From a50f49d1007826bc317e3ea384b3695aa95881b7 Mon Sep 17 00:00:00 2001
From: Robert Leahy <rleahy@rleahy.ca>
Date: Sat, 1 Aug 2026 11:20:05 -0400
Subject: [PATCH 1/3] exec::asio::completion_token: Use STDEXEC Invocation
 Utilities

---
 include/exec/asio/completion_token.hpp | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/exec/asio/completion_token.hpp b/include/exec/asio/completion_token.hpp
index f8ad7b2cb..a7af06ab9 100644
--- a/include/exec/asio/completion_token.hpp
+++ b/include/exec/asio/completion_token.hpp
@@ -27,12 +27,12 @@
 #include "../../stdexec/__detail/__queries.hpp"
 #include "../../stdexec/__detail/__receivers.hpp"
 #include "../../stdexec/__detail/__type_traits.hpp"
+#include "../../stdexec/functional.hpp"
 #include "../../stdexec/stop_token.hpp"
 #include "as_default_on.hpp"
 
 #include <concepts>
 #include <exception>
-#include <functional>
 #include <mutex>
 #include <optional>
 #include <tuple>
@@ -377,9 +377,9 @@ namespace experimental::execution::asio
           std::apply(
             [&](auto&&... args)
             {
-              std::invoke(static_cast<Initiation&&>(init_),
-                          completion_handler<Signatures, Receiver>(*this),
-                          static_cast<decltype(args)&&>(args)...);
+              ::STDEXEC::__invoke(static_cast<Initiation&&>(init_),
+                                  completion_handler<Signatures, Receiver>(*this),
+                                  static_cast<decltype(args)&&>(args)...);
             },
             std::move(args_));
         }
@@ -618,7 +618,7 @@ namespace ASIOEXEC_ASIO_NAMESPACE
   };
 
   template <typename Signatures, typename Receiver, typename Allocator>
-    requires requires(Receiver const & r) { ::STDEXEC::get_allocator(::STDEXEC::get_env(r)); }
+    requires ::STDEXEC::__callable<::STDEXEC::get_allocator_t, ::STDEXEC::env_of_t<Receiver>>
   struct associated_allocator<
     ::exec::asio::detail::completion_token::completion_handler<Signatures, Receiver>,
     Allocator>

From d9d52c2635db83158a072af48bc1a25c38229e5e Mon Sep 17 00:00:00 2001
From: Robert Leahy <rleahy@rleahy.ca>
Date: Fri, 13 Feb 2026 15:59:18 -0500
Subject: [PATCH 2/3] exec::asio::completion_token: Remove std::unique_lock
 From "Frame"

Reduces the size of a "frame" by removing the std::unique_lock member
variable and making the "frame" itself the lock guard. This is the lock
management method shown when presenting exec::asio::completion_token in
the CppCon 2025 talk "std::execution in Asio Codebases: Adopting Senders
Without a Rewrite."
---
 include/exec/asio/completion_token.hpp | 52 ++++++++++++++------------
 1 file changed, 28 insertions(+), 24 deletions(-)

diff --git a/include/exec/asio/completion_token.hpp b/include/exec/asio/completion_token.hpp
index a7af06ab9..4fbead55f 100644
--- a/include/exec/asio/completion_token.hpp
+++ b/include/exec/asio/completion_token.hpp
@@ -179,13 +179,11 @@ namespace experimental::execution::asio
 
       class frame_
       {
-        operation_state_base&                  self_;
-        std::unique_lock<std::recursive_mutex> l_;
-        frame_*                                prev_;
+        operation_state_base* self_;
+        frame_*               prev_;
        public:
         explicit frame_(operation_state_base& self) noexcept
-          : self_(self)
-          , l_(self.m_)
+          : self_((self.m_.lock(), &self))
           , prev_(self.frames_)
         {
           self.frames_ = this;
@@ -195,23 +193,24 @@ namespace experimental::execution::asio
 
