diff --git a/benchmarks/parsestream.upb_table.c b/benchmarks/parsestream.upb_table.c
index 61078942b2..00eb1bbee2 100644
--- a/benchmarks/parsestream.upb_table.c
+++ b/benchmarks/parsestream.upb_table.c
@@ -61,9 +61,10 @@ static bool initialize()
     return false;
   }
 
-  upb_handlers_init(&handlers, def);
+  upb_handlers_init(&handlers);
   // Cause all messages to be read, but do nothing when they are.
-  upb_register_all(&handlers, NULL, NULL, value, startsubmsg, NULL);
+  upb_handlerset hset = {NULL, NULL, value, startsubmsg, NULL};
+  upb_handlers_reghandlerset(&handlers, def, &hset);
   upb_decoder_init(&decoder, &handlers);
   upb_stringsrc_init(&stringsrc);
   return true;
diff --git a/benchmarks/parsetostruct.upb_table.c b/benchmarks/parsetostruct.upb_table.c
index 397f964f61..10d1481d4b 100644
--- a/benchmarks/parsetostruct.upb_table.c
+++ b/benchmarks/parsetostruct.upb_table.c
@@ -53,8 +53,8 @@ static bool initialize()
   msg = upb_msg_new(def);
 
   upb_stringsrc_init(&strsrc);
-  upb_handlers_init(&h, def);
-  upb_msg_regdhandlers(&h);
+  upb_handlers_init(&h);
+  upb_msg_reghandlers(&h, def);
   upb_decoder_init(&d, &h);
 
   if (!BYREF) {
diff --git a/src/upb_decoder.c b/src/upb_decoder.c
index 0087b8633a..24cfd646a9 100644
--- a/src/upb_decoder.c
+++ b/src/upb_decoder.c
@@ -341,7 +341,7 @@ void upb_decoder_init(upb_decoder *d, upb_handlers *handlers) {
 
   // Set function pointers for each field's decode function.
   for (int i = 0; i < handlers->msgs_len; i++) {
-    upb_mhandlers *m = &handlers->msgs[i];
+    upb_mhandlers *m = handlers->msgs[i];
     for(upb_inttable_iter i = upb_inttable_begin(&m->fieldtab); !upb_inttable_done(i);
         i = upb_inttable_next(&m->fieldtab, i)) {
       upb_fhandlers *f = upb_inttable_iter_value(i);
diff --git a/src/upb_def.c b/src/upb_def.c
index 338bd3d825..d87c7e96b8 100644
--- a/src/upb_def.c
+++ b/src/upb_def.c
@@ -264,8 +264,8 @@ struct _upb_defbuilder {
 };
 
 // Forward declares for top-level file descriptors.
-static void upb_msgdef_register_DescriptorProto(upb_handlers *h);
-static void upb_enumdef_register_EnumDescriptorProto(upb_handlers *h);
+static upb_mhandlers *upb_msgdef_register_DescriptorProto(upb_handlers *h);
+static upb_mhandlers * upb_enumdef_register_EnumDescriptorProto(upb_handlers *h);
 
 upb_defbuilder *upb_defbuilder_new(upb_symtab *s) {
   upb_defbuilder *b = malloc(sizeof(*b));
@@ -344,28 +344,27 @@ static upb_flow_t upb_defbuilder_FileDescriptorProto_package(void *_b,
   return UPB_CONTINUE;
 }
 
-static void upb_defbuilder_register_FileDescriptorProto(upb_handlers *h) {
-  upb_register_startend(h, upb_defbuilder_FileDescriptorProto_startmsg,
-      upb_defbuilder_FileDescriptorProto_endmsg);
-  upb_register_typed_value(h,
-      GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_PACKAGE__FIELDNUM,
-      GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_PACKAGE__FIELDTYPE, false,
-      &upb_defbuilder_FileDescriptorProto_package, UPB_NO_VALUE);
+static upb_mhandlers *upb_defbuilder_register_FileDescriptorProto(
+    upb_handlers *h) {
+  upb_mhandlers *m = upb_handlers_newmsg(h);
+  upb_mhandlers_setstartmsg(m, &upb_defbuilder_FileDescriptorProto_startmsg);
+  upb_mhandlers_setendmsg(m, &upb_defbuilder_FileDescriptorProto_endmsg);
 
-  upb_handlers_typed_push(h,
-      GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_MESSAGE_TYPE__FIELDNUM,
-      GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_MESSAGE_TYPE__FIELDTYPE, true);
-  upb_msgdef_register_DescriptorProto(h);
-  upb_handlers_typed_pop(h);
+#define FNUM(field) GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_ ## field ## __FIELDNUM
+#define FTYPE(field) GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_ ## field ## __FIELDTYPE
+  upb_fhandlers *f =
+      upb_mhandlers_newfield(m, FNUM(PACKAGE), FTYPE(PACKAGE), false);
+  upb_fhandlers_setvalue(f, &upb_defbuilder_FileDescriptorProto_package);
 
-  upb_handlers_typed_push(h,
-      GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_ENUM_TYPE__FIELDNUM,
-      GOOGLE_PROTOBUF_FILEDESCRIPTORPROTO_ENUM_TYPE__FIELDTYPE, true);
-  upb_enumdef_register_EnumDescriptorProto(h);
-  upb_handlers_typed_pop(h);
-
-  // TODO: services and extensions.
+  upb_mhandlers_newsubmsgfield(m, FNUM(MESSAGE_TYPE), FTYPE(MESSAGE_TYPE), true,
+                               upb_msgdef_register_DescriptorProto(h));
+  upb_mhandlers_newsubmsgfield(m, FNUM(ENUM_TYPE), FTYPE(ENUM_TYPE), true,
+                               upb_enumdef_register_EnumDescriptorProto(h));
+  // TODO: services, extensions
+  return m;
 }
+#undef FNUM
+#undef FTYPE
 
 // Handlers for google.protobuf.FileDescriptorSet.
 static bool upb_symtab_add_defs(upb_symtab *s, upb_def **defs, int num_defs,
@@ -379,17 +378,22 @@ static void upb_defbuilder_FileDescriptorSet_onendmsg(void *_b,
   upb_defbuilder_free(b);
 }
 
