[Bug]: T3 Code scheduler is not fully compatible with Codex scheduled tasks #20865

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to investigate.

Area

packages/contracts or packages/shared

Steps to reproduce

1. Migrate a Codex scheduled task that should run once on a future date, or an hourly task scheduled for minute :10 of each hour.
2. Configure the equivalent in T3 Code using its available interval or fixed daily/weekly schedules.
3. Observe that a one-time task needs a daily date-check prompt, and an hourly interval follows its creation-time offset instead of the configured minute.

Expected behavior

T3 Code should support a one-time trigger at a chosen date and time, and interval schedules should be able to keep a precise clock alignment. Migrating Codex schedules should not require daily no-op agent runs or change the intended firing time.

Actual behavior

T3 Code currently supports interval and fixed daily/weekly schedules, but no one-time trigger. An hourly interval preserves the one-hour cadence but not a chosen minute such as :10; I used a daily date check as a workaround for Codex tasks with annual dates or a one-time trigger, which runs on dates when it has nothing to do.

Impact

Major degradation or frequent failure. The workarounds add unnecessary scheduled runs and make it harder to move all scheduled tasks from Codex into T3 Code.

Screenshots, recordings, or supporting files

Workaround

Use a daily scheduled task that checks the date and exits when it is not the target date. This avoids missing the task, but creates an extra no-op run each day.

Related feature requests

• Support one-time scheduled tasks. This proposal adds a durable schedule for one chosen date and time that completes after firing. It would remove daily date-check runs for one-time and date-based Codex automations.
• Cron expressions for scheduled tasks. This proposal supports precise clock patterns, including hourly runs at a chosen minute such as :10. It would preserve the intended run times of Codex tasks during migration.

I consider this a bug because I remember Theo and others saying, “You can now schedule things in T3 Code like in other harnesses like Codex and ...”. Maybe I misremember, but these two compatibility gaps seem feasible to fix, and addressing them would let users fully migrate scheduled tasks away from Codex to T3 Code.