Your HTTP cache exists on two targets and is a stub on two others
OkHttp and NSURLSession cache to disk, the browser's cache is the browser's, and the common engine has none. Measured hit rates differ by a factor nobody budgeted for.
Engineering
Compose, Kotlin, and multiplatform work — the mechanism under the symptom.
296 posts
appleMain exists only if your targets justify it
The hierarchy template inserts nodes based on declared targets. A directory for a node that does not exist compiles nowhere and warns about nothing.
Dispatchers.Main throws on a target you forgot to configure
Main is supplied by a platform integration, so it exists on Android and iOS and fails at runtime on desktop tests — a crash whose message names a module, not a mistake.
We shared 60% of the code and one platform used all of it
Measured per target rather than per line: the iOS app reached a third of the shared surface because the API was shaped around Android's lifecycle.
The transaction that was atomic on Android and not on the web
Nested transactions, savepoints and write locking vary per driver. Code written against one driver's guarantees loses them silently on another.
One version, four numbering schemes, and a release that could not be rolled back
A monotonic integer, a build string, a semantic version and a cache-busting hash have to agree. Deriving all four from one source is the only shape that survives a hotfix.
Nothing reconnects your WebSocket, on any target
A dropped socket is a normal event with no exception on some engines. Reconnection with jitter and a resume token is application code, and it is the same code on all four.
A framework builds for one architecture. iOS consumers need an XCFramework
A simulator-only framework works on your machine and fails on the device, and the error names a missing architecture rather than the packaging decision that caused it.
commonTest runs on every target, which is the point and the cost
One test, five executions. That is how you find platform bugs — and how one flaky test fails five jobs.
composeResources is not Android resources, and qualifiers resolve differently
Same folder names, different resolution. The accessor is typed, and a missing qualifier fails somewhere new.
Extending MaterialTheme beats replacing it, until it doesn't
Material models colour, type and shape. Everything else a design system needs — spacing, motion, semantic colour — has to be added. Extending with a parallel CompositionLocal is usually right; a full custom system rarely is.
kotlinx-datetime has no Calendar, and the timezone database ships per platform
Instant is unambiguous. LocalDateTime is not. The same arithmetic can disagree across targets.