Jetpack Compose LazyColumn items not recomposing when data changes

Problem

LazyColumn items do not update when the underlying list data changes. The list shows stale data even after the state is updated.

Symptoms

• LazyColumn shows old data after update
• Items do not recompose when list changes
• Adding/removing items works but editing does not reflect

Stack

Solution

Provide a stable key to LazyColumn items. Without a key, Compose uses the index and cannot detect item changes. Use a unique identifier from your data model.

Code

// BAD: no key, items won't recompose on data change
LazyColumn {
    items(users) { user ->
        UserCard(user)
    }
}

// GOOD: use a unique key
LazyColumn {
    items(users, key = { it.id }) { user ->
        UserCard(user)
    }
}

// Also ensure your data class is not mutated in-place:
// BAD: users[0].name = "new" (mutation, no recomposition)
// GOOD: users = users.toMutableList().also { it[0] = it[0].copy(name = "new") }

Caveats

The key must be truly unique and stable. Using hashCode() or object reference can cause issues.