-static void upb_defbuilder_register_FileDescriptorSet(upb_handlers *h) {
-  upb_register_startend(h, NULL, upb_defbuilder_FileDescriptorSet_onendmsg);
-  upb_handlers_typed_push(h,
-      GOOGLE_PROTOBUF_FILEDESCRIPTORSET_FILE__FIELDNUM,
-      GOOGLE_PROTOBUF_FILEDESCRIPTORSET_FILE__FIELDTYPE, true);
-  upb_defbuilder_register_FileDescriptorProto(h);
-  upb_handlers_typed_pop(h);
+static upb_mhandlers *upb_defbuilder_register_FileDescriptorSet(upb_handlers *h) {
+  upb_mhandlers *m = upb_handlers_newmsg(h);
+  upb_mhandlers_setendmsg(m, upb_defbuilder_FileDescriptorSet_onendmsg);
+
+#define FNUM(field) GOOGLE_PROTOBUF_FILEDESCRIPTORSET_ ## field ## __FIELDNUM
+#define FTYPE(field) GOOGLE_PROTOBUF_FILEDESCRIPTORSET_ ## field ## __FIELDTYPE
+  upb_mhandlers_newsubmsgfield(m, FNUM(FILE), FTYPE(FILE), true,
+                               upb_defbuilder_register_FileDescriptorProto(h));
+  return m;
 }
-void upb_defbuilder_reghandlers(upb_handlers *h) {
-  upb_defbuilder_register_FileDescriptorSet(h);
+#undef FNUM
+#undef FTYPE
+
+upb_mhandlers *upb_defbuilder_reghandlers(upb_handlers *h) {
   h->should_jit = false;
+  return upb_defbuilder_register_FileDescriptorSet(h);
 }
 
 
@@ -488,18 +492,24 @@ static void upb_enumdef_EnumValueDescriptorProto_endmsg(void *_b,
   b->name = NULL;
 }
 
-static void upb_enumdef_register_EnumValueDescriptorProto(upb_handlers *h) {
-  upb_register_startend(h, upb_enumdef_EnumValueDescriptorProto_startmsg,
-      upb_enumdef_EnumValueDescriptorProto_endmsg);
-  upb_register_typed_value(h,
-      GOOGLE_PROTOBUF_ENUMVALUEDESCRIPTORPROTO_NAME__FIELDNUM,
-      GOOGLE_PROTOBUF_ENUMVALUEDESCRIPTORPROTO_NAME__FIELDTYPE, false,
-      &upb_enumdef_EnumValueDescriptorProto_name, UPB_NO_VALUE);
-  upb_register_typed_value(h,
-      GOOGLE_PROTOBUF_ENUMVALUEDESCRIPTORPROTO_NUMBER__FIELDNUM,
-      GOOGLE_PROTOBUF_ENUMVALUEDESCRIPTORPROTO_NUMBER__FIELDTYPE, false,
-      &upb_enumdef_EnumValueDescriptorProto_number, UPB_NO_VALUE);
+static upb_mhandlers *upb_enumdef_register_EnumValueDescriptorProto(
+    upb_handlers *h) {
+  upb_mhandlers *m = upb_handlers_newmsg(h);
+  upb_mhandlers_setstartmsg(m, &upb_enumdef_EnumValueDescriptorProto_startmsg);
+  upb_mhandlers_setendmsg(m, &upb_enumdef_EnumValueDescriptorProto_endmsg);
+
+#define FNUM(f) GOOGLE_PROTOBUF_ENUMVALUEDESCRIPTORPROTO_ ## f ## __FIELDNUM
+#define FTYPE(f) GOOGLE_PROTOBUF_ENUMVALUEDESCRIPTORPROTO_ ## f ## __FIELDTYPE
+  upb_fhandlers *f;
+  f = upb_mhandlers_newfield(m, FNUM(NAME), FTYPE(NAME), false);
+  upb_fhandlers_setvalue(f, &upb_enumdef_EnumValueDescriptorProto_name);
+
+  f = upb_mhandlers_newfield(m, FNUM(NUMBER), FTYPE(NUMBER), false);
+  upb_fhandlers_setvalue(f, &upb_enumdef_EnumValueDescriptorProto_number);
+  return m;
 }
+#undef FNUM
+#undef FTYPE
 
 // google.protobuf.EnumDescriptorProto.
 static upb_flow_t upb_enumdef_EnumDescriptorProto_startmsg(void *_b) {
@@ -536,20 +546,22 @@ static upb_flow_t upb_enumdef_EnumDescriptorProto_name(void *_b,
   return UPB_CONTINUE;
 }
 
-static void upb_enumdef_register_EnumDescriptorProto(upb_handlers *h) {
-  upb_register_startend(h, &upb_enumdef_EnumDescriptorProto_startmsg,
-    &upb_enumdef_EnumDescriptorProto_endmsg);
-  upb_register_typed_value(h,
-      GOOGLE_PROTOBUF_ENUMDESCRIPTORPROTO_NAME__FIELDNUM,
-      GOOGLE_PROTOBUF_ENUMDESCRIPTORPROTO_NAME__FIELDTYPE, false,
-      &upb_enumdef_EnumDescriptorProto_name, UPB_NO_VALUE);
+static upb_mhandlers *upb_enumdef_register_EnumDescriptorProto(upb_handlers *h) {
+  upb_mhandlers *m = upb_handlers_newmsg(h);
+  upb_mhandlers_setstartmsg(m, &upb_enumdef_EnumDescriptorProto_startmsg);
+  upb_mhandlers_setendmsg(m, &upb_enumdef_EnumDescriptorProto_endmsg);
 
-  upb_handlers_typed_push(h,
-      GOOGLE_PROTOBUF_ENUMDESCRIPTORPROTO_VALUE__FIELDNUM,
-      GOOGLE_PROTOBUF_ENUMDESCRIPTORPROTO_VALUE__FIELDTYPE, true);
-  upb_enumdef_register_EnumValueDescriptorProto(h);
-  upb_handlers_typed_pop(h);
+#define FNUM(f) GOOGLE_PROTOBUF_ENUMDESCRIPTORPROTO_ ## f ## __FIELDNUM
+#define FTYPE(f) GOOGLE_PROTOBUF_ENUMDESCRIPTORPROTO_ ## f ## __FIELDTYPE
+  upb_fhandlers *f = upb_mhandlers_newfield(m, FNUM(NAME), FTYPE(NAME), false);
+  upb_fhandlers_setvalue(f, &upb_enumdef_EnumDescriptorProto_name);
+
+  upb_mhandlers_newsubmsgfield(m, FNUM(VALUE), FTYPE(VALUE), true,
+                               upb_enumdef_register_EnumValueDescriptorProto(h));
+  return m;
 }
+#undef FNUM
+#undef FTYPE
 
 upb_enum_iter upb_enum_begin(upb_enumdef *e) {
   // We could iterate over either table here; the choice is arbitrary.
@@ -810,33 +822,29 @@ static upb_flow_t upb_fielddef_ondefaultval(void *_b, upb_value fval,
   return UPB_CONTINUE;
 }
 
