diff -urN boost_1_91_0/boost/optional/detail/optional_select_implementation.hpp boost_1_91_0/boost/optional/detail/optional_select_implementation.hpp
--- boost_1_91_0/boost/optional/detail/optional_select_implementation.hpp	2026-04-15 10:38:58.000000000 -0400
+++ boost_1_91_0/boost/optional/detail/optional_select_implementation.hpp	2026-05-13 22:49:40.940892042 -0400
@@ -23,7 +23,8 @@
     !defined(BOOST_NO_CXX11_TRAILING_RESULT_TYPES) && \
     !defined(BOOST_NO_CXX11_UNRESTRICTED_UNION) &&    \
     !defined(BOOST_NO_CXX11_NOEXCEPT) &&              \
-    !defined(BOOST_NO_CXX11_DEFAULTED_MOVES)
+    !defined(BOOST_NO_CXX11_DEFAULTED_MOVES) &&       \
+    !defined(BOOST_OPTIONAL_CONFIG_DISABLE_UNION_OPTIONAL)
 # define BOOST_OPTIONAL_USES_UNION_IMPLEMENTATION
 #endif

diff -urN boost_1_91_0/boost/optional/detail/union_optional.hpp boost_1_91_0/boost/optional/detail/union_optional.hpp
--- boost_1_91_0/boost/optional/detail/union_optional.hpp	2026-04-15 10:38:58.000000000 -0400
+++ boost_1_91_0/boost/optional/detail/union_optional.hpp	2026-05-13 22:49:40.940892042 -0400
@@ -391,7 +391,9 @@
     template <typename U,
               BOOST_OPTIONAL_REQUIRES(::std::is_constructible<T, U&&>),
               BOOST_OPTIONAL_REQUIRES(!optional_detail::is_typed_in_place_factory<U>),
-              BOOST_OPTIONAL_REQUIRES(!optional_detail::is_in_place_factory<U>)>
+              BOOST_OPTIONAL_REQUIRES(!optional_detail::is_in_place_factory<U>),
+              BOOST_OPTIONAL_REQUIRES(!BOOST_OPTIONAL_IS_TAGGED(optional_detail::optional_tag, U))
+              >
     constexpr explicit optional(U&& v)
     : storage(optional_ns::in_place_init, optional_detail::forward_<U>(v))
     {}
diff -urN boost_1_91_0/libs/optional/doc/92_relnotes.qbk boost_1_91_0/libs/optional/doc/92_relnotes.qbk
--- boost_1_91_0/libs/optional/doc/92_relnotes.qbk	2026-04-15 10:38:58.000000000 -0400
+++ boost_1_91_0/libs/optional/doc/92_relnotes.qbk	2026-05-13 22:49:07.461219775 -0400
@@ -11,6 +11,10 @@

 [section:relnotes Release Notes]

+[heading Boost Release 1.xx]
+
+* Fixed regression in the copy-initialization of `optional<bool>`. This fixes [@https://github.com/boostorg/optional/issues/146 issue #146].
+
 [heading Boost Release 1.91]

 * For compilers with full C++11 support (including "unrestricted  unions" and ref-qualifiers)
diff -urN boost_1_91_0/libs/optional/test/Jamfile.v2 boost_1_91_0/libs/optional/test/Jamfile.v2
--- boost_1_91_0/libs/optional/test/Jamfile.v2	2026-04-15 10:38:58.000000000 -0400
+++ boost_1_91_0/libs/optional/test/Jamfile.v2	2026-05-13 22:49:17.870117881 -0400
@@ -40,6 +40,7 @@
 compile optional_test_wuninitialized.cpp ;
 compile optional_test_fwd_header.cpp ;
 run optional_test_conversions_from_U.cpp ;
+run optional_test_constructors.cpp ;
 run optional_test_convert_from_T.cpp ;
 run optional_test_convert_assign.cpp ;
 run optional_test_empty_braces.cpp ;
diff -urN boost_1_91_0/libs/optional/test/optional_test_constructors.cpp boost_1_91_0/libs/optional/test/optional_test_constructors.cpp
--- boost_1_91_0/libs/optional/test/optional_test_constructors.cpp	1969-12-31 19:00:00.000000000 -0500
+++ boost_1_91_0/libs/optional/test/optional_test_constructors.cpp	2026-05-13 22:49:17.870117881 -0400
@@ -0,0 +1,287 @@
+// Copyright (C) 2026 Andrzej Krzemienski.
