diff --git a/lib/mammoth/file/file.cpp b/lib/mammoth/file/file.cpp
index ed6ce66..0dfa605 100644
--- a/lib/mammoth/file/file.cpp
+++ b/lib/mammoth/file/file.cpp
@@ -3,6 +3,7 @@
 #include <glacier/string/str_split.h>
 #include <victoriafalls/victoriafalls.yunq.client.h>
 #include <yellowstone/yellowstone.yunq.client.h>
+#include <zcall.h>
 #include <zglobal.h>
 
 #include "util/debug.h"
@@ -14,7 +15,11 @@ VFSClient* gVfsClient = nullptr;
 
 void GetVfsClientIfNeeded() {
   if (gVfsClient == nullptr) {
-    YellowstoneClient client(gInitEndpointCap);
+    // TODO: Add an unowned client so we don't have to duplicate this cap every
+    // time.
+    uint64_t dup_cap;
+    check(ZCapDuplicate(gInitEndpointCap, kZionPerm_All, &dup_cap));
+    YellowstoneClient client(dup_cap);
 
     GetEndpointRequest yreq;
     yreq.set_endpoint_name("victoriafalls");
diff --git a/lib/mammoth/input/keyboard.cpp b/lib/mammoth/input/keyboard.cpp
index 377cc22..19d0100 100644
--- a/lib/mammoth/input/keyboard.cpp
+++ b/lib/mammoth/input/keyboard.cpp
@@ -24,7 +24,9 @@ KeyboardListenerBase::KeyboardListenerBase() {
 }
 
 void KeyboardListenerBase::Register() {
-  YellowstoneClient client(gInitEndpointCap);
+  uint64_t dup_cap;
+  check(ZCapDuplicate(gInitEndpointCap, kZionPerm_All, &dup_cap));
+  YellowstoneClient client(dup_cap);
 
   GetEndpointRequest req;
   req.set_endpoint_name("voyageurs");
diff --git a/sys/denali/lib/denali/denali.yunq.client.cpp b/sys/denali/lib/denali/denali.yunq.client.cpp
index a8c29f0..2020331 100644
--- a/sys/denali/lib/denali/denali.yunq.client.cpp
+++ b/sys/denali/lib/denali/denali.yunq.client.cpp
@@ -3,10 +3,18 @@
 
 #include <glacier/buffer/byte_buffer.h>
 #include <glacier/buffer/cap_buffer.h>
+#include <mammoth/util/debug.h>
 #include <zcall.h>
 
 
 
+DenaliClient::~DenaliClient() {
+  if (endpoint_ != 0) {
+    check(ZCapRelease(endpoint_));
+    }
+}
+
+
 
 
 glcr::ErrorCode DenaliClient::Read(const ReadRequest& request, ReadResponse& response) {
diff --git a/sys/denali/lib/denali/denali.yunq.client.h b/sys/denali/lib/denali/denali.yunq.client.h
index c0e2d42..ee80aca 100644
--- a/sys/denali/lib/denali/denali.yunq.client.h
+++ b/sys/denali/lib/denali/denali.yunq.client.h
@@ -13,6 +13,7 @@ class DenaliClient {
   DenaliClient(z_cap_t Denali_cap) : endpoint_(Denali_cap) {}
   DenaliClient(const DenaliClient&) = delete;
   DenaliClient(DenaliClient&& other) : endpoint_(other.endpoint_) {other.endpoint_ = 0;};
+  ~DenaliClient();
 
   z_cap_t Capability() { return endpoint_; }
 
diff --git a/sys/denali/lib/denali/denali.yunq.server.cpp b/sys/denali/lib/denali/denali.yunq.server.cpp
index 1fda418..9b1d83f 100644
--- a/sys/denali/lib/denali/denali.yunq.server.cpp
+++ b/sys/denali/lib/denali/denali.yunq.server.cpp
@@ -35,6 +35,12 @@ DenaliServerBase::~DenaliServerBase() {
   }
 }
 