-static void upb_fielddef_register_FieldDescriptorProto(upb_handlers *h) {
-  upb_register_startend(h, upb_fielddef_startmsg, upb_fielddef_endmsg);
-  upb_register_typed_value(h,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE__FIELDNUM,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE__FIELDTYPE, false,
-      &upb_fielddef_ontype, UPB_NO_VALUE);
-  upb_register_typed_value(h,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_LABEL__FIELDNUM,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_LABEL__FIELDTYPE, false,
-      &upb_fielddef_onlabel, UPB_NO_VALUE);
-  upb_register_typed_value(h,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_NUMBER__FIELDNUM,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_NUMBER__FIELDTYPE, false,
-      &upb_fielddef_onnumber, UPB_NO_VALUE);
-  upb_register_typed_value(h,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_NAME__FIELDNUM,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_NAME__FIELDTYPE, false,
-      &upb_fielddef_onname, UPB_NO_VALUE);
-  upb_register_typed_value(h,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE_NAME__FIELDNUM,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE_NAME__FIELDTYPE, false,
-      &upb_fielddef_ontypename, UPB_NO_VALUE);
-  upb_register_typed_value(h,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_DEFAULT_VALUE__FIELDNUM,
-      GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_DEFAULT_VALUE__FIELDTYPE, false,
-      &upb_fielddef_ondefaultval, UPB_NO_VALUE);
+static upb_mhandlers *upb_fielddef_register_FieldDescriptorProto(
+    upb_handlers *h) {
+  upb_mhandlers *m = upb_handlers_newmsg(h);
+  upb_mhandlers_setstartmsg(m, &upb_fielddef_startmsg);
+  upb_mhandlers_setendmsg(m, &upb_fielddef_endmsg);
+
+#define FIELD(name, handler) \
+  upb_fhandlers_setvalue( \
+      upb_mhandlers_newfield(m, \
+          GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_ ## name ## __FIELDNUM, \
+          GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_ ## name ## __FIELDTYPE, \
+          false), \
+      handler);
+  FIELD(TYPE, &upb_fielddef_ontype);
+  FIELD(LABEL, &upb_fielddef_onlabel);
+  FIELD(NUMBER, &upb_fielddef_onnumber);
+  FIELD(NAME, &upb_fielddef_onname);
+  FIELD(TYPE_NAME, &upb_fielddef_ontypename);
+  FIELD(DEFAULT_VALUE, &upb_fielddef_ondefaultval);
+  return m;
 }
+#undef FNUM
+#undef FTYPE
 
 
 /* upb_msgdef *****************************************************************/
@@ -951,32 +959,30 @@ static upb_flow_t upb_msgdef_onname(void *_b, upb_value fval, upb_value val) {
   return UPB_CONTINUE;
 }
 
-static void upb_msgdef_register_DescriptorProto(upb_handlers *h) {
-  upb_register_startend(h, &upb_msgdef_startmsg, &upb_msgdef_endmsg);
-  upb_register_typed_value(h,
-      GOOGLE_PROTOBUF_DESCRIPTORPROTO_NAME__FIELDNUM,
-      GOOGLE_PROTOBUF_DESCRIPTORPROTO_NAME__FIELDTYPE, false,
-      &upb_msgdef_onname, UPB_NO_VALUE);
+static upb_mhandlers *upb_msgdef_register_DescriptorProto(upb_handlers *h) {
+  upb_mhandlers *m = upb_handlers_newmsg(h);
+  upb_mhandlers_setstartmsg(m, &upb_msgdef_startmsg);
+  upb_mhandlers_setendmsg(m, &upb_msgdef_endmsg);
 
-  upb_handlers_typed_push(h,
-      GOOGLE_PROTOBUF_DESCRIPTORPROTO_FIELD__FIELDNUM,
-      GOOGLE_PROTOBUF_DESCRIPTORPROTO_FIELD__FIELDTYPE, true);
-  upb_fielddef_register_FieldDescriptorProto(h);
-  upb_handlers_typed_pop(h);
+#define FNUM(f) GOOGLE_PROTOBUF_DESCRIPTORPROTO_ ## f ## __FIELDNUM
+#define FTYPE(f) GOOGLE_PROTOBUF_DESCRIPTORPROTO_ ## f ## __FIELDTYPE
+  upb_fhandlers *f = upb_mhandlers_newfield(m, FNUM(NAME), FTYPE(NAME), false);
+  upb_fhandlers_setvalue(f, &upb_msgdef_onname);
 
-  // DescriptorProto is self-recursive, so we must link the definition.
-  upb_handlers_typed_link(h,
-      GOOGLE_PROTOBUF_DESCRIPTORPROTO_NESTED_TYPE__FIELDNUM,
-      GOOGLE_PROTOBUF_DESCRIPTORPROTO_NESTED_TYPE__FIELDTYPE, true, 0);
+  upb_mhandlers_newsubmsgfield(m, FNUM(FIELD), FTYPE(FIELD), true,
+                               upb_fielddef_register_FieldDescriptorProto(h));
+  upb_mhandlers_newsubmsgfield(m, FNUM(ENUM_TYPE), FTYPE(ENUM_TYPE), true,
+                               upb_enumdef_register_EnumDescriptorProto(h));
 
-  upb_handlers_typed_push(h,
-      GOOGLE_PROTOBUF_DESCRIPTORPROTO_ENUM_TYPE__FIELDNUM,
-      GOOGLE_PROTOBUF_DESCRIPTORPROTO_ENUM_TYPE__FIELDTYPE, true);
-  upb_enumdef_register_EnumDescriptorProto(h);
-  upb_handlers_typed_pop(h);
+  // DescriptorProto is self-recursive, so we must link the definition.
+  upb_mhandlers_newsubmsgfield(
+      m, FNUM(NESTED_TYPE), FTYPE(NESTED_TYPE), true, m);
 
