diff --git a/.circleci/config.yml b/.circleci/config.yml
index 2111850e65..69ac4fc5dc 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -26,7 +26,7 @@ setup_arm64_machine: &setup_arm64_machine
 
 docker_default: &docker_default
     docker:
-      - image: pikaorg/pika-ci-base:14
+      - image: pikaorg/pika-ci-base:15
 
 defaults: &defaults
     <<: *working_dir_default
diff --git a/.github/workflows/linux_coverage.yml b/.github/workflows/linux_coverage.yml
index cc2182ac36..508be29380 100644
--- a/.github/workflows/linux_coverage.yml
+++ b/.github/workflows/linux_coverage.yml
@@ -15,7 +15,7 @@ jobs:
   build:
     name: github/linux/coverage
     runs-on: ubuntu-latest
-    container: pikaorg/pika-ci-base:14
+    container: pikaorg/pika-ci-base:15
 
     steps:
     - uses: actions/checkout@v3
diff --git a/.github/workflows/linux_debug.yml b/.github/workflows/linux_debug.yml
index f9e68ee529..0aa4b251dd 100644
--- a/.github/workflows/linux_debug.yml
+++ b/.github/workflows/linux_debug.yml
@@ -20,7 +20,7 @@ jobs:
   build:
     name: github/linux/debug/fast
     runs-on: ubuntu-latest
-    container: pikaorg/pika-ci-base:14
+    container: pikaorg/pika-ci-base:15
 
     steps:
     - uses: actions/checkout@v3
diff --git a/.github/workflows/linux_hip.yml b/.github/workflows/linux_hip.yml
index f4c63adc75..7ea639155e 100644
--- a/.github/workflows/linux_hip.yml
+++ b/.github/workflows/linux_hip.yml
@@ -20,7 +20,7 @@ jobs:
   build:
     name: github/linux/hip/fast
     runs-on: ubuntu-latest
-    container: pikaorg/pika-ci-hip:7
+    container: pikaorg/pika-ci-hip:8
     steps:
     - uses: actions/checkout@v3
     - name: Update apt repositories for ccache
diff --git a/.github/workflows/linux_release_fetchcontent.yml b/.github/workflows/linux_release_fetchcontent.yml
index d3608e1387..d618cc3d04 100644
--- a/.github/workflows/linux_release_fetchcontent.yml
+++ b/.github/workflows/linux_release_fetchcontent.yml
@@ -20,7 +20,7 @@ jobs:
   build:
     name: github/linux/fetchcontent/fast
     runs-on: ubuntu-latest
-    container: pikaorg/pika-ci-base:14
+    container: pikaorg/pika-ci-base:15
 
     steps:
     - uses: actions/checkout@v3
diff --git a/.github/workflows/linux_sanitizers.yml b/.github/workflows/linux_sanitizers.yml
index 2a04cdfa4e..e5ecb049cf 100644
--- a/.github/workflows/linux_sanitizers.yml
+++ b/.github/workflows/linux_sanitizers.yml
@@ -20,7 +20,7 @@ jobs:
   build:
     name: github/linux/sanitizers/fast
     runs-on: ubuntu-latest
-    container: pikaorg/pika-ci-base:14
+    container: pikaorg/pika-ci-base:15
 
     steps:
     - uses: actions/checkout@v3
diff --git a/.github/workflows/linux_tracy.yml b/.github/workflows/linux_tracy.yml
index 43f9601757..c5150ff45a 100644
--- a/.github/workflows/linux_tracy.yml
+++ b/.github/workflows/linux_tracy.yml
@@ -20,7 +20,7 @@ jobs:
   build:
     name: github/linux/tracy/fast
     runs-on: ubuntu-latest
-    container: pikaorg/pika-ci-base:14
+    container: pikaorg/pika-ci-base:15
 
     steps:
     - name: Check out Tracy
diff --git a/.jenkins/cscs-ault/env-hipcc.sh b/.jenkins/cscs-ault/env-hipcc.sh
index 3a95f02a32..5cdc4e5e16 100644
--- a/.jenkins/cscs-ault/env-hipcc.sh
+++ b/.jenkins/cscs-ault/env-hipcc.sh
@@ -12,7 +12,7 @@ hip_version="5.3.3"
 hwloc_version="2.6.0"
 spack_compiler="gcc@${gcc_version}"
 spack_arch="linux-centos8-zen"
-stdexec_version="c0fe16f451137b00ceb85d912ec3a288990ce766"
+stdexec_version="6510f5bd69cc03b24668f26eda3dd3cca7e81bb2"
 
 # The xnack- architectures are not supported by rocblas@5.3.3
 spack_spec="pika@main+rocm+p2300 amdgpu_target='gfx906:xnack-' arch=${spack_arch} %${spack_compiler} malloc=system cxxstd=${cxx_std} ^boost@${boost_version} ^hwloc@${hwloc_version} ^hip@${hip_version} ^whip amdgpu_target='gfx906:xnack-' ^stdexec@${stdexec_version}"
diff --git a/.jenkins/cscs/env-clang-13.sh b/.jenkins/cscs/env-clang-13.sh
index d46dac2eca..a0053f539a 100644
--- a/.jenkins/cscs/env-clang-13.sh
+++ b/.jenkins/cscs/env-clang-13.sh
@@ -10,7 +10,7 @@ boost_version="1.79.0"
 hwloc_version="2.6.0"
 spack_compiler="clang@${clang_version}"
 spack_arch="cray-cnl7-broadwell"
-stdexec_version="c0fe16f451137b00ceb85d912ec3a288990ce766"
+stdexec_version="6510f5bd69cc03b24668f26eda3dd3cca7e81bb2"
 
 spack_spec="pika@main arch=${spack_arch} %${spack_compiler} cxxflags=-stdlib=libc++ malloc=system cxxstd=${cxx_std} +p2300 ^boost@${boost_version} ^hwloc@${hwloc_version} ^fmt cxxflags=-stdlib=libc++ ^stdexec@${stdexec_version}"
 
diff --git a/.jenkins/cscs/env-clang-14-cuda.sh b/.jenkins/cscs/env-clang-14-cuda.sh
index b7f8db6fad..b945872b23 100644
--- a/.jenkins/cscs/env-clang-14-cuda.sh
+++ b/.jenkins/cscs/env-clang-14-cuda.sh
@@ -11,7 +11,7 @@ hwloc_version="2.7.0"
 cuda_version="11.5.0"
 spack_compiler="clang@${clang_version}"
 spack_arch="cray-cnl7-haswell"
-stdexec_version="c0fe16f451137b00ceb85d912ec3a288990ce766"
+stdexec_version="6510f5bd69cc03b24668f26eda3dd3cca7e81bb2"
 
 spack_spec="pika@main arch=${spack_arch} %${spack_compiler} +cuda malloc=system cxxstd=${cxx_std} +p2300 ^boost@${boost_version} ^cuda@${cuda_version} +allow-unsupported-compilers ^hwloc@${hwloc_version} ^stdexec@${stdexec_version}"
 
diff --git a/README.rst b/README.rst
index 8d03ecdd8b..42f1d17748 100644
--- a/README.rst
+++ b/README.rst
@@ -49,8 +49,8 @@ pika optionally requires:
 * `Boost.Context, Thread, and Chrono <https://boost.org>`_ on macOS
 * `stdexec <https://github.com/NVIDIA/stdexec>`_ when
   ``PIKA_WITH_P2300_REFERENCE_IMPLEMENTATION`` is enabled (currently tested with commit
-  `c0fe16f451137b00ceb85d912ec3a288990ce766
-  <https://github.com/NVIDIA/stdexec/commit/c0fe16f451137b00ceb85d912ec3a288990ce766>`).
+  `6510f5bd69cc03b24668f26eda3dd3cca7e81bb2
+  <https://github.com/NVIDIA/stdexec/commit/6510f5bd69cc03b24668f26eda3dd3cca7e81bb2>`).
   The integration is experimental.
 
 
diff --git a/libs/pika/async_cuda/include/pika/async_cuda/then_on_host.hpp b/libs/pika/async_cuda/include/pika/async_cuda/then_on_host.hpp
index f61b8b8792..712bc6b0d7 100644
--- a/libs/pika/async_cuda/include/pika/async_cuda/then_on_host.hpp
+++ b/libs/pika/async_cuda/include/pika/async_cuda/then_on_host.hpp
@@ -39,6 +39,8 @@ namespace pika::cuda::experimental {
         struct then_on_host_receiver_impl<Receiver,
             F>::then_on_host_receiver_type
         {
+            using is_receiver = void;
+
             PIKA_NO_UNIQUE_ADDRESS std::decay_t<Receiver> receiver;
             PIKA_NO_UNIQUE_ADDRESS std::decay_t<F> f;
             cuda_scheduler sched;
@@ -117,7 +119,7 @@ namespace pika::cuda::experimental {
                     });
             }
 
