Version mobile APIs before fields multiply past recovery
Silent additive fields feel safe until clients deserialize differently. Contract discipline starts earlier than most teams expect.
Mobile clients freeze schemas longer than web frontends. A backend team that ships weekly field renames forces store-bound apps into fragile adapters and hotfix builds.
In advisory work across Taiwan product teams, we ask leads to name a versioning policy before the tenth consumer lands: URI versions, header versions, or explicit envelope versions — pick one and document who may break it.
Additive fields still need owners. If three teams may attach optional keys without review, clients accumulate dead parsers. A lightweight contract review gate beats another compatibility shim.
Pair the policy with a deprecation calendar clients can trust. Without dates, “deprecated” is gossip, not engineering.