checkin_conflict

HTTP 409: Check-in conflict

When it occurs

A check-in already exists for this person on this local calendar date, originated by a different consumer (MW-05, ENT-07): one check-in per person per day, regardless of who wrote it first. This is the case /docs/contract/how-to/shared-log walks end to end.

What to do next

GET the existing check-in and PATCH it instead of creating a second one; see /docs/contract/how-to/shared-log for the writer/reader setup that avoids hitting this in the first place.