-            friend constexpr pika::execution::experimental::detail::empty_env
+            friend constexpr pika::execution::experimental::empty_env
             tag_invoke(pika::execution::experimental::get_env_t,
                 then_on_host_receiver_type const&) noexcept
             {
@@ -138,6 +140,8 @@ namespace pika::cuda::experimental {
         template <typename Sender, typename F>
         struct then_on_host_sender_impl<Sender, F>::then_on_host_sender_type
         {
+            using is_sender = void;
+
             std::decay_t<Sender> sender;
             std::decay_t<F> f;
             cuda_scheduler sched;
@@ -169,7 +173,7 @@ namespace pika::cuda::experimental {
 
             using completion_signatures =
                 pika::execution::experimental::make_completion_signatures<
-                    Sender, pika::execution::experimental::detail::empty_env,
+                    Sender, pika::execution::experimental::empty_env,
                     pika::execution::experimental::completion_signatures<
                         pika::execution::experimental::set_error_t(
                             std::exception_ptr)>,
@@ -226,12 +230,11 @@ namespace pika::cuda::experimental {
                         PIKA_FORWARD(Receiver, receiver), s.f, s.sched});
             }
 
-            friend cuda_scheduler tag_invoke(
-                pika::execution::experimental::get_completion_scheduler_t<
-                    pika::execution::experimental::set_value_t>,
-                then_on_host_sender_type const& s) noexcept
+            friend constexpr auto tag_invoke(
+                pika::execution::experimental::get_env_t,
+                then_on_host_sender_type const& s)
             {
-                return s.sched;
+                return pika::execution::experimental::get_env(s.sender);
             }
         };
     }    // namespace then_on_host_detail
diff --git a/libs/pika/async_cuda/include/pika/async_cuda/then_with_stream.hpp b/libs/pika/async_cuda/include/pika/async_cuda/then_with_stream.hpp
index 65036c39bf..c83ece7c91 100644
--- a/libs/pika/async_cuda/include/pika/async_cuda/then_with_stream.hpp
+++ b/libs/pika/async_cuda/include/pika/async_cuda/then_with_stream.hpp
@@ -149,6 +149,8 @@ namespace pika::cuda::experimental::then_with_stream_detail {
     struct then_with_cuda_stream_sender_impl<Sender,
         F>::then_with_cuda_stream_sender_type
     {
+        using is_sender = void;
+
         PIKA_NO_UNIQUE_ADDRESS std::decay_t<Sender> sender;
         PIKA_NO_UNIQUE_ADDRESS std::decay_t<F> f;
         cuda_scheduler sched;
@@ -185,8 +187,7 @@ namespace pika::cuda::experimental::then_with_stream_detail {
 
         using completion_signatures =
             pika::execution::experimental::make_completion_signatures<
-                std::decay_t<Sender>,
-                pika::execution::experimental::detail::empty_env,
+                std::decay_t<Sender>, pika::execution::experimental::empty_env,
                 pika::execution::experimental::completion_signatures<
                     pika::execution::experimental::set_error_t(
                         std::exception_ptr)>,
@@ -249,6 +250,7 @@ namespace pika::cuda::experimental::then_with_stream_detail {
 
             struct then_with_cuda_stream_receiver
             {
+                using is_receiver = void;
                 using then_with_cuda_stream_receiver_tag = void;
 
                 operation_state& op_state;
@@ -465,10 +467,9 @@ namespace pika::cuda::experimental::then_with_stream_detail {
                         });
                 }
 
-                friend constexpr pika::execution::experimental::detail::
-                    empty_env
-                    tag_invoke(pika::execution::experimental::get_env_t,
-                        then_with_cuda_stream_receiver const&) noexcept
+                friend constexpr pika::execution::experimental::empty_env
+                tag_invoke(pika::execution::experimental::get_env_t,
+                    then_with_cuda_stream_receiver const&) noexcept
                 {
                     return {};
                 }
@@ -502,8 +503,8 @@ namespace pika::cuda::experimental::then_with_stream_detail {
                 pika::util::detail::transform_t<
                     pika::execution::experimental::value_types_of_t<
                         std::decay_t<Sender>,
-                        pika::execution::experimental::detail::empty_env,
-                        std::tuple, pika::detail::variant>,
+                        pika::execution::experimental::empty_env, std::tuple,
+                        pika::detail::variant>,
                     value_types_helper>,
                 pika::detail::monostate>;
 #else
@@ -551,7 +552,7 @@ namespace pika::cuda::experimental::then_with_stream_detail {
                     pika::util::detail::transform_t<
                         pika::execution::experimental::value_types_of_t<
                             then_with_cuda_stream_sender_type,
-                            pika::execution::experimental::detail::empty_env,
+                            pika::execution::experimental::empty_env,
                             pika::util::detail::pack, pika::util::detail::pack>,
                         result_types_helper>,
                     pika::detail::monostate>>>;
@@ -603,12 +604,11 @@ namespace pika::cuda::experimental::then_with_stream_detail {
                 PIKA_FORWARD(Receiver, receiver), s.f, s.sched, s.sender);
         }
 
-        friend cuda_scheduler tag_invoke(
-            pika::execution::experimental::get_completion_scheduler_t<
-                pika::execution::experimental::set_value_t>,
-            then_with_cuda_stream_sender_type const& s) noexcept
+        friend constexpr auto tag_invoke(
+            pika::execution::experimental::get_env_t,
+            then_with_cuda_stream_sender_type const& s)
         {
-            return s.sched;
+            return pika::execution::experimental::get_env(s.sender);
         }
     };
 
@@ -619,7 +619,8 @@ namespace pika::cuda::experimental::then_with_stream_detail {
     {
         auto completion_sched =
             pika::execution::experimental::get_completion_scheduler<
-                pika::execution::experimental::set_value_t>(sender);
+                pika::execution::experimental::set_value_t>(
+                pika::execution::experimental::get_env(sender));
         static_assert(std::is_same_v<std::decay_t<decltype(completion_sched)>,
                           cuda_scheduler>,
             "then_with_cuda_stream can only be used with senders whose "
diff --git a/libs/pika/async_mpi/include/pika/async_mpi/transform_mpi.hpp b/libs/pika/async_mpi/include/pika/async_mpi/transform_mpi.hpp
index 18b1bb8a77..0edf35339b 100644
--- a/libs/pika/async_mpi/include/pika/async_mpi/transform_mpi.hpp
+++ b/libs/pika/async_mpi/include/pika/async_mpi/transform_mpi.hpp
@@ -101,6 +101,8 @@ namespace pika::mpi::experimental {
         template <typename Sender, typename F>
         struct transform_mpi_sender_impl<Sender, F>::transform_mpi_sender_type
         {
+            using is_sender = void;
+
             std::decay_t<Sender> sender;
             std::decay_t<F> f;
             stream_type stream;
@@ -117,7 +119,7 @@ namespace pika::mpi::experimental {
             using completion_signatures =
                 pika::execution::experimental::make_completion_signatures<
                     std::decay_t<Sender>,
-                    pika::execution::experimental::detail::empty_env,
+                    pika::execution::experimental::empty_env,
                     pika::execution::experimental::completion_signatures<
                         pika::execution::experimental::set_error_t(
                             std::exception_ptr)>,
@@ -164,6 +166,8 @@ namespace pika::mpi::experimental {
 
                 struct transform_mpi_receiver
                 {
+                    using is_receiver = void;
+
                     operation_state& op_state;
 
                     template <typename Error>
@@ -264,10 +268,9 @@ namespace pika::mpi::experimental {
                             });
                     }
 
-                    friend constexpr pika::execution::experimental::detail::
-                        empty_env
-                        tag_invoke(pika::execution::experimental::get_env_t,
-                            transform_mpi_receiver const&) noexcept
+                    friend constexpr pika::execution::experimental::empty_env
+                    tag_invoke(pika::execution::experimental::get_env_t,
+                        transform_mpi_receiver const&) noexcept
                     {
                         return {};
                     }
@@ -290,7 +293,7 @@ namespace pika::mpi::experimental {
                     pika::util::detail::transform_t<
                         pika::execution::experimental::value_types_of_t<
                             std::decay_t<Sender>,
-                            pika::execution::experimental::detail::empty_env,
+                            pika::execution::experimental::empty_env,
                             std::tuple, pika::detail::variant>,
                         value_types_helper>,
                     pika::detail::monostate>;
@@ -342,8 +345,7 @@ namespace pika::mpi::experimental {
                         pika::util::detail::transform_t<
                             pika::execution::experimental::value_types_of_t<
                                 transform_mpi_sender_type,
-                                pika::execution::experimental::detail::
-                                    empty_env,
+                                pika::execution::experimental::empty_env,
                                 pika::util::detail::pack,
                                 pika::util::detail::pack>,
                             result_types_helper>,
diff --git a/libs/pika/execution/include/pika/execution/algorithms/bulk.hpp b/libs/pika/execution/include/pika/execution/algorithms/bulk.hpp
index c48c1961cb..173d06125b 100644
--- a/libs/pika/execution/include/pika/execution/algorithms/bulk.hpp
+++ b/libs/pika/execution/include/pika/execution/algorithms/bulk.hpp
@@ -64,20 +64,10 @@ namespace pika::bulk_detail {
 
         static constexpr bool sends_done = false;
 
