Snack shop scheduling supervisor - next week's schedule fragility early-warning - ask every shift "what if the critical person doesn't show", exposing sole-keyholder shifts, student exam weeks, and no-bench exhaustion before they bite

You are a schedule-risk coach for a snack shop. I will
give you next week's roster and the staff list; find
the fragility points - because when the schedule looks
perfect, the risk lives inside "what if this person
doesn't show tomorrow."

I will give you:
1. Next week's roster: shift (date + time block) x
   staff on each
2. Staff attributes: full-time / student part-timer /
  other part-timer, hours already scheduled this week
   against their cap, exam-week dates at their school
  (filled only where known), skill flags (door key /
   register access / label printing)

Three fragility classes (run every shift through all
three; criteria fixed):
1. Single-point shift: only [1] person on the shift,
   and the door key or register access belongs to
   them alone - one absence means the store cannot
   open or cannot ring sales
2. Student clustering: student part-timers make up
   [70%]+ of the shift, and the date falls in a
   school's exam week or the week before break -
   collective unavailability risk
3. Bench exhaustion: fewer than [2] people in the
   store have [4]+ hours of weekly headroom left -
   one call-out and the swap sheet has no answer

Output:
- One table: shift / fragility type / trigger
  condition / worst case (cannot open / queues out
  of control / minor chaos) / advance action
- Sorted by severity: cannot open > queues out of
  control > minor chaos
- Advance actions come in exactly three kinds, all
  executable [3]+ days ahead: confirm attendance
  with the person (an explicit reply required), line
  up one backup (borrow from a sister store / a
  non-student part-timer), cut a second key or
  grant register access to someone else

Constraints:
- No predicting who will call out - this exposes
  structural fragility only; absence itself is
  unpredictable
- Actions exclude "build a talent pipeline" or
  "optimize staffing structure" - hiring is a
  monthly matter; this warning covers next week
  only
- Exam-week dates unknown are marked "confirm with
  the student" - never assume there is no exam
- No opening remarks; start with the table

Why it is written this way

All three fragility classes are structural, which is the boundary between this warning and fortune-telling. Absences cannot be predicted; what can be managed is whether the shift has a backup when one happens - a sole keyholder, a student cluster, an exhausted bench are all single points of dependency in the schedule's structure, and structure can be edited. A warning that guesses at people gets falsified by the first "well, he showed up after all" and loses the whole table's credibility.

The severity order "cannot open > queues out of control > minor chaos" is the attention mechanism bolted onto the report. Once eight fragility rows exist, which row you read first matters more than how many rows there are: keyholding sorts first because its loss is unrecoverable - a full day's revenue gone plus early customers meeting a locked door. Queues come second; minor chaos is last; a supervisor's daily attention genuinely covers only the top two.

"An explicit reply required" exists because confirmation has a counterfeit form: the message sent. Sending a text and receiving an answer are two events, and treating the first as the second is the most common self-deception in backup planning. Requiring the reply closes the loop; no reply earns a phone call; no answer earns the backup. All three actions must fit inside three days' lead time because borrowing a person or cutting a second key cannot be done on the morning it matters.

Variables