diff --git a/include/beman/execution/detail/basic_sender.hpp b/include/beman/execution/detail/basic_sender.hpp
index 2cf03d79..5f46cf82 100644
--- a/include/beman/execution/detail/basic_sender.hpp
+++ b/include/beman/execution/detail/basic_sender.hpp
@@ -17,6 +17,7 @@ import beman.execution.detail.completion_signatures_for;
 import beman.execution.detail.connect;
 import beman.execution.detail.connect_all;
 import beman.execution.detail.decays_to;
+import beman.execution.detail.dependent_sender;
 import beman.execution.detail.get_completion_signatures;
 import beman.execution.detail.impls_for;
 import beman.execution.detail.product_type;
@@ -28,6 +29,7 @@ import beman.execution.detail.sender_decompose;
 #include <beman/execution/detail/completion_signatures_for.hpp>
 #include <beman/execution/detail/connect.hpp>
 #include <beman/execution/detail/decays_to.hpp>
+#include <beman/execution/detail/dependent_sender.hpp>
 #include <beman/execution/detail/get_completion_signatures.hpp>
 #include <beman/execution/detail/impls_for.hpp>
 #include <beman/execution/detail/product_type.hpp>
@@ -110,6 +112,7 @@ struct basic_sender : ::beman::execution::detail::product_type<Tag, Data, Child.
     }
 #endif
     template <::beman::execution::detail::decays_to<basic_sender> Self, typename... Env>
+        requires(sizeof...(Env) == 1) || (... && !::beman::execution::dependent_sender<Child>)
     static consteval auto get_completion_signatures() noexcept {
         if constexpr (requires { Tag::template get_completion_signatures<Self, Env...>(); })
             return Tag::template get_completion_signatures<Self, Env...>();
diff --git a/include/beman/execution/detail/common.hpp b/include/beman/execution/detail/common.hpp
index 77235773..2f86f712 100644
--- a/include/beman/execution/detail/common.hpp
+++ b/include/beman/execution/detail/common.hpp
@@ -17,6 +17,17 @@
 #define BEMAN_SPECIALIZE_EXPORT template <>
 #endif
 
+#define BEMAN_EXECUTION_TRY_EVAL(rcvr, expr)                                                    \
+    do {                                                                                        \
+        try {                                                                                   \
+            (expr);                                                                             \
+        } catch (...) {                                                                         \
+            if constexpr (!noexcept((expr))) {                                                  \
+                ::beman::execution::set_error(::std::move((rcvr)), ::std::current_exception()); \
+            }                                                                                   \
+        }                                                                                       \
+    } while (false)
+
 // ----------------------------------------------------------------------------
 /*!
  * \mainpage Asynchronous Operation Support
diff --git a/include/beman/execution/detail/dependent_sender.hpp b/include/beman/execution/detail/dependent_sender.hpp
new file mode 100644
index 00000000..e643309c
--- /dev/null
+++ b/include/beman/execution/detail/dependent_sender.hpp
@@ -0,0 +1,41 @@
+// include/beman/execution/detail/dependent_sender.hpp                     -*-C++-*-
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef INCLUDED_BEMAN_EXECUTION_DETAIL_DEPENDENT_SENDER
+#define INCLUDED_BEMAN_EXECUTION_DETAIL_DEPENDENT_SENDER
+
+#include <beman/execution/detail/common.hpp>
+#ifdef BEMAN_HAS_IMPORT_STD
+import std;
+#else
+#include <concepts>
+#endif
+#ifdef BEMAN_HAS_MODULES
+import beman.execution.detail.get_completion_signatures;
+import beman.execution.detail.sender;
+#else
+#include <beman/execution/detail/get_completion_signatures.hpp>
+#include <beman/execution/detail/sender.hpp>
+#endif
+
+// ----------------------------------------------------------------------------
+
+namespace beman::execution::detail {
+template <auto>
+auto non_dependent_sender_helper() noexcept -> void {}
+
+template <typename Sender>
+concept non_dependent_sender = ::beman::execution::sender<Sender> && requires {