-        template <typename CPO,
-            // clang-format off
-                PIKA_CONCEPT_REQUIRES_(
-                    pika::execution::experimental::detail::is_receiver_cpo_v<CPO> &&
-                    pika::execution::experimental::detail::has_completion_scheduler_v<
-                        CPO, std::decay_t<Sender>>)
-            // clang-format on
-            >
-        friend constexpr auto tag_invoke(
-            pika::execution::experimental::get_completion_scheduler_t<CPO>,
-            bulk_sender_type const& sender)
+        friend constexpr decltype(auto) tag_invoke(
+            pika::execution::experimental::get_env_t, bulk_sender_type const& s)
         {
-            return pika::execution::experimental::get_completion_scheduler<CPO>(
-                sender.sender);
+            return pika::execution::experimental::get_env(s.sender);
         }
 
         template <typename Receiver>
@@ -183,7 +173,8 @@ namespace pika::execution::experimental {
         {
             auto scheduler =
                 pika::execution::experimental::get_completion_scheduler<
-                    pika::execution::experimental::set_value_t>(sender);
+                    pika::execution::experimental::set_value_t>(
+                    tag_invoke(pika::execution::experimental::get_env, sender));
             return pika::functional::tag_invoke(bulk_t{}, PIKA_MOVE(scheduler),
                 PIKA_FORWARD(Sender, sender), shape, PIKA_FORWARD(F, f));
         }
diff --git a/libs/pika/execution/include/pika/execution/algorithms/drop_value.hpp b/libs/pika/execution/include/pika/execution/algorithms/drop_value.hpp
index 942642192c..9b31f0e255 100644
--- a/libs/pika/execution/include/pika/execution/algorithms/drop_value.hpp
+++ b/libs/pika/execution/include/pika/execution/algorithms/drop_value.hpp
@@ -34,6 +34,8 @@ namespace pika::drop_value_detail {
     template <typename Receiver>
     struct drop_value_receiver_impl<Receiver>::drop_value_receiver_type
     {
+        using is_receiver = void;
+
         PIKA_NO_UNIQUE_ADDRESS std::decay_t<Receiver> receiver;
 
         template <typename Error>
@@ -57,8 +59,8 @@ namespace pika::drop_value_detail {
             pika::execution::experimental::set_value(PIKA_MOVE(r.receiver));
         }
 
-        friend constexpr pika::execution::experimental::detail::empty_env
-        tag_invoke(pika::execution::experimental::get_env_t,
+        friend constexpr pika::execution::experimental::empty_env tag_invoke(
+            pika::execution::experimental::get_env_t,
             drop_value_receiver_type const&) noexcept
         {
             return {};
@@ -78,6 +80,8 @@ namespace pika::drop_value_detail {
     template <typename Sender>
     struct drop_value_sender_impl<Sender>::drop_value_sender_type
     {
+        using is_sender = void;
+
         PIKA_NO_UNIQUE_ADDRESS std::decay_t<Sender> sender;
 
 #if defined(PIKA_HAVE_P2300_REFERENCE_IMPLEMENTATION)
@@ -88,7 +92,7 @@ namespace pika::drop_value_detail {
 
         using completion_signatures =
             pika::execution::experimental::make_completion_signatures<Sender,
-                pika::execution::experimental::detail::empty_env,
+                pika::execution::experimental::empty_env,
                 pika::execution::experimental::completion_signatures<>,
                 empty_set_value>;
 #else
@@ -106,22 +110,6 @@ namespace pika::drop_value_detail {
         static constexpr bool sends_done = false;
 #endif
 
-        template <typename CPO,
-            // clang-format off
-                PIKA_CONCEPT_REQUIRES_(
-                    pika::execution::experimental::detail::is_receiver_cpo_v<CPO> &&
-                    pika::execution::experimental::detail::has_completion_scheduler_v<
-                        CPO, std::decay_t<Sender>>)
-            // clang-format on
-            >
-        friend constexpr auto tag_invoke(
-            pika::execution::experimental::get_completion_scheduler_t<CPO>,
-            drop_value_sender_type const& sender)
-        {
-            return pika::execution::experimental::get_completion_scheduler<CPO>(
-                sender.sender);
-        }
-
         template <typename Receiver>
         friend auto tag_invoke(pika::execution::experimental::connect_t,
             drop_value_sender_type&& s, Receiver&& receiver)
@@ -139,6 +127,13 @@ namespace pika::drop_value_detail {
                 drop_value_receiver<Receiver>{
                     PIKA_FORWARD(Receiver, receiver)});
         }
+
+        friend constexpr decltype(auto) tag_invoke(
+            pika::execution::experimental::get_env_t,
+            drop_value_sender_type const& s)
+        {
+            return pika::execution::experimental::get_env(s.sender);
+        }
     };
 }    // namespace pika::drop_value_detail
 
diff --git a/libs/pika/execution/include/pika/execution/algorithms/keep_future.hpp b/libs/pika/execution/include/pika/execution/algorithms/keep_future.hpp
index b44c7feb48..5c93152d6a 100644
--- a/libs/pika/execution/include/pika/execution/algorithms/keep_future.hpp
+++ b/libs/pika/execution/include/pika/execution/algorithms/keep_future.hpp
@@ -62,6 +62,8 @@ namespace pika::keep_future_detail {
     template <typename Future>
     struct keep_future_sender_base
     {
+        using is_sender = void;
+
         std::decay_t<Future> future;
 
         template <template <typename...> class Tuple,
diff --git a/libs/pika/execution/include/pika/execution/algorithms/make_future.hpp b/libs/pika/execution/include/pika/execution/algorithms/make_future.hpp
index 3c4e5f6732..079ed83497 100644
--- a/libs/pika/execution/include/pika/execution/algorithms/make_future.hpp
+++ b/libs/pika/execution/include/pika/execution/algorithms/make_future.hpp
@@ -58,6 +58,8 @@ namespace pika::make_future_detail {
     template <typename T, typename Allocator>
     struct make_future_receiver
     {
+        using is_receiver = void;
+
         pika::intrusive_ptr<
             resettable_operation_state_future_data<T, Allocator>>
             data;
@@ -99,8 +101,8 @@ namespace pika::make_future_detail {
             r_local.data.reset();
         }
 
-        friend constexpr pika::execution::experimental::detail::empty_env
-        tag_invoke(pika::execution::experimental::get_env_t,
+        friend constexpr pika::execution::experimental::empty_env tag_invoke(
+            pika::execution::experimental::get_env_t,
             make_future_receiver const&) noexcept
         {
             return {};
@@ -150,8 +152,8 @@ namespace pika::make_future_detail {
             r_local.data.reset();
         }
 
-        friend constexpr pika::execution::experimental::detail::empty_env
-        tag_invoke(pika::execution::experimental::get_env_t,
+        friend constexpr pika::execution::experimental::empty_env tag_invoke(
+            pika::execution::experimental::get_env_t,
             make_future_receiver const&) noexcept
         {
             return {};
@@ -203,8 +205,7 @@ namespace pika::make_future_detail {
 #if defined(PIKA_HAVE_P2300_REFERENCE_IMPLEMENTATION)
         using value_types =
             typename pika::execution::experimental::value_types_of_t<
-                std::decay_t<Sender>,
-                pika::execution::experimental::detail::empty_env,
+                std::decay_t<Sender>, pika::execution::experimental::empty_env,
                 pika::util::detail::pack, pika::util::detail::pack>;
 #else
         using value_types = typename pika::execution::experimental::
diff --git a/libs/pika/execution/include/pika/execution/algorithms/schedule_from.hpp b/libs/pika/execution/include/pika/execution/algorithms/schedule_from.hpp
index a4eec9ec65..53c4752add 100644
--- a/libs/pika/execution/include/pika/execution/algorithms/schedule_from.hpp
+++ b/libs/pika/execution/include/pika/execution/algorithms/schedule_from.hpp
@@ -74,38 +74,35 @@ namespace pika::schedule_from_detail {
 
         static constexpr bool sends_done = false;
 
-        template <typename CPO,
-            // clang-format off
-                PIKA_CONCEPT_REQUIRES_(
-                    pika::execution::experimental::detail::is_receiver_cpo_v<CPO> &&
-                    (std::is_same_v<CPO, pika::execution::experimental::set_value_t> ||
-                        pika::execution::experimental::detail::has_completion_scheduler_v<
-                                pika::execution::experimental::set_error_t,
-                                std::decay_t<Sender>> ||
-                        pika::execution::experimental::detail::has_completion_scheduler_v<
-                                pika::execution::experimental::set_stopped_t,
-                                std::decay_t<Sender>>))
-            // clang-format on
-            >
-        friend constexpr auto tag_invoke(
-            pika::execution::experimental::get_completion_scheduler_t<CPO>,
-            schedule_from_sender_type const& sender)
+        template <typename Env>
+        struct env
         {
-            if constexpr (std::is_same_v<std::decay_t<CPO>,
-                              pika::execution::experimental::set_value_t>)
+            PIKA_NO_UNIQUE_ADDRESS Env e;
+            PIKA_NO_UNIQUE_ADDRESS std::decay_t<Scheduler> scheduler;
+
+            friend constexpr auto tag_invoke(
+                pika::execution::experimental::get_completion_scheduler_t<
+                    pika::execution::experimental::set_value_t>,
+                env const& e) noexcept
             {
-                return sender.scheduler;
+                return e.scheduler;
             }
-            else
+
+            template <typename Tag,
+                PIKA_CONCEPT_REQUIRES_(std::is_invocable_v<Tag, env const&>)>
+            friend constexpr decltype(auto) tag_invoke(Tag, env const& e)
             {
-                return pika::execution::experimental::get_completion_scheduler<
-                    CPO>(sender.predecessor_sender);
+                return Tag{}(e.e);
             }
-            // This silences a bogus warning from nvcc about no return from
-            // a non-void function.
-#if defined(__NVCC__)
-            __builtin_unreachable();
-#endif
+        };
+
+        friend constexpr auto tag_invoke(
+            pika::execution::experimental::get_env_t,
+            schedule_from_sender_type const& s)
+        {
+            auto e =
+                pika::execution::experimental::get_env(s.predecessor_sender);
+            return env<std::decay_t<decltype(e)>>{std::move(e), s.scheduler};
         }
 
