Telling customers their car is ready

What this actually looks like

Ringing round at five o’clock finds nobody, and a voicemail is not a collection. A sealed workshop channel reaches every customer who joined it when they dropped the car off, and the alert names the job number rather than the person: “Job 3184 — ready, collection until 18:00.”

How you would set it up

1. Create a private channel for the workshop and hand out its invite QR code on the job sheet when a car comes in.
2. Send one line when a job is finished: the job number and the collection deadline. Normal priority.
3. Use the same channel for what everybody needs — bank-holiday hours, courtesy-car returns, a recall notice.

Private means sealed, not merely unlisted

A private channel is not one that is simply missing from a directory. It requires an invite code both to subscribe AND to read anything about it, and a request without one gets exactly the same “not found” as a handle that never existed — because a different answer would let anybody confirm that a school’s or an ops team’s channel exists by guessing its name. Invite codes can carry a use limit and can be revoked; revoking is a timestamp and by default removes nobody who already joined.

Nothing that could identify anybody

Subscribing needs no account, no email address and no phone number. What a subscription actually holds is a random identifier the app generated, a platform, an app version, a language and a time zone — coarse enough that hundreds of millions of people share one. There is no name, no contact detail, no advertising identifier and no location, and there is no export that would let an operator build one. You cannot leak a list you never collected.

One handle, printed once, permanent

A channel lives at drop.top followed by its handle, and that address never changes. It cannot be edited after creation, because it ends up on a poster in a school entrance, on a festival gate and inside a QR code somebody has already laminated. The page behind it explains what the channel is, what it asks a phone for, and how to subscribe — so a stranger reading a poster can decide before installing anything. We generate the QR code for you, server-side, and it is never sent to a third-party image service.