+    ::beman::execution::detail::non_dependent_sender_helper<::beman::execution::get_completion_signatures<Sender>()>();
+};
+} // namespace beman::execution::detail
+
+namespace beman::execution {
+template <typename Sender>
+concept dependent_sender =
+    ::beman::execution::sender<Sender> && !::beman::execution::detail::non_dependent_sender<Sender>;
+} // namespace beman::execution
+
+// ----------------------------------------------------------------------------
+
+#endif // INCLUDED_BEMAN_EXECUTION_DETAIL_DEPENDENT_SENDER
diff --git a/include/beman/execution/detail/into_variant.hpp b/include/beman/execution/detail/into_variant.hpp
index 54a89484..167e3892 100644
--- a/include/beman/execution/detail/into_variant.hpp
+++ b/include/beman/execution/detail/into_variant.hpp
@@ -20,6 +20,9 @@ import beman.execution.detail.completion_signatures;
 import beman.execution.detail.completion_signatures_for;
 import beman.execution.detail.decayed_tuple;
 import beman.execution.detail.default_impls;
+import beman.execution.detail.dependent_sender;
+import beman.execution.detail.dependent_sender_error;
+import beman.execution.detail.env;
 import beman.execution.detail.env_of_t;
 import beman.execution.detail.error_types_of_t;
 import beman.execution.detail.get_domain_early;
@@ -27,6 +30,7 @@ import beman.execution.detail.impls_for;
 import beman.execution.detail.make_sender;
 import beman.execution.detail.meta.combine;
 import beman.execution.detail.sender;
+import beman.execution.detail.sender_adaptor_closure;
 import beman.execution.detail.sends_stopped;
 import beman.execution.detail.set_error;
 import beman.execution.detail.set_stopped;
@@ -39,6 +43,9 @@ import beman.execution.detail.variant_or_empty;
 #include <beman/execution/detail/completion_signatures_for.hpp>
 #include <beman/execution/detail/decayed_tuple.hpp>
 #include <beman/execution/detail/default_impls.hpp>
+#include <beman/execution/detail/dependent_sender.hpp>
+#include <beman/execution/detail/dependent_sender_error.hpp>
+#include <beman/execution/detail/env.hpp>
 #include <beman/execution/detail/env_of_t.hpp>
 #include <beman/execution/detail/error_types_of_t.hpp>
 #include <beman/execution/detail/get_domain_early.hpp>
@@ -46,6 +53,7 @@ import beman.execution.detail.variant_or_empty;
 #include <beman/execution/detail/make_sender.hpp>
 #include <beman/execution/detail/meta_combine.hpp>
 #include <beman/execution/detail/sender.hpp>
+#include <beman/execution/detail/sender_adaptor_closure.hpp>
 #include <beman/execution/detail/sends_stopped.hpp>
 #include <beman/execution/detail/set_error.hpp>
 #include <beman/execution/detail/set_value.hpp>
@@ -56,25 +64,25 @@ import beman.execution.detail.variant_or_empty;
 // ----------------------------------------------------------------------------
 
 namespace beman::execution::detail {
-struct into_variant_t {
+struct into_variant_t : ::beman::execution::sender_adaptor_closure<into_variant_t> {
     template <::beman::execution::sender Sender>
     auto operator()(Sender&& sender) const {
-        // auto domain{::beman::execution::detail::get_domain_early(sender)};
-        //(void)domain;
-        return ::beman::execution::detail::make_sender(*this, {}, ::std::forward<Sender>(sender));
-        // return ::beman::execution::transform_sender(
-        //     ::std::move(domain),
-        //     ::beman::execution::detail::make_sender(*this, {}, ::std::forward<Sender>(sender))
-        //);
+        return ::beman::execution::transform_sender(
+            ::beman::execution::detail::get_domain_early(sender),
+            ::beman::execution::detail::make_sender(*this, {}, ::std::forward<Sender>(sender)));
     }
 
+    auto operator()() const noexcept { return ::beman::execution::detail::make_sender_adaptor(*this); }
+
   private:
     template <typename... E>
     using make_error_types = ::beman::execution::completion_signatures<::beman::execution::set_error_t(E)...>;
 
   private:
-    template <typename, typename>
+    template <typename, typename...>
     struct get_signatures;
+    template <typename Sender>
+    struct get_signatures<Sender> : get_signatures<Sender, ::beman::execution::env<>> {};
