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understanding-stability-inference

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Use this skill to explain why the Compose compiler classified a class or composable parameter as stable, runtime, unknown, or unstable. Covers the 12-phase inference algorithm, the five compiler-level stability types (Certain / Runtime / Unknown / Parameter / Combined), the generic bitmask encoding (Pair=0b11, ImmutableList=0b1), the Known Stable Constructs registry, and the runtime `$stable: Int` field generated by `@StabilityInferred`. Use when the developer asks "why is X classified as Y?", when a stability report shows a surprising `runtime stable`, `unknown`, or `unstable` verdict, when generics, inheritance, cycles, interfaces, or cross-module classes are involved, or when the user mentions `$stable`, `@StabilityInferred`, separate compilation, or "the compiler thinks my class is unstable but it looks fine".

stability/understanding-stability-inference/SKILL.md

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# Understanding Stability Inference — read the compiler's mind

Stability is decided by a 12-phase algorithm baked into the Compose compiler. This skill teaches Claude how the algorithm walks a type so it can explain *why* a report says what it says, and predict classifications before the report is even generated. Pair this with `../diagnosing-compose-stability/SKILL.md` (which generates the report) and `../stabilizing-compose-types/SKILL.md` (which fixes obvious unstable types). Reach for this skill when the simpler skills produce a verdict that surprises the developer.

## When to use this skill

- The developer asks "why is `Foo` classified as `runtime stable` and not `stable`?"
- A report shows `runtime` or `unknown` for a class that "looks fine".
- Generics involved: `Box<T>`, `Wrapper<A, B>`, `Pair<String, Int>`, `ImmutableList<User>`.
- The class lives in another module and ships as a `.class`/`.kotlin_metadata` artifact.
- The developer asks about the `$stable: Int` field, `@StabilityInferred`, or cross-module classification.
- A self-referential type (`class Node(val children: List<Node>)`) is unstable for non-obvious reasons.
- A Java type, an interface, or an abstract base appears in a parameter list and surprises the developer.