Prisma Chat Persistence

The deliverable is one file in the app — src/lib/chat-persistence.ts — exporting a ChatPersistence built from the app's existing PrismaClient. Plus four models added to the app's existing schema.prisma and a migration created with the app's own prisma migrate.

Do not create a package, a second client, a datasource block, a generator, or a hand-written SQL migration. The app has those.

Read the Build Your Own Adapter guide (docs/persistence/build-your-own-adapter.md) for the store contracts and invariants, and ai-persistence/stores for the shape rules. Every store below mirrors the reference in-memory backend in @tanstack/ai-persistence (memory.ts); the shared conformance testkit is the proof.

1. Read the app before writing anything

Prisma 6 and 7 both work: the delegate query API (findUnique, upsert, update, findMany, delete) is unchanged, so it does not matter which client the app generated.

Never invent a migration path. Add the models, then have the user run their own npx prisma migrate dev --name chat-persistence (or db push) and prisma generate.

2. Add the models to their schema

IDs are String, timestamps are BigInt (portable epoch ms — Int overflows in 2038, DateTime forces a conversion at every boundary), JSON payloads are String. Use @map/@@map to match the app's database naming.

model ChatThread {
  threadId     String @id @map("thread_id")
  messagesJson String @map("messages_json")
  updatedAt    BigInt @map("updated_at")

  @@map("chat_threads")
}

model ChatRun {
  runId      String  @id @map("run_id")
  threadId   String  @map("thread_id")
  status     String
  startedAt  BigInt  @map("started_at")
  finishedAt BigInt? @map("finished_at")
  error      String?
  usageJson  String? @map("usage_json")

  @@index([threadId, status])
  @@map("chat_runs")
}

model ChatInterrupt {
  interruptId  String  @id @map("interrupt_id")
  runId        String  @map("run_id")
  threadId     String  @map("thread_id")
  status       String
  requestedAt  BigInt  @map("requested_at")
  resolvedAt   BigInt? @map("resolved_at")
  payloadJson  String  @map("payload_json")
  responseJson String? @map("response_json")

  @@index([threadId, requestedAt])
  @@map("chat_interrupts")
}

model ChatMetadata {
  namespace String
  key       String
  valueJson String @map("value_json")

  @@id([namespace, key])
  @@map("chat_metadata")
}

Rename models freely to fit the app — the store code below is the only thing that references them. Extra app-owned fields (a userId, audit columns) are fine as long as they are optional or defaulted, so the stores' creates still succeed. namespace is the MetadataStore first argument; the stock SQL in the guide calls the same column scope.

On Postgres or MySQL you can switch the *Json fields to Prisma's Json type and drop the JSON.stringify/parse in the mappers below. Keep String if the app targets SQLite or if it is multi-provider.

3. Write src/lib/chat-persistence.ts

Two conversions the SQL backends do not need: BigInt timestamps in and out, and JSON as strings. Everything else is the shared invariant set.

import { defineAIPersistence } from '@tanstack/ai-persistence'
import type {
  ChatInterrupt,
  ChatRun,
  Prisma,
  PrismaClient,
} from '@prisma/client'
import type { ModelMessage, TokenUsage } from '@tanstack/ai'
import type {
  ChatPersistence,
  InterruptRecord,
  InterruptStatus,
  InterruptStore,
  MessageStore,
  MetadataStore,
  RunRecord,
  RunStatus,
  RunStore,
} from '@tanstack/ai-persistence'

import { prisma } from '@/lib/prisma'

// Trusts the shape the stores themselves wrote — nothing else writes these
// columns.
function parseJson<T>(raw: string): T {
  return JSON.parse(raw)
}

const RUN_STATUSES: ReadonlyArray<RunStatus> = [
  'running',
  'completed',
  'failed',
  'interrupted',
]
const INTERRUPT_STATUSES: ReadonlyArray<InterruptStatus> = [
  'pending',
  'resolved',
  'cancelled',
]

// The column is a plain String, so narrow instead of trusting it.
function toRunStatus(value: string): RunStatus {
  const status = RUN_STATUSES.find((candidate) => candidate === value)
  if (!status) throw new Error(`Unknown run status: ${value}`)
  return status
}

function toInterruptStatus(value: string): InterruptStatus {
  const status = INTERRUPT_STATUSES.find((candidate) => candidate === value)
  if (!status) throw new Error(`Unknown interrupt status: ${value}`)
  return status
}

