The Reminders feature turns channel topics into cron schedules. When the bot starts (or a channel is created or updated), it reads the topic, parses any reminder definitions, and schedules recurring messages with threads.
Embed one or more reminders in a channel’s topic using the following syntax:
[reminder:CRON_EXPRESSION:MESSAGE]
Weekly standup channel. [reminder:0 9 * * 1:Weekly standup time!] [reminder:0 17 * * 5:Week in review!]
Standard 5-field cron expressions are supported (minute, hour, day-of-month, month, day-of-week). Effect’s Cron module parses the expression — invalid expressions are logged and skipped.
What happens on schedule
When a cron fires, the bot:
- Posts the reminder message to the channel.
- Creates a thread from that message named
{date} - {message} (e.g. Mon Mar 25 2026 - Weekly standup time!).
If the thread creation fails, it retries up to 3 times with a 1-second delay between attempts.
const createThreadPolicy = Schedule.spaced("1 seconds").pipe(
Schedule.both(Schedule.recurs(3)),
)
Parsing the topic
The parseTopic function uses a regular expression to extract all [reminder:...:...] blocks and parses each cron expression independently:
const parseTopic = (topic: string) =>
Effect.partition(
Array.from(topic.matchAll(/\[reminder:(.+?):(.+?)\]/g)),
(matches) => {
const [match, expression, message] = matches
if (
match === undefined ||
expression === undefined ||
message === undefined
) {
return Effect.fail(
new InvalidTopic({
reason: "invalid reminder format",
match: String(match),
}),
)
}
return parseExpression(match, expression, message)
},
)
Gateway events
The bot listens to the following Discord gateway events to keep schedules in sync:
| Event | Action |
|---|
GUILD_CREATE | Schedules reminders for all channels in the guild on startup. |
CHANNEL_CREATE | Schedules reminders for the new channel. |
CHANNEL_UPDATE | Cancels existing schedules and re-parses the updated topic. |
CHANNEL_DELETE | Cancels any running schedules for the deleted channel. |
Example
To post a weekly standup reminder every Monday at 9:00 AM UTC, set the channel topic to:
[reminder:0 9 * * 1:Weekly standup time!]