintChatAccessToken(chatId: string) {
return auth.createPublicToken({
scopes: { read: { sessions: chatId }, write: { sessions: chatId } },
expirationTime: "1h",
});
}
export async function getChatMessages(chatId: string) {
const found = await db.chat.findUnique({ where: { id: chatId } });
return found?.messages ?? [];
}
export async function getAllSessions() {
const sessions = await db.chatSession.findMany();
const result: Record<
string,
{
publicAccessToken: string;
lastEventId?: string;
}
> = {};
for (const s of sessions) {
result[s.id] = {
publicAccessToken: s.publicAccessToken,
lastEventId: s.lastEventId ?? undefined,
};
}
return result;
}
export async function deleteSession(chatId: string) {
await db.chatSession.delete({ where: { id: chatId } }).catch(() => {});
}
```
```tsx app/components/chat.tsx
"use client";
import { useChat } from "@ai-sdk/react";
import { useTriggerChatTransport } from "@trigger.dev/sdk/chat/react";
import type { myChat } from "@/trigger/chat";
import { mintChatAccessToken, startChatSession, deleteSession } from "@/app/actions";
export function Chat({ chatId, initialMessages, initialSessions }) {
const transport = useTriggerChatTransport<typeof myChat>({
task: "my-chat",
accessToken: ({ chatId }) => mintChatAccessToken(chatId),
startSession: ({ chatId, clientData }) =>
startChatSession({ chatId, clientData }),
clientData: { userId: currentUser.id }, // Type-checked against clientDataSchema
sessions: initialSessions,
onSessionChange: (id, session) => {
if (!session) deleteSession(id);
},
});
const { messages, sendMessage, stop, status } = useChat({
id: chatId,
messages: initialMessages,
transport,
resume: initialMessages.length > 0,
});
return (
<div>
{messages.map((m) => (
<div key={m.id}>
<strong>{m.role}:</strong>
{m.parts.map((part, i) =>
part.type === "text" ? <span key={i}>{part.text}</span> : null
)}
</div>
))}
<form
onSubmit={(e) => {
e.preventDefault();
const input = e.currentTarget.querySelector("input");
if (input?.value) {
sendMessage({ text: input.value });
input.value = "";
}
}}
>
<input placeholder="Type a message..." />
<button type="submit" disabled={status === "streaming"}>
Send
</button>
{status === "streaming" && (
<button type="button" onClick={stop}>
Stop
</button>
)}
</form>
</div>
);
}
```
</CodeGroup>
## See also
- [Lifecycle hooks](/ai-chat/lifecycle-hooks)
- [Session management](/ai-chat/frontend#session-management) — `resume`, `lastEventId`, transport
- [`chat.defer()`](/ai-chat/background-injection#chat-defer-standalone) — non-blocking writes during a turn
- [Code execution sandbox](/ai-chat/patterns/code-sandbox) — combines **`onWait`** / **`onComplete`** with this persistence model