         ~frame_() noexcept
         {
-          if (l_)
+          if (self_)
           {
-            STDEXEC_ASSERT(self_.frames_ == this);
-            self_.frames_ = prev_;
-            if (!self_.frames_ && self_.abandoned_)
+            std::unique_lock l(self_->m_, std::adopt_lock);
+            STDEXEC_ASSERT(self_->frames_ == this);
+            self_->frames_ = prev_;
+            if (!self_->frames_ && self_->abandoned_)
             {
               //  We are the last frame and the handler is gone so it's up to us to
               //  finalize the operation
-              l_.unlock();
-              self_.callback_.reset();
-              if (self_.ex_)
+              l.unlock();
+              self_->callback_.reset();
+              if (self_->ex_)
               {
-                ::STDEXEC::set_error(static_cast<Receiver&&>(self_.r_), std::move(self_.ex_));
+                ::STDEXEC::set_error(static_cast<Receiver&&>(self_->r_), std::move(self_->ex_));
               }
               else
               {
-                ::STDEXEC::set_stopped(static_cast<Receiver&&>(self_.r_));
+                ::STDEXEC::set_stopped(static_cast<Receiver&&>(self_->r_));
               }
             }
           }
@@ -219,22 +218,27 @@ namespace experimental::execution::asio
 
         explicit operator bool() const noexcept
         {
-          return bool(l_);
+          return bool(self_);
         }
 
         void release() noexcept
         {
-          auto ptr = this;
-          do
+          auto&& self = *self_;
+          STDEXEC_ASSERT(this == self.frames_);
+          for (;;)
           {
-            STDEXEC_ASSERT(ptr->l_);
-            STDEXEC_ASSERT(self_.frames_ == ptr);
-            ptr = ptr->prev_;
-            self_.frames_->l_.unlock();
-            self_.frames_->prev_ = nullptr;
-            self_.frames_        = ptr;
+            STDEXEC_ASSERT(self.frames_);
+            STDEXEC_ASSERT(self.frames_->self_ == &self);
+            auto const current = std::exchange(self.frames_, self.frames_->prev_);
+            current->self_     = nullptr;
+            current->prev_     = nullptr;
+            self.m_.unlock();
+            if (!self.frames_)
+            {
+              break;
+            }
           }
-          while (ptr);
+          STDEXEC_ASSERT(!self_);
         }
       };
 

From 6ffbd0ac4a1c795fe85a935c932746f10fc460c7 Mon Sep 17 00:00:00 2001
From: Robert Leahy <rleahy@rleahy.ca>
Date: Fri, 13 Feb 2026 16:03:28 -0500
Subject: [PATCH 3/3] exec::asio::thread_unsafe_completion_token & _use_sender

For general purpose (i.e. potentially multithreaded) use the
asynchronous operations which result when passing the exec::asio::
completion_token and ::use_sender completion tokens must use a recursive
mutex internally. However if the user knows that no multithreaded use
will occur this recursive mutex is pure overhead. Provided the
exec::asio::thread_unsafe_completion_token and _use_sender completion
tokens which do not make use of a recursive mutex for the aforementioned
use case.
---
 include/asioexec/completion_token.hpp    |  15 +++
 include/asioexec/use_sender.hpp          |  11 ++
 include/exec/asio/completion_token.hpp   | 142 +++++++++++++----------
 include/exec/asio/use_sender.hpp         |  31 +++--
 test/exec/asio/test_completion_token.cpp |   2 +-
 test/exec/asio/test_use_sender.cpp       |   2 +-
 6 files changed, 129 insertions(+), 74 deletions(-)

diff --git a/include/asioexec/completion_token.hpp b/include/asioexec/completion_token.hpp
index 36bbba072..cfb8cbda7 100644
--- a/include/asioexec/completion_token.hpp
+++ b/include/asioexec/completion_token.hpp
@@ -36,9 +36,24 @@ namespace asioexec
                                         "exec::asio::completion_token_t "
                                         "instead.")]] = exec::asio::completion_token_t;
 
