diff --git a/lang/src/mir/builder/internal/lower_return_bool_box.hako b/lang/src/mir/builder/internal/lower_return_bool_box.hako
index b85da136..daf72f05 100644
--- a/lang/src/mir/builder/internal/lower_return_bool_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_bool_box.hako
@@ -8,9 +8,13 @@ static box LowerReturnBoolBox {
     local s = "" + program_json
     local k_ret = s.indexOf("\"type\":\"Return\"")
     if k_ret < 0 { return null }
-    // find Bool value true/false after Return
-    local k_bool = s.indexOf("\"type\":\"Bool\"", k_ret)
+    // Restrict to Return(expr=Bool …): require expr 開始直後に Bool が来る
+    // 例: "expr":{"type":"Bool","value":true}
+    local k_expr = s.indexOf("\"expr\":", k_ret)
+    if k_expr < 0 { return null }
+    local k_bool = s.indexOf("\"type\":\"Bool\"", k_expr)
     if k_bool < 0 { return null }
+    // Ensure this Bool belongs to the same expr (次の '}' までに value があることを確認)
     local k_val = s.indexOf("\"value\":", k_bool)
     if k_val < 0 { return null }
     local is_true = JsonFragBox.read_bool_after(s, k_val+8)
diff --git a/lang/src/mir/builder/internal/lower_return_logical_box.hako b/lang/src/mir/builder/internal/lower_return_logical_box.hako
index 35f1dda8..792d71d7 100644
--- a/lang/src/mir/builder/internal/lower_return_logical_box.hako
+++ b/lang/src/mir/builder/internal/lower_return_logical_box.hako
@@ -62,23 +62,19 @@ static box LowerReturnLogicalBox {
     }
     if rhs_true == null { return null }
 
-    // Build MIR: const r1=lhs, rT=1, rF=0; branch on lhs
-    // For &&: if lhs==0 → ret 0; else ret rhs
-    // For ||: if lhs==1 → ret 1; else ret rhs
-    local b0 = new ArrayBox()
-    b0.push(MirSchemaBox.inst_const(1, lhs_true))
-    b0.push(MirSchemaBox.inst_branch(1, 1, 2))
-
+    // Build MIR(JSON v0) string directly (functions[]/name="main"/blocks.id)
+    local json_head = "{\"functions\":[{\"name\":\"main\",\"params\":[],\"locals\":[],\"blocks\":["
+    local bb0 = "{\"id\":0,\"instructions\":[{\"op\":\"const\",\"dst\":1,\"value\":{\"type\":\"i64\",\"value\":" + lhs_true + "}},{\"op\":\"branch\",\"cond\":1,\"then\":1,\"else\":2}]}"
     if op == "&&" {
-      local b1 = new ArrayBox(); b1.push(MirSchemaBox.inst_const(3, rhs_true)); b1.push(MirSchemaBox.inst_ret(3))
-      local b2 = new ArrayBox(); b2.push(MirSchemaBox.inst_const(4, 0)); b2.push(MirSchemaBox.inst_ret(4))
-      local blocks = new ArrayBox(); blocks.push(MirSchemaBox.block(0, b0)); blocks.push(MirSchemaBox.block(1, b1)); blocks.push(MirSchemaBox.block(2, b2))
-      return MirSchemaBox.module(MirSchemaBox.fn_main(blocks))
+      // then: ret rhs_true; else: ret 0
+      local bb1 = "{\"id\":1,\"instructions\":[{\"op\":\"const\",\"dst\":3,\"value\":{\"type\":\"i64\",\"value\":" + rhs_true + "}},{\"op\":\"ret\",\"value\":3}]}"
+      local bb2 = "{\"id\":2,\"instructions\":[{\"op\":\"const\",\"dst\":4,\"value\":{\"type\":\"i64\",\"value\":0}},{\"op\":\"ret\",\"value\":4}]}"
+      return json_head + bb0 + "," + bb1 + "," + bb2 + "]}]}"
     } else {
-      local b1 = new ArrayBox(); b1.push(MirSchemaBox.inst_const(3, 1)); b1.push(MirSchemaBox.inst_ret(3))
-      local b2 = new ArrayBox(); b2.push(MirSchemaBox.inst_const(4, rhs_true)); b2.push(MirSchemaBox.inst_ret(4))
-      local blocks = new ArrayBox(); blocks.push(MirSchemaBox.block(0, b0)); blocks.push(MirSchemaBox.block(1, b1)); blocks.push(MirSchemaBox.block(2, b2))