         template <typename Receiver>
diff --git a/libs/pika/execution/include/pika/execution/algorithms/split_tuple.hpp b/libs/pika/execution/include/pika/execution/algorithms/split_tuple.hpp
index d81fc53f72..91855dd935 100644
--- a/libs/pika/execution/include/pika/execution/algorithms/split_tuple.hpp
+++ b/libs/pika/execution/include/pika/execution/algorithms/split_tuple.hpp
@@ -80,7 +80,7 @@ namespace pika::split_tuple_detail {
         using value_type = typename std::decay<
             pika::execution::experimental::detail::single_result_t<
                 typename pika::execution::experimental::value_types_of_t<Sender,
-                    pika::execution::experimental::detail::empty_env,
+                    pika::execution::experimental::empty_env,
                     pika::util::detail::pack, pika::util::detail::pack>>>::type;
 #else
         using value_type = typename std::decay<
@@ -95,8 +95,7 @@ namespace pika::split_tuple_detail {
             pika::util::detail::unique_t<pika::util::detail::prepend_t<
                 pika::util::detail::transform_t<
                     typename pika::execution::experimental::error_types_of_t<
-                        Sender,
-                        pika::execution::experimental::detail::empty_env,
+                        Sender, pika::execution::experimental::empty_env,
                         pika::detail::variant>,
                     std::decay>,
                 std::exception_ptr>>;
@@ -120,6 +119,8 @@ namespace pika::split_tuple_detail {
 
         struct split_tuple_receiver
         {
+            using is_receiver = void;
+
             shared_state& state;
 
             template <typename Error>
@@ -144,8 +145,7 @@ namespace pika::split_tuple_detail {
             using value_type = typename std::decay<
                 pika::execution::experimental::detail::single_result_t<
                     typename pika::execution::experimental::value_types_of_t<
-                        Sender,
-                        pika::execution::experimental::detail::empty_env,
+                        Sender, pika::execution::experimental::empty_env,
                         pika::util::detail::pack, pika::util::detail::pack>>>::
                 type;
 #else
@@ -170,7 +170,7 @@ namespace pika::split_tuple_detail {
                 r.state.set_predecessor_done();
             }
 
-            friend constexpr pika::execution::experimental::detail::empty_env
+            friend constexpr pika::execution::experimental::empty_env
             tag_invoke(pika::execution::experimental::get_env_t,
                 split_tuple_receiver const&) noexcept
             {
@@ -213,7 +213,7 @@ namespace pika::split_tuple_detail {
                 constexpr bool sends_stopped =
 #if defined(PIKA_HAVE_P2300_REFERENCE_IMPLEMENTATION)
                     pika::execution::experimental::sends_stopped<Sender,
-                        pika::execution::experimental::detail::empty_env>
+                        pika::execution::experimental::empty_env>
 #else
                     pika::execution::experimental::sender_traits<
                         Sender>::sends_done
@@ -405,6 +405,8 @@ namespace pika::split_tuple_detail {
     struct split_tuple_sender_impl<Sender, Allocator,
         Index>::split_tuple_sender_type
     {
+        using is_sender = void;
+
         using allocator_type = Allocator;
         using shared_state_type = shared_state<Sender, Allocator>;
 
@@ -413,7 +415,7 @@ namespace pika::split_tuple_detail {
         using value_type = typename std::decay<
             pika::execution::experimental::detail::single_result_t<
                 typename pika::execution::experimental::value_types_of_t<Sender,
-                    pika::execution::experimental::detail::empty_env,
+                    pika::execution::experimental::empty_env,
                     pika::util::detail::pack, pika::util::detail::pack>>>::type;
 #else
         using value_type = typename std::decay<
@@ -449,7 +451,7 @@ namespace pika::split_tuple_detail {
 
         using completion_signatures =
             pika::execution::experimental::make_completion_signatures<Sender,
-                pika::execution::experimental::detail::empty_env,
+                pika::execution::experimental::empty_env,
                 pika::execution::experimental::completion_signatures<
                     pika::execution::experimental::set_error_t(
                         std::exception_ptr)>,
@@ -567,7 +569,7 @@ namespace pika::split_tuple_detail {
         using value_type = typename std::decay<
             pika::execution::experimental::detail::single_result_t<
                 typename pika::execution::experimental::value_types_of_t<Sender,
-                    pika::execution::experimental::detail::empty_env,
+                    pika::execution::experimental::empty_env,
                     pika::util::detail::pack, pika::util::detail::pack>>>::type;
 #else
         using value_type = typename std::decay<
diff --git a/libs/pika/execution/include/pika/execution/algorithms/sync_wait.hpp b/libs/pika/execution/include/pika/execution/algorithms/sync_wait.hpp
index fc72fd511e..ac3b1ab60a 100644
--- a/libs/pika/execution/include/pika/execution/algorithms/sync_wait.hpp
+++ b/libs/pika/execution/include/pika/execution/algorithms/sync_wait.hpp
@@ -63,13 +63,12 @@ namespace pika::sync_wait_detail {
             template <typename...> class Variant>
         using predecessor_value_types =
             pika::execution::experimental::value_types_of_t<Sender,
-                pika::execution::experimental::detail::empty_env, Tuple,
-                Variant>;
+                pika::execution::experimental::empty_env, Tuple, Variant>;
 
         template <template <typename...> class Variant>
         using predecessor_error_types =
             pika::execution::experimental::error_types_of_t<Sender,
-                pika::execution::experimental::detail::empty_env, Variant>;
+                pika::execution::experimental::empty_env, Variant>;
 
         // The type of the single void or non-void result that we store. If
         // there are multiple variants or multiple values sync_wait will
@@ -231,8 +230,8 @@ namespace pika::sync_wait_detail {
             r.signal_set_called();
         }
 
-        friend constexpr pika::execution::experimental::detail::empty_env
-        tag_invoke(pika::execution::experimental::get_env_t,
+        friend constexpr pika::execution::experimental::empty_env tag_invoke(
+            pika::execution::experimental::get_env_t,
             sync_wait_receiver_type const&) noexcept
         {
             return {};
diff --git a/libs/pika/execution/include/pika/execution/algorithms/then.hpp b/libs/pika/execution/include/pika/execution/algorithms/then.hpp
index 408f3540a8..ea4f23fe8a 100644
--- a/libs/pika/execution/include/pika/execution/algorithms/then.hpp
+++ b/libs/pika/execution/include/pika/execution/algorithms/then.hpp
@@ -148,22 +148,6 @@ namespace pika::then_detail {
 
         static constexpr bool sends_done = false;
 
-        template <typename CPO,
-            // clang-format off
-                PIKA_CONCEPT_REQUIRES_(
-                    pika::execution::experimental::detail::is_receiver_cpo_v<CPO> &&
-                    pika::execution::experimental::detail::has_completion_scheduler_v<
-                        CPO, std::decay_t<Sender>>)
-            // clang-format on
-            >
-        friend constexpr auto tag_invoke(
-            pika::execution::experimental::get_completion_scheduler_t<CPO>,
-            then_sender_type const& sender)
-        {
-            return pika::execution::experimental::get_completion_scheduler<CPO>(
-                sender.sender);
-        }
-
         template <typename Receiver>
         friend auto tag_invoke(pika::execution::experimental::connect_t,
             then_sender_type&& s, Receiver&& receiver)
@@ -181,6 +165,12 @@ namespace pika::then_detail {
                 then_receiver<Receiver, F>{
                     PIKA_FORWARD(Receiver, receiver), r.f});
         }
+
+        friend constexpr decltype(auto) tag_invoke(
+            pika::execution::experimental::get_env_t, then_sender_type const& s)
+        {
+            return pika::execution::experimental::get_env(s.sender);
+        }
     };
 }    // namespace pika::then_detail
 
diff --git a/libs/pika/execution/include/pika/execution/algorithms/when_all_vector.hpp b/libs/pika/execution/include/pika/execution/algorithms/when_all_vector.hpp
index 8b3710dc27..ab2847aa53 100644
--- a/libs/pika/execution/include/pika/execution/algorithms/when_all_vector.hpp
+++ b/libs/pika/execution/include/pika/execution/algorithms/when_all_vector.hpp
@@ -47,6 +47,8 @@ namespace pika::when_all_vector_detail {
     template <typename Sender>
     struct when_all_vector_sender_impl<Sender>::when_all_vector_sender_type
     {
+        using is_sender = void;
+
         using senders_type = std::vector<Sender>;
         senders_type senders;
 