+//
+// Use, modification, and distribution is subject to the Boost Software
+// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/optional/optional.hpp"
+#include "boost/core/lightweight_test.hpp"
+#include <string>
+
+
+using boost::optional;
+using boost::none;
+
+struct MyBool
+{
+  bool b;
+  MyBool (bool b) : b(b) {}
+  operator bool() const { return b; };
+};
+
+struct MyExplicitBool
+{
+  bool b;
+  MyExplicitBool (bool b) : b(b) {}
+  operator bool() const { return b; };
+};
+
+struct Any
+{
+  template <typename... T>
+  Any(T&&...) {}
+};
+
+struct JustCopyMoveCtor
+{
+  JustCopyMoveCtor(JustCopyMoveCtor&&) = default;
+  JustCopyMoveCtor(JustCopyMoveCtor const&) = default;
+  JustCopyMoveCtor& operator=(JustCopyMoveCtor&&) = delete;
+  JustCopyMoveCtor& operator=(JustCopyMoveCtor const&) = delete;
+  JustCopyMoveCtor() = delete;
+};
+
+struct JustDefault
+{
+  JustDefault() = default;
+  JustDefault(JustDefault&&) = delete;
+};
+
+template <typename T>
+optional<T> empty_optional()
+{
+    return optional<T>(); // this is to avoid "the most vexing parse"
+}
+
+
+template <typename T, typename U>
+void direct_test_ctor_optional_T_from_empty_optional_T()
+{
+  optional<U> om;
+  const optional<U> oc;
+  BOOST_TEST(!om);
+  BOOST_TEST(!oc);
+
+  {
+    optional<T> ox = om;
+    BOOST_TEST(!ox);
+
+    optional<T> oy = oc;
+    BOOST_TEST(!oy);
+
+    optional<T> oz = empty_optional<U>();
+    BOOST_TEST(!oz);
+  }
+
+  {
+    optional<T> ox = {om};
+    BOOST_TEST(!ox);
+
+    optional<T> oy = {oc};
+    BOOST_TEST(!oy);
+
+    optional<T> oz = {empty_optional<U>()};
+    BOOST_TEST(!oz);
+  }
+
+  {
+    optional<T> ox{om};
+    BOOST_TEST(!ox);
+
+    optional<T> oy{oc};
+    BOOST_TEST(!oy);
+
+    optional<T> oz{empty_optional<U>()};
+    BOOST_TEST(!oz);
+  }
+
+  {
+    optional<T> ox(om);
+    BOOST_TEST(!ox);
+
+    optional<T> oy(oc);
+    BOOST_TEST(!oy);
+
+    optional<T> oz(empty_optional<U>());
+    BOOST_TEST(!oz);
+  }
+}
+
+template <typename T, typename U>
+void test_ctor_optional_T_from_empty_optional_T()
+{
+  direct_test_ctor_optional_T_from_empty_optional_T<T, U>();
+  direct_test_ctor_optional_T_from_empty_optional_T<const T, const U>();
+  direct_test_ctor_optional_T_from_empty_optional_T<optional<T>, optional<U>>();
+  direct_test_ctor_optional_T_from_empty_optional_T<optional<const T>, optional<const U>>();
+  direct_test_ctor_optional_T_from_empty_optional_T<const optional<T>, const optional<U>>();
+}
+
+template <typename T, typename U>
+void direct_test_ctor_optional_T_from_optional_U(U val)
+{
+  optional<U> om;
+  const optional<U> oc;
+  BOOST_TEST(!om);
+  BOOST_TEST(!oc);
+
+  {
+    optional<T> ox{om};
+    BOOST_TEST(!ox);
+
+    optional<T> oy{oc};
+    BOOST_TEST(!oy);
+
+    optional<T> oz{empty_optional<U>()};
+    BOOST_TEST(!oz);
+  }
+
+  {
+    optional<T> ox(om);
+    BOOST_TEST(!ox);
+
+    optional<T> oy(oc);
+    BOOST_TEST(!oy);
+
+    optional<T> oz(empty_optional<U>());
+    BOOST_TEST(!oz);
+  }
+
+  {
+    optional<U> om {val};
+    const optional<U> oc {val};
+
+    {
+      optional<T> ox{om};
+      BOOST_TEST(ox);
+
+      optional<T> oy{oc};
+      BOOST_TEST(oy);
+
+      optional<T> oz{boost::make_optional(val)};
+      BOOST_TEST(oz);
+    }
+    {
+      optional<T> ox(om);