     template <::beman::execution::sender Child, typename State, typename Env>
     struct get_signatures<
         ::beman::execution::detail::basic_sender<::beman::execution::detail::into_variant_t, State, Child>,
@@ -99,9 +107,9 @@ struct into_variant_t {
     };
 
   public:
-    template <::beman::execution::sender Sender, typename Env>
+    template <::beman::execution::sender Sender, typename... Env>
     static consteval auto get_completion_signatures() {
-        return get_signatures<::std::remove_cvref_t<Sender>, Env>::get();
+        return get_signatures<::std::remove_cvref_t<Sender>, Env...>::get();
     }
     struct impls_for : ::beman::execution::detail::default_impls {
         struct get_state_impl {
@@ -119,14 +127,14 @@ struct into_variant_t {
                 if constexpr (::std::same_as<Tag, ::beman::execution::set_value_t>) {
                     using variant_type = typename State::type;
                     using tuple_type   = ::beman::execution::detail::decayed_tuple<Args...>;
-                    try {
-                        if constexpr (sizeof...(Args) == 0u)
-                            ::beman::execution::set_value(::std::move(receiver));
-                        else
+                    if constexpr (std::same_as<variant_type, ::beman::execution::detail::empty_variant>) {
+                        static_assert(sizeof...(Args) == 0);
+                        BEMAN_EXECUTION_TRY_EVAL(receiver, ::beman::execution::set_value(std::move(receiver)));
+                    } else {
+                        BEMAN_EXECUTION_TRY_EVAL(
+                            receiver,
                             ::beman::execution::set_value(::std::move(receiver),
-                                                          variant_type(tuple_type{::std::forward<Args>(args)...}));
-                    } catch (...) {
-                        ::beman::execution::set_error(::std::move(receiver), ::std::current_exception());
+                                                          variant_type(tuple_type{::std::forward<Args>(args)...})));
                     }
                 } else {
                     Tag()(::std::move(receiver), ::std::forward<Args>(args)...);
diff --git a/include/beman/execution/detail/read_env.hpp b/include/beman/execution/detail/read_env.hpp
index 0082bd2d..5ab59ed8 100644
--- a/include/beman/execution/detail/read_env.hpp
+++ b/include/beman/execution/detail/read_env.hpp
@@ -17,6 +17,7 @@ import beman.execution.detail.basic_sender;
 import beman.execution.detail.completion_signatures;
 import beman.execution.detail.completion_signatures_for;
 import beman.execution.detail.default_impls;
+import beman.execution.detail.env_of_t;
 import beman.execution.detail.get_env;
 import beman.execution.detail.impls_for;
 import beman.execution.detail.make_sender;
@@ -27,6 +28,7 @@ import beman.execution.detail.set_value;
 #include <beman/execution/detail/completion_signatures.hpp>
 #include <beman/execution/detail/completion_signatures_for.hpp>
 #include <beman/execution/detail/default_impls.hpp>
+#include <beman/execution/detail/env_of_t.hpp>
 #include <beman/execution/detail/get_env.hpp>
 #include <beman/execution/detail/impls_for.hpp>
 #include <beman/execution/detail/make_sender.hpp>
@@ -59,18 +61,21 @@ struct read_env_t {
     };
 
   public:
-    template <typename Sender, typename... Env>
+    template <typename Sender, typename Env>
     static consteval auto get_completion_signatures() {
-        return typename get_signatures<::std::remove_cvref_t<Sender>, Env...>::type{};
+        return typename get_signatures<::std::remove_cvref_t<Sender>, Env>::type{};
     }
     struct impls_for : ::beman::execution::detail::default_impls {
         struct start_impl {
-            auto operator()(auto query, auto& receiver) const noexcept -> void {
+            template <typename Query, typename Receiver>
+            auto operator()(Query query, Receiver& receiver) const noexcept -> void {
                 try {
                     auto env{::beman::execution::get_env(receiver)};
                     ::beman::execution::set_value(::std::move(receiver), query(env));
                 } catch (...) {