+  using thread_unsafe_completion_token_t
+    [[deprecated("asioexec::thread_unsafe_completion_token_t "
+                 "is deprecated. Please use "
+                 "exec::asio::thread_unsafe_completion_token_"
+                 "t instead.")]] = exec::asio::thread_unsafe_completion_token_t;
+
   inline constexpr auto const & completion_token [[deprecated("asioexec::completion_token is "
                                                               "deprecated. Please use "
                                                               "exec::asio::completion_token "
                                                               "instead.")]]
   = exec::asio::completion_token;
+
+  inline constexpr auto const & thread_unsafe_completion_token [[deprecated("asioexec::thread_"
+                                                                            "unsafe_completion_"
+                                                                            "token is deprecated. "
+                                                                            "Please use "
+                                                                            "exec::asio::thread_"
+                                                                            "unsafe_completion_"
+                                                                            "token instead.")]]
+  = exec::asio::thread_unsafe_completion_token;
 }  // namespace asioexec
diff --git a/include/asioexec/use_sender.hpp b/include/asioexec/use_sender.hpp
index 9883b9b95..4008e3e4f 100644
--- a/include/asioexec/use_sender.hpp
+++ b/include/asioexec/use_sender.hpp
@@ -36,8 +36,19 @@ namespace asioexec
                                   "exec::asio::use_sender_t "
                                   "instead.")]] = exec::asio::use_sender_t;
 
+  using thread_unsafe_use_sender_t [[deprecated(
+    "asioexec::thread_unsafe_use_sender_t is deprecated. Please use "
+    "exec::asio::thread_unsafe_use_sender_t instead.")]] = exec::asio::thread_unsafe_use_sender_t;
+
   inline constexpr auto const & use_sender [[deprecated("asioexec::use_sender is deprecated. "
                                                         "Please use exec::asio::use_sender "
                                                         "instead.")]]
   = exec::asio::use_sender;
+
+  inline constexpr auto const & thread_unsafe_use_sender [[deprecated("asioexec::thread_unsafe_use_"
+                                                                      "sender is deprecated. "
+                                                                      "Please use "
+                                                                      "exec::asio::thread_unsafe_"
+                                                                      "use_sender instead.")]]
+  = exec::asio::thread_unsafe_use_sender;
 }  // namespace asioexec
diff --git a/include/exec/asio/completion_token.hpp b/include/exec/asio/completion_token.hpp
index 4fbead55f..c1dda4f47 100644
--- a/include/exec/asio/completion_token.hpp
+++ b/include/exec/asio/completion_token.hpp
@@ -154,10 +154,7 @@ namespace experimental::execution::asio
                                        ::STDEXEC::set_error_t(std::exception_ptr),
                                        ::STDEXEC::set_stopped_t()>;
 
-    template <typename, typename>
-    class completion_handler;
-
-    template <typename Signatures, typename Receiver>
+    template <typename Mutex, typename Signatures, typename Receiver>
     struct operation_state_base
     {
       class frame_;
@@ -172,7 +169,8 @@ namespace experimental::execution::asio
 
       Receiver                       r_;
       asio_impl::cancellation_signal signal_;
-      std::recursive_mutex           m_;
+      STDEXEC_IMMOVABLE_NO_UNIQUE_ADDRESS
+      Mutex                          m_;
       frame_*                        frames_{nullptr};
       std::exception_ptr             ex_;
       bool                           abandoned_{false};
@@ -278,12 +276,13 @@ namespace experimental::execution::asio
         callback_;
     };
 
-    template <typename Signatures, typename Receiver>
+    template <typename Mutex, typename Signatures, typename Receiver>
     class completion_handler
     {
-      operation_state_base<Signatures, Receiver>* self_;
+      using operation_state_type_ = operation_state_base<Mutex, Signatures, Receiver>;
+      operation_state_type_* self_;
      public:
-      explicit completion_handler(operation_state_base<Signatures, Receiver>& self) noexcept
+      explicit completion_handler(operation_state_type_& self) noexcept
         : self_(&self)
       {}
 
