Payloads grow like leftover condiments. A partner asks for one more property “for diagnostics.” A growth manager wants the full UTM blob “for later.” A year later privacy review cannot explain the JSON, and performance traces show the same click ID under two keys. App Analytics — Deep Link Performance Tracking gets slower and less honest at the same time.
Duplicate identifiers
The most common double-count we still see in 2026 is the same click ID sent as click_id and again as transaction_id or a partner alias. Incident notes in Signal Path start here. If your MMP and your warehouse both increment on either key, you will celebrate a spike that is just a rhyme.
Vanity fields that never changed a route
Device marketing names, approximate city, “engagement score,” and the entire web query string forwarded into the app. If routing does not read it, and credit does not read it, it is not telemetry — it is luggage. Delete it before the store hop so deferred reconstruction has less junk to mis-attach.
PII adjacent leftovers
Email hashes collected “in case we do CRM later,” phone prefixes from a form that was not part of the link, and advertising IDs copied into a custom packet because a slide said to. Thailand’s PDPA conversations get simpler when the deep-link payload is boring. Boring is a feature.
What we keep
A stable click identifier (one), a campaign token that matches the naming contract, a timestamp, and the surface the link intended to open. Optional: a window label if your wrapper can carry it without exploding Universal Link length. Everything else must win an argument in Quiet SDK Telemetry or it stays off the wire.
Flutter coverage in that block is still thinner than native; several Atelier notes mention it. Bring your mobile lead anyway. Catalogue: programmes. Map: deep link tracking.