-                    ::beman::execution::set_error(::std::move(receiver), ::std::current_exception());
+                    if constexpr (!std::is_nothrow_invocable_v<Query, ::beman::execution::env_of_t<Receiver>>) {
+                        ::beman::execution::set_error(::std::move(receiver), ::std::current_exception());
+                    }
                 }
             }
         };
diff --git a/include/beman/execution/detail/sender.hpp b/include/beman/execution/detail/sender.hpp
index 3b43d36d..80de7c50 100644
--- a/include/beman/execution/detail/sender.hpp
+++ b/include/beman/execution/detail/sender.hpp
@@ -42,7 +42,10 @@ concept enable_sender =
 } // namespace beman::execution::detail
 namespace beman::execution {
 template <typename Sender>
-concept sender = ::beman::execution::detail::enable_sender<::std::remove_cvref_t<Sender>> &&
+inline constexpr bool enable_sender = ::beman::execution::detail::enable_sender<Sender>;
+
+template <typename Sender>
+concept sender = ::beman::execution::enable_sender<::std::remove_cvref_t<Sender>> &&
                  requires(const ::std::remove_cvref_t<Sender>& sndr) {
                      { ::beman::execution::get_env(sndr) } -> ::beman::execution::detail::queryable;
                  } && ::std::move_constructible<::std::remove_cvref_t<Sender>> &&
diff --git a/include/beman/execution/detail/then.hpp b/include/beman/execution/detail/then.hpp
index 85d59dd1..2f4b239d 100644
--- a/include/beman/execution/detail/then.hpp
+++ b/include/beman/execution/detail/then.hpp
@@ -21,6 +21,9 @@ import beman.execution.detail.completion_signatures;
 import beman.execution.detail.completion_signatures_for;
 import beman.execution.detail.completion_signatures_of_t;
 import beman.execution.detail.default_impls;
+import beman.execution.detail.dependent_sender;
+import beman.execution.detail.dependent_sender_error;
+import beman.execution.detail.env;
 import beman.execution.detail.get_domain_early;
 import beman.execution.detail.impls_for;
 import beman.execution.detail.make_sender;
@@ -41,6 +44,9 @@ import beman.execution.detail.transform_sender;
 #include <beman/execution/detail/completion_signatures_for.hpp>
 #include <beman/execution/detail/completion_signatures_of_t.hpp>
 #include <beman/execution/detail/default_impls.hpp>
+#include <beman/execution/detail/dependent_sender.hpp>
+#include <beman/execution/detail/dependent_sender_error.hpp>
+#include <beman/execution/detail/env.hpp>
 #include <beman/execution/detail/get_domain_early.hpp>
 #include <beman/execution/detail/impls_for.hpp>
 #include <beman/execution/detail/make_sender.hpp>
@@ -125,17 +131,19 @@ struct then_t : ::beman::execution::sender_adaptor_closure<then_t<Completion>> {
   private:
     template <typename, typename...>
     struct get_signatures;
-    template <typename Comp, typename Fun, typename Child, typename... Env>
+    template <typename Sender>
+    struct get_signatures<Sender> : get_signatures<Sender, ::beman::execution::env<>> {};
+    template <typename Comp, typename Fun, typename Child, typename Env>
     struct get_signatures<
         ::beman::execution::detail::basic_sender<::beman::execution::detail::then_t<Comp>, Fun, Child>,
-        Env...> {
+        Env> {
         using type = ::beman::execution::detail::meta::unique<::beman::execution::detail::meta::combine<
             ::beman::execution::detail::meta::transform<
                 ::beman::execution::detail::then_transform_t<Fun, Comp>::template transform,
-                ::beman::execution::completion_signatures_of_t<Child, Env...>>,
+                ::beman::execution::completion_signatures_of_t<Child, Env>>,
             ::std::conditional_t<
                 ::beman::execution::detail::
-                    then_exception<Comp, Fun, ::beman::execution::completion_signatures_of_t<Child, Env...>>::value,
+                    then_exception<Comp, Fun, ::beman::execution::completion_signatures_of_t<Child, Env>>::value,
                 ::beman::execution::completion_signatures<::beman::execution::set_error_t(::std::exception_ptr)>,
                 ::beman::execution::completion_signatures<>>>>;
     };