+glcr::ErrorOr<z_cap_t> DenaliServerBase::CreateClientCap() {
+  uint64_t client_cap;
+  RET_ERR(ZCapDuplicate(endpoint_, ~(kZionPerm_Read), &client_cap));
+  return client_cap;
+}
+
 glcr::ErrorOr<DenaliClient> DenaliServerBase::CreateClient() {
   uint64_t client_cap;
   RET_ERR(ZCapDuplicate(endpoint_, ~(kZionPerm_Read), &client_cap));
diff --git a/sys/denali/lib/denali/denali.yunq.server.h b/sys/denali/lib/denali/denali.yunq.server.h
index b10e187..41083ed 100644
--- a/sys/denali/lib/denali/denali.yunq.server.h
+++ b/sys/denali/lib/denali/denali.yunq.server.h
@@ -17,6 +17,7 @@ class DenaliServerBase {
   DenaliServerBase(DenaliServerBase&&) = delete;
   virtual ~DenaliServerBase();
 
+  glcr::ErrorOr<z_cap_t> CreateClientCap();
   glcr::ErrorOr<DenaliClient> CreateClient();
 
   [[nodiscard]] Thread RunServer();
diff --git a/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.client.cpp b/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.client.cpp
index 142625a..cbd3c3a 100644
--- a/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.client.cpp
+++ b/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.client.cpp
@@ -3,10 +3,18 @@
 
 #include <glacier/buffer/byte_buffer.h>
 #include <glacier/buffer/cap_buffer.h>
+#include <mammoth/util/debug.h>
 #include <zcall.h>
 
 
 
+VFSClient::~VFSClient() {
+  if (endpoint_ != 0) {
+    check(ZCapRelease(endpoint_));
+    }
+}
+
+
 
 
 glcr::ErrorCode VFSClient::OpenFile(const OpenFileRequest& request, OpenFileResponse& response) {
diff --git a/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.client.h b/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.client.h
index d0ffcdc..ba62714 100644
--- a/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.client.h
+++ b/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.client.h
@@ -13,6 +13,7 @@ class VFSClient {
   VFSClient(z_cap_t VFS_cap) : endpoint_(VFS_cap) {}
   VFSClient(const VFSClient&) = delete;
   VFSClient(VFSClient&& other) : endpoint_(other.endpoint_) {other.endpoint_ = 0;};
+  ~VFSClient();
 
   z_cap_t Capability() { return endpoint_; }
 
diff --git a/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.server.cpp b/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.server.cpp
index 995f8cb..64aa20a 100644
--- a/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.server.cpp
+++ b/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.server.cpp
@@ -35,6 +35,12 @@ VFSServerBase::~VFSServerBase() {
   }
 }
 
+glcr::ErrorOr<z_cap_t> VFSServerBase::CreateClientCap() {
+  uint64_t client_cap;
+  RET_ERR(ZCapDuplicate(endpoint_, ~(kZionPerm_Read), &client_cap));
+  return client_cap;
+}
+
 glcr::ErrorOr<VFSClient> VFSServerBase::CreateClient() {
   uint64_t client_cap;
   RET_ERR(ZCapDuplicate(endpoint_, ~(kZionPerm_Read), &client_cap));
diff --git a/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.server.h b/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.server.h
index d7cabe0..1be2e9f 100644
--- a/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.server.h
+++ b/sys/victoriafalls/lib/victoriafalls/victoriafalls.yunq.server.h
@@ -17,6 +17,7 @@ class VFSServerBase {
   VFSServerBase(VFSServerBase&&) = delete;
   virtual ~VFSServerBase();
 
+  glcr::ErrorOr<z_cap_t> CreateClientCap();
   glcr::ErrorOr<VFSClient> CreateClient();
 
   [[nodiscard]] Thread RunServer();
diff --git a/sys/voyageurs/lib/voyageurs/voyageurs.yunq.client.cpp b/sys/voyageurs/lib/voyageurs/voyageurs.yunq.client.cpp
index 65f4d26..df1c323 100644
--- a/sys/voyageurs/lib/voyageurs/voyageurs.yunq.client.cpp
+++ b/sys/voyageurs/lib/voyageurs/voyageurs.yunq.client.cpp
@@ -3,10 +3,18 @@
 
 #include <glacier/buffer/byte_buffer.h>
 #include <glacier/buffer/cap_buffer.h>
+#include <mammoth/util/debug.h>
 #include <zcall.h>
 
 
 