@@ -67,7 +69,7 @@ namespace pika::when_all_vector_detail {
         using element_value_type =
             std::decay_t<pika::execution::experimental::detail::single_result_t<
                 pika::execution::experimental::value_types_of_t<Sender,
-                    pika::execution::experimental::detail::empty_env,
+                    pika::execution::experimental::empty_env,
                     pika::util::detail::pack, pika::util::detail::pack>>>;
 
         static constexpr bool is_void_value_type =
@@ -82,10 +84,13 @@ namespace pika::when_all_vector_detail {
         // This sender sends a single vector of the type sent by the
         // predecessor senders or nothing if the predecessor senders send
         // nothing
-        template <template <typename...> class Tuple,
-            template <typename...> class Variant>
-        using value_types = Variant<std::conditional_t<is_void_value_type,
-            Tuple<>, Tuple<std::vector<element_value_type>>>>;
+        template <typename...>
+        using set_value_helper =
+            pika::execution::experimental::completion_signatures<
+                std::conditional_t<is_void_value_type,
+                    pika::execution::experimental::set_value_t(),
+                    pika::execution::experimental::set_value_t(
+                        std::vector<element_value_type>)>>;
 
         // This sender sends any error types sent by the predecessor senders
         // or std::exception_ptr
@@ -93,19 +98,19 @@ namespace pika::when_all_vector_detail {
         using error_types = pika::util::detail::unique_concat_t<
             pika::util::detail::transform_t<
                 pika::execution::experimental::error_types_of_t<Sender,
-                    pika::execution::experimental::detail::empty_env, Variant>,
+                    pika::execution::experimental::empty_env, Variant>,
                 std::decay>,
             Variant<std::exception_ptr>>;
 
         static constexpr bool sends_done = false;
 
         using completion_signatures =
-            pika::execution::experimental::completion_signatures<
-                std::conditional_t<is_void_value_type,
-                    pika::execution::experimental::set_value_t(),
-                    pika::execution::experimental::set_value_t(
-                        std::vector<element_value_type>)>,
-                pika::execution::experimental::set_error_t(std::exception_ptr)>;
+            pika::execution::experimental::make_completion_signatures<Sender,
+                pika::execution::experimental::empty_env,
+                pika::execution::experimental::completion_signatures<
+                    pika::execution::experimental::set_error_t(
+                        std::exception_ptr)>,
+                set_value_helper>;
 #else
         // We expect a single value type or nothing from the predecessor
         // sender type
@@ -150,6 +155,8 @@ namespace pika::when_all_vector_detail {
         {
             struct when_all_vector_receiver
             {
+                using is_receiver = void;
+
                 operation_state& op_state;
                 std::size_t const i;
 
@@ -215,10 +222,9 @@ namespace pika::when_all_vector_detail {
                     r.op_state.finish();
                 }
 
-                friend constexpr pika::execution::experimental::detail::
-                    empty_env
-                    tag_invoke(pika::execution::experimental::get_env_t,
-                        when_all_vector_receiver const&) noexcept
+                friend constexpr pika::execution::experimental::empty_env
+                tag_invoke(pika::execution::experimental::get_env_t,
+                    when_all_vector_receiver const&) noexcept
                 {
                     return {};
                 }
@@ -323,8 +329,21 @@ namespace pika::when_all_vector_detail {
                     }
                     else
                     {
-                        pika::execution::experimental::set_stopped(
-                            PIKA_MOVE(receiver));
+#if defined(PIKA_HAVE_P2300_REFERENCE_IMPLEMENTATION)
+                        if constexpr (pika::execution::experimental::
+                                          sends_stopped<Sender>)
+#else
+                        if constexpr (pika::execution::experimental::
+                                          sender_traits<Sender>::sends_done)
+#endif
+                        {
+                            pika::execution::experimental::set_stopped(
+                                PIKA_MOVE(receiver));
+                        }
+                        else
+                        {
+                            PIKA_UNREACHABLE;
+                        }
                     }
                 }
             }
diff --git a/libs/pika/execution/tests/include/algorithm_test_utils.hpp b/libs/pika/execution/tests/include/algorithm_test_utils.hpp
index a778d0a17c..4b64266c90 100644
--- a/libs/pika/execution/tests/include/algorithm_test_utils.hpp
+++ b/libs/pika/execution/tests/include/algorithm_test_utils.hpp
@@ -163,8 +163,8 @@ struct callback_receiver
         r.set_value_called = true;
     }
 
-    friend constexpr pika::execution::experimental::detail::empty_env
-    tag_invoke(pika::execution::experimental::get_env_t,
+    friend constexpr pika::execution::experimental::empty_env tag_invoke(
+        pika::execution::experimental::get_env_t,
         callback_receiver const&) noexcept
     {
         return {};
@@ -199,8 +199,8 @@ struct error_callback_receiver
         PIKA_TEST(r.expect_set_value);
     }
 
-    friend constexpr pika::execution::experimental::detail::empty_env
-    tag_invoke(pika::execution::experimental::get_env_t,
+    friend constexpr pika::execution::experimental::empty_env tag_invoke(
+        pika::execution::experimental::get_env_t,
         error_callback_receiver const&) noexcept
     {
         return {};
@@ -502,10 +502,25 @@ struct scheduler
             return operation_state<R>{std::forward<R>(r)};
         }
 
-        friend scheduler tag_invoke(
-            pika::execution::experimental::get_completion_scheduler_t<
-                pika::execution::experimental::set_value_t>,
-            sender const& s) noexcept
+        struct env
+        {
+            std::reference_wrapper<std::atomic<bool>> schedule_called;
+            std::reference_wrapper<std::atomic<bool>> execute_called;
+            std::reference_wrapper<std::atomic<bool>>
+                tag_invoke_overload_called;
+
+            friend scheduler tag_invoke(
+                pika::execution::experimental::get_completion_scheduler_t<
+                    pika::execution::experimental::set_value_t>,
+                env const& e) noexcept
+            {
+                return {e.schedule_called, e.execute_called,
+                    e.tag_invoke_overload_called};
+            }
+        };
+
+        friend env tag_invoke(
+            pika::execution::experimental::get_env_t, sender const& s)
         {
             return {s.schedule_called, s.execute_called,
                 s.tag_invoke_overload_called};
@@ -583,10 +598,25 @@ struct scheduler2
             return operation_state<R>{std::forward<R>(r)};
         }
 
-        friend scheduler2 tag_invoke(
-            pika::execution::experimental::get_completion_scheduler_t<
-                pika::execution::experimental::set_value_t>,
-            sender const& s) noexcept
+        struct env
+        {
+            std::reference_wrapper<std::atomic<bool>> schedule_called;
+            std::reference_wrapper<std::atomic<bool>> execute_called;
+            std::reference_wrapper<std::atomic<bool>>
+                tag_invoke_overload_called;
+
+            friend scheduler2 tag_invoke(
+                pika::execution::experimental::get_completion_scheduler_t<
+                    pika::execution::experimental::set_value_t>,
+                env const& e) noexcept
+            {
+                return {e.schedule_called, e.execute_called,
+                    e.tag_invoke_overload_called};
+            }
+        };
+
+        friend env tag_invoke(
+            pika::execution::experimental::get_env_t, sender const& s)
         {
             return {s.schedule_called, s.execute_called,
                 s.tag_invoke_overload_called};
@@ -690,6 +720,23 @@ namespace my_namespace {
             {
                 return {};
             }
+
+            struct env
+            {
+                friend my_scheduler tag_invoke(
+                    pika::execution::experimental::get_completion_scheduler_t<
+                        pika::execution::experimental::set_value_t>,
+                    env const&) noexcept
+                {
+                    return {};
+                }
+            };
+
+            friend env tag_invoke(
+                pika::execution::experimental::get_env_t, sender const&)
+            {
+                return {};
+            }
         };
 
         friend sender tag_invoke(
diff --git a/libs/pika/execution/tests/unit/algorithm_bulk.cpp b/libs/pika/execution/tests/unit/algorithm_bulk.cpp
index 9e03367a7c..0b7b1e3b37 100644
--- a/libs/pika/execution/tests/unit/algorithm_bulk.cpp
+++ b/libs/pika/execution/tests/unit/algorithm_bulk.cpp
@@ -49,10 +49,6 @@ auto tag_invoke(ex::bulk_t, S&& s, int num, custom_bulk_operation t)
 
 int main()
 {
-    // TODO: bulk does not have a fallback implementation in the reference
-    // implementation. With P2300 enabled bulk is tested in
-    // thread_pool_scheduler_test.
-#if !defined(PIKA_HAVE_P2300_REFERENCE_IMPLEMENTATION)
     // Success path
     {
         std::atomic<bool> set_value_called{false};
@@ -263,10 +259,6 @@ int main()
     }
 
     test_adl_isolation(ex::bulk(ex::just(), 1, my_namespace::my_type{}));
-#else
-    // No tests with the P2300 reference implementation
-    PIKA_TEST(true);
-#endif
 
     return 0;
 }
diff --git a/libs/pika/execution/tests/unit/algorithm_execute.cpp b/libs/pika/execution/tests/unit/algorithm_execute.cpp
index 7fdc605b80..7fdea2a8bb 100644
--- a/libs/pika/execution/tests/unit/algorithm_execute.cpp
+++ b/libs/pika/execution/tests/unit/algorithm_execute.cpp
@@ -43,10 +43,19 @@ struct sender
         return {};
     }
 
