diff --git a/crates/origin-chain-runtime/src/lib.rs b/crates/origin-chain-runtime/src/lib.rs
index c0f45e4..75ae9d4 100644
--- a/crates/origin-chain-runtime/src/lib.rs
+++ b/crates/origin-chain-runtime/src/lib.rs
@@ -49,6 +49,41 @@ pub mod configs;
 pub mod genesis_config_presets;
 pub mod opaque;
 
+// ============================================================
+// WASM binary (Slice 4 Paso 4a — WASM_BINARY export v0.0.48)
+// ============================================================
+//
+// `build.rs` genera `OUT_DIR/wasm_binary.rs` con `pub const WASM_BINARY:
+// Option<&[u8]>` cuando el feature `wasm-build` está activo (vía
+// substrate-wasm-builder). El node lo consume para construir el ChainSpec real
+// (`sc_service::GenericChainSpec`) en Slice 4 Paso 4b.
+//
+// Gate: el `include!` solo corre con `wasm-build` on (si está off, el archivo
+// generado no existe → error de compilación). El fallback `None` cubre los
+// builds host-only (`cargo test`/`cargo check`). El inner build wasm32 que
+// dispara substrate-wasm-builder NO hereda `wasm-build` (no es default feature),
+// lo que evita recursión en build.rs.
+#[cfg(feature = "wasm-build")]
+include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
+
+/// Fallback de `WASM_BINARY` para builds host-only (feature `wasm-build` off).
+/// Para obtener el binary real: `cargo build --features wasm-build` + env vars
+/// `CC=/opt/homebrew/opt/llvm/bin/clang` (ver SLICE_2E). El node activa
+/// `origin-chain-runtime/wasm-build` para embeberlo en el ChainSpec.
+#[cfg(not(feature = "wasm-build"))]
+pub const WASM_BINARY: Option<&[u8]> = None;
+
+/// Devuelve el `WASM_BINARY` o falla con un mensaje claro si no está disponible.
+/// Consumido por el node al construir ChainSpecs (Slice 4 Paso 4b).
+#[cfg(feature = "std")]
+pub fn wasm_binary_unwrap() -> &'static [u8] {
+    WASM_BINARY.expect(
+        "WASM binary no disponible: build con `--features wasm-build` + \
+         CC=LLVM env vars (ver SLICE_2E). El node debe activar \
+         origin-chain-runtime/wasm-build.",
+    )
+}
+
 // ============================================================
 // WASM binary canonical (Slice 2b investigation registered, Slice 2c deferred)
 // ============================================================