   // TODO: extensions.
+  return m;
 }
+#undef FNUM
+#undef FTYPE
 
 static void upb_msgdef_free(upb_msgdef *m)
 {
diff --git a/src/upb_def.h b/src/upb_def.h
index ba1c4104f5..d02fbf4071 100644
--- a/src/upb_def.h
+++ b/src/upb_def.h
@@ -328,6 +328,7 @@ upb_def **upb_symtab_getdefs(upb_symtab *s, int *count, upb_deftype_t type);
 struct _upb_defbuilder;
 typedef struct _upb_defbuilder upb_defbuilder;
 struct _upb_handlers;
+struct _upb_handlers;
 
 // Allocates a new defbuilder that will add defs to the given symtab.
 upb_defbuilder *upb_defbuilder_new(upb_symtab *s);
@@ -337,7 +338,7 @@ upb_defbuilder *upb_defbuilder_new(upb_symtab *s);
 //
 // TODO: should this allow redefinition?  Either is possible, but which is
 // more useful?  Maybe it should be an option.
-void upb_defbuilder_reghandlers(struct _upb_handlers *h);
+struct _upb_mhandlers *upb_defbuilder_reghandlers(struct _upb_handlers *h);
 
 
 /* upb_def casts **************************************************************/
diff --git a/src/upb_glue.c b/src/upb_glue.c
index b6a027385f..d54b446469 100644
--- a/src/upb_glue.c
+++ b/src/upb_glue.c
@@ -18,8 +18,8 @@ void upb_strtomsg(upb_string *str, upb_msg *msg, upb_msgdef *md,
   upb_stringsrc_reset(&strsrc, str);
 
   upb_handlers h;
-  upb_handlers_init(&h, md);
-  upb_msg_regdhandlers(&h);
+  upb_handlers_init(&h);
+  upb_msg_reghandlers(&h, md);
 
   upb_decoder d;
   upb_decoder_init(&d, &h);
@@ -39,8 +39,8 @@ void upb_msgtotext(upb_string *str, upb_msg *msg, upb_msgdef *md,
 
   upb_textprinter *p = upb_textprinter_new();
   upb_handlers h;
-  upb_handlers_init(&h, md);
-  upb_textprinter_reghandlers(&h);
+  upb_handlers_init(&h);
+  upb_textprinter_reghandlers(&h, md);
   upb_textprinter_reset(p, upb_stringsink_bytesink(&strsink), single_line);
 
   upb_status status = UPB_STATUS_INIT;
@@ -60,7 +60,7 @@ void upb_parsedesc(upb_symtab *symtab, upb_string *str, upb_status *status) {
   upb_stringsrc_reset(&strsrc, str);
 
   upb_handlers h;
-  upb_handlers_init(&h, NULL);
+  upb_handlers_init(&h);
   upb_defbuilder_reghandlers(&h);
 
   upb_decoder d;
diff --git a/src/upb_handlers.c b/src/upb_handlers.c
index 25448da730..5f976497d0 100644
--- a/src/upb_handlers.c
+++ b/src/upb_handlers.c
@@ -9,8 +9,6 @@
 #include "upb_handlers.h"
 
 
-/* upb_handlers ***************************************************************/
-
 upb_flow_t upb_startmsg_nop(void *closure) {
   (void)closure;
   return UPB_CONTINUE;
@@ -39,220 +37,162 @@ upb_flow_t upb_endsubmsg_nop(void *closure, upb_value fval) {
   return UPB_CONTINUE;
 }
 
-upb_flow_t upb_unknownval_nop(void *closure, upb_field_number_t fieldnum,
-                              upb_value val) {
-  (void)closure;
-  (void)fieldnum;
-  (void)val;
-  return UPB_CONTINUE;
-}
-
-static void upb_msgent_init(upb_mhandlers *e) {
-  upb_inttable_init(&e->fieldtab, 8, sizeof(upb_fhandlers));
-  e->startmsg = &upb_startmsg_nop;
-  e->endmsg = &upb_endmsg_nop;
-  e->tablearray = NULL;
-  e->is_group = false;
-}
-
-void upb_handlers_init(upb_handlers *h, upb_msgdef *md) {
-  h->msgs_len = 1;
-  h->msgs_size = 4;
-  h->msgs = malloc(h->msgs_size * sizeof(*h->msgs));
-  h->top = &h->stack[0];
-  h->limit = &h->stack[UPB_MAX_TYPE_DEPTH];
-  h->toplevel_msgdef = md;
-  h->should_jit = true;
-  if (md) upb_msgdef_ref(md);
 
-  h->top->msgent_index = 0;
-  h->top->msgdef = md;
-  h->msgent = &h->msgs[0];
-  upb_msgent_init(h->msgent);
-}
+/* upb_mhandlers **************************************************************/
 
-void upb_handlers_uninit(upb_handlers *h) {
-  for (int i = 0; i < h->msgs_len; i++) {
-    upb_inttable_free(&h->msgs[i].fieldtab);
-    free(h->msgs[i].tablearray);
-  }
-  free(h->msgs);
-  upb_msgdef_unref(h->toplevel_msgdef);
+static upb_mhandlers *upb_mhandlers_new() {
+  upb_mhandlers *m = malloc(sizeof(*m));
+  upb_inttable_init(&m->fieldtab, 8, sizeof(upb_fhandlers));
+  m->startmsg = &upb_startmsg_nop;
+  m->endmsg = &upb_endmsg_nop;
+  m->tablearray = NULL;
+  m->is_group = false;
+  return m;
 }
 