@@ -300,7 +299,7 @@ namespace experimental::execution::asio
           //  When this goes out of scope it might send set stopped or set error, or
           //  it might defer that to the executor frames above us on the call stack
           //  (if any)
-          typename operation_state_base<Signatures, Receiver>::frame_ const frame(*self_);
+          typename operation_state_type_::frame_ const frame(*self_);
           self_->abandoned_ = true;
         }
       }
@@ -347,17 +346,21 @@ namespace experimental::execution::asio
         return self_->signal_.slot();
       }
 
-      operation_state_base<Signatures, Receiver>& state() const noexcept
+      operation_state_type_& state() const noexcept
       {
         STDEXEC_ASSERT(self_);
         return *self_;
       }
     };
 
-    template <typename Signatures, typename Receiver, typename Initiation, typename Args>
-    class operation_state : operation_state_base<Signatures, Receiver>
+    template <typename Mutex,
+              typename Signatures,
+              typename Receiver,
+              typename Initiation,
+              typename Args>
+    class operation_state : operation_state_base<Mutex, Signatures, Receiver>
     {
-      using base_ = operation_state_base<Signatures, Receiver>;
+      using base_ = operation_state_base<Mutex, Signatures, Receiver>;
       Initiation init_;
       Args       args_;
      public:
@@ -382,7 +385,7 @@ namespace experimental::execution::asio
             [&](auto&&... args)
             {
               ::STDEXEC::__invoke(static_cast<Initiation&&>(init_),
-                                  completion_handler<Signatures, Receiver>(*this),
+                                  completion_handler<Mutex, Signatures, Receiver>(*this),
                                   static_cast<decltype(args)&&>(args)...);
             },
             std::move(args_));
@@ -407,10 +410,13 @@ namespace experimental::execution::asio
       }
     };
 
-    template <typename Signatures, typename Initiation, typename... Args>
+    template <typename Mutex, typename Signatures, typename Initiation, typename... Args>
     class sender
     {
       using args_type_ = std::tuple<std::decay_t<Args>...>;
+      template <typename Receiver>
+      using operation_state_type_ =
+        operation_state<Mutex, Signatures, std::remove_cvref_t<Receiver>, Initiation, args_type_>;
      public:
       using sender_concept = ::STDEXEC::sender_tag;
 
@@ -437,16 +443,12 @@ namespace experimental::execution::asio
           std::remove_cvref_t<Receiver>,
           ::STDEXEC::completion_signatures_of_t<sender const &, ::STDEXEC::env_of_t<Receiver>>>
       constexpr auto connect(Receiver&& receiver) const & noexcept(
-        std::is_nothrow_constructible_v<
-          operation_state<Signatures, std::remove_cvref_t<Receiver>, Initiation, args_type_>,
-          Receiver,
-          Initiation const &,
-          args_type_ const &>)
+        std::is_nothrow_constructible_v<operation_state_type_<Receiver>,
+                                        Receiver,
+                                        Initiation const &,
+                                        args_type_ const &>)
       {
-        return operation_state<Signatures, std::remove_cvref_t<Receiver>, Initiation, args_type_>(
-          static_cast<Receiver&&>(receiver),
-          init_,
-          args_);
+        return operation_state_type_<Receiver>(static_cast<Receiver&&>(receiver), init_, args_);
       }
 