diff --git a/include/beman/execution/detail/when_all.hpp b/include/beman/execution/detail/when_all.hpp
index 0868c2c2..47ce6fde 100644
--- a/include/beman/execution/detail/when_all.hpp
+++ b/include/beman/execution/detail/when_all.hpp
@@ -26,6 +26,8 @@ import beman.execution.detail.decayed_tuple;
 import beman.execution.detail.decayed_type_list;
 import beman.execution.detail.default_domain;
 import beman.execution.detail.default_impls;
+import beman.execution.detail.dependent_sender;
+import beman.execution.detail.dependent_sender_error;
 import beman.execution.detail.env;
 import beman.execution.detail.env_of_t;
 import beman.execution.detail.error_types_of_t;
@@ -63,6 +65,8 @@ import beman.execution.detail.value_types_of_t;
 #include <beman/execution/detail/decayed_type_list.hpp>
 #include <beman/execution/detail/default_domain.hpp>
 #include <beman/execution/detail/default_impls.hpp>
+#include <beman/execution/detail/dependent_sender.hpp>
+#include <beman/execution/detail/dependent_sender_error.hpp>
 #include <beman/execution/detail/env.hpp>
 #include <beman/execution/detail/env_of_t.hpp>
 #include <beman/execution/detail/error_types_of_t.hpp>
@@ -102,15 +106,27 @@ struct when_all_value_types<::beman::execution::detail::type_list<T...>> {
     using type = ::beman::execution::completion_signatures<::beman::execution::set_value_t(T...)>;
 };
 
+template <typename Sender>
+concept valid_when_all_sender = ::beman::execution::dependent_sender<Sender> ||
+                                ::beman::execution::detail::meta::size_v<
+                                    ::beman::execution::value_types_of_t<Sender,
+                                                                         ::beman::execution::env<>,
+                                                                         ::std::tuple,
+                                                                         ::beman::execution::detail::type_list>> == 1u;
+
+inline constexpr auto make_when_all_env = [](const ::beman::execution::inplace_stop_source& stop_src,
+                                             const auto&                                    env) noexcept {
+    return ::beman::execution::detail::join_env(
+        ::beman::execution::detail::make_env(::beman::execution::get_stop_token, stop_src.get_token()), env);
+};
+
+template <typename Env>
+using when_all_env =
+    decltype(make_when_all_env(::std::declval<::beman::execution::inplace_stop_source>(), ::std::declval<Env>()));
+
 struct when_all_t {
     template <::beman::execution::sender... Sender>
-        requires(0u != sizeof...(Sender)) &&
-                ((::beman::execution::detail::meta::size_v<
-                      ::beman::execution::value_types_of_t<Sender,
-                                                           ::beman::execution::env<>,
-                                                           ::std::tuple,
-                                                           ::beman::execution::detail::type_list>> == 1u) &&
-                 ...) &&
+        requires(0u != sizeof...(Sender)) && (... && beman::execution::detail::valid_when_all_sender<Sender>) &&
                 requires(Sender&&... s) {
                     typename ::std::common_type_t<decltype(::beman::execution::detail::get_domain_early(s))...>;
                 }
@@ -122,8 +138,10 @@ struct when_all_t {
     }
 
   private:
-    template <typename, typename>
+    template <typename, typename...>
     struct get_signatures;
+    template <typename Sender>
+    struct get_signatures<Sender> : get_signatures<Sender, ::beman::execution::env<>> {};
     template <typename Data, typename Env, typename... Sender>
     struct get_signatures<
         ::beman::execution::detail::basic_sender<::beman::execution::detail::when_all_t, Data, Sender...>,
@@ -170,20 +188,30 @@ struct when_all_t {
         struct get_env_impl {
             template <typename State, typename Receiver>
             auto operator()(auto&&, State& state, const Receiver& receiver) const noexcept {
-                return ::beman::execution::detail::join_env(
-                    ::beman::execution::detail::make_env(::beman::execution::get_stop_token,
