Versions: @cloudflare/think 0.20.2. Still reproduces on 0.21.0, and the inspected main at fc7f59f has the same code.

What happens

getScheduledTasks() may read app-owned data. The docs say to call internal_reconcileScheduledTasks() after changing it. Three problems follow:

1. Strict plurals. The interval grammar accepts minute|minutes|hour|hours, then throws Use singular unit for "every 1 minutes" or Use plural unit for "every 2 minute". The meaning is unambiguous either way. A model or a user writing a schedule gets this wrong often, and the ThinkIntervalSchedule template type allows both forms.
2. Checked only at reconcile. Nothing public validates a schedule before the app stores it. _declaredScheduleValidationError exists but is private. The error surfaces after the row is written.
3. All or nothing. _normalizeDeclaredScheduledTasks() throws on the first invalid task, so no task is armed or updated, including valid ones. On startup the same throw is caught by _runBestEffortOnStartStep, which logs "Declared scheduled tasks were not reconciled on this wake; the next successful wake will reconcile them". But no wake will succeed until the bad row is gone.

Reproduction

export class ScheduleAgent extends Think<Env> {
  getDefaultTimezone() { return "UTC"; }
  getScheduledTasks() {
    const tasks: ThinkScheduledTasks = {};
    for (const j of this.sql`SELECT id, schedule FROM jobs`) tasks[j.id] = { schedule: j.schedule, handler: async () => {} };
    return tasks;
  }
  async set(schedules: string[]) {
    /* replace the jobs rows */
    await this.internal_reconcileScheduledTasks();   // throws for the cases below
  }
}

Expected: accept either plural form and normalise it. Skip an invalid task with a warning, or report it per task, and arm the rest. Offer a public validator so apps can reject bad wording before storing it.

Proposed fix

• In parseDeclaredTaskScheduleUnchecked, drop the two plural checks and normalise to every N minute(s).
• In _normalizeDeclaredScheduledTasks, use tryParseDeclaredTaskSchedule, then console.warn and continue on error.
• Export validateScheduledTaskSchedule(schedule, { timezone?, defaultTimezone? }): string | null, the public form of _declaredScheduleValidationError.

With the first two applied to the 0.21.0 build, all four cases above arm every valid task. ["every 2 minutes", "every 1 minutes", "every day at 9:00"] arms 2 tasks and logs Scheduled task "job2" skipped: Unsupported schedule DSL "every day at 9:00".