diff --git a/src/irx/builders/llvmliteir.py b/src/irx/builders/llvmliteir.py
index e2fe53b..9676ea8 100644
--- a/src/irx/builders/llvmliteir.py
+++ b/src/irx/builders/llvmliteir.py
@@ -174,6 +174,12 @@ def __init__(self) -> None:
             codemodel="small"
         )
 
+        self._llvm.module.triple = self.target_machine.triple
+        self._llvm.module.data_layout = str(self.target_machine.target_data)
+
+        if self._llvm.SIZE_T_TYPE is None:
+            self._llvm.SIZE_T_TYPE = self._get_size_t_type_from_triple()
+
         self._add_builtins()
 
     def translate(self, node: astx.AST) -> str:
@@ -184,7 +190,30 @@ def translate(self, node: astx.AST) -> str:
     def _init_native_size_types(self) -> None:
         """Initialize pointer/size_t types from host."""
         self._llvm.POINTER_BITS = ctypes.sizeof(ctypes.c_void_p) * 8
-        self._llvm.SIZE_T_TYPE = ir.IntType(ctypes.sizeof(ctypes.c_size_t) * 8)
+        self._llvm.SIZE_T_TYPE = None
+
+    def _get_size_t_type_from_triple(self) -> ir.IntType:
+        """Determine size_t type from target triple using LLVM API."""
+        triple = self.target_machine.triple.lower()
+
+        if any(
+            arch in triple
+            for arch in [
+                "x86_64",
+                "amd64",
+                "aarch64",
+                "arm64",
+                "ppc64",
+                "mips64",
+            ]
+        ):
+            return ir.IntType(64)
+        elif any(arch in triple for arch in ["i386", "i686", "arm", "mips"]):
+            if "64" in triple:
+                return ir.IntType(64)
+            return ir.IntType(32)
+
+        return ir.IntType(ctypes.sizeof(ctypes.c_size_t) * 8)
 
     def initialize(self) -> None:
         """Initialize self."""
@@ -241,8 +270,8 @@ def initialize(self) -> None:
                 self._llvm.INT32_TYPE,
             ]
         )
-        # Platform-sized unsigned integer (assume 64-bit for CI targets)
-        self._llvm.SIZE_T_TYPE = ir.IntType(64)
+        # SIZE_T_TYPE already initialized based on host; do not override with a
+        # fixed width here to avoid mismatches on non-64-bit targets.
 
     def _add_builtins(self) -> None:
         # The C++ tutorial adds putchard() simply by defining it in the host
diff --git a/tests/test_llvmlite_helpers.py b/tests/test_llvmlite_helpers.py
index ae63dfd..2681add 100644
--- a/tests/test_llvmlite_helpers.py
+++ b/tests/test_llvmlite_helpers.py
@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 from typing import Any, cast
+from unittest.mock import Mock
 
 from irx.builders.llvmliteir import (
     LLVMLiteIRVisitor,
@@ -97,6 +98,66 @@ def test_emit_int_div_signed_and_unsigned() -> None:
     assert getattr(unsigned, "opname", "") == "udiv"
 
 
+def test_get_size_t_type_from_triple_32bit() -> None:
+    """Test _get_size_t_type_from_triple for 32-bit architectures."""
+    visitor = LLVMLiteIRVisitor()
+
+    mock_tm = Mock()
+    mock_tm.triple = "i386-unknown-linux-gnu"
+    visitor.target_machine = mock_tm
+
+    size_t_ty = visitor._get_size_t_type_from_triple()
+    assert size_t_ty.width == 32  # noqa: PLR2004
+
+
+def test_get_size_t_type_from_triple_fallback() -> None:
+    """Test _get_size_t_type_from_triple fallback for unknown architectures."""
+    visitor = LLVMLiteIRVisitor()
+
+    mock_tm = Mock()
+    mock_tm.triple = "unknown-arch-unknown-os"
+    visitor.target_machine = mock_tm
+
+    size_t_ty = visitor._get_size_t_type_from_triple()
+    assert isinstance(size_t_ty, ir.IntType)
+    assert size_t_ty.width in (32, 64)
+
+
+def test_scalar_vector_float_conversion_fptrunc() -> None:
+    """Test scalar-vector promotion with float truncation."""
+    visitor = LLVMLiteIRVisitor()
+    _prime_builder(visitor)
+
+    double_ty = visitor._llvm.DOUBLE_TYPE
+    float_ty = visitor._llvm.FLOAT_TYPE
+    vec_ty = ir.VectorType(float_ty, 2)
+
+    scalar = ir.Constant(double_ty, 3.14)
+    converted = visitor._llvm.ir_builder.fptrunc(scalar, float_ty, "test")
+    result = splat_scalar(visitor._llvm.ir_builder, converted, vec_ty)
+
+    assert isinstance(result.type, ir.VectorType)
+    assert result.type.element == float_ty
+
+
+def test_scalar_vector_float_conversion_fpext() -> None:
+    """Test scalar-vector promotion with float extension."""
+    visitor = LLVMLiteIRVisitor()
+    _prime_builder(visitor)
+
+    float_ty = visitor._llvm.FLOAT_TYPE
+    double_ty = visitor._llvm.DOUBLE_TYPE
+    vec_ty = ir.VectorType(double_ty, 2)
+
+    scalar = ir.Constant(float_ty, 3.14)
+
+    converted = visitor._llvm.ir_builder.fpext(scalar, double_ty, "test")
+    result = splat_scalar(visitor._llvm.ir_builder, converted, vec_ty)
+
+    assert isinstance(result.type, ir.VectorType)
+    assert result.type.element == double_ty
+
+
 def test_set_fast_math_marks_float_ops() -> None:
     """set_fast_math should add fast flag to floating instructions."""
     visitor = LLVMLiteIRVisitor()