Identifiers

Vehicle IDs are globally unique

A vehicle receives a globally unique identifier the moment it enters OVP, independent of OpenDiag or any other provider:

ovp:01K0Y5F8G3QZJH2R7T9XN4B6C1

The exact encoding (ULID, UUID, or something else) isn’t fixed yet — what matters is the property: this ID never changes, is never reused, and carries no information about who currently hosts the passport or who currently owns the vehicle. It is not the VIN. The VIN is a fact about the vehicle, recorded as (or alongside) an event; the OVP ID is the handle used to look the vehicle up at all, and needs properties the VIN doesn’t have (VINs are reused, get typo’d, and aren’t guaranteed unique across all vehicle types and eras).

Every passport has a home

An address combines the vehicle ID with its current provider, the same way an email address combines a mailbox with a domain:

ovp:01K0Y5...@passport.opendiag.io
ovp:01K0Y5...@garage.racetune.ee
ovp:01K0Y5...@mygarage.example

Today, that’s passport.opendiag.io. Tomorrow it could be a competing cloud, or a workshop’s self-hosted instance, or a NAS in someone’s garage. The vehicle doesn’t move — the label after the @ does, and only that label changes.

The vehicle chooses the provider, not the software

Exactly like choosing an email provider: the client (OpenDiag, a dealer tool, a workshop app) is not the thing that decides where the passport lives. The vehicle’s current administrative Grant holders do. Migrating providers should look like: export the timeline, sign a redirect, publish it, done — not “beg the incumbent vendor for a data dump.”

Delegation, borrowed from Matrix

The permanent ID should be able to resolve to a different current home without changing the identifier itself:

ovp:01K0Y5...   -->  passport.opendiag.io   (today)
ovp:01K0Y5...   -->  garage.racetune.ee     (later)

This is the same trick Matrix uses to let a user ID (@alice:matrix.org) outlive which homeserver actually hosts Alice’s account, and the same trick email delegation (MX records) uses to let alice@example.com outlive which mail server actually holds Alice’s mailbox. See DISCOVERY.md for how resolution actually works.

QR (and eventually NFC) philosophy

The physical anchor — a QR sticker under the bonnet — encodes the vehicle ID only, never a provider, never an owner, never an OpenDiag URL. That’s the entire reason it can survive twenty years and multiple provider migrations without being replaced: the sticker is a constant, and everything mutable is one discovery lookup away, not baked into the printed code.

A secondary, and almost accidental, benefit: the QR code doubles as a physical prompt. Seeing it under the bonnet is a reminder to log whatever maintenance just happened, the same way a service sticker on a windshield reminds you it’s time for an oil change — except this one never goes stale, because it isn’t tied to a date.

NFC is a natural future extension — same identifier, tap instead of scan, and potentially able to carry a short-lived proof of physical presence for workshop write events (see TRUST.md).