-                                                         state.stop_src.get_token()),
-                    ::beman::execution::get_env(receiver));
+                return make_when_all_env(state.stop_src, ::beman::execution::get_env(receiver));
             }
         };
         static constexpr auto get_env{get_env_impl{}};
 
         enum class disposition : unsigned char { started, error, stopped };
 
+        template <typename... Values>
+        struct is_nothrow_decay_copy_constructible
+            : ::std::bool_constant<(... && ::std::is_nothrow_constructible_v<::std::decay_t<Values>, Values>)> {};
+
         template <typename Receiver, typename... Sender>
         struct state_type {
             struct nonesuch {};
-            using env_t        = ::beman::execution::env_of_t<Receiver>;
+            using env_t     = ::beman::execution::env_of_t<Receiver>;
+            using copy_fail = ::std::conditional_t<
+                (... && ::beman::execution::value_types_of_t<Sender,
+                                                             env_t,
+                                                             is_nothrow_decay_copy_constructible,
+                                                             ::std::type_identity_t>::value) &&
+                    (... &&
+                     ::beman::execution::error_types_of_t<Sender, env_t, is_nothrow_decay_copy_constructible>::value),
+                nonesuch,
+                std::exception_ptr>;
             using values_tuple = ::std::tuple<
                 ::beman::execution::
                     value_types_of_t<Sender, env_t, ::beman::execution::detail::decayed_tuple, ::std::optional>...>;
@@ -192,7 +220,7 @@ struct when_all_t {
                 ::beman::execution::detail::meta::unique<::beman::execution::detail::meta::prepend<
                     nonesuch,
                     ::beman::execution::detail::meta::prepend<
-                        ::std::exception_ptr,
+                        copy_fail,
                         ::beman::execution::detail::meta::combine<::beman::execution::detail::meta::to<
                             ::beman::execution::detail::type_list,
                             ::beman::execution::detail::meta::combine<::beman::execution::error_types_of_t<
@@ -224,21 +252,21 @@ struct when_all_t {
                 } break;
                 case disposition::error:
                     this->on_stop.reset();
-                    try {
-                        ::std::visit(
-                            [&]<typename Error>(Error& error) noexcept {
-                                if constexpr (!::std::same_as<Error, nonesuch>) {
-                                    ::beman::execution::set_error(::std::move(recvr), ::std::move(error));
-                                }
-                            },
-                            this->errors);
-                    } catch (...) {
-                        ::beman::execution::set_error(::std::move(recvr), ::std::current_exception());
-                    }
+                    ::std::visit(
+                        [&]<typename Error>(Error& error) noexcept {
+                            if constexpr (!::std::same_as<Error, nonesuch>) {
+                                ::beman::execution::set_error(::std::move(recvr), ::std::move(error));
+                            }
+                        },
+                        this->errors);
                     break;
                 case disposition::stopped:
-                    this->on_stop.reset();
-                    ::beman::execution::set_stopped(::std::move(recvr));
+                    if constexpr ((... ||
+                                   ::beman::execution::
+                                       sends_stopped<Sender, when_all_env<::beman::execution::env_of_t<Receiver>>>)) {
+                        this->on_stop.reset();
+                        ::beman::execution::set_stopped(::std::move(recvr));
+                    }
                     break;
                 }
             }
@@ -282,12 +310,7 @@ struct when_all_t {
                 state.receiver = &receiver;