-    friend Scheduler tag_invoke(
-        pika::execution::experimental::get_completion_scheduler_t<
-            pika::execution::experimental::set_value_t>,
-        sender const&) noexcept
+    struct env
+    {
+        friend Scheduler tag_invoke(
+            pika::execution::experimental::get_completion_scheduler_t<
+                pika::execution::experimental::set_value_t>,
+            env const&) noexcept
+        {
+            return {};
+        }
+    };
+
+    friend env tag_invoke(
+        pika::execution::experimental::get_env_t, sender const&) noexcept
     {
         return {};
     }
diff --git a/libs/pika/execution/tests/unit/algorithm_split.cpp b/libs/pika/execution/tests/unit/algorithm_split.cpp
index 496268fbf0..ff5f82b488 100644
--- a/libs/pika/execution/tests/unit/algorithm_split.cpp
+++ b/libs/pika/execution/tests/unit/algorithm_split.cpp
@@ -65,9 +65,6 @@ int main()
         PIKA_TEST(set_value_called);
     }
 
-    // The P2300 reference implementation still requires copyable senders (see
-    // issue https://github.com/NVIDIA/stdexec/issues/641).
-#if !defined(PIKA_HAVE_P2300_REFERENCE_IMPLEMENTATION)
     {
         std::atomic<bool> set_value_called{false};
         auto s1 =
@@ -91,7 +88,6 @@ int main()
         ex::start(os);
         PIKA_TEST(set_value_called);
     }
-#endif
 
     // operator| overload
     {
diff --git a/libs/pika/execution_base/include/pika/execution_base/any_sender.hpp b/libs/pika/execution_base/include/pika/execution_base/any_sender.hpp
index abcd069d57..c6696f5af8 100644
--- a/libs/pika/execution_base/include/pika/execution_base/any_sender.hpp
+++ b/libs/pika/execution_base/include/pika/execution_base/any_sender.hpp
@@ -552,8 +552,8 @@ namespace pika::execution::experimental::detail {
             PIKA_MOVE(moved_storage.get()).set_stopped();
         }
 
-        friend constexpr pika::execution::experimental::detail::empty_env
-        tag_invoke(pika::execution::experimental::get_env_t,
+        friend constexpr pika::execution::experimental::empty_env tag_invoke(
+            pika::execution::experimental::get_env_t,
             any_receiver const&) noexcept
         {
             return {};
@@ -930,7 +930,7 @@ namespace pika::execution::experimental {
 #if defined(PIKA_HAVE_P2300_REFERENCE_IMPLEMENTATION)
             using value_types_pack =
                 pika::execution::experimental::value_types_of_t<Sender,
-                    pika::execution::experimental::detail::empty_env,
+                    pika::execution::experimental::empty_env,
                     pika::util::detail::pack, pika::util::detail::pack>;
 #else
             using value_types_pack = typename pika::execution::experimental::
diff --git a/libs/pika/execution_base/include/pika/execution_base/completion_scheduler.hpp b/libs/pika/execution_base/include/pika/execution_base/completion_scheduler.hpp
index 043ba09bf0..8b306f8e0b 100644
--- a/libs/pika/execution_base/include/pika/execution_base/completion_scheduler.hpp
+++ b/libs/pika/execution_base/include/pika/execution_base/completion_scheduler.hpp
@@ -21,8 +21,8 @@ namespace pika::execution::experimental::detail {
     template <typename CPO, typename Sender>
     struct has_completion_scheduler_impl<true, CPO, Sender>
       : pika::execution::experimental::is_scheduler<
-            pika::functional::tag_invoke_result_t<
-                get_completion_scheduler_t<CPO>, std::decay_t<Sender> const&>>
+            std::invoke_result_t<get_completion_scheduler_t<CPO>,
+                std::invoke_result_t<get_env_t, std::decay_t<Sender> const&>>>
     {
     };
 
@@ -30,7 +30,8 @@ namespace pika::execution::experimental::detail {
     struct has_completion_scheduler
       : has_completion_scheduler_impl<
             pika::functional::is_tag_invocable_v<
-                get_completion_scheduler_t<CPO>, std::decay_t<Sender> const&>,
+                get_completion_scheduler_t<CPO>,
+                std::invoke_result_t<get_env_t, std::decay_t<Sender> const&>>,
             CPO, Sender>
     {
     };
@@ -46,16 +47,15 @@ namespace pika::execution::experimental::detail {
 #include <type_traits>
 
 namespace pika::execution::experimental {
-    template <typename Scheduler>
+    template <typename CPO>
     struct get_completion_scheduler_t final
-      : pika::functional::tag<get_completion_scheduler_t<Scheduler>>
+      : pika::functional::tag<get_completion_scheduler_t<CPO>>
     {
     };
 
-    template <typename Scheduler>
-    PIKA_HOST_DEVICE_INLINE_CONSTEXPR_VARIABLE
-        get_completion_scheduler_t<Scheduler>
-            get_completion_scheduler{};
+    template <typename CPO>
+    PIKA_HOST_DEVICE_INLINE_CONSTEXPR_VARIABLE get_completion_scheduler_t<CPO>
+        get_completion_scheduler{};
 
     namespace detail {
         template <bool TagInvocable, typename CPO, typename Sender>
@@ -65,17 +65,18 @@ namespace pika::execution::experimental {
 
         template <typename CPO, typename Sender>
         struct has_completion_scheduler_impl<true, CPO, Sender>
-          : pika::execution::experimental::is_scheduler<pika::functional::
-                    tag_invoke_result_t<get_completion_scheduler_t<CPO>,
-                        std::decay_t<Sender> const&>>
+          : pika::execution::experimental::is_scheduler<std::invoke_result_t<
+                get_completion_scheduler_t<CPO>,
+                std::invoke_result_t<get_env_t, std::decay_t<Sender> const&>>>
         {
         };
 
         template <typename CPO, typename Sender>
         struct has_completion_scheduler
-          : has_completion_scheduler_impl<pika::functional::is_tag_invocable_v<
-                                              get_completion_scheduler_t<CPO>,
-                                              std::decay_t<Sender> const&>,
+          : has_completion_scheduler_impl<
+                std::is_invocable_v<get_completion_scheduler_t<CPO>,
+                    std::invoke_result_t<get_env_t,
+                        std::decay_t<Sender> const&>>,
                 CPO, Sender>
         {
         };
@@ -95,11 +96,13 @@ namespace pika::execution::experimental {
         struct is_completion_scheduler_tag_invocable_impl<true, ReceiverCPO,
             Sender, AlgorithmCPO, Ts...>
           : std::integral_constant<bool,
-                pika::functional::is_tag_invocable_v<AlgorithmCPO,
-                    pika::functional::tag_invoke_result_t<
+                std::is_invocable_v<AlgorithmCPO,
+                    std::invoke_result_t<
                         pika::execution::experimental::
                             get_completion_scheduler_t<ReceiverCPO>,
-                        Sender>,
+                        std::invoke_result_t<
+                            pika::execution::experimental::get_env_t,
+                            std::decay_t<Sender> const&>>,
                     Sender, Ts...>>
         {
         };
diff --git a/libs/pika/execution_base/include/pika/execution_base/receiver.hpp b/libs/pika/execution_base/include/pika/execution_base/receiver.hpp
index 328d6a48c7..11376664cf 100644
--- a/libs/pika/execution_base/include/pika/execution_base/receiver.hpp
+++ b/libs/pika/execution_base/include/pika/execution_base/receiver.hpp
@@ -29,12 +29,6 @@ namespace pika::execution::experimental {
     {
         static constexpr bool value = is_receiver_of_v<Receiver, Completions>;
     };
-
-    namespace detail {
-        struct empty_env
-        {
-        };
-    }    // namespace detail
 }    // namespace pika::execution::experimental
 #else
 #include <pika/config/constexpr.hpp>
@@ -202,16 +196,6 @@ namespace pika::execution::experimental {
 
     template <typename T, typename... As>
     inline constexpr bool is_receiver_of_v = is_receiver_of<T, As...>::value;
-
-    namespace detail {
-        struct empty_env
-        {
-        };
-    }    // namespace detail
-
-    inline constexpr struct get_env_t
-    {
-    } get_env{};
 }    // namespace pika::execution::experimental
 #endif
 
diff --git a/libs/pika/execution_base/include/pika/execution_base/sender.hpp b/libs/pika/execution_base/include/pika/execution_base/sender.hpp
index 8852cb21b8..c1563b6e73 100644
--- a/libs/pika/execution_base/include/pika/execution_base/sender.hpp
+++ b/libs/pika/execution_base/include/pika/execution_base/sender.hpp
@@ -42,8 +42,8 @@ namespace pika::execution::experimental {
 #include <pika/config/constexpr.hpp>
 #include <pika/execution_base/operation_state.hpp>
 #include <pika/execution_base/receiver.hpp>
+#include <pika/functional/detail/tag_fallback_invoke.hpp>
 #include <pika/functional/invoke_result.hpp>
-#include <pika/functional/tag_invoke.hpp>
 #include <pika/type_support/equality.hpp>
 