// Records omit absent optionals so they compare cleanly against the reference
// in-memory backend.
function mapRun(row: ChatRun): RunRecord {
  return {
    runId: row.runId,
    threadId: row.threadId,
    status: toRunStatus(row.status),
    startedAt: Number(row.startedAt),
    ...(row.finishedAt != null ? { finishedAt: Number(row.finishedAt) } : {}),
    ...(row.error != null ? { error: row.error } : {}),
    ...(row.usageJson != null
      ? { usage: parseJson<TokenUsage>(row.usageJson) }
      : {}),
  }
}

function mapInterrupt(row: ChatInterrupt): InterruptRecord {
  return {
    interruptId: row.interruptId,
    runId: row.runId,
    threadId: row.threadId,
    status: toInterruptStatus(row.status),
    requestedAt: Number(row.requestedAt),
    payload: parseJson<Record<string, unknown>>(row.payloadJson),
    ...(row.resolvedAt != null ? { resolvedAt: Number(row.resolvedAt) } : {}),
    ...(row.responseJson != null
      ? { response: parseJson<unknown>(row.responseJson) }
      : {}),
  }
}

function createMessageStore(db: PrismaClient): MessageStore {
  return {
    async loadThread(threadId) {
      const row = await db.chatThread.findUnique({ where: { threadId } })
      // Unknown thread is [], never null.
      return row ? parseJson<Array<ModelMessage>>(row.messagesJson) : []
    },
    // Full overwrite — `messages` is the complete authoritative transcript.
    async saveThread(threadId, messages) {
      const messagesJson = JSON.stringify(messages)
      const updatedAt = BigInt(Date.now())
      await db.chatThread.upsert({
        where: { threadId },
        create: { threadId, messagesJson, updatedAt },
        update: { messagesJson, updatedAt },
      })
    },
  }
}

function createRunStore(db: PrismaClient): RunStore {
  return {
    async get(runId) {
      const row = await db.chatRun.findUnique({ where: { runId } })
      return row ? mapRun(row) : null
    },
    // An empty `update` is Prisma's ON CONFLICT DO NOTHING: an existing runId
    // comes back untouched, so resume and double-submit are safe.
    async createOrResume({ runId, threadId, startedAt, status }) {
      const row = await db.chatRun.upsert({
        where: { runId },
        create: {
          runId,
          threadId,
          status: status ?? 'running',
          startedAt: BigInt(startedAt),
        },
        update: {},
      })
      return mapRun(row)
    },
    // Patching an unknown runId is a no-op: never throws, never inserts.
    async update(runId, patch) {
      const data: Prisma.ChatRunUpdateManyMutationInput = {}
      if (patch.status !== undefined) data.status = patch.status
      if (patch.finishedAt !== undefined) {
        data.finishedAt = BigInt(patch.finishedAt)
      }
      if (patch.error !== undefined) data.error = patch.error
      if (patch.usage !== undefined)
        data.usageJson = JSON.stringify(patch.usage)
      if (Object.keys(data).length === 0) return

      await db.chatRun.updateMany({ where: { runId }, data })
    },
    // Optional in the contract; enables reconnect without a client-held run id.
    async findActiveRun(threadId) {
      const row = await db.chatRun.findFirst({
        where: { threadId, status: 'running' },
        orderBy: { startedAt: 'desc' },
      })
      return row ? mapRun(row) : null
    },
  }
}

function createInterruptStore(db: PrismaClient): InterruptStore {
  // Every listing is ordered by requestedAt ascending.
  const listWhere = async (where: Prisma.ChatInterruptWhereInput) => {
    const rows = await db.chatInterrupt.findMany({
      where,
      orderBy: { requestedAt: 'asc' },
    })
    return rows.map(mapInterrupt)
  }

  return {
    // Insert-if-absent: a duplicate create must never clobber a resolved
    // interrupt back to pending.
    async create(record) {
      await db.chatInterrupt.upsert({
        where: { interruptId: record.interruptId },
        create: {
          interruptId: record.interruptId,
          runId: record.runId,
          threadId: record.threadId,
          status: 'pending',
          requestedAt: BigInt(record.requestedAt),
          payloadJson: JSON.stringify(record.payload),
          ...(record.response !== undefined
            ? { responseJson: JSON.stringify(record.response) }
            : {}),
        },
        update: {},
      })
    },
    async resolve(interruptId, response) {
      await db.chatInterrupt.updateMany({
        where: { interruptId },
        data: {
          status: 'resolved',
          resolvedAt: BigInt(Date.now()),
          ...(response !== undefined
            ? { responseJson: JSON.stringify(response) }
            : {}),
        },
      })
    },
    async cancel(interruptId) {
      await db.chatInterrupt.updateMany({
        where: { interruptId },
        data: { status: 'cancelled', resolvedAt: BigInt(Date.now()) },
      })
    },
    async get(interruptId) {
      const row = await db.chatInterrupt.findUnique({ where: { interruptId } })
      return row ? mapInterrupt(row) : null
    },
    list: (threadId) => listWhere({ threadId }),
    listPending: (threadId) => listWhere({ threadId, status: 'pending' }),
    listByRun: (runId) => listWhere({ runId }),
    listPendingByRun: (runId) => listWhere({ runId, status: 'pending' }),
  }
}

