ADR 0004: Core engine is plain C, not C++

Status

Accepted (revisit if RAII/container needs grow painful)

Context

Spec section 4 allows either plain C or "C with a thin C++ wrapper for RAII/containers." Section 4 also requires a stable C ABI for compiled feature modules and the plugin host. Starting in C++ and exposing a C ABI on top is more moving parts than starting in C and staying there.

Decision

The core engine (core/) is written in plain C (C11), compiled as a library with a plain C header (core/include/ase/*.h, wrapped in extern "C" for C++ consumers like the Qt GUI). A C++ wrapper layer may be added later, inside core/ or as a separate adapter, if RAII/container ergonomics become a real maintenance burden — not preemptively.

Consequences

No name-mangling or ABI-stability surprises between core and consumers. Slightly more manual memory/lifetime management inside the engine itself, which is an acceptable cost given the "robust, no data loss" pillar demands careful manual attention to buffer/undo lifetimes either way.