+VoyageursClient::~VoyageursClient() {
+  if (endpoint_ != 0) {
+    check(ZCapRelease(endpoint_));
+    }
+}
+
+
 
 
 glcr::ErrorCode VoyageursClient::RegisterKeyboardListener(const KeyboardListener& request) {
diff --git a/sys/voyageurs/lib/voyageurs/voyageurs.yunq.client.h b/sys/voyageurs/lib/voyageurs/voyageurs.yunq.client.h
index ecf97fe..48b784c 100644
--- a/sys/voyageurs/lib/voyageurs/voyageurs.yunq.client.h
+++ b/sys/voyageurs/lib/voyageurs/voyageurs.yunq.client.h
@@ -13,6 +13,7 @@ class VoyageursClient {
   VoyageursClient(z_cap_t Voyageurs_cap) : endpoint_(Voyageurs_cap) {}
   VoyageursClient(const VoyageursClient&) = delete;
   VoyageursClient(VoyageursClient&& other) : endpoint_(other.endpoint_) {other.endpoint_ = 0;};
+  ~VoyageursClient();
 
   z_cap_t Capability() { return endpoint_; }
 
diff --git a/sys/voyageurs/lib/voyageurs/voyageurs.yunq.server.cpp b/sys/voyageurs/lib/voyageurs/voyageurs.yunq.server.cpp
index a062b02..bd90ab2 100644
--- a/sys/voyageurs/lib/voyageurs/voyageurs.yunq.server.cpp
+++ b/sys/voyageurs/lib/voyageurs/voyageurs.yunq.server.cpp
@@ -35,6 +35,12 @@ VoyageursServerBase::~VoyageursServerBase() {
   }
 }
 
+glcr::ErrorOr<z_cap_t> VoyageursServerBase::CreateClientCap() {
+  uint64_t client_cap;
+  RET_ERR(ZCapDuplicate(endpoint_, ~(kZionPerm_Read), &client_cap));
+  return client_cap;
+}
+
 glcr::ErrorOr<VoyageursClient> VoyageursServerBase::CreateClient() {
   uint64_t client_cap;
   RET_ERR(ZCapDuplicate(endpoint_, ~(kZionPerm_Read), &client_cap));
diff --git a/sys/voyageurs/lib/voyageurs/voyageurs.yunq.server.h b/sys/voyageurs/lib/voyageurs/voyageurs.yunq.server.h
index 7c85b40..f349e3b 100644
--- a/sys/voyageurs/lib/voyageurs/voyageurs.yunq.server.h
+++ b/sys/voyageurs/lib/voyageurs/voyageurs.yunq.server.h
@@ -17,6 +17,7 @@ class VoyageursServerBase {
   VoyageursServerBase(VoyageursServerBase&&) = delete;
   virtual ~VoyageursServerBase();
 
+  glcr::ErrorOr<z_cap_t> CreateClientCap();
   glcr::ErrorOr<VoyageursClient> CreateClient();
 
   [[nodiscard]] Thread RunServer();
diff --git a/sys/yellowstone/lib/yellowstone/yellowstone.yunq.client.cpp b/sys/yellowstone/lib/yellowstone/yellowstone.yunq.client.cpp
index 2a016c5..4dd4d8b 100644
--- a/sys/yellowstone/lib/yellowstone/yellowstone.yunq.client.cpp
+++ b/sys/yellowstone/lib/yellowstone/yellowstone.yunq.client.cpp
@@ -3,10 +3,18 @@
 
 #include <glacier/buffer/byte_buffer.h>
 #include <glacier/buffer/cap_buffer.h>
+#include <mammoth/util/debug.h>
 #include <zcall.h>
 
 
 