function createMetadataStore(db: PrismaClient): MetadataStore {
  return {
    async get(namespace, key) {
      const row = await db.chatMetadata.findUnique({
        where: { namespace_key: { namespace, key } },
      })
      return row ? parseJson<unknown>(row.valueJson) : null
    },
    async set(namespace, key, value) {
      // JSON.stringify(undefined) is undefined, which Prisma rejects against a
      // required column with an opaque error. Fail clearly instead.
      if (value == null) {
        throw new TypeError(
          `Cannot store ${value} for (${namespace}, ${key}) — use delete() to clear metadata.`,
        )
      }
      const valueJson = JSON.stringify(value)
      await db.chatMetadata.upsert({
        where: { namespace_key: { namespace, key } },
        create: { namespace, key, valueJson },
        update: { valueJson },
      })
    },
    async delete(namespace, key) {
      await db.chatMetadata.deleteMany({ where: { namespace, key } })
    },
  }
}

/** The four chat state stores backed by the app's Prisma client. */
export const chatPersistence: ChatPersistence = defineAIPersistence({
  stores: {
    messages: createMessageStore(prisma),
    runs: createRunStore(prisma),
    interrupts: createInterruptStore(prisma),
    metadata: createMetadataStore(prisma),
  },
})

Notes that bite:

• updateMany, not update, for patches. update throws P2025 on a missing row; the contract says a patch to an unknown id is a silent no-op.
• namespace_key is Prisma's generated alias for the @@id([namespace, key]) composite. If you rename the fields, the alias name changes with them.
• Annotate ChatPersistence — bare AIPersistence is the all-optional bag and withPersistence rejects it. There is no locks store: stores accepts only those four keys, and coordination is wired separately with withLocks (see ai-core/locks).
• If the app renamed the models, the delegate accessors are camelCase (prisma.chatThread for model ChatThread), and the row types imported from the client are PascalCase.

4. Wire it into the chat route

import {
  chat,
  chatParamsFromRequest,
  toServerSentEventsResponse,
} from '@tanstack/ai'
import { openaiText } from '@tanstack/ai-openai'
import { withPersistence } from '@tanstack/ai-persistence'
import { chatPersistence } from '@/lib/chat-persistence'

export async function POST(request: Request) {
  const params = await chatParamsFromRequest(request)
  const stream = chat({
    adapter: openaiText('gpt-5.5'),
    messages: params.messages,
    threadId: params.threadId,
    runId: params.runId,
    ...(params.resume ? { resume: params.resume } : {}),
    middleware: [withPersistence(chatPersistence)],
  })
  return toServerSentEventsResponse(stream)
}

threadId is a bare string to the stores. Authorize thread access at the route — derive the user from the session, never trust a client-supplied id.

5. Verify

import { runPersistenceConformance } from '@tanstack/ai-persistence/testkit'
import { chatPersistence } from '../src/lib/chat-persistence'

runPersistenceConformance('app-prisma', () => chatPersistence, {
  skip: ['generationRuns', 'artifacts', 'blobs'],
})

Point the client at a throwaway database with the migration applied (a scratch SQLite file is enough) and reset it between runs. All four state stores are provided; the suite also covers the three generation stores, so declare those as skipped until you add them. skip never accepts 'locks', which is not a store.

Only if you are publishing this as a package

Everything above assumes the file lives in the app. For a reusable npm adapter, the same store bodies apply, plus:

• Peer dep @prisma/client >=6.7.0. Ship no datasource, generator, connection URL, or prebuilt SQL migration — those stay in the consumer's schema.
• Type the client structurally (a PrismaClientLike shape) and read model delegates off it at runtime, so Prisma 6 and 7 clients both satisfy it regardless of where they were generated.
• Ship the models as a raw string asset plus a CLI (tanstack-ai-prisma-models) that copies a provider-neutral fragment into the consumer's multi-file schema directory. They then run prisma migrate.
• Let consumers rename: prismaPersistence(prisma, { models: { messages: 'chatMessage' } }), where map values are the camelCase client accessors. Throw a PrismaModelError naming every store whose delegate cannot be found. Keep the field surface and the composite-id alias fixed; database names and extra app-owned fields are theirs.
• Run runPersistenceConformance over a temporary SQLite database generated from the fragment.