       template <typename Receiver>
@@ -454,27 +456,26 @@ namespace experimental::execution::asio
           std::remove_cvref_t<Receiver>,
           ::STDEXEC::completion_signatures_of_t<sender, ::STDEXEC::env_of_t<Receiver>>>
       constexpr auto connect(Receiver&& receiver) && noexcept(
-        std::is_nothrow_constructible_v<
-          operation_state<Signatures, std::remove_cvref_t<Receiver>, Initiation, args_type_>,
-          Receiver,
-          Initiation,
-          args_type_>)
+        std::is_nothrow_constructible_v<operation_state_type_<Receiver>,
+                                        Receiver,
+                                        Initiation,
+                                        args_type_>)
       {
-        return operation_state<Signatures, std::remove_cvref_t<Receiver>, Initiation, args_type_>(
-          static_cast<Receiver&&>(receiver),
-          static_cast<Initiation&&>(init_),
-          static_cast<args_type_&&>(args_));
+        return operation_state_type_<Receiver>(static_cast<Receiver&&>(receiver),
+                                               static_cast<Initiation&&>(init_),
+                                               static_cast<args_type_&&>(args_));
       }
      private:
       Initiation init_;
       args_type_ args_;
     };
 
-    template <typename Signatures, typename Receiver, typename Executor>
+    template <typename Mutex, typename Signatures, typename Receiver, typename Executor>
     class executor
     {
-      operation_state_base<Signatures, Receiver>& self_;
-      Executor                                    ex_;
+      using operation_state_type_ = operation_state_base<Mutex, Signatures, Receiver>;
+      operation_state_type_& self_;
+      Executor               ex_;
 
       template <typename F>
       constexpr auto wrap_(F f) const noexcept(std::is_nothrow_move_constructible_v<F>)
@@ -485,8 +486,7 @@ namespace experimental::execution::asio
         };
       }
      public:
-      constexpr explicit executor(operation_state_base<Signatures, Receiver>& self,
-                                  Executor const &                            ex) noexcept
+      constexpr explicit executor(operation_state_type_& self, Executor const & ex) noexcept
         : self_(self)
         , ex_(ex)
       {}
@@ -507,7 +507,7 @@ namespace experimental::execution::asio
       constexpr decltype(auto) prefer(Args&&... args) const noexcept
       {
         auto const ex = asio_impl::prefer(ex_, static_cast<Args&&>(args)...);
-        return executor<Signatures, Receiver, std::remove_cvref_t<decltype(ex)>>(self_, ex);
+        return executor<Mutex, Signatures, Receiver, std::remove_cvref_t<decltype(ex)>>(self_, ex);
       }
 
       template <typename... Args>
@@ -517,7 +517,7 @@ namespace experimental::execution::asio
       constexpr decltype(auto) require(Args&&... args) const noexcept
       {
         auto const ex = asio_impl::require(ex_, static_cast<Args&&>(args)...);
-        return executor<Signatures, Receiver, std::remove_cvref_t<decltype(ex)>>(self_, ex);
+        return executor<Mutex, Signatures, Receiver, std::remove_cvref_t<decltype(ex)>>(self_, ex);
       }
 
       template <typename T>
@@ -573,17 +573,32 @@ namespace experimental::execution::asio
       bool operator!=(executor const & rhs) const = default;
     };
 
+    template <typename Mutex>
+    struct token
+    {
+      static constexpr auto as_default_on = asio::as_default_on<token>;
+      template <typename IoObject>
+      using as_default_on_t = asio::as_default_on_t<token, IoObject>;
+    };
+
+    struct null_basic_lockable
+    {
+      constexpr void lock() noexcept {}
+
+      constexpr void unlock() noexcept {}
+    };
+
   }  // namespace detail::completion_token
 
-  struct completion_token_t
-  {
-    static constexpr auto as_default_on = asio::as_default_on<completion_token_t>;
-    template <typename IoObject>
-    using as_default_on_t = asio::as_default_on_t<completion_token_t, IoObject>;
-  };
+  using completion_token_t = detail::completion_token::token<std::recursive_mutex>;
 
   inline completion_token_t const completion_token{};
 