 #include <cstddef>
@@ -467,6 +467,28 @@ namespace pika::execution::experimental {
     template <typename S, typename R>
     using connect_result_t =
         typename pika::util::detail::invoke_result<connect_t, S, R>::type;
+
+    struct empty_env
+    {
+    };
+
+    inline constexpr struct get_env_t final
+      : pika::functional::detail::tag_fallback<get_env_t>
+    {
+        template <typename T>
+        friend constexpr auto
+        tag_fallback_invoke(get_env_t const&, T const&) noexcept
+        {
+            if constexpr (is_sender_v<T>)
+            {
+                return empty_env{};
+            }
+            else
+            {
+                static_assert(sizeof(T) == 0, "No environment for type T");
+            }
+        }
+    } get_env{};
 }    // namespace pika::execution::experimental
 #endif
 
diff --git a/libs/pika/execution_base/tests/unit/any_sender.cpp b/libs/pika/execution_base/tests/unit/any_sender.cpp
index d6d9d41ead..9c7cf75ef0 100644
--- a/libs/pika/execution_base/tests/unit/any_sender.cpp
+++ b/libs/pika/execution_base/tests/unit/any_sender.cpp
@@ -291,8 +291,8 @@ struct callback_receiver
         r.set_value_called = true;
     }
 
-    friend constexpr pika::execution::experimental::detail::empty_env
-    tag_invoke(pika::execution::experimental::get_env_t,
+    friend constexpr pika::execution::experimental::empty_env tag_invoke(
+        pika::execution::experimental::get_env_t,
         callback_receiver const&) noexcept
     {
         return {};
@@ -334,8 +334,8 @@ struct error_receiver
         PIKA_TEST(false);
     }
 
-    friend constexpr pika::execution::experimental::detail::empty_env
-    tag_invoke(pika::execution::experimental::get_env_t,
+    friend constexpr pika::execution::experimental::empty_env tag_invoke(
+        pika::execution::experimental::get_env_t,
         error_receiver const&) noexcept
     {
         return {};
diff --git a/libs/pika/execution_base/tests/unit/basic_receiver.cpp b/libs/pika/execution_base/tests/unit/basic_receiver.cpp
index e4c69643cf..5b48b0cc02 100644
--- a/libs/pika/execution_base/tests/unit/basic_receiver.cpp
+++ b/libs/pika/execution_base/tests/unit/basic_receiver.cpp
@@ -5,6 +5,7 @@
 //  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
 #include <pika/execution_base/receiver.hpp>
+#include <pika/execution_base/sender.hpp>
 #include <pika/testing.hpp>
 
 #include <exception>
@@ -37,7 +38,7 @@ namespace mylib {
             value_called = true;
         }
 
-        friend constexpr ex::detail::empty_env tag_invoke(
+        friend constexpr ex::empty_env tag_invoke(
             ex::get_env_t, receiver_1 const&) noexcept
         {
             return {};
@@ -56,7 +57,7 @@ namespace mylib {
             error_called = true;
         }
 
-        friend constexpr ex::detail::empty_env tag_invoke(
+        friend constexpr ex::empty_env tag_invoke(
             ex::get_env_t, receiver_2 const&) noexcept
         {
             return {};
@@ -81,7 +82,7 @@ namespace mylib {
             value_called = true;
         }
 
-        friend constexpr ex::detail::empty_env tag_invoke(
+        friend constexpr ex::empty_env tag_invoke(
             ex::get_env_t, receiver_3 const&) noexcept
         {
             return {};
@@ -163,7 +164,7 @@ namespace mylib {
             value_called = true;
         }
 
-        friend constexpr ex::detail::empty_env tag_invoke(
+        friend constexpr ex::empty_env tag_invoke(
             ex::get_env_t, non_receiver_4 const&) noexcept
         {
             return {};
diff --git a/libs/pika/execution_base/tests/unit/basic_schedule.cpp b/libs/pika/execution_base/tests/unit/basic_schedule.cpp
index c34e27bca7..6028b6830b 100644
--- a/libs/pika/execution_base/tests/unit/basic_schedule.cpp
+++ b/libs/pika/execution_base/tests/unit/basic_schedule.cpp
@@ -48,8 +48,17 @@ struct sender
         return {};
     }
 
-    friend Scheduler tag_invoke(
-        ex::get_completion_scheduler_t<ex::set_value_t>, sender const&) noexcept
+    struct env
+    {
+        friend Scheduler tag_invoke(
+            ex::get_completion_scheduler_t<ex::set_value_t>,
+            env const&) noexcept
+        {
+            return {};
+        }
+    };
+
+    friend env tag_invoke(ex::get_env_t, sender const&) noexcept
     {
         return {};
     }
diff --git a/libs/pika/execution_base/tests/unit/basic_sender.cpp b/libs/pika/execution_base/tests/unit/basic_sender.cpp
index c08a69c7ed..b9ba3bdd93 100644
--- a/libs/pika/execution_base/tests/unit/basic_sender.cpp
+++ b/libs/pika/execution_base/tests/unit/basic_sender.cpp
@@ -84,7 +84,7 @@ struct receiver
         r.i.get() = v;
     }
 
-    friend constexpr ex::detail::empty_env tag_invoke(
+    friend constexpr ex::empty_env tag_invoke(
         ex::get_env_t, receiver const&) noexcept
     {
         return {};
@@ -171,7 +171,7 @@ struct void_receiver
         ++void_receiver_set_value_calls;
     }
 
-    friend constexpr ex::detail::empty_env tag_invoke(
+    friend constexpr ex::empty_env tag_invoke(
         ex::get_env_t, void_receiver const&) noexcept
     {
         return {};
diff --git a/libs/pika/executors/include/pika/executors/std_thread_scheduler.hpp b/libs/pika/executors/include/pika/executors/std_thread_scheduler.hpp
index dda7a8ea8b..792e022b6c 100644
--- a/libs/pika/executors/include/pika/executors/std_thread_scheduler.hpp
+++ b/libs/pika/executors/include/pika/executors/std_thread_scheduler.hpp
@@ -76,6 +76,8 @@ namespace pika::execution::experimental {
 
         struct sender
         {
+            using is_sender = void;
+
             template <template <typename...> class Tuple,
                 template <typename...> class Variant>
             using value_types = Variant<Tuple<>>;
@@ -98,12 +100,19 @@ namespace pika::execution::experimental {
                 return {PIKA_FORWARD(Receiver, receiver)};
             }
 
-            template <typename CPO,
-                PIKA_CONCEPT_REQUIRES_(std::is_same_v<CPO,
-                    pika::execution::experimental::set_value_t>)>
-            friend constexpr std_thread_scheduler tag_invoke(
-                pika::execution::experimental::get_completion_scheduler_t<CPO>,
-                sender const&) noexcept
+            struct env
+            {
+                friend constexpr std_thread_scheduler tag_invoke(
+                    pika::execution::experimental::get_completion_scheduler_t<
+                        pika::execution::experimental::set_value_t>,
+                    env const&) noexcept
+                {
+                    return {};
+                }
+            };
+
+            friend constexpr env tag_invoke(
+                pika::execution::experimental::get_env_t, sender const&)
             {
                 return {};
             }
diff --git a/libs/pika/executors/include/pika/executors/thread_pool_scheduler.hpp b/libs/pika/executors/include/pika/executors/thread_pool_scheduler.hpp
index 15231fe210..b1ad9327ce 100644
--- a/libs/pika/executors/include/pika/executors/thread_pool_scheduler.hpp
+++ b/libs/pika/executors/include/pika/executors/thread_pool_scheduler.hpp
@@ -197,6 +197,8 @@ namespace pika::execution::experimental {
         template <typename Scheduler>
         struct sender
         {
+            using is_sender = void;
+
             PIKA_NO_UNIQUE_ADDRESS std::decay_t<Scheduler> scheduler;
 
             // We explicitly get the fallback annotation when constructing the
@@ -237,14 +239,23 @@ namespace pika::execution::experimental {
                     s.fallback_annotation};
             }
 
-            template <typename CPO,
-                PIKA_CONCEPT_REQUIRES_(std::is_same_v<CPO,
-                    pika::execution::experimental::set_value_t>)>
-            friend constexpr auto tag_invoke(
-                pika::execution::experimental::get_completion_scheduler_t<CPO>,
-                sender const& s) noexcept
+            struct env
+            {
+                PIKA_NO_UNIQUE_ADDRESS std::decay_t<Scheduler> scheduler;
+
+                friend constexpr auto tag_invoke(
+                    pika::execution::experimental::get_completion_scheduler_t<
+                        pika::execution::experimental::set_value_t>,
+                    env const& e) noexcept
+                {
+                    return e.scheduler;
+                }
+            };
+
+            friend constexpr env tag_invoke(
+                pika::execution::experimental::get_env_t, sender const& s)
             {
-                return s.scheduler;
+                return {s.scheduler};
             }
         };
 
diff --git a/libs/pika/executors/include/pika/executors/thread_pool_scheduler_bulk.hpp b/libs/pika/executors/include/pika/executors/thread_pool_scheduler_bulk.hpp
index 3fea5f1c59..80905010ed 100644
--- a/libs/pika/executors/include/pika/executors/thread_pool_scheduler_bulk.hpp
+++ b/libs/pika/executors/include/pika/executors/thread_pool_scheduler_bulk.hpp
@@ -85,23 +85,24 @@ namespace pika::thread_pool_bulk_detail {
             thread_pool_bulk_sender const&) = default;
 
