diff --git a/aarch64.c b/aarch64.c
index 59162f20..b3ffcc49 100644
--- a/aarch64.c
+++ b/aarch64.c
@@ -59,10 +59,6 @@ static void co_init() {
   #endif
 }
 
-const char* co_method() {
-  return "aarch64";
-}
-
 cothread_t co_active() {
   if(!co_active_handle) co_active_handle = &co_active_buffer;
   return co_active_handle;
@@ -102,6 +98,10 @@ void co_switch(cothread_t handle) {
   co_swap(co_active_handle = handle, co_previous_handle);
 }
 
+int co_serializable() {
+  return 1;
+}
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/amd64.c b/amd64.c
index e9aef889..e9424c0b 100644
--- a/amd64.c
+++ b/amd64.c
@@ -115,10 +115,6 @@ static void crash() {
   assert(0);  /* called only if cothread_t entrypoint returns */
 }
 
-const char* co_method() {
-  return "amd64";
-}
-
 cothread_t co_active() {
   if(!co_active_handle) co_active_handle = &co_active_buffer;
   return co_active_handle;
@@ -158,6 +154,10 @@ void co_switch(cothread_t handle) {
   co_swap(co_active_handle = handle, co_previous_handle);
 }
 
+int co_serializable() {
+  return 1;
+}
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/arm.c b/arm.c
index 8d872bf5..95adf6b2 100644
--- a/arm.c
+++ b/arm.c
@@ -35,10 +35,6 @@ static void co_init() {
   #endif
 }
 
-const char* co_method() {
-  return "arm";
-}
-
 cothread_t co_active() {
   if(!co_active_handle) co_active_handle = &co_active_buffer;
   return co_active_handle;
@@ -77,6 +73,10 @@ void co_switch(cothread_t handle) {
   co_swap(co_active_handle = handle, co_previous_handle);
 }
 
+int co_serializable() {
+  return 1;
+}
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/fiber.c b/fiber.c
index f508b0f8..dd539c37 100644
--- a/fiber.c
+++ b/fiber.c
@@ -16,10 +16,6 @@ static void __stdcall co_thunk(void* coentry) {
   ((void (*)(void))coentry)();
 }
 
-const char* co_method() {
-  return "fiber";
-}
-
 cothread_t co_active() {
   if(!co_active_) {
     ConvertThreadToFiber(0);
@@ -50,6 +46,10 @@ void co_switch(cothread_t cothread) {
   SwitchToFiber(cothread);
 }
 
+int co_serializable() {
+  return 0;
+}
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/libco.h b/libco.h
index 0b94c2e9..88d00a72 100644
--- a/libco.h
+++ b/libco.h
@@ -13,12 +13,12 @@ extern "C" {
 
 typedef void* cothread_t;
 
-const char* co_method();
 cothread_t co_active();
 cothread_t co_derive(void*, unsigned int, void (*)(void));
 cothread_t co_create(unsigned int, void (*)(void));
 void co_delete(cothread_t);
 void co_switch(cothread_t);
+int co_serializable();
 
 #ifdef __cplusplus
 }
diff --git a/ppc.c b/ppc.c
index 314997c8..6b7f4acd 100644
--- a/ppc.c
+++ b/ppc.c
@@ -413,10 +413,6 @@ static void co_init_(void) {
   co_active_handle = co_create_(state_size, (uintptr_t)&co_switch);
 }
 
-const char* co_method() {
-  return "ppc";
-}
-
 cothread_t co_active() {
   if(!co_active_handle) co_init_();
 
@@ -429,3 +425,7 @@ void co_switch(cothread_t t) {
 
   CO_SWAP_ASM(t, old);
 }
+
+int co_serializable() {
+  return 0;
+}
diff --git a/ppc64v2.c b/ppc64v2.c
index fac464a6..3c296959 100644
--- a/ppc64v2.c
+++ b/ppc64v2.c
@@ -221,10 +221,6 @@ __asm__(
   ".size swap_context, .-swap_context\n"
 );
 
-const char* co_method() {
-  return "ppc64v2";
-}
-
 cothread_t co_active() {
   if(!co_active_handle) {
     co_active_handle = (struct ppc64_context*)malloc(MIN_STACK + sizeof(struct ppc64_context));
@@ -274,6 +270,10 @@ void co_switch(cothread_t to) {
   swap_context((struct ppc64_context*)to, from);
 }
 
+int co_serializable() {
+  return 1;
+}
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/sjlj.c b/sjlj.c
index b4faf17b..5af14729 100644
--- a/sjlj.c
+++ b/sjlj.c
@@ -33,10 +33,6 @@ static void springboard(int ignored) {
   }
 }
 
-const char* co_method() {
-  return "sjlj";
-}
-
 cothread_t co_active() {
   if(!co_running) co_running = &co_primary;
   return (cothread_t)co_running;
@@ -140,6 +136,10 @@ void co_switch(cothread_t cothread) {
   }
 }
 
+int co_serializable() {
+  return 0;
+}
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/ucontext.c b/ucontext.c
index 49fa976c..5ff76af3 100644
--- a/ucontext.c
+++ b/ucontext.c
@@ -26,10 +26,6 @@ extern "C" {
 static thread_local ucontext_t co_primary;
 static thread_local ucontext_t* co_running = 0;
 
-const char* co_module() {
-  return "ucontext";
-}
-
 cothread_t co_active() {
   if(!co_running) co_running = &co_primary;
   return (cothread_t)co_running;
@@ -81,6 +77,10 @@ void co_switch(cothread_t cothread) {
   swapcontext(old_thread, co_running);
 }
 
+int co_serializable() {
+  return 0;
+}
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/x86.c b/x86.c
index 8effa0d4..fa1c538f 100644
--- a/x86.c
+++ b/x86.c
@@ -69,10 +69,6 @@ static void crash() {
   assert(0);  /* called only if cothread_t entrypoint returns */
 }
 
-const char* co_method() {
-  return "x86";
-}
-
 cothread_t co_active() {
   if(!co_active_handle) co_active_handle = &co_active_buffer;
   return co_active_handle;
@@ -112,6 +108,10 @@ void co_switch(cothread_t handle) {
   co_swap(co_active_handle = handle, co_previous_handle);
 }
 
+int co_serializable() {
+  return 1;
+}
+
 #ifdef __cplusplus
 }
 #endif