+  using thread_unsafe_completion_token_t =
+    detail::completion_token::token<detail::completion_token::null_basic_lockable>;
+
+  inline thread_unsafe_completion_token_t const thread_unsafe_completion_token{};
+
 }  // namespace experimental::execution::asio
 
 namespace exec = experimental::execution;
@@ -591,48 +606,53 @@ namespace exec = experimental::execution;
 namespace ASIOEXEC_ASIO_NAMESPACE
 {
 
-  template <typename... Signatures>
-  struct async_result<::exec::asio::completion_token_t, Signatures...>
+  template <typename Mutex, typename... Signatures>
+  struct async_result<::exec::asio::detail::completion_token::token<Mutex>, Signatures...>
   {
     template <typename Initiation, typename... Args>
       requires(std::is_constructible_v<std::decay_t<Args>, Args> && ...)
-    static constexpr auto
-    initiate(Initiation&& i, ::exec::asio::completion_token_t const &, Args&&... args)
+    static constexpr auto initiate(Initiation&& i,
+                                   ::exec::asio::detail::completion_token::token<Mutex> const &,
+                                   Args&&... args)
     {
       return ::exec::asio::detail::completion_token::sender<
+        Mutex,
         ::exec::asio::detail::completion_token::completion_signatures<Signatures...>,
         std::remove_cvref_t<Initiation>,
         Args...>(static_cast<Initiation&&>(i), static_cast<Args&&>(args)...);
     }
   };
 
-  template <typename Signatures, typename Receiver, typename Executor>
+  template <typename Mutex, typename Signatures, typename Receiver, typename Executor>
   struct associated_executor<
-    ::exec::asio::detail::completion_token::completion_handler<Signatures, Receiver>,
+    ::exec::asio::detail::completion_token::completion_handler<Mutex, Signatures, Receiver>,
     Executor>
   {
-    using type = ::exec::asio::detail::completion_token::executor<Signatures, Receiver, Executor>;
+    using type =
+      ::exec::asio::detail::completion_token::executor<Mutex, Signatures, Receiver, Executor>;
 
-    static type
-    get(::exec::asio::detail::completion_token::completion_handler<Signatures, Receiver> const & h,
-        Executor const & ex) noexcept
+    static type get(::exec::asio::detail::completion_token::completion_handler<Mutex,
+                                                                               Signatures,
+                                                                               Receiver> const & h,
+                    Executor const & ex) noexcept
     {
       return type(h.state(), ex);
     }
   };
 
-  template <typename Signatures, typename Receiver, typename Allocator>
+  template <typename Mutex, typename Signatures, typename Receiver, typename Allocator>
     requires ::STDEXEC::__callable<::STDEXEC::get_allocator_t, ::STDEXEC::env_of_t<Receiver>>
   struct associated_allocator<
-    ::exec::asio::detail::completion_token::completion_handler<Signatures, Receiver>,
+    ::exec::asio::detail::completion_token::completion_handler<Mutex, Signatures, Receiver>,
     Allocator>
   {
     using type = std::remove_cvref_t<decltype(::STDEXEC::get_allocator(
       ::STDEXEC::get_env(std::declval<Receiver const &>())))>;
 
-    static type
-    get(::exec::asio::detail::completion_token::completion_handler<Signatures, Receiver> const & h,
-        ::STDEXEC::__ignore = {}) noexcept
+    static type get(::exec::asio::detail::completion_token::completion_handler<Mutex,
+                                                                               Signatures,
+                                                                               Receiver> const & h,
+                    ::STDEXEC::__ignore = {}) noexcept
     {
       return ::STDEXEC::get_allocator(::STDEXEC::get_env(h.state().r_));
     }
diff --git a/include/exec/asio/use_sender.hpp b/include/exec/asio/use_sender.hpp
index 760b7b8d4..bb1ff8023 100644
--- a/include/exec/asio/use_sender.hpp
+++ b/include/exec/asio/use_sender.hpp
@@ -33,6 +33,7 @@
 
 #include <concepts>
 #include <exception>
+#include <mutex>
 #include <system_error>
 #include <type_traits>
 #include <utility>
@@ -215,17 +216,25 @@ namespace experimental::execution::asio
     template <typename Sender>
     explicit sender(Sender) -> sender<Sender>;
 