 #if defined(PIKA_HAVE_P2300_REFERENCE_IMPLEMENTATION)
+        using is_sender = void;
+
         template <template <typename...> class Tuple,
             template <typename...> class Variant>
         using value_types =
             pika::execution::experimental::value_types_of_t<Sender,
-                pika::execution::experimental::detail::empty_env, Tuple,
-                Variant>;
+                pika::execution::experimental::empty_env, Tuple, Variant>;
 
         template <template <typename...> class Variant>
         using error_types =
             pika::util::detail::unique_t<pika::util::detail::prepend_t<
                 pika::execution::experimental::error_types_of_t<Sender,
-                    pika::execution::experimental::detail::empty_env, Variant>,
+                    pika::execution::experimental::empty_env, Variant>,
                 std::exception_ptr>>;
 
         using completion_signatures =
             pika::execution::experimental::make_completion_signatures<Sender,
-                pika::execution::experimental::detail::empty_env,
+                pika::execution::experimental::empty_env,
                 pika::execution::experimental::completion_signatures<
                     pika::execution::experimental::set_error_t(
                         std::exception_ptr)>>;
@@ -122,41 +123,14 @@ namespace pika::thread_pool_bulk_detail {
         static constexpr bool sends_done = false;
 #endif
 
-        template <typename CPO,
-            // clang-format off
-                PIKA_CONCEPT_REQUIRES_(
-                    pika::execution::experimental::detail::is_receiver_cpo_v<CPO> &&
-                    (std::is_same_v<CPO, pika::execution::experimental::set_value_t> ||
-                        pika::execution::experimental::detail::has_completion_scheduler_v<
-                                pika::execution::experimental::set_error_t,
-                                std::decay_t<Sender>> ||
-                        pika::execution::experimental::detail::has_completion_scheduler_v<
-                                pika::execution::experimental::set_stopped_t,
-                                std::decay_t<Sender>>))
-            // clang-format on
-            >
-        friend constexpr auto tag_invoke(
-            pika::execution::experimental::get_completion_scheduler_t<CPO>,
-            thread_pool_bulk_sender const& s) noexcept
-        {
-            if constexpr (std::is_same_v<std::decay_t<CPO>,
-                              pika::execution::experimental::set_value_t>)
-            {
-                return s.scheduler;
-            }
-            else
-            {
-                return pika::execution::experimental::get_completion_scheduler<
-                    CPO>(s);
-            }
-        }
-
     private:
         template <typename Receiver>
         struct operation_state
         {
             struct bulk_receiver
             {
+                using is_receiver = void;
+
                 operation_state* op_state;
 
                 template <typename E>
@@ -503,10 +477,9 @@ namespace pika::thread_pool_bulk_detail {
                     r.do_work_local(n, chunk_size, local_worker_thread);
                 }
 
-                friend constexpr pika::execution::experimental::detail::
-                    empty_env
-                    tag_invoke(pika::execution::experimental::get_env_t,
-                        bulk_receiver const&) noexcept
+                friend constexpr pika::execution::experimental::empty_env
+                tag_invoke(pika::execution::experimental::get_env_t,
+                    bulk_receiver const&) noexcept
                 {
                     return {};
                 }
@@ -573,6 +546,13 @@ namespace pika::thread_pool_bulk_detail {
             return operation_state<std::decay_t<Receiver>>{s.scheduler,
                 s.sender, s.shape, s.f, PIKA_FORWARD(Receiver, receiver)};
         }
+
+        friend constexpr auto tag_invoke(
+            pika::execution::experimental::get_env_t,
+            thread_pool_bulk_sender const& s)
+        {
+            return pika::execution::experimental::get_env(s.sender);
+        }
     };
 }    // namespace pika::thread_pool_bulk_detail
 
diff --git a/libs/pika/executors/tests/unit/std_thread_scheduler.cpp b/libs/pika/executors/tests/unit/std_thread_scheduler.cpp
index f8ac5da1a8..f5e9685e80 100644
--- a/libs/pika/executors/tests/unit/std_thread_scheduler.cpp
+++ b/libs/pika/executors/tests/unit/std_thread_scheduler.cpp
@@ -79,8 +79,8 @@ struct check_context_receiver
         r.cond.notify_one();
     }
 
-    friend constexpr pika::execution::experimental::detail::empty_env
-    tag_invoke(pika::execution::experimental::get_env_t,
+    friend constexpr pika::execution::experimental::empty_env tag_invoke(
+        pika::execution::experimental::get_env_t,
         check_context_receiver const&) noexcept
     {
         return {};
@@ -248,8 +248,8 @@ struct callback_receiver
         r.cond.notify_one();
     }
 
-    friend constexpr pika::execution::experimental::detail::empty_env
-    tag_invoke(pika::execution::experimental::get_env_t,
+    friend constexpr pika::execution::experimental::empty_env tag_invoke(
+        pika::execution::experimental::get_env_t,
         callback_receiver const&) noexcept
     {
         return {};
@@ -1316,7 +1316,7 @@ void test_completion_scheduler()
     {
         auto sender = ex::schedule(ex::std_thread_scheduler{});
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::std_thread_scheduler>,
@@ -1327,7 +1327,7 @@ void test_completion_scheduler()
         auto sender =
             ex::then(ex::schedule(ex::std_thread_scheduler{}), []() {});
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::std_thread_scheduler>,
@@ -1337,7 +1337,7 @@ void test_completion_scheduler()
     {
         auto sender = ex::transfer_just(ex::std_thread_scheduler{}, 42);
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::std_thread_scheduler>,
@@ -1349,7 +1349,7 @@ void test_completion_scheduler()
         auto sender =
             ex::bulk(ex::schedule(ex::std_thread_scheduler{}), 10, [](int) {});
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::std_thread_scheduler>,
@@ -1362,7 +1362,7 @@ void test_completion_scheduler()
                          10, [](int, int) {}),
                 [](int) {});
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::std_thread_scheduler>,
@@ -1375,7 +1375,7 @@ void test_completion_scheduler()
                          [](int) {}),
                 10, [](int, int) {});
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::std_thread_scheduler>,
diff --git a/libs/pika/executors/tests/unit/thread_pool_scheduler.cpp b/libs/pika/executors/tests/unit/thread_pool_scheduler.cpp
index 2336c9b4af..ac75204a05 100644
--- a/libs/pika/executors/tests/unit/thread_pool_scheduler.cpp
+++ b/libs/pika/executors/tests/unit/thread_pool_scheduler.cpp
@@ -88,8 +88,8 @@ struct check_context_receiver
         r.cond.notify_one();
     }
 
-    friend constexpr pika::execution::experimental::detail::empty_env
-    tag_invoke(pika::execution::experimental::get_env_t,
+    friend constexpr pika::execution::experimental::empty_env tag_invoke(
+        pika::execution::experimental::get_env_t,
         check_context_receiver const&) noexcept
     {
         return {};
@@ -257,8 +257,8 @@ struct callback_receiver
         r.cond.notify_one();
     }
 
-    friend constexpr pika::execution::experimental::detail::empty_env
-    tag_invoke(pika::execution::experimental::get_env_t,
+    friend constexpr pika::execution::experimental::empty_env tag_invoke(
+        pika::execution::experimental::get_env_t,
         callback_receiver const&) noexcept
     {
         return {};
@@ -1868,7 +1868,7 @@ void test_completion_scheduler()
     {
         auto sender = ex::schedule(ex::thread_pool_scheduler{});
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::thread_pool_scheduler>,
@@ -1879,7 +1879,7 @@ void test_completion_scheduler()
         auto sender =
             ex::then(ex::schedule(ex::thread_pool_scheduler{}), []() {});
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::thread_pool_scheduler>,
@@ -1889,7 +1889,7 @@ void test_completion_scheduler()
     {
         auto sender = ex::transfer_just(ex::thread_pool_scheduler{}, 42);
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::thread_pool_scheduler>,
@@ -1900,7 +1900,7 @@ void test_completion_scheduler()
         auto sender =
             ex::bulk(ex::schedule(ex::thread_pool_scheduler{}), 10, [](int) {});
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::thread_pool_scheduler>,
@@ -1913,7 +1913,7 @@ void test_completion_scheduler()
                 [](int, int) {}),
             [](int) {});
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::thread_pool_scheduler>,
@@ -1926,7 +1926,7 @@ void test_completion_scheduler()
                 ex::transfer_just(ex::thread_pool_scheduler{}, 42), [](int) {}),
             10, [](int, int) {});
         auto completion_scheduler =
-            ex::get_completion_scheduler<ex::set_value_t>(sender);
+            ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sender));
         static_assert(
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>,
                 ex::thread_pool_scheduler>,
diff --git a/libs/pika/futures/include/pika/futures/future.hpp b/libs/pika/futures/include/pika/futures/future.hpp
index 41cf3d5794..c36ee425ec 100644
--- a/libs/pika/futures/include/pika/futures/future.hpp
+++ b/libs/pika/futures/include/pika/futures/future.hpp
@@ -334,6 +334,8 @@ namespace pika::lcos::detail {
     class future_base
     {
     public:
+        using is_sender = void;
+
         using result_type = R;
         using shared_state_type =
             future_data_base<traits::detail::shared_state_ptr_result_t<R>>;