When your mobile app must work without internet as a standard, not an edge case, the sync layer is just the first decision. What comes after — preserving user intent offline, trusting a "success" your server never actually confirmed, resolving conflicts as a human decision — is where offline-first actually gets hard. Field notes from a production KMP winery app.

Offline-First KMP

When offline is the standard, not the edge case, picking a sync layer is the easy part — the hard part is everything after. Field notes from a KMP app.

Choosing an offline-first sync layer for KMP

Two writes for every tap

Minting IDs Before the Server

The Write You Never Clean Up

HTTP 200 Is Not Success

Your Schema Is Not Your Payload

You Cannot Fix a Generated File

Every Synced Row Needs an ID

Your Sync Stack Fits in Three Containers

HTTP 500 Is Not a Retry