= Core Contract
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This document is the *source of truth* for what the project guarantees today.

== Invariants

* Determinism: given identical inputs and identical host responses, outputs are identical.
* Explicit effects: host interaction is explicit and observable (no hidden channels).
* Versioned surface: public API changes require a version bump and changelog entry.

== What “done” means

A feature is done only when:

* it has at least one golden test, and
* it has at least one negative/edge test, and
* its error modes are specified.

== Out of scope

Anything not required to satisfy the invariants is not core.
