diff --git a/lib/mammoth/proc/process.cpp b/lib/mammoth/proc/process.cpp
index 5c4596d..c7a79e5 100644
--- a/lib/mammoth/proc/process.cpp
+++ b/lib/mammoth/proc/process.cpp
@@ -103,8 +103,8 @@ uint64_t LoadElfProgram(uint64_t base, uint64_t as_cap) {
 
 }  // namespace
 
-glcr::ErrorCode SpawnProcessFromElfRegion(uint64_t program,
-                                          z_cap_t yellowstone_client) {
+glcr::ErrorOr<z_cap_t> SpawnProcessFromElfRegion(uint64_t program,
+                                                 z_cap_t yellowstone_client) {
   uint64_t proc_cap;
   uint64_t as_cap;
   uint64_t foreign_port_id;
@@ -130,7 +130,9 @@ glcr::ErrorCode SpawnProcessFromElfRegion(uint64_t program,
   uint64_t thread_cap;
   RET_ERR(ZThreadCreate(proc_cap, &thread_cap));
 
-  RET_ERR(pclient.WriteMessage<uint64_t>(Z_INIT_SELF_PROC, proc_cap));
+  uint64_t dup_proc_cap;
+  RET_ERR(ZCapDuplicate(proc_cap, kZionPerm_All, &dup_proc_cap));
+  RET_ERR(pclient.WriteMessage<uint64_t>(Z_INIT_SELF_PROC, dup_proc_cap));
   RET_ERR(pclient.WriteMessage<uint64_t>(Z_INIT_SELF_VMAS, as_cap));
   RET_ERR(pclient.WriteMessage<uint64_t>(Z_INIT_ENDPOINT, yellowstone_client));
 
@@ -139,7 +141,7 @@ glcr::ErrorCode SpawnProcessFromElfRegion(uint64_t program,
 #endif
   RET_ERR(ZThreadStart(thread_cap, entry_point, foreign_port_id, 0));
 
-  return glcr::OK;
+  return proc_cap;
 }
 
 }  // namespace mmth
diff --git a/lib/mammoth/proc/process.h b/lib/mammoth/proc/process.h
index 1506f4f..c5a0ef4 100644
--- a/lib/mammoth/proc/process.h
+++ b/lib/mammoth/proc/process.h
@@ -1,12 +1,12 @@
 #pragma once
 
-#include <glacier/status/error.h>
+#include <glacier/status/error_or.h>
 #include <stdint.h>
 #include <ztypes.h>
 
 namespace mmth {
 
-glcr::ErrorCode SpawnProcessFromElfRegion(uint64_t program,
-                                          z_cap_t yellowstone_client);
+glcr::ErrorOr<z_cap_t> SpawnProcessFromElfRegion(uint64_t program,
+                                                 z_cap_t yellowstone_client);
 
 }  // namespace mmth
diff --git a/sys/teton/terminal.cpp b/sys/teton/terminal.cpp
index b436093..fda6396 100644
--- a/sys/teton/terminal.cpp
+++ b/sys/teton/terminal.cpp
@@ -4,6 +4,7 @@
 #include <glacier/string/str_split.h>
 #include <mammoth/file/file.h>
 #include <mammoth/proc/process.h>
+#include <mammoth/util/debug.h>
 #include <mammoth/util/init.h>
 
 void Terminal::HandleCharacter(char c) {
@@ -68,7 +69,19 @@ void Terminal::ExecuteCommand(const glcr::String& command) {
     auto file = mmth::File::Open(tokens[1]);
 
     // TODO: Wait until the process exits.
-    mmth::SpawnProcessFromElfRegion((uint64_t)file.raw_ptr(), gInitEndpointCap);
+    auto error_or_cap = mmth::SpawnProcessFromElfRegion(
+        (uint64_t)file.raw_ptr(), gInitEndpointCap);
+    if (!error_or_cap.ok()) {
+      console_.WriteString(
+          glcr::StrFormat("Error: {}\n", error_or_cap.error()));
+      return;
+    }
+    uint64_t err_code;
+    check(ZProcessWait(error_or_cap.value(), &err_code));
+    if (err_code != 0) {
+      console_.WriteString(glcr::StrFormat(
+          "Process Error: {}\n", static_cast<glcr::ErrorCode>(err_code)));
+    }
 
   } else {
     console_.WriteString("Unknown command: ");
diff --git a/sys/yellowstone/yellowstone.cpp b/sys/yellowstone/yellowstone.cpp
index d23c81a..ced7332 100644
--- a/sys/yellowstone/yellowstone.cpp
+++ b/sys/yellowstone/yellowstone.cpp
@@ -15,7 +15,12 @@
 glcr::ErrorCode SpawnProcess(z_cap_t vmmo_cap, z_cap_t yellowstone_cap) {
   mmth::OwnedMemoryRegion region =
       mmth::OwnedMemoryRegion::FromCapability(vmmo_cap);
-  return mmth::SpawnProcessFromElfRegion(region.vaddr(), yellowstone_cap);
+  auto error_or =
+      mmth::SpawnProcessFromElfRegion(region.vaddr(), yellowstone_cap);
+  if (error_or.ok()) {
+    return glcr::OK;
+  }
+  return error_or.error();
 }
 
 uint64_t main(uint64_t port_cap) {
@@ -48,8 +53,11 @@ uint64_t main(uint64_t port_cap) {
           mmth::File::Open(glcr::StrFormat("/bin/{}", files[i]));
 
       ASSIGN_OR_RETURN(client_cap, server->CreateClientCap());
-      check(mmth::SpawnProcessFromElfRegion((uint64_t)binary.raw_ptr(),
-                                            client_cap));
+      auto error_or = mmth::SpawnProcessFromElfRegion(
+          (uint64_t)binary.raw_ptr(), client_cap);
+      if (!error_or.ok()) {
+        check(error_or.error());
+      }
     }
   }