Schedule Slack posts with Next.js, Workflow, and Neon

Chat SDK Documentation

Vercel · 2026-04-06 · via Chat SDK Documentation

This guide walks through scheduling Slack channel posts with Chat SDK, persisting schedules in Neon, and using Workflow sleep timers for durable delivery.

Chat SDK already supports native scheduled messages on Slack with thread.schedule() and channel.schedule(). That is useful for simple Slack-only cases.

This guide uses a different pattern: Workflow owns the timer with sleep(), and Neon stores the schedule as your source of truth. That gives you a more durable scheduling system you can extend with cancellation, rescheduling, approvals, and cross-platform delivery later.

The example uses Slack slash commands to schedule top-level channel posts.

Node.js 18+
pnpm (or npm/yarn)
A Next.js App Router project
A Slack workspace where you can install apps
A Neon Postgres database

If you still need Slack app setup and the webhook route, start with Slack bot with Next.js and Redis, then come back here and swap the state adapter to PostgreSQL.

Install Chat SDK, the Slack adapter, the PostgreSQL state adapter, Workflow, and pg:

pnpm add chat @chat-adapter/slack @chat-adapter/state-pg workflow pg

Create a Neon project, copy its pooled Postgres connection string, and store it as POSTGRES_URL.

createPostgresState() already supports POSTGRES_URL and DATABASE_URL, so the same Neon database can back both Chat SDK state and your app's schedule table.

Create a .env.local file:

SLACK_BOT_TOKEN=xoxb-your-bot-token
SLACK_SIGNING_SECRET=your-signing-secret
POSTGRES_URL=postgresql://user:password@your-neon-host-pooler.neon.tech/neondb?sslmode=require

Wrap your Next.js config with withWorkflow() so "use workflow" and "use step" directives are compiled:

import { withWorkflow } from "workflow/next";
import type { NextConfig } from "next";

const nextConfig: NextConfig = {
  // ...your existing config
};

export default withWorkflow(nextConfig);

If your app uses proxy.ts, exclude .well-known/workflow/ from the matcher so Workflow's internal routes are not intercepted.

Add two slash commands to your Slack app and point both at your webhook route:

features:
  slash_commands:
    - command: /remind
      url: https://your-domain.com/api/webhooks/slack
      description: Schedule a channel post
      usage_hint: "<ISO-8601 timestamp> <message>"
      should_escape: false
    - command: /remind-cancel
      url: https://your-domain.com/api/webhooks/slack
      description: Cancel a scheduled post
      usage_hint: "<schedule-id>"
      should_escape: false

If you're starting from scratch rather than the Slack guide, make sure your app also has the commands and chat:write bot scopes in OAuth & Permissions, then reinstall the app after changing scopes.

This guide keeps parsing simple by accepting an ISO timestamp like 2026-03-15T09:00:00Z.

Run this SQL in the Neon SQL Editor:

CREATE TABLE scheduled_posts (
  id text PRIMARY KEY,
  channel_id text NOT NULL,
  message text NOT NULL,
  post_at timestamptz NOT NULL,
  status text NOT NULL CHECK (status IN ('pending', 'sent', 'canceled')),
  workflow_run_id text,
  created_by text NOT NULL,
  sent_at timestamptz,
  canceled_at timestamptz,
  created_at timestamptz NOT NULL DEFAULT now()
);

CREATE INDEX scheduled_posts_status_post_at_idx
  ON scheduled_posts (status, post_at);

Create the Postgres client

Use a shared pg pool for your own schedule records:

import pg from "pg";

if (!process.env.POSTGRES_URL) {
  throw new Error("POSTGRES_URL is required");
}

export const pool = new pg.Pool({
  connectionString: process.env.POSTGRES_URL,
});

Use Neon for Chat SDK state by switching to the PostgreSQL state adapter:

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

export const bot = new Chat({
  userName: "reminder-bot",
  adapters: {
    slack: createSlackAdapter(),
  },
  state: createPostgresState(),
});