-static upb_fhandlers *upb_handlers_getorcreate_without_fval(
-    upb_handlers *h, upb_field_number_t fieldnum, upb_fieldtype_t type, bool repeated) {
-  uint32_t tag = fieldnum << 3 | upb_types[type].native_wire_type;
-  upb_fhandlers *f = upb_inttable_lookup(&h->msgent->fieldtab, tag);
-  if (!f) {
-    upb_fhandlers new_f = {false, type, repeated,
-        repeated && upb_isprimitivetype(type), fieldnum, -1, UPB_NO_VALUE,
-        {&upb_value_nop}, &upb_endsubmsg_nop, 0, 0, 0, NULL};
-    if (upb_issubmsgtype(type)) new_f.cb.startsubmsg = &upb_startsubmsg_nop;
-    upb_inttable_insert(&h->msgent->fieldtab, tag, &new_f);
-
-    f = upb_inttable_lookup(&h->msgent->fieldtab, tag);
-    assert(f);
-  }
+static upb_fhandlers *_upb_mhandlers_newfield(upb_mhandlers *m, uint32_t n,
+                                              upb_fieldtype_t type,
+                                              bool repeated) {
+  uint32_t tag = n << 3 | upb_types[type].native_wire_type;
+  upb_fhandlers *f = upb_inttable_lookup(&m->fieldtab, tag);
+  if (f) abort();
+  upb_fhandlers new_f = {false, type, repeated,
+      repeated && upb_isprimitivetype(type), n, NULL, UPB_NO_VALUE,
+      &upb_value_nop, &upb_startsubmsg_nop, &upb_endsubmsg_nop, 0, 0, 0, NULL};
+  if (upb_issubmsgtype(type)) new_f.startsubmsg = &upb_startsubmsg_nop;
+  upb_inttable_insert(&m->fieldtab, tag, &new_f);
+  f = upb_inttable_lookup(&m->fieldtab, tag);
+  assert(f);
   assert(f->type == type);
   return f;
 }
 
-static upb_fhandlers *upb_handlers_getorcreate(
-    upb_handlers *h, upb_field_number_t fieldnum,
-    upb_fieldtype_t type, bool repeated, upb_value fval) {
-  upb_fhandlers *f =
-      upb_handlers_getorcreate_without_fval(h, fieldnum, type, repeated);
-  f->fval = fval;
-  return f;
+upb_fhandlers *upb_mhandlers_newfield(upb_mhandlers *m, uint32_t n,
+                                      upb_fieldtype_t type, bool repeated) {
+  assert(type != UPB_TYPE(MESSAGE));
+  assert(type != UPB_TYPE(GROUP));
+  return _upb_mhandlers_newfield(m, n, type, repeated);
 }
 
-void upb_register_startend(upb_handlers *h, upb_startmsg_handler *startmsg,
-                           upb_endmsg_handler *endmsg) {
-  h->msgent->startmsg = startmsg ? startmsg : &upb_startmsg_nop;
-  h->msgent->endmsg = endmsg ? endmsg : &upb_endmsg_nop;
+upb_fhandlers *upb_mhandlers_newsubmsgfield(upb_mhandlers *m, uint32_t n,
+                                            upb_fieldtype_t type, bool repeated,
+                                            upb_mhandlers *subm) {
+  assert(type == UPB_TYPE(MESSAGE) || type == UPB_TYPE(GROUP));
+  assert(subm);
+  upb_fhandlers *f = _upb_mhandlers_newfield(m, n, type, repeated);
+  f->submsg = subm;
+  if (type == UPB_TYPE(GROUP))
+    _upb_mhandlers_newfield(subm, n, UPB_TYPE_ENDGROUP, false);
+  return f;
 }
 
-// TODO:
-// void upb_register_unknownval(upb_handlers *h,
-//                              upb_unknownval_handler *unknown);
-// bool upb_handlers_link(upb_handlers *h, upb_fielddef *f);
-// void upb_register_path_value(upb_handlers *h, const char *path,
-//                              upb_value_handler *value, upb_value fval);
-
-void upb_register_all(upb_handlers *h, upb_startmsg_handler *start,
-                      upb_endmsg_handler *end,
-                      upb_value_handler *value,
-                      upb_startsubmsg_handler *startsubmsg,
-                      upb_endsubmsg_handler *endsubmsg) {
-  upb_register_startend(h, start, end);
-  //upb_register_unknownval(h, unknown);
-  upb_msgdef *m = h->top->msgdef;
+typedef struct {
+  upb_strtable_entry e;
+  upb_mhandlers *mh;
+} upb_mtab_ent;
+
+static upb_mhandlers *upb_regmsg_dfs(upb_handlers *h, upb_msgdef *m,
+                                     upb_onmsgreg *msgreg_cb,
+                                     upb_onfieldreg *fieldreg_cb,
+                                     void *closure, upb_strtable *mtab) {
+  upb_mhandlers *mh = upb_handlers_newmsg(h);
+  upb_mtab_ent e = {{m->base.fqname, 0}, mh};
+  printf("Inserting: " UPB_STRFMT "\n", UPB_STRARG(m->base.fqname));
+  upb_strtable_insert(mtab, &e.e);
+  if (msgreg_cb) msgreg_cb(closure, mh, m);
   upb_msg_iter i;
   for(i = upb_msg_begin(m); !upb_msg_done(i); i = upb_msg_next(m, i)) {
     upb_fielddef *f = upb_msg_iter_field(i);
-    upb_value fval;
-    upb_value_setfielddef(&fval, f);
+    upb_fhandlers *fh;
     if (upb_issubmsg(f)) {
-      upb_handlers_push(h, f, startsubmsg, endsubmsg, fval, false);
-      upb_register_all(h, start, end, value, startsubmsg, endsubmsg);
-      upb_handlers_pop(h, f);
+      upb_mhandlers *sub_mh;
+      upb_mtab_ent *subm_ent;
+      // The table lookup is necessary to break the DFS for type cycles.
+      printf("Testing: " UPB_STRFMT "\n", UPB_STRARG(f->def->fqname));
+      if ((subm_ent = upb_strtable_lookup(mtab, f->def->fqname)) != NULL) {
+        sub_mh = subm_ent->mh;
+      } else {
+        sub_mh = upb_regmsg_dfs(h, upb_downcast_msgdef(f->def), msgreg_cb,
+                                fieldreg_cb, closure, mtab);
+      }
+      fh = upb_mhandlers_newsubmsgfield(
+          mh, f->number, f->type, upb_isarray(f), sub_mh);
     } else {
-      upb_register_value(h, f, value, fval);
+      fh = upb_mhandlers_newfield(mh, f->number, f->type, upb_isarray(f));
     }
+    if (fieldreg_cb) fieldreg_cb(closure, fh, f);
   }
+  return mh;
 }
 
