diff --git a/ostd/concurrency.hh b/ostd/concurrency.hh
index 160c1db..bbe6942 100644
--- a/ostd/concurrency.hh
+++ b/ostd/concurrency.hh
@@ -80,6 +80,62 @@ private:
     std::mutex p_lock;
 };
 
+namespace detail {
+    struct csched_task;
+
+    OSTD_EXPORT extern thread_local csched_task *current_csched_task;
+
+    struct csched_task: coroutine_context {
+        friend struct coroutine_context;
+
+        csched_task() = delete;
+        csched_task(csched_task const &) = delete;
+        csched_task(csched_task &&) = delete;
+        csched_task &operator=(csched_task const &) = delete;
+        csched_task &operator=(csched_task &&) = delete;
+
+        template<typename F, typename SA>
+        csched_task(F &&f, SA &&sa): p_func(std::forward<F>(f)) {
+            if (!p_func) {
+                this->set_dead();
+                return;
+            }
+            this->make_context<csched_task>(sa);
+        }
+
+        void operator()() {
+            this->set_exec();
+            csched_task *curr = std::exchange(current_csched_task, this);
+            this->coro_jump();
+            current_csched_task = curr;
+            this->rethrow();
+        }
+
+        void yield() {
+            /* we'll yield back to the thread we were scheduled to, which
+             * will appropriately notify one or all other waiting threads
+             * so we either get re-scheduled or the whole scheduler dies
+             */
+            this->yield_jump();
+        }
+
+        bool dead() const {
+            return this->is_dead();
+        }
+
+        static csched_task *current() {
+            return current_csched_task;
+        }
+
+    private:
+        void resume_call() {
+            p_func();
+        }
+
+        std::function<void()> p_func;
+    };
+}
+
 template<typename TR, bool Protected>
 struct basic_simple_coroutine_scheduler {
 private:
@@ -126,9 +182,9 @@ public:
         size_t cs = basic_stack_pool<TR, Protected>::DEFAULT_CHUNK_SIZE
     ):
         p_stacks(ss, cs),
-        p_dispatcher([this](auto yield_main) {
-            this->dispatch(yield_main);
-        }),
+        p_dispatcher([this]() {
+            dispatch();
+        }, basic_fixedsize_stack<TR, Protected>{ss}),
         p_coros()
     {}
 
@@ -148,32 +204,27 @@ public:
     template<typename F, typename ...A>
     void spawn(F func, A &&...args) {
         if constexpr(sizeof...(A) == 0) {
-            p_coros.emplace_back([lfunc = std::move(func)](auto) {
+            p_coros.emplace_back([lfunc = std::move(func)]() {
                 lfunc();
             }, p_stacks.get_allocator());
         } else {
             p_coros.emplace_back([lfunc = std::bind(
                 std::move(func), std::forward<A>(args)...
-            )](auto) mutable {
+            )]() mutable {
                 lfunc();
             }, p_stacks.get_allocator());
         }
     }
 
     void yield() {
-        auto ctx = coroutine_context::current();
+        auto ctx = detail::csched_task::current();
         if (!ctx) {
             /* yield from main means go to dispatcher and call first task */
             p_idx = p_coros.begin();
             p_dispatcher();
             return;
         }
-        coro *c = dynamic_cast<coro *>(ctx);
-        if (c) {
-            typename coro::yield_type{*c}();
-            return;
-        }
-        throw std::runtime_error{"attempt to yield outside coroutine"};
+        ctx->yield();
     }
 
     template<typename T>
@@ -183,22 +234,18 @@ public:
         }};
     }
 private:
-    struct coro: coroutine<void()> {
-        using coroutine<void()>::coroutine;
-    };
-
-    void dispatch(typename coro::yield_type &yield_main) {
+    void dispatch() {
         while (!p_coros.empty()) {
             if (p_idx == p_coros.end()) {
                 /* we're at the end; it's time to return to main and
                  * continue there (potential yield from main results
                  * in continuing from this point with the first task)
                  */
-                yield_main();
+                detail::csched_task::current()->yield();
                 continue;
             }
             (*p_idx)();
-            if (!*p_idx) {
+            if (p_idx->dead()) {
                 p_idx = p_coros.erase(p_idx);
             } else {
                 ++p_idx;
@@ -217,9 +264,9 @@ private:
     }
 
     basic_stack_pool<TR, Protected> p_stacks;
-    coro p_dispatcher;
-    std::list<coro> p_coros;
-    typename std::list<coro>::iterator p_idx = p_coros.end();
+    detail::csched_task p_dispatcher;
+    std::list<detail::csched_task> p_coros;
+    typename std::list<detail::csched_task>::iterator p_idx = p_coros.end();
 };
 
 using simple_coroutine_scheduler =
@@ -228,71 +275,46 @@ using simple_coroutine_scheduler =
 using protected_simple_coroutine_scheduler =
     basic_simple_coroutine_scheduler<stack_traits, true>;
 
-namespace detail {
-    struct csched_task;
-
-    OSTD_EXPORT extern thread_local csched_task *current_csched_task;
-
-    struct csched_task: coroutine_context {
-        std::function<void()> func;
-        void *waiting_on = nullptr;
-        csched_task *next_waiting = nullptr;
-        typename std::list<csched_task>::iterator pos;
-
-        csched_task() = delete;
-        csched_task(csched_task const &) = delete;
-        csched_task(csched_task &&) = delete;
-        csched_task &operator=(csched_task const &) = delete;
-        csched_task &operator=(csched_task &&) = delete;
-
-        template<typename F, typename SA>
-        csched_task(F &&f, SA &&sa): func(std::forward<F>(f)) {
-            if (!func) {
-                this->set_dead();
-                return;
-            }
-            this->make_context<csched_task>(sa);
-        }
-
-        void operator()() {
-            this->set_exec();
-            csched_task *curr = std::exchange(current_csched_task, this);
-            this->coro_jump();
-            current_csched_task = curr;
-            this->rethrow();
-        }
-
-        void yield() {
-            /* we'll yield back to the thread we were scheduled to, which
-             * will appropriately notify one or all other waiting threads
-             * so we either get re-scheduled or the whole scheduler dies
-             */
-            this->yield_jump();
-        }
-
-        bool dead() const {
-            return this->is_dead();
-        }
-
-        static csched_task *current() {
-            return current_csched_task;
-        }
-
-        void resume_call() {
-            func();
-        }
-    };
-}
-
 template<typename TR, bool Protected>
 struct basic_coroutine_scheduler {
 private:
     struct task_cond;
-    using task = detail::csched_task;
+    struct task;
 
     using tlist = std::list<task>;
     using titer = typename tlist::iterator;
 
+    struct task {
+    private:
+        detail::csched_task p_func;
+
+    public:
+        void *waiting_on = nullptr;
+        task *next_waiting = nullptr;
+        titer pos;
+
+        template<typename F, typename SA>
+        task(F &&f, SA &&sa):
+            p_func(std::forward<F>(f), std::forward<SA>(sa))
+        {}
+
+        void operator()() {
+            p_func();
+        }
+
+        void yield() {
+            p_func.yield();
+        }
+
+        bool dead() const {
+            return p_func.dead();
+        }
+
+        static task *current() {
+            return reinterpret_cast<task *>(detail::csched_task::current());
+        }
+    };
+
     struct task_cond {
         task_cond() = delete;
         task_cond(task_cond const &) = delete;