+    template <typename Mutex>
+    struct token
+    {
+      static constexpr auto as_default_on = asio::as_default_on<token>;
+      template <typename IoObject>
+      using as_default_on_t = asio::as_default_on_t<token, IoObject>;
+    };
+
   }  // namespace detail::use_sender
 
-  struct use_sender_t
-  {
-    static constexpr auto as_default_on = asio::as_default_on<use_sender_t>;
-    template <typename IoObject>
-    using as_default_on_t = asio::as_default_on_t<use_sender_t, IoObject>;
-  };
+  using use_sender_t = detail::use_sender::token<std::recursive_mutex>;
 
   inline use_sender_t const use_sender{};
 
+  using thread_unsafe_use_sender_t =
+    detail::use_sender::token<detail::completion_token::null_basic_lockable>;
+
+  inline thread_unsafe_use_sender_t const thread_unsafe_use_sender{};
+
 }  // namespace experimental::execution::asio
 
 namespace exec = experimental::execution;
@@ -233,18 +242,18 @@ namespace exec = experimental::execution;
 namespace ASIOEXEC_ASIO_NAMESPACE
 {
 
-  template <typename... Signatures>
-  struct async_result<::exec::asio::use_sender_t, Signatures...>
+  template <typename Mutex, typename... Signatures>
+  struct async_result<::exec::asio::detail::use_sender::token<Mutex>, Signatures...>
   {
     template <typename Initiation, typename... Args>
       requires(std::is_constructible_v<std::decay_t<Args>, Args> && ...)
     static constexpr auto
-    initiate(Initiation&& i, ::exec::asio::use_sender_t const &, Args&&... args)
+    initiate(Initiation&& i, ::exec::asio::detail::use_sender::token<Mutex> const &, Args&&... args)
     {
       return ::exec::asio::detail::use_sender::sender(
-        async_result<::exec::asio::completion_token_t, Signatures...>::initiate(
+        async_result<::exec::asio::detail::completion_token::token<Mutex>, Signatures...>::initiate(
           static_cast<Initiation&&>(i),
-          ::exec::asio::completion_token,
+          ::exec::asio::detail::completion_token::token<Mutex>{},
           static_cast<Args&&>(args)...));
     }
   };
diff --git a/test/exec/asio/test_completion_token.cpp b/test/exec/asio/test_completion_token.cpp
index 4cbcf63e6..b96bd1d2b 100644
--- a/test/exec/asio/test_completion_token.cpp
+++ b/test/exec/asio/test_completion_token.cpp
@@ -166,7 +166,7 @@ namespace
     asio_impl::io_context   ctx;
     asio_impl::system_timer t(ctx);
     t.expires_after(std::chrono::years(1));
-    auto sender = t.async_wait(completion_token);
+    auto sender = t.async_wait(thread_unsafe_completion_token);
     static_assert(set_equivalent<completion_signatures_of_t<decltype(sender), env<>>,
                                  completion_signatures<set_stopped_t(),
                                                        set_error_t(std::exception_ptr),
diff --git a/test/exec/asio/test_use_sender.cpp b/test/exec/asio/test_use_sender.cpp
index 4ecaed0b6..61aabf02c 100644
--- a/test/exec/asio/test_use_sender.cpp
+++ b/test/exec/asio/test_use_sender.cpp
@@ -81,7 +81,7 @@ namespace
     asio_impl::io_context   ctx;
     asio_impl::system_timer t(ctx);
     t.expires_after(std::chrono::years(1));
-    auto sender = t.async_wait(use_sender);
+    auto sender = t.async_wait(thread_unsafe_use_sender);
     static_assert(::STDEXEC::sender_in<decltype(sender)>);
     static_assert(::STDEXEC::sender_of<decltype(sender), ::STDEXEC::set_value_t()>);
     static_assert(