+YellowstoneClient::~YellowstoneClient() {
+  if (endpoint_ != 0) {
+    check(ZCapRelease(endpoint_));
+    }
+}
+
+
 
 
 glcr::ErrorCode YellowstoneClient::RegisterEndpoint(const RegisterEndpointRequest& request) {
diff --git a/sys/yellowstone/lib/yellowstone/yellowstone.yunq.client.h b/sys/yellowstone/lib/yellowstone/yellowstone.yunq.client.h
index 1d8dfaa..93371e8 100644
--- a/sys/yellowstone/lib/yellowstone/yellowstone.yunq.client.h
+++ b/sys/yellowstone/lib/yellowstone/yellowstone.yunq.client.h
@@ -13,6 +13,7 @@ class YellowstoneClient {
   YellowstoneClient(z_cap_t Yellowstone_cap) : endpoint_(Yellowstone_cap) {}
   YellowstoneClient(const YellowstoneClient&) = delete;
   YellowstoneClient(YellowstoneClient&& other) : endpoint_(other.endpoint_) {other.endpoint_ = 0;};
+  ~YellowstoneClient();
 
   z_cap_t Capability() { return endpoint_; }
 
diff --git a/sys/yellowstone/lib/yellowstone/yellowstone.yunq.server.cpp b/sys/yellowstone/lib/yellowstone/yellowstone.yunq.server.cpp
index 88afc31..e05cda0 100644
--- a/sys/yellowstone/lib/yellowstone/yellowstone.yunq.server.cpp
+++ b/sys/yellowstone/lib/yellowstone/yellowstone.yunq.server.cpp
@@ -35,6 +35,12 @@ YellowstoneServerBase::~YellowstoneServerBase() {
   }
 }
 
+glcr::ErrorOr<z_cap_t> YellowstoneServerBase::CreateClientCap() {
+  uint64_t client_cap;
+  RET_ERR(ZCapDuplicate(endpoint_, ~(kZionPerm_Read), &client_cap));
+  return client_cap;
+}
+
 glcr::ErrorOr<YellowstoneClient> YellowstoneServerBase::CreateClient() {
   uint64_t client_cap;
   RET_ERR(ZCapDuplicate(endpoint_, ~(kZionPerm_Read), &client_cap));
diff --git a/sys/yellowstone/lib/yellowstone/yellowstone.yunq.server.h b/sys/yellowstone/lib/yellowstone/yellowstone.yunq.server.h
index 316a8d3..1b829ef 100644
--- a/sys/yellowstone/lib/yellowstone/yellowstone.yunq.server.h
+++ b/sys/yellowstone/lib/yellowstone/yellowstone.yunq.server.h
@@ -17,6 +17,7 @@ class YellowstoneServerBase {
   YellowstoneServerBase(YellowstoneServerBase&&) = delete;
   virtual ~YellowstoneServerBase();
 
+  glcr::ErrorOr<z_cap_t> CreateClientCap();
   glcr::ErrorOr<YellowstoneClient> CreateClient();
 
   [[nodiscard]] Thread RunServer();
diff --git a/sys/yellowstone/yellowstone.cpp b/sys/yellowstone/yellowstone.cpp
index 7e575a0..b4f16ae 100644
--- a/sys/yellowstone/yellowstone.cpp
+++ b/sys/yellowstone/yellowstone.cpp
@@ -25,13 +25,13 @@ uint64_t main(uint64_t port_cap) {
   ASSIGN_OR_RETURN(auto server, YellowstoneServer::Create());
   Thread server_thread = server->RunServer();
 
-  ASSIGN_OR_RETURN(YellowstoneClient client1, server->CreateClient());
-  check(SpawnProcess(gBootDenaliVmmoCap, client1.Capability()));
+  ASSIGN_OR_RETURN(uint64_t client_cap, server->CreateClientCap());
+  check(SpawnProcess(gBootDenaliVmmoCap, client_cap));
 
   server->WaitDenaliRegistered();
 
-  ASSIGN_OR_RETURN(YellowstoneClient client2, server->CreateClient());
-  check(SpawnProcess(gBootVictoriaFallsVmmoCap, client2.Capability()));
+  ASSIGN_OR_RETURN(client_cap, server->CreateClientCap());
+  check(SpawnProcess(gBootVictoriaFallsVmmoCap, client_cap));
 
   server->WaitVictoriaFallsRegistered();
 
@@ -47,9 +47,9 @@ uint64_t main(uint64_t port_cap) {
       mmth::File binary =
           mmth::File::Open(glcr::StrFormat("/bin/{}", files[i]));
 
