Routines: hourly cron minute is silently rewritten to the save-time minute (undocumented)

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

What's Wrong?

When a Routine's cron is set to an hourly schedule, the stored cron_expression has its
minute field silently overwritten with the minute-of-day at which the routine was saved,
instead of the value I specified.

Concretely: saving cron_expression = "0 * * * *" at 05:46 results in the trigger storing
46 * * * *, and next_run_at becomes the next :46 (e.g. 06:46). Re-saving at a different
minute changes the run minute again — so the effective schedule tracks when I last saved,
not what I entered. There is no way to pin an hourly Routine to a specific minute (e.g. :00).

What Should Happen?

The stored cron should preserve the minute I entered (0 * * * * → runs near :00 each hour).
A small documented stagger is fine, but it should not rewrite the cron's minute field, and it
should be possible to target a specific minute (or the docs should state that exact-minute
scheduling is unsupported for Routines).

Error Messages/Logs

# sent
cron_expression: "0 * * * *"

# stored back (saved at 05:46)
cron_expression: "46 * * * *"
next_run_at:      2026-...T06:46:00Z

Contrast — a weekly cron is NOT rewritten: 0 0 * * 1 stays 0 0 * * 1, and only
next_run_at carries a few-seconds stagger (e.g. 00:01:31, 00:05:27). The minute is
preserved. So the rewrite appears specific to hourly/frequent schedules.

Steps to Reproduce

1. Create/update a Routine with cron_expression = "0 * * * *" (intent: top of every hour).
2. Save at, e.g., 05:46.
3. Inspect the trigger's stored cron_expression and next_run_at.
4. Observe the minute is now the save-time minute (46), not 0.

Claude Model

Not applicable (scheduling/infrastructure behavior).

Is this a regression?

Not sure / haven't verified against an earlier version.

Claude Code Version

N/A — Claude Code Routines (cloud), managed via the routines API.

Platform

Claude Code on the web / Routines (cloud).

Operating System

N/A (cloud-managed execution).

Terminal/Shell

N/A.

Additional Information

Docs gap: routines.md only mentions "runs may start a few minutes after the scheduled time
due to stagger" and "the offset is consistent per routine." It does not mention rewriting the
cron minute field, and the observed offset (:46 from :00) exceeds the 30-min jitter cap
documented for Scheduled Tasks.

Requests:

1. Document the exact minute-jitter/rewrite rule for Routines (when it applies, how the minute

is chosen).

1. Provide a way to pin an exact minute (opt out of stagger), or state clearly that

exact-minute scheduling is unsupported for Routines.

1. If rewriting the stored cron_expression is unintended, treat as a bug.

Observed: 2026-07-20.