-      return MirSchemaBox.module(MirSchemaBox.fn_main(blocks))
+      // then: ret 1; else: ret rhs_true
+      local bb1 = "{\"id\":1,\"instructions\":[{\"op\":\"const\",\"dst\":3,\"value\":{\"type\":\"i64\",\"value\":1}},{\"op\":\"ret\",\"value\":3}]}"
+      local bb2 = "{\"id\":2,\"instructions\":[{\"op\":\"const\",\"dst\":4,\"value\":{\"type\":\"i64\",\"value\":" + rhs_true + "}},{\"op\":\"ret\",\"value\":4}]}"
+      return json_head + bb0 + "," + bb1 + "," + bb2 + "]}]}"
     }
   }
 }
diff --git a/lang/src/mir/builder/internal/runner_min_box.hako b/lang/src/mir/builder/internal/runner_min_box.hako
index 6b83ae11..202bd330 100644
--- a/lang/src/mir/builder/internal/runner_min_box.hako
+++ b/lang/src/mir/builder/internal/runner_min_box.hako
@@ -13,6 +13,7 @@ using "hako.mir.builder.internal.lower_typeop_check" as LowerTypeOpCheckBox
 using "hako.mir.builder.internal.lower_typeop_cast" as LowerTypeOpCastBox
 using "hako.mir.builder.internal.lower_return_int" as LowerReturnIntBox
 using "hako.mir.builder.internal.lower_return_binop" as LowerReturnBinOpBox
+using "hako.mir.builder.internal.lower.logical" as LowerReturnLogicalBox
 
 static box BuilderRunnerMinBox {
   run(program_json) {
@@ -44,6 +45,7 @@ static box BuilderRunnerMinBox {
       { local o = LowerTypeOpCheckBox.try_lower(s); if o != null { return o } }
       { local o = LowerTypeOpCastBox.try_lower(s); if o != null { return o } }
     }
+    { local o = LowerReturnLogicalBox.try_lower(s); if o != null { return o } }
     { local o = LowerReturnBinOpBox.try_lower(s); if o != null { return o } }
     { local o = LowerReturnIntBox.try_lower(s); if o != null { return o } }
     { local o = LowerNewboxConstructorBox.try_lower(s); if o != null { return o } }
diff --git a/tools/smokes/v2/profiles/quick/core/phase2044/hako_primary_no_fallback_return_logical_and_only_core_exec_canary_vm.sh b/tools/smokes/v2/profiles/quick/core/phase2044/hako_primary_no_fallback_return_logical_and_only_core_exec_canary_vm.sh
new file mode 100644
index 00000000..db9ca285
--- /dev/null
+++ b/tools/smokes/v2/profiles/quick/core/phase2044/hako_primary_no_fallback_return_logical_and_only_core_exec_canary_vm.sh
@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"; if ROOT_GIT=$(git -C "$SCRIPT_DIR" rev-parse --show-toplevel 2>/dev/null); then ROOT="$ROOT_GIT"; else ROOT="$(cd "$SCRIPT_DIR/../../../../../../../../.." && pwd)"; fi
+source "$ROOT/tools/smokes/v2/lib/test_runner.sh"; require_env || exit 2
+
+prog_json_path="/tmp/prog_2044_return_logical_and_only_$$.json"
+cat >"$prog_json_path" <<'JSON'
+{"version":0,"kind":"Program","body":[
+  {"type":"Return","expr":{"type":"Logical","op":"&&","lhs":{"type":"Bool","value":true},"rhs":{"type":"Bool","value":false}}}
+]}
+JSON
+
+set +e
+HAKO_PRIMARY_NO_FALLBACK=1 \
+HAKO_MIR_BUILDER_INTERNAL=1 \
+NYASH_ENABLE_USING=1 HAKO_ENABLE_USING=1 \
+NYASH_USING_AST=1 NYASH_RESOLVE_FIX_BRACES=1 \
+NYASH_DISABLE_NY_COMPILER=1 NYASH_PARSER_STAGE3=1 HAKO_PARSER_STAGE3=1 \
+NYASH_ENTRY_ALLOW_TOPLEVEL_MAIN=1 \
+verify_program_via_builder_to_core "$prog_json_path"
+rc=$?
+set -e
+rm -f "$prog_json_path"
+if [ "$rc" -ne 0 ]; then
+  echo "[FAIL] Return(Logical AND only) rc=$rc (expected 0)" >&2; exit 1
+fi
+
+echo "[PASS] phase2044/hako_primary_no_fallback_return_logical_and_only_core_exec_canary_vm"
+exit 0