-      ASSIGN_OR_RETURN(YellowstoneClient client3, server->CreateClient());
+      ASSIGN_OR_RETURN(client_cap, server->CreateClientCap());
       check(mmth::SpawnProcessFromElfRegion((uint64_t)binary.raw_ptr(),
-                                            client3.Capability()));
+                                            client_cap));
     }
   }
 
diff --git a/sys/yellowstone/yellowstone_server.cpp b/sys/yellowstone/yellowstone_server.cpp
index ed7ccd1..f22b36e 100644
--- a/sys/yellowstone/yellowstone_server.cpp
+++ b/sys/yellowstone/yellowstone_server.cpp
@@ -87,7 +87,9 @@ glcr::ErrorCode YellowstoneServer::HandleRegisterEndpoint(
   dbgln("Registering {}.", req.endpoint_name().view());
   check(endpoint_map_.Insert(req.endpoint_name(), req.endpoint_capability()));
   if (req.endpoint_name() == "denali") {
-    auto part_info_or = HandleDenaliRegistration(req.endpoint_capability());
+    z_cap_t dup_cap;
+    check(ZCapDuplicate(req.endpoint_capability(), kZionPerm_All, &dup_cap));
+    auto part_info_or = HandleDenaliRegistration(dup_cap);
     if (!part_info_or.ok()) {
       check(part_info_or.error());
     }
diff --git a/yunq/client.cpp.jinja b/yunq/client.cpp.jinja
index 7a88c90..e17b64b 100644
--- a/yunq/client.cpp.jinja
+++ b/yunq/client.cpp.jinja
@@ -3,9 +3,17 @@
 
 #include <glacier/buffer/byte_buffer.h>
 #include <glacier/buffer/cap_buffer.h>
+#include <mammoth/util/debug.h>
 #include <zcall.h>
 
 {% for interface in interfaces %}
+
+{{interface.name}}Client::~{{interface.name}}Client() {
+  if (endpoint_ != 0) {
+    check(ZCapRelease(endpoint_));
+    }
+}
+
 {% for method in interface.methods %}
 
 {% if method.request == None %}
diff --git a/yunq/client.h.jinja b/yunq/client.h.jinja
index a1c2936..5684d5f 100644
--- a/yunq/client.h.jinja
+++ b/yunq/client.h.jinja
@@ -14,6 +14,7 @@ class {{interface.name}}Client {
   {{interface.name}}Client(z_cap_t {{interface.name}}_cap) : endpoint_({{interface.name}}_cap) {}
   {{interface.name}}Client(const {{interface.name}}Client&) = delete;
   {{interface.name}}Client({{interface.name}}Client&& other) : endpoint_(other.endpoint_) {other.endpoint_ = 0;};
+  ~{{interface.name}}Client();
 
   z_cap_t Capability() { return endpoint_; }
 
diff --git a/yunq/server.cpp.jinja b/yunq/server.cpp.jinja
index 595b278..1695ffb 100644
--- a/yunq/server.cpp.jinja
+++ b/yunq/server.cpp.jinja
@@ -35,6 +35,12 @@ void {{interface.name}}ServerBaseThreadBootstrap(void* server_base) {
   }
 }
 
+glcr::ErrorOr<z_cap_t> {{interface.name}}ServerBase::CreateClientCap() {
+  uint64_t client_cap;
+  RET_ERR(ZCapDuplicate(endpoint_, ~(kZionPerm_Read), &client_cap));
+  return client_cap;
+}
+
 glcr::ErrorOr<{{interface.name}}Client> {{interface.name}}ServerBase::CreateClient() {
   uint64_t client_cap;
   RET_ERR(ZCapDuplicate(endpoint_, ~(kZionPerm_Read), &client_cap));
diff --git a/yunq/server.h.jinja b/yunq/server.h.jinja
index 5b487ac..a053d63 100644
--- a/yunq/server.h.jinja
+++ b/yunq/server.h.jinja
@@ -17,6 +17,7 @@ class {{interface.name}}ServerBase {
   {{interface.name}}ServerBase({{interface.name}}ServerBase&&) = delete;
   virtual ~{{interface.name}}ServerBase();
 
+  glcr::ErrorOr<z_cap_t> CreateClientCap();
   glcr::ErrorOr<{{interface.name}}Client> CreateClient();
 
   [[nodiscard]] Thread RunServer();