Create a small data layer for inserting, loading, updating, and canceling scheduled posts:

import { randomUUID } from "node:crypto";
import { pool } from "@/lib/db";

export interface ScheduledPost {
  id: string;
  channelId: string;
  message: string;
  postAt: string;
  status: "pending" | "sent" | "canceled";
  workflowRunId: string | null;
}

export async function createScheduledPost(input: {
  channelId: string;
  createdBy: string;
  message: string;
  postAt: Date;
}) {
  const id = randomUUID();

  await pool.query(
    `INSERT INTO scheduled_posts (
      id, channel_id, message, post_at, status, created_by
    ) VALUES ($1, $2, $3, $4, 'pending', $5)`,
    [id, input.channelId, input.message, input.postAt, input.createdBy]
  );

  return { id, ...input, postAt: input.postAt.toISOString() };
}

export async function getScheduledPost(id: string): Promise<ScheduledPost | null> {
  const result = await pool.query(
    `SELECT id, channel_id, message, post_at, status, workflow_run_id
     FROM scheduled_posts
     WHERE id = $1
     LIMIT 1`,
    [id]
  );

  if (result.rows.length === 0) {
    return null;
  }

  const row = result.rows[0];
  return {
    id: row.id as string,
    channelId: row.channel_id as string,
    message: row.message as string,
    postAt: (row.post_at as Date).toISOString(),
    status: row.status as ScheduledPost["status"],
    workflowRunId: (row.workflow_run_id as string | null) ?? null,
  };
}

export async function attachWorkflowRun(id: string, runId: string) {
  await pool.query(
    `UPDATE scheduled_posts
     SET workflow_run_id = $2
     WHERE id = $1`,
    [id, runId]
  );
}

export async function markScheduledPostSent(id: string) {
  await pool.query(
    `UPDATE scheduled_posts
     SET status = 'sent', sent_at = now()
     WHERE id = $1 AND status = 'pending'`,
    [id]
  );
}

export async function cancelScheduledPost(id: string, createdBy: string) {
  const result = await pool.query(
    `UPDATE scheduled_posts
     SET status = 'canceled', canceled_at = now()
     WHERE id = $1 AND created_by = $2 AND status = 'pending'`,
    [id, createdBy]
  );

  return (result.rowCount ?? 0) > 0;
}

The workflow only orchestrates. All Postgres access and Slack posting stay in "use step" functions:

import { sleep } from "workflow";
import { bot } from "@/lib/bot";
import {
  getScheduledPost,
  markScheduledPostSent,
} from "@/lib/scheduled-posts";

async function loadScheduledPost(scheduleId: string) {
  "use step";
  return getScheduledPost(scheduleId);
}

async function postToChannel(channelId: string, message: string) {
  "use step";

  await bot.initialize();

  const channel = bot.channel(channelId);
  await channel.post(message);
}

async function completeScheduledPost(scheduleId: string) {
  "use step";
  await markScheduledPostSent(scheduleId);
}

export async function sendScheduledPost(scheduleId: string) {
  "use workflow";

  const schedule = await loadScheduledPost(scheduleId);
  if (!schedule || schedule.status !== "pending") {
    return;
  }

  await sleep(new Date(schedule.postAt));

  // Re-check the row after waking up in case it was canceled.
  const fresh = await loadScheduledPost(scheduleId);
  if (!fresh || fresh.status !== "pending") {
    return;
  }

  await postToChannel(fresh.channelId, fresh.message);
  await completeScheduledPost(scheduleId);
}

This is the key Workflow pattern:

schedule creation writes a row in Neon first
the workflow sleeps until postAt
the workflow reloads the row after waking up
canceled schedules no-op instead of posting

That makes cancellation simple and durable.

