Root cause: sx_primitives.ml registered "effect" as a native no-op (for SSR).
The bytecode compiler's (primitive? "effect") returned true, so it emitted
OP_CALL_PRIM instead of OP_GLOBAL_GET + OP_CALL. The VM's CALL_PRIM handler
found the native Nil-returning stub and never called the real effect function
from core-signals.sx.
Fix: Remove effect and register-in-scope from the primitives table. The server
overrides them via env_bind in sx_server.ml (after compilation), which doesn't
affect primitive? checks.
Also: VM CALL_PRIM now falls back to cek_call for non-NativeFn values (safety
net for any other functions that get misclassified).
15/15 source mode, 15/15 bytecode mode.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
giles
a7efcaf679