vercel__chat/packages/state-pg

@chat-adapter/state-pg

npm package: @chat-adapter/state-pg

Production PostgreSQL state adapter for Chat SDK built with pg (node-postgres). Use this when PostgreSQL is your primary datastore and you want state persistence without a separate Redis dependency.

Documentation: chat-sdk.dev/adapters/official/postgres · Guides: vercel.com/kb/chat-sdk

Installation

pnpm add @chat-adapter/state-pg

Scaffold with the CLI

To scaffold a new Slack bot that uses PostgreSQL for state:

npx create-chat-sdk@latest my-bot --adapter slack postgres

Visit the adapters directory to see other available official and vendor-official adapters.

Usage

createPostgresState() auto-detects POSTGRES_URL (or DATABASE_URL) so you can call it with no arguments:

import { Chat } from "chat";
import { createPostgresState } from "@chat-adapter/state-pg";

const bot = new Chat({
  userName: "mybot",
  adapters: { /* ... */ },
  state: createPostgresState(),
});

To provide a URL explicitly:

const state = createPostgresState({
  url: "postgres://postgres:postgres@localhost:5432/chat",
});

Using an existing client

import pg from "pg";

const client = new pg.Pool({ connectionString: process.env.POSTGRES_URL! });
const state = createPostgresState({ client });

Configuration

Option	Required	Description
url	No*	Postgres connection URL
client	No	Existing pg.Pool instance
keyPrefix	No	Prefix for all state rows (default: "chat-sdk")
logger	No	Logger instance (defaults to ConsoleLogger("info").child("postgres"))

*Either url, POSTGRES_URL/DATABASE_URL, or client is required.

Environment variables

POSTGRES_URL=postgres://postgres:postgres@localhost:5432/chat

Data model

The adapter creates these tables automatically on connect():

chat_state_subscriptions
chat_state_locks
chat_state_cache
chat_state_lists
chat_state_queues

All rows are namespaced by key_prefix.

Features

Feature	Supported
Persistence	Yes
Multi-instance	Yes
Subscriptions	Yes
Distributed locking	Yes
Key-value caching	Yes (with TTL)
Automatic table creation	Yes
Key prefix namespacing	Yes

Locking considerations

The Redis state adapters use atomic SET NX PX for lock acquisition, which is a single atomic operation. The PostgreSQL adapter uses INSERT ... ON CONFLICT DO UPDATE WHERE expires_at <= now(), which relies on Postgres row-level locking. This is safe for most workloads but under extreme contention (many processes competing for the same lock simultaneously) may behave slightly differently than Redis. For high-contention distributed locking, prefer the Redis adapter.

Expired row cleanup

Unlike Redis (which handles TTL expiry natively), PostgreSQL does not automatically delete expired rows. The adapter performs opportunistic cleanup — expired locks are overwritten on the next acquireLock() call, expired cache entries are deleted on the next get() call for that key, and expired queue entries for a given thread are purged on the next enqueue() or dequeue() call. Expired list entries are filtered out on read but never deleted by the adapter.

For high-throughput deployments, you may want to run a periodic cleanup job:

DELETE FROM chat_state_locks WHERE expires_at <= now();
DELETE FROM chat_state_cache WHERE expires_at <= now();
DELETE FROM chat_state_lists WHERE expires_at <= now();
DELETE FROM chat_state_queues WHERE expires_at <= now();

AI Coding Agents

If you use an AI coding agent such as OpenAI Codex, Claude Code, or Cursor, install the Chat SDK skill so it knows the SDK APIs, adapter patterns, and project conventions before writing code.

npx skills add vercel/chat

The skill references bundled documentation in node_modules/chat/docs, plus adapter guides and starter templates in the published package.

You can also install the Vercel Plugin for a broader agent toolkit — it includes the Chat SDK skill alongside specialist agents, agent slash commands, and more:

npx plugins add vercel/vercel-plugin

The plugin is optional; the skill alone is enough to build with Chat SDK.

For agent-readable documentation, see chat-sdk.dev/llms.txt (page index) or chat-sdk.dev/llms-full.txt (full text).

License

MIT