-void upb_register_typed_value(upb_handlers *h, upb_field_number_t fieldnum,
-                              upb_fieldtype_t type, bool repeated,
-                              upb_value_handler *value, upb_value fval) {
-  upb_handlers_getorcreate(h, fieldnum, type, repeated, fval)->cb.value =
-      value ? value : &upb_value_nop;
+upb_mhandlers *upb_handlers_regmsgdef(upb_handlers *h, upb_msgdef *m,
+                                      upb_onmsgreg *msgreg_cb,
+                                      upb_onfieldreg *fieldreg_cb,
+                                      void *closure) {
+  upb_strtable mtab;
+  upb_strtable_init(&mtab, 8, sizeof(upb_mtab_ent));
+  upb_mhandlers *ret =
+      upb_regmsg_dfs(h, m, msgreg_cb, fieldreg_cb, closure, &mtab);
+  upb_strtable_free(&mtab);
+  return ret;
 }
 
-void upb_register_value(upb_handlers *h, upb_fielddef *f,
-                        upb_value_handler *value, upb_value fval) {
-  assert(f->msgdef == h->top->msgdef);
-  upb_register_typed_value(h, f->number, f->type, upb_isarray(f), value, fval);
-}
 
-void upb_register_typed_submsg(upb_handlers *h, upb_field_number_t fieldnum,
-                               upb_fieldtype_t type, bool repeated,
-                               upb_startsubmsg_handler *start,
-                               upb_endsubmsg_handler *end,
-                               upb_value fval) {
-  upb_fhandlers *f = upb_handlers_getorcreate(h, fieldnum, type, repeated, fval);
-  f->cb.startsubmsg = start ? start : &upb_startsubmsg_nop;
-  f->endsubmsg = end ? end : &upb_endsubmsg_nop;
-}
+/* upb_handlers ***************************************************************/
 
-void upb_handlers_typed_link(upb_handlers *h, upb_field_number_t fieldnum,
-                             upb_fieldtype_t type, bool repeated, int frames) {
-  assert(frames <= (h->top - h->stack));
-  upb_fhandlers *f =
-      upb_handlers_getorcreate_without_fval(h, fieldnum, type, repeated);
-  f->msgent_index = (h->top - frames)->msgent_index;
+void upb_handlers_init(upb_handlers *h) {
+  h->msgs_len = 0;
+  h->msgs_size = 4;
+  h->msgs = malloc(h->msgs_size * sizeof(*h->msgs));
+  h->should_jit = true;
 }
 
-void upb_handlers_typed_push(upb_handlers *h, upb_field_number_t fieldnum,
-                             upb_fieldtype_t type, bool repeated) {
-  upb_fhandlers *f =
-      upb_handlers_getorcreate_without_fval(h, fieldnum, type, repeated);
-  if (h->top == h->limit) abort();  // TODO: make growable.
-  ++h->top;
-  if (f->msgent_index == -1) {
-    // Need to push a new msgent.
-    if (h->msgs_size == h->msgs_len) {
-      h->msgs_size *= 2;
-      h->msgs = realloc(h->msgs, h->msgs_size * sizeof(*h->msgs));
-    }
-    f->msgent_index = h->msgs_len++;
-    h->msgent = &h->msgs[f->msgent_index];
-    upb_msgent_init(h->msgent);
-  } else {
-    h->msgent = &h->msgs[f->msgent_index];
-  }
-  h->top->msgent_index = f->msgent_index;
-  if (h->toplevel_msgdef) {
-    upb_fielddef *f = upb_msgdef_itof((h->top - 1)->msgdef, fieldnum);
-    assert(f);
-    h->top->msgdef = upb_downcast_msgdef(f->def);
-  }
-  if (type == UPB_TYPE(GROUP)) {
-    // Insert a fieldent for ENDGROUP so we can easily dispatch endgroup when
-    // we see it in the submessage.
-    // TODO: assert that no other fields in the group are registered with the
-    // same name or number.
-    upb_register_typed_submsg(h, fieldnum, UPB_TYPE_ENDGROUP, false, NULL, NULL,
-                              UPB_NO_VALUE);
-    h->msgent->is_group = true;
+void upb_handlers_uninit(upb_handlers *h) {
+  for (int i = 0; i < h->msgs_len; i++) {
+    upb_mhandlers *mh = h->msgs[i];
+    upb_inttable_free(&mh->fieldtab);
+    free(mh->tablearray);
+    free(mh);
   }
+  free(h->msgs);
 }
 
-void upb_handlers_push(upb_handlers *h, upb_fielddef *f,
-                       upb_startsubmsg_handler *start,
-                       upb_endsubmsg_handler *end, upb_value fval,
-                       bool delegate) {
-  assert(f->msgdef == h->top->msgdef);
-  (void)delegate;  // TODO
-  upb_register_typed_submsg(h, f->number, f->type, upb_isarray(f), start, end, fval);
-  upb_handlers_typed_push(h, f->number, f->type, upb_isarray(f));
-}
-
-void upb_handlers_typed_pop(upb_handlers *h) {
-  assert(h->top > h->stack);
-  --h->top;
-  h->msgent = &h->msgs[h->top->msgent_index];
+upb_mhandlers *upb_handlers_newmsg(upb_handlers *h) {
+  if (h->msgs_len == h->msgs_size) {
+    h->msgs_size *= 2;
+    h->msgs = realloc(h->msgs, h->msgs_size * sizeof(*h->msgs));
+  }
+  upb_mhandlers *mh = upb_mhandlers_new();
+  h->msgs[h->msgs_len++] = mh;
+  return mh;
 }
 
-void upb_handlers_pop(upb_handlers *h, upb_fielddef *f) {
-  (void)f; // TODO: Check that this matches the corresponding push.
-  upb_handlers_typed_pop(h);
-}
 