+      BOOST_TEST(ox);
+
+      optional<T> oy(oc);
+      BOOST_TEST(oy);
+
+      optional<T> oz(boost::make_optional(val));
+      BOOST_TEST(oz);
+    }
+  }
+}
+
+template <typename T, typename U>
+void test_ctor_optional_T_from_optional_U(U val)
+{
+  direct_test_ctor_optional_T_from_optional_U<T>(val);
+}
+
+template <typename T>
+void direct_test_ctor_optional_T_from_valued_optional_T(T val)
+{
+  optional<T> om(val);
+  const optional<T> oc(val);
+  BOOST_TEST(om);
+  BOOST_TEST(oc);
+
+  {
+    optional<T> ox = om;
+    BOOST_TEST(ox);
+
+    optional<T> oy = oc;
+    BOOST_TEST(oy);
+
+    optional<T> oz = optional<T>(val);
+    BOOST_TEST(oz);
+  }
+  {
+    optional<T> ox = {om};
+    BOOST_TEST(ox);
+
+    optional<T> oy = {oc};
+    BOOST_TEST(oy);
+
+    optional<T> oz = {optional<T>(val)};
+    BOOST_TEST(oz);
+  }
+}
+
+template <typename T>
+void test_ctor_optional_T_from_valued_optional_T(T val)
+{
+  direct_test_ctor_optional_T_from_valued_optional_T<T>(val);
+  direct_test_ctor_optional_T_from_valued_optional_T<optional<T>>(val);
+  direct_test_ctor_optional_T_from_valued_optional_T<const T>(val);
+  direct_test_ctor_optional_T_from_optional_U<T, T>(val);
+  direct_test_ctor_optional_T_from_optional_U<optional<T>, optional<T>>(val);
+}
+
+template <typename T>
+void direct_test_inplace_tag_constructor()
+{
+  {
+    optional<T> ox (boost::in_place_init);
+    BOOST_TEST(ox);
+  }
+  {
+    optional<T> ox {boost::in_place_init};
+    BOOST_TEST(ox);
+  }
+}
+
+template <typename T>
+void test_inplace_tag_constructor()
+{
+  direct_test_inplace_tag_constructor<T>();
+  direct_test_inplace_tag_constructor<optional<T>>();
+}
+
+
+int main()
+{
+    test_ctor_optional_T_from_empty_optional_T<int, int>();
+    test_ctor_optional_T_from_empty_optional_T<long, long>();
+    test_ctor_optional_T_from_empty_optional_T<std::string, std::string>();
+    test_ctor_optional_T_from_empty_optional_T<JustCopyMoveCtor, JustCopyMoveCtor>();
+    test_ctor_optional_T_from_empty_optional_T<MyBool, MyBool>();
+
+    test_ctor_optional_T_from_empty_optional_T<MyExplicitBool, MyExplicitBool>();
+
+    test_ctor_optional_T_from_empty_optional_T<bool, bool>();
+    test_ctor_optional_T_from_empty_optional_T<Any, Any>();
+
+    test_inplace_tag_constructor<int>();
+    test_inplace_tag_constructor<Any>();
+    test_inplace_tag_constructor<JustDefault>();
+
+    test_ctor_optional_T_from_optional_U<int>(1);
+    test_ctor_optional_T_from_optional_U<long>(1);
+    test_ctor_optional_T_from_optional_U<bool>(MyBool{true});
+    test_ctor_optional_T_from_optional_U<bool>(MyBool{false});
+    test_ctor_optional_T_from_optional_U<MyBool>(true);
+    test_ctor_optional_T_from_optional_U<MyBool>(false);
+    test_ctor_optional_T_from_optional_U<bool>(MyExplicitBool{true});
+    test_ctor_optional_T_from_optional_U<bool>(MyExplicitBool{false});
+    test_ctor_optional_T_from_optional_U<MyExplicitBool>(true);
+    test_ctor_optional_T_from_optional_U<MyExplicitBool>(false);
+    test_ctor_optional_T_from_optional_U<Any>(true);
+    test_ctor_optional_T_from_optional_U<Any>(Any{});
+
+    test_ctor_optional_T_from_valued_optional_T(1);
+
+    optional<MyBool> ob;
+    optional<bool> oa;
+    oa = ob;
+    BOOST_TEST(!oa);
+
+    return boost::report_errors();
+}