casc.aether, compiled to direct Elixir function calls -- ~2x throughput per Ichor's own docs, now that the grammar has stopped changing weekly.

The compiled lexer/parser itself lives in this module's own Native alias (@moduledoc false on purpose -- it's generated, not hand-authored), generated ahead of time by mix ichor.gen, checked in like any other source file, rather than produced by use Ichor, grammar:, actions: at this module's own compile time. That's a deliberate architectural choice, not just style: use Ichor needs ichor proper (the Aether front-end, Grammar.Analysis, the native codegen backend -- most of that library) at Cooper's own compile time, every single time Cooper compiles; a pre-generated Native module only ever calls into ichor_runtime, the small support library the generated code actually needs at runtime (capture dispatch, error formatting, the compiled Tokenizer/Parser). Generating ahead of time is what lets mix.exs mark ichor itself only: [:dev, :test], runtime: false -- the bulk of Ichor genuinely never ships in a mix release build of an app depending on cooper. This module exists so that split is invisible to every other caller in Cooper: Cooper.Grammar's run_with_context/3 and everything built on it still just calls Cooper.NativeGrammar.parse/1, exactly as if the grammar were compiled the old way.

Regenerate whenever priv/grammar/casc.aether changes -- there's no automatic staleness check between the checked-in file and its source grammar:

mix ichor.gen priv/grammar/casc.aether \
  --module Cooper.NativeGrammar.Native \
  --actions Cooper.Actions \
  --out lib/cooper/native_grammar/native.ex

run/2 itself still isn't used directly by Cooper.Grammar -- it discards the final context, and Cooper.Loader needs it back for cross-file variable propagation (see Cooper.Grammar's own run_with_context/3 and this module's other generated companion, CaptureShapes, for how that's done without needing ichor proper at runtime either).