diff --git a/.gitignore b/.gitignore
index 6cf26001..c9c9ddd0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,4 +7,6 @@ obj/
 /tests/golangworker/golangworker
 /.vs
 /.vscode
-/.idea
\ No newline at end of file
+/.idea
+/.zed
+Temporalio.sln.DotSettings.user
diff --git a/src/Temporalio/Bridge/include/temporal-sdk-bridge.h b/src/Temporalio/Bridge/include/temporal-sdk-bridge.h
index bc821b99..131ed307 100644
--- a/src/Temporalio/Bridge/include/temporal-sdk-bridge.h
+++ b/src/Temporalio/Bridge/include/temporal-sdk-bridge.h
@@ -391,9 +391,12 @@ typedef struct SlotReserveCtx {
   bool is_sticky;
 } SlotReserveCtx;
 
-typedef void (*CustomReserveSlotCallback)(struct SlotReserveCtx ctx);
+typedef void (*CustomReserveSlotCallback)(struct SlotReserveCtx ctx, void *sender);
 
-typedef void (*CustomTryReserveSlotCallback)(struct SlotReserveCtx ctx);
+/**
+ * Must return pointer to a C# object inheriting from SlotPermit
+ */
+typedef const void *(*CustomTryReserveSlotCallback)(struct SlotReserveCtx ctx);
 
 typedef enum SlotInfo_Tag {
   WorkflowSlotInfo,
@@ -689,6 +692,8 @@ struct WorkerReplayPushResult worker_replay_push(struct Worker *worker,
                                                  struct ByteArrayRef workflow_id,
                                                  struct ByteArrayRef history);
 
+void complete_async_reserve(void *sender, const void *permit);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif // __cplusplus
diff --git a/src/Temporalio/Bridge/src/worker.rs b/src/Temporalio/Bridge/src/worker.rs
index 8be43573..af03fb57 100644
--- a/src/Temporalio/Bridge/src/worker.rs
+++ b/src/Temporalio/Bridge/src/worker.rs
@@ -24,6 +24,7 @@ use temporal_sdk_core_protos::coresdk::ActivityHeartbeat;
 use temporal_sdk_core_protos::coresdk::ActivityTaskCompletion;
 use temporal_sdk_core_protos::temporal::api::history::v1::History;
 use tokio::sync::mpsc::{channel, Sender};
+use tokio::sync::oneshot;
 use tokio_stream::wrappers::ReceiverStream;
 
 use std::collections::HashMap;
@@ -84,8 +85,20 @@ pub struct ResourceBasedSlotSupplier {
     tuner_options: ResourceBasedTunerOptions,
 }
 
-type CustomReserveSlotCallback = unsafe extern "C" fn(ctx: SlotReserveCtx);
-type CustomTryReserveSlotCallback = unsafe extern "C" fn(ctx: SlotReserveCtx);
+#[repr(C)]
+pub struct CustomSlotSupplier<SK> {
+    inner: CustomSlotSupplierCallbacksImpl,
+    _pd: std::marker::PhantomData<SK>,
+}
+
+unsafe impl<SK> Send for CustomSlotSupplier<SK> {}
+unsafe impl<SK> Sync for CustomSlotSupplier<SK> {}
+
+type CustomReserveSlotCallback =
+    unsafe extern "C" fn(ctx: SlotReserveCtx, sender: *mut libc::c_void);
+/// Must return pointer to a C# object inheriting from SlotPermit
+type CustomTryReserveSlotCallback =
+    unsafe extern "C" fn(ctx: SlotReserveCtx) -> *const libc::c_void;
 type CustomMarkSlotUsedCallback = unsafe extern "C" fn(ctx: SlotMarkUsedCtx);
 type CustomReleaseSlotCallback = unsafe extern "C" fn(ctx: SlotReleaseCtx);
 
@@ -113,15 +126,6 @@ impl CustomSlotSupplierCallbacksImpl {
     }
 }
 
-#[repr(C)]
-pub struct CustomSlotSupplier<SK> {
-    inner: CustomSlotSupplierCallbacksImpl,
-    _pd: std::marker::PhantomData<SK>,
-}
-
-unsafe impl<SK> Send for CustomSlotSupplier<SK> {}
-unsafe impl<SK> Sync for CustomSlotSupplier<SK> {}
-
 #[repr(C)]
 pub enum SlotKindType {
     WorkflowSlotKindType,
@@ -173,11 +177,13 @@ impl<SK: SlotKind + Send + Sync> temporal_sdk_core_api::worker::SlotSupplier
     type SlotKind = SK;
 
     async fn reserve_slot(&self, ctx: &dyn SlotReservationContext) -> SlotSupplierPermit {
+        let (tx, rx) = oneshot::channel();
         let ctx = Self::convert_reserve_ctx(ctx);
+        let tx = Box::into_raw(Box::new(tx)) as *mut libc::c_void;
         unsafe {
-            ((*self.inner.0).reserve)(ctx);
+            ((*self.inner.0).reserve)(ctx, tx);
         }
-        unimplemented!()
+        rx.await.expect("reserve channel is not closed")
     }
 
     fn try_reserve_slot(&self, ctx: &dyn SlotReservationContext) -> Option<SlotSupplierPermit> {
@@ -727,6 +733,20 @@ pub extern "C" fn worker_replay_push(
     }
 }
 
+#[no_mangle]
+pub extern "C" fn complete_async_reserve(sender: *mut libc::c_void, permit: *const libc::c_void) {
+    if !sender.is_null() && !permit.is_null() {
+        unsafe {
+            let sender = Box::from_raw(sender as *mut Sender<SlotSupplierPermit>);
+            let permit =
+                SlotSupplierPermit::with_user_data(UserDataHandle(permit as *mut libc::c_void));
+            let _ = sender.send(permit);
+        }
+    } else {
+        panic!("ReserveSlot sender & permit must not be null!");
+    }
+}
+
 impl TryFrom<&WorkerOptions> for temporal_sdk_core::WorkerConfig {
     type Error = anyhow::Error;