 /* upb_dispatcher *************************************************************/
 
 static upb_fhandlers toplevel_f = {
   false, UPB_TYPE(GROUP), false, false, 0,
-  0, // msgent_index
+  NULL, // submsg
 #ifdef NDEBUG
   {{0}},
 #else
   {{0}, UPB_VALUETYPE_RAW},
 #endif
-  {NULL}, NULL, 0, 0, 0, NULL};
+  NULL, NULL, NULL, 0, 0, 0, NULL};
 
 void upb_dispatcher_init(upb_dispatcher *d, upb_handlers *h) {
   d->handlers = h;
-  for (int i = 0; i < h->msgs_len; i++)
-    upb_inttable_compact(&h->msgs[i].fieldtab);
+  for (int i = 0; i < h->msgs_len; i++) {
+    upb_mhandlers *m = h->msgs[i];
+    upb_inttable_compact(&m->fieldtab);
+  }
   d->stack[0].f = &toplevel_f;
   d->limit = &d->stack[UPB_MAX_NESTING];
   upb_status_init(&d->status);
 }
 
 void upb_dispatcher_reset(upb_dispatcher *d, void *top_closure, uint32_t top_end_offset) {
-  d->msgent = &d->handlers->msgs[0];
+  d->msgent = d->handlers->msgs[0];
   d->dispatch_table = &d->msgent->fieldtab;
   d->current_depth = 0;
   d->skip_depth = INT_MAX;
@@ -296,7 +236,7 @@ upb_flow_t upb_dispatch_startsubmsg(upb_dispatcher *d, upb_fhandlers *f,
                                     size_t userval) {
   ++d->current_depth;
   if (upb_dispatcher_skipping(d)) return UPB_SKIPSUBMSG;
-  upb_sflow_t sflow = f->cb.startsubmsg(d->top->closure, f->fval);
+  upb_sflow_t sflow = f->startsubmsg(d->top->closure, f->fval);
   if (sflow.flow != UPB_CONTINUE) {
     d->noframe_depth = d->current_depth;
     d->skip_depth = (sflow.flow == UPB_BREAK) ?
@@ -315,7 +255,7 @@ upb_flow_t upb_dispatch_startsubmsg(upb_dispatcher *d, upb_fhandlers *f,
   d->top->end_offset = userval;
   d->top->closure = sflow.closure;
   d->top->is_packed = false;
-  d->msgent = upb_handlers_getmsgent(d->handlers, f);
+  d->msgent = f->submsg;
   d->dispatch_table = &d->msgent->fieldtab;
   return upb_dispatch_startmsg(d);
 }
@@ -329,7 +269,8 @@ upb_flow_t upb_dispatch_endsubmsg(upb_dispatcher *d) {
     upb_fhandlers *old_f = d->top->f;
     d->msgent->endmsg(d->top->closure, &d->status);
     --d->top;
-    d->msgent = upb_handlers_getmsgent(d->handlers, d->top->f);
+    d->msgent = d->top->f->submsg;
+    if (!d->msgent) d->msgent = d->handlers->msgs[0];
     d->dispatch_table = &d->msgent->fieldtab;
     d->noframe_depth = INT_MAX;
     if (!upb_dispatcher_skipping(d)) d->skip_depth = INT_MAX;
diff --git a/src/upb_handlers.h b/src/upb_handlers.h
index f36f1dd92a..d155b2bf8f 100644
--- a/src/upb_handlers.h
+++ b/src/upb_handlers.h
@@ -108,33 +108,12 @@ upb_flow_t upb_value_nop(void *closure, upb_value fval, upb_value val);
 upb_sflow_t upb_startsubmsg_nop(void *closure, upb_value fval);
 upb_flow_t upb_endsubmsg_nop(void *closure, upb_value fval);
 
-struct _upb_decoder;
-typedef struct _upb_fieldent {
-  bool junk;
-  upb_fieldtype_t type;
-  bool repeated;
-  bool is_repeated_primitive;
-  uint32_t number;
-  // For upb_issubmsg(f) only, the index into the msgdef array of the submsg.
-  // -1 if unset (indicates that submsg should be skipped).
-  int32_t msgent_index;
-  upb_value fval;
-  union {
-    upb_value_handler *value;
-    upb_startsubmsg_handler *startsubmsg;
-  } cb;
-  upb_endsubmsg_handler *endsubmsg;
-  uint32_t jit_pclabel;
-  uint32_t jit_pclabel_notypecheck;
-  uint32_t jit_submsg_done_pclabel;
-  void (*decode)(struct _upb_decoder *d, struct _upb_fieldent *f);
-} upb_fhandlers;
-
-typedef struct _upb_msgent {
+// Structure definitions.  Do not access any fields directly!  Accessors are
+// provided for the fields that may be get/set.
+typedef struct _upb_mhandlers {
   upb_startmsg_handler *startmsg;
   upb_endmsg_handler *endmsg;
-  // Maps field number -> upb_fhandlers.
-  upb_inttable fieldtab;
+  upb_inttable fieldtab;  // Maps field number -> upb_fhandlers.
   uint32_t jit_startmsg_pclabel;
   uint32_t jit_endofbuf_pclabel;
   uint32_t jit_endofmsg_pclabel;
@@ -147,25 +126,33 @@ typedef struct _upb_msgent {
   void **tablearray;
 } upb_mhandlers;
 
-typedef struct {
-  upb_msgdef *msgdef;
-  int msgent_index;
-} upb_handlers_frame;
+struct _upb_decoder;
+typedef struct _upb_fieldent {
+  bool junk;
+  upb_fieldtype_t type;
+  bool repeated;
+  bool is_repeated_primitive;
+  uint32_t number;
+  upb_mhandlers *submsg;  // Must be set iff upb_issubmsgtype(type) == true.
+  upb_value fval;
+  upb_value_handler *value;
+  upb_startsubmsg_handler *startsubmsg;
+  upb_endsubmsg_handler *endsubmsg;
+  uint32_t jit_pclabel;
+  uint32_t jit_pclabel_notypecheck;
+  uint32_t jit_submsg_done_pclabel;
+  void (*decode)(struct _upb_decoder *d, struct _upb_fieldent *f);
+} upb_fhandlers;
 
 struct _upb_handlers {
   // Array of msgdefs, [0]=toplevel.
-  upb_mhandlers *msgs;
+  upb_mhandlers **msgs;
   int msgs_len, msgs_size;
-  upb_msgdef *toplevel_msgdef;  // We own a ref.
-  upb_mhandlers *msgent;
-  upb_handlers_frame stack[UPB_MAX_TYPE_DEPTH], *top, *limit;
   bool should_jit;
 };
 typedef struct _upb_handlers upb_handlers;
 
-// The handlers object takes a ref on md.  md can be NULL iff the client calls
-// only upb_*_typed_*() (only upb_symtab should do this).
-void upb_handlers_init(upb_handlers *h, upb_msgdef *md);
+void upb_handlers_init(upb_handlers *h);
 void upb_handlers_uninit(upb_handlers *h);
 