                 state.on_stop.emplace(::beman::execution::get_stop_token(::beman::execution::get_env(receiver)),
                                       ::beman::execution::detail::on_stop_request{state});
-                if (state.stop_src.stop_requested()) {
-                    state.on_stop.reset();
-                    ::beman::execution::set_stopped(std::move(receiver));
-                } else {
-                    (::beman::execution::start(ops), ...);
-                }
+                (::beman::execution::start(ops), ...);
             }
         };
         static constexpr auto start{start_impl{}};
@@ -297,11 +320,16 @@ struct when_all_t {
                 if constexpr (::std::same_as<Set, ::beman::execution::set_error_t>) {
                     if (disposition::error != state.disp.exchange(disposition::error)) {
                         state.stop_src.request_stop();
+                        using error_t          = typename std::type_identity<Args...>::type;
+                        constexpr bool nothrow = ::std::is_nothrow_constructible_v<::std::decay_t<error_t>, error_t>;
                         try {
-                            state.errors.template emplace<typename ::std::decay<Args...>::type>(
-                                ::std::forward<Args>(args)...);
+                            [&]() noexcept(nothrow) {
+                                state.errors.template emplace<::std::decay_t<error_t>>(::std::forward<Args>(args)...);
+                            }();
                         } catch (...) {
-                            state.errors.template emplace<::std::exception_ptr>(::std::current_exception());
+                            if constexpr (!nothrow) {
+                                state.errors.template emplace<::std::exception_ptr>(::std::current_exception());
+                            }
                         }
                     }
                 } else if constexpr (::std::same_as<Set, ::beman::execution::set_stopped_t>) {
@@ -311,13 +339,17 @@ struct when_all_t {
                     }
                 } else if constexpr (!::std::same_as<decltype(State::values), ::std::tuple<>>) {
                     if (state.disp == disposition::started) {
-                        auto& opt = ::std::get<Index::value>(state.values);
+                        auto& opt              = ::std::get<Index::value>(state.values);
+                        using decayed_tuple_t  = typename ::std::decay_t<decltype(opt)>::value_type;
+                        constexpr bool nothrow = std::is_nothrow_constructible_v<decayed_tuple_t, Args...>;
                         try {
-                            opt.emplace(::std::forward<Args>(args)...);
+                            [&]() noexcept(nothrow) { opt.emplace(::std::forward<Args>(args)...); }();
                         } catch (...) {
-                            if (disposition::error != state.disp.exchange(disposition::error)) {
-                                state.stop_src.request_stop();
-                                state.errors.template emplace<::std::exception_ptr>(::std::current_exception());
+                            if constexpr (!nothrow) {
+                                if (disposition::error != state.disp.exchange(disposition::error)) {
+                                    state.stop_src.request_stop();
+                                    state.errors.template emplace<::std::exception_ptr>(::std::current_exception());
+                                }
                             }
                         }
                     }
diff --git a/include/beman/execution/execution.hpp b/include/beman/execution/execution.hpp
index 6d632826..5f526386 100644
--- a/include/beman/execution/execution.hpp
+++ b/include/beman/execution/execution.hpp
@@ -18,6 +18,7 @@ import beman.execution.detail.completion_signatures;
 import beman.execution.detail.connect;
 import beman.execution.detail.continues_on;
 import beman.execution.detail.counting_scope;
+import beman.execution.detail.dependent_sender;
 import beman.execution.detail.env;
 import beman.execution.detail.execution_policy;
 import beman.execution.detail.forwarding_query;