Create a side-effect module that parses commands, writes rows to Neon, starts workflows, and handles cancellation:

import { start } from "workflow/api";
import { bot } from "@/lib/bot";
import {
  attachWorkflowRun,
  cancelScheduledPost,
  createScheduledPost,
} from "@/lib/scheduled-posts";
import { sendScheduledPost } from "@/workflows/send-scheduled-post";

function parseReminderInput(input: string) {
  const trimmed = input.trim();
  const firstSpace = trimmed.indexOf(" ");

  if (firstSpace === -1) {
    return null;
  }

  const timestamp = trimmed.slice(0, firstSpace);
  const message = trimmed.slice(firstSpace + 1).trim();
  const postAt = new Date(timestamp);

  if (!message || Number.isNaN(postAt.getTime()) || postAt <= new Date()) {
    return null;
  }

  return { message, postAt };
}

bot.onSlashCommand("/remind", async (event) => {
  const parsed = parseReminderInput(event.text);

  if (!parsed) {
    await event.channel.postEphemeral(
      event.user,
      "Usage: `/remind 2026-03-15T09:00:00Z Review launch checklist`",
      { fallbackToDM: false }
    );
    return;
  }

  const scheduled = await createScheduledPost({
    channelId: event.channel.id,
    createdBy: event.user.userId,
    message: parsed.message,
    postAt: parsed.postAt,
  });

  const run = await start(sendScheduledPost, [scheduled.id]);
  await attachWorkflowRun(scheduled.id, run.runId);

  await event.channel.postEphemeral(
    event.user,
    `Scheduled \`${scheduled.id}\` for ${parsed.postAt.toISOString()}.`,
    { fallbackToDM: false }
  );
});

bot.onSlashCommand("/remind-cancel", async (event) => {
  const scheduleId = event.text.trim();

  if (!scheduleId) {
    await event.channel.postEphemeral(
      event.user,
      "Usage: `/remind-cancel <schedule-id>`",
      { fallbackToDM: false }
    );
    return;
  }

  const canceled = await cancelScheduledPost(scheduleId, event.user.userId);

  await event.channel.postEphemeral(
    event.user,
    canceled
      ? `Canceled \`${scheduleId}\`.`
      : `No pending schedule found for \`${scheduleId}\`.`,
    { fallbackToDM: false }
  );
});

The cancellation path is intentionally simple. It only updates the database row, and it only allows the creator of the schedule to cancel it. If the workflow wakes up later, it re-checks the row and exits without posting.

If you want workspace admins or moderators to cancel other users' schedules, extend the cancellation query with your own permission rules instead of removing the ownership check.

Import the handler module once so the slash command handlers are registered:

import "@/lib/reminder-handlers";
import { after } from "next/server";
import { bot } from "@/lib/bot";

type Platform = keyof typeof bot.webhooks;

export async function POST(
  request: Request,
  context: RouteContext<"/api/webhooks/[platform]">
) {
  const { platform } = await context.params;

  const handler = bot.webhooks[platform as Platform];
  if (!handler) {
    return new Response(`Unknown platform: ${platform}`, { status: 404 });
  }

  return handler(request, {
    waitUntil: (task) => after(() => task),
  });
}

Start your development server with pnpm dev
Expose it with a tunnel such as ngrok http 3000
Update your Slack slash command URLs to the tunnel URL
In Slack, run /remind 2026-03-15T09:00:00Z Review launch checklist
Confirm that you receive an ephemeral confirmation with a schedule ID
Wait for the scheduled time and verify the bot posts to the channel
Create another one and cancel it with /remind-cancel <schedule-id>

From here you can add:

rescheduling by canceling the old row and creating a new one
recurring posts by having the workflow create the next schedule before it exits
approvals by pausing the workflow with a hook before posting
thread reminders by storing thread.toJSON() instead of channelId and restoring it with bot.reviver()

Slack bot with Next.js and Redis — Base Slack app and webhook setup
Slash Commands — Command handling patterns
PostgreSQL State Adapter — Using Postgres for Chat SDK state
Channel API — Posting to channels and working with channel IDs
Chat API — bot.channel() and lifecycle management

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推荐订阅源

Chat SDK Documentation

Create the Postgres client