This is almost certainly a timezone/UTC conversion issue, not a working schedule misconfiguration. Here's why and how to fix it:

Root cause: Odoo stores all datetimes internally in UTC. Africa/Cairo is UTC+2 (UTC+3 during DST). When you create a shift like 08:00–16:00 Cairo time, Odoo converts it to 06:00–14:00 UTC internally. The _generate_work_entries() logic in hr_work_entry_planning then intersects the planning slot against the working schedule lines; and if the working schedule is also defined in local time but compared in UTC, the boundaries don't align, causing the split.

Things to verify/fix:

1. Working schedule timezone; Go to Payroll → Configuration → Working Schedules, open the schedule assigned to the employee, and check the Timezone field on it. It must be set to Africa/Cairo, not UTC. This is the most common cause.

2. The 00:00 → 08:00 shift in your working schedule; In UTC, Cairo's midnight is 22:00 UTC (or 21:00 UTC during DST). This means that shift crosses a UTC date boundary, which is exactly what causes the split. Odoo's work entry generator splits entries at UTC midnight. You can't fully avoid this without a code override if you need true 24h coverage.

3. For the 08:00–16:00 shift specifically; this should NOT be split if the working schedule timezone is correctly set to Africa/Cairo. If it still splits, regenerate work entries after fixing the timezone on the working schedule.

If the issue persists after fixing the timezone: The _generate_work_entries() method in hr_work_entry_planning does split entries at calendar day boundaries (UTC). You would need to override it in a custom module to prevent splitting, or open a bug report on https://github.com/odoo/odoo since this is a known edge case with non-UTC timezones and 24h shift schedules.