@@ -79,6 +80,7 @@ import beman.execution.detail.write_env;
 #include <beman/execution/detail/connect.hpp>
 #include <beman/execution/detail/continues_on.hpp>
 #include <beman/execution/detail/counting_scope.hpp>
+#include <beman/execution/detail/dependent_sender.hpp>
 #include <beman/execution/detail/env.hpp>
 #include <beman/execution/detail/execution_policy.hpp>
 #include <beman/execution/detail/forwarding_query.hpp>
diff --git a/src/beman/execution/CMakeLists.txt b/src/beman/execution/CMakeLists.txt
index 9344e402..674d52c5 100644
--- a/src/beman/execution/CMakeLists.txt
+++ b/src/beman/execution/CMakeLists.txt
@@ -68,6 +68,7 @@ target_sources(
                 ${PROJECT_SOURCE_DIR}/include/beman/execution/detail/decays_to.hpp
                 ${PROJECT_SOURCE_DIR}/include/beman/execution/detail/default_domain.hpp
                 ${PROJECT_SOURCE_DIR}/include/beman/execution/detail/default_impls.hpp
+                ${PROJECT_SOURCE_DIR}/include/beman/execution/detail/dependent_sender.hpp
                 ${PROJECT_SOURCE_DIR}/include/beman/execution/detail/dependent_sender_error.hpp
                 ${PROJECT_SOURCE_DIR}/include/beman/execution/detail/execution_policy.hpp
                 ${PROJECT_SOURCE_DIR}/include/beman/execution/detail/emplace_from.hpp
@@ -259,6 +260,7 @@ if(BEMAN_USE_MODULES)
                     decays_to.cppm
                     default_domain.cppm
                     default_impls.cppm
+                    dependent_sender.cppm
                     dependent_sender_error.cppm
                     execution_policy.cppm
                     emplace_from.cppm
diff --git a/src/beman/execution/dependent_sender.cppm b/src/beman/execution/dependent_sender.cppm
new file mode 100644
index 00000000..93129e75
--- /dev/null
+++ b/src/beman/execution/dependent_sender.cppm
@@ -0,0 +1,11 @@
+module;
+// src/beman/execution/dependent_sender.cppm                    -*-C++-*-
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <beman/execution/detail/dependent_sender.hpp>
+
+export module beman.execution.detail.dependent_sender;
+
+namespace beman::execution {
+export using beman::execution::dependent_sender;
+} // namespace beman::execution
diff --git a/src/beman/execution/execution.cppm b/src/beman/execution/execution.cppm
index 3bf9e4c2..3de60d3c 100644
--- a/src/beman/execution/execution.cppm
+++ b/src/beman/execution/execution.cppm
@@ -94,9 +94,8 @@ export import beman.execution.detail.receiver_of;
 // [exec.snd], senders
 export import beman.execution.detail.sender;
 export import beman.execution.detail.sender_in;
-//-dk:TODO export using ::beman::execution::sender_to;
 export import beman.execution.detail.sender_to;
-
+export import beman.execution.detail.dependent_sender;
 export import beman.execution.detail.sends_stopped;
 
 namespace beman::execution {
diff --git a/src/beman/execution/sender.cppm b/src/beman/execution/sender.cppm
index 6443867f..3049e8a3 100644
--- a/src/beman/execution/sender.cppm
+++ b/src/beman/execution/sender.cppm
@@ -9,4 +9,5 @@ export module beman.execution.detail.sender;
 namespace beman::execution {
 export using beman::execution::sender_t;
 export using beman::execution::sender;
+export using beman::execution::enable_sender;
 } // namespace beman::execution
diff --git a/tests/beman/execution/exec-snd-expos.test.cpp b/tests/beman/execution/exec-snd-expos.test.cpp
index b831b915..aca8b075 100644
--- a/tests/beman/execution/exec-snd-expos.test.cpp
+++ b/tests/beman/execution/exec-snd-expos.test.cpp
@@ -1146,7 +1146,10 @@ auto test_basic_sender() -> void {
     static_assert(
         std::same_as<basic_sender_tag::sender,
                      decltype(test_std::transform_sender(test_std::default_domain{}, basic_sender{}, local_env{}))>);
-    static_assert(test_std::sender_in<basic_sender>);
+    static_assert(test_std::dependent_sender<sender0>);
+    // According to https://eel.is/c++draft/exec#adapt.general-3.5, basic_sender shall be a dependent-sender
+    static_assert(test_std::dependent_sender<basic_sender>);
+    static_assert(test_std::sender_in<basic_sender, local_env>);
 #if 0
         //-dk:TODO restore completion_sigatures_for test
         static_assert(std::same_as<