diff --git a/App/lib/core/Gen/Call/CallGenLeafKit.vp b/App/lib/core/Gen/Call/CallGenLeafKit.vp
index a005a9f..a009942 100644
--- a/App/lib/core/Gen/Call/CallGenLeafKit.vp
+++ b/App/lib/core/Gen/Call/CallGenLeafKit.vp
@@ -117,6 +117,23 @@ novirtual class CallGenLeafKit(CallGenCBuiltin.CallGenCBuiltin):
     # ============================================================
     def _emit_eh_guarded_call(self, builder: mlirlite.IRBuilder*, pool: memhub.MemBuddy*, mod: mlirlite.LLVMModule*, trans: HT.Translator*, func: mlirlite.Function*, call_name: str, head: mlirlite.Value*, count: int, ret_ty: mlirlite.LLVMType*, is_variadic: int) -> mlirlite.Value*:
         """Call a function with try-except EH detection; returns the call result (positioned at ok block)"""
+        # Argument-count check (fail-fast at the front end instead of leaking to the LLVM verifier).
+        # Callee params include the injected EH out-params (%__eh_msg_out__/__eh_code_out__), which the
+        # caller does not pass explicitly (they are appended later in this function), so subtract them.
+        if func is not None and is_variadic == 0:
+            n_declared: int = 0
+            p_chk: mlirlite.Param* = mlirlite.function_get_param_head(func)
+            while p_chk is not None:
+                n_declared += 1
+                p_chk = mlirlite.param_get_next(p_chk)
+            if self._func_has_eh_params(func) == 1: n_declared = n_declared - 2
+            if n_declared >= 0 and count != n_declared:
+                fname_chk: str = mlirlite.function_get_name(func)
+                if fname_chk is None: fname_chk = call_name
+                self.Gen.TypeGenErr.fatal_error(
+                    None,
+                    f"Argument count mismatch calling '{fname_chk}': the callee declares {n_declared} parameter(s) but the call passes {count} argument(s)",
+                    "TypeError")
         if trans is None or self._func_has_eh_params(func) == 0: return mlirlite.build_call(builder, call_name, head, count, ret_ty, is_variadic)
         # ---- 1. determine output pointers ----
         i8_ty_g: mlirlite.LLVMType* = mlirlite.Int8(pool)