 // The startsubmsg handler needs to also pass a closure to the submsg.
@@ -180,75 +167,84 @@ INLINE upb_sflow_t UPB_SFLOW(upb_flow_t flow, void *closure) {
 #define UPB_CONTINUE_WITH(c) UPB_SFLOW(UPB_CONTINUE, c)
 #define UPB_S_BREAK UPB_SFLOW(UPB_BREAK, NULL)
 
-// Functions to register the above handlers.
-void upb_register_startend(upb_handlers *h, upb_startmsg_handler *startmsg,
-                           upb_endmsg_handler *endmsg);
-void upb_register_value(upb_handlers *h, upb_fielddef *f,
-                        upb_value_handler *value, upb_value fval);
-
-// To register handlers for a submessage, push the fielddef and pop it
-// when you're done.  This can be used to delegate a submessage to a
-// different processing component which does not need to be aware whether
-// it is at the top level or not.
-void upb_handlers_push(upb_handlers *h, upb_fielddef *f,
-                       upb_startsubmsg_handler *start,
-                       upb_endsubmsg_handler *end, upb_value fval,
-                       bool delegate);
-void upb_handlers_pop(upb_handlers *h, upb_fielddef *f);
-
-// In the case where types are self-recursive or mutually recursive, you can
-// use this function which will link a set of handlers to a set that is
-// already on our stack.  This allows us to handle a tree of arbitrary
-// depth without having to register an arbitrary number of levels of handlers.
-// Returns "true" if the given type is indeed on the stack already and was
-// linked.
+// Appends a new message to the graph of handlers and returns it.  This message
+// can be obtained later at index upb_handlers_msgcount()-1.  All handlers will
+// be initialized to no-op handlers.
+upb_mhandlers *upb_handlers_newmsg(upb_handlers *h);
+upb_mhandlers *upb_handlers_getmsg(upb_handlers *h, int index);
+
+// Creates a new field with the given name and number.  There must not be an
+// existing field with either this name or number or abort() will be called.
+// TODO: this should take a name also.
+upb_fhandlers *upb_mhandlers_newfield(upb_mhandlers *m, uint32_t n,
+                                      upb_fieldtype_t type, bool repeated);
+// Like the previous but for MESSAGE or GROUP fields.  For GROUP fields, the
+// given submessage must not have any fields with this field number.
+upb_fhandlers *upb_mhandlers_newsubmsgfield(upb_mhandlers *m, uint32_t n,
+                                            upb_fieldtype_t type, bool repeated,
+                                            upb_mhandlers *subm);
+
+// upb_mhandlers accessors.
+#define UPB_MHANDLERS_ACCESSORS(name, type) \
+  INLINE void upb_mhandlers_set ## name(upb_mhandlers *m, type v){m->name = v;} \
+  INLINE type upb_mhandlers_get ## name(upb_mhandlers *m) { return m->name; }
+UPB_MHANDLERS_ACCESSORS(startmsg, upb_startmsg_handler*);
+UPB_MHANDLERS_ACCESSORS(endmsg, upb_endmsg_handler*);
+
+// upb_fhandlers accessors
+#define UPB_FHANDLERS_ACCESSORS(name, type) \
+  INLINE void upb_fhandlers_set ## name(upb_fhandlers *f, type v){f->name = v;} \
+  INLINE type upb_fhandlers_get ## name(upb_fhandlers *f) { return f->name; }
+UPB_FHANDLERS_ACCESSORS(fval, upb_value)
+UPB_FHANDLERS_ACCESSORS(value, upb_value_handler*)
+UPB_FHANDLERS_ACCESSORS(startsubmsg, upb_startsubmsg_handler*)
+UPB_FHANDLERS_ACCESSORS(endsubmsg, upb_endsubmsg_handler*)
+UPB_FHANDLERS_ACCESSORS(submsg, upb_mhandlers*)
+
+// Convenience function for registering handlers for all messages and
+// fields in a msgdef and all its children.  For every registered message
+// "msgreg_cb" will be called with the newly-created mhandlers, and likewise
+// with "fieldreg_cb"
 //
-// If more than one message of this type is on the stack, it chooses the
-// one that is deepest in the tree (if necessary, we could give the caller
-// more control over this).
-bool upb_handlers_link(upb_handlers *h, upb_fielddef *f);
-
-// Convenience function for registering the given handler for the given
-// field path.  This will overwrite any startsubmsg handlers that were
-// previously registered along the path.  These can be overwritten again
-// later if desired.
-// TODO: upb_register_path_submsg()?
-void upb_register_path_value(upb_handlers *h, const char *path,
-                             upb_value_handler *value, upb_value fval);
-
-// Convenience function for registering a single set of handlers on every
-// message in our hierarchy.  mvals are bound to upb_msgdef* and fvals are
-// bound to upb_fielddef*.  Any of the handlers can be NULL.
-void upb_register_all(upb_handlers *h, upb_startmsg_handler *start,
-                      upb_endmsg_handler *end,
-                      upb_value_handler *value,
-                      upb_startsubmsg_handler *startsubmsg,
-                      upb_endsubmsg_handler *endsubmsg);
-
-// TODO: for clients that want to increase efficiency by preventing bytesrcs
-// from automatically being converted to strings in the value callback.
-// INLINE void upb_handlers_use_bytesrcs(upb_handlers *h, bool use_bytesrcs);
-
-// Low-level functions -- internal-only.
-void upb_register_typed_value(upb_handlers *h, upb_field_number_t fieldnum,
-                              upb_fieldtype_t type, bool repeated,
-                              upb_value_handler *value, upb_value fval);
-void upb_register_typed_submsg(upb_handlers *h, upb_field_number_t fieldnum,
-                               upb_fieldtype_t type, bool repeated,
-                               upb_startsubmsg_handler *start,
-                               upb_endsubmsg_handler *end,
-                               upb_value fval);
-void upb_handlers_typed_link(upb_handlers *h, upb_field_number_t fieldnum,
-                             upb_fieldtype_t type, bool repeated, int frames);
-void upb_handlers_typed_push(upb_handlers *h, upb_field_number_t fieldnum,
-                             upb_fieldtype_t type, bool repeated);
-void upb_handlers_typed_pop(upb_handlers *h);
-
-INLINE upb_mhandlers *upb_handlers_getmsgent(upb_handlers *h, upb_fhandlers *f) {
-  assert(f->msgent_index != -1);
-  return &h->msgs[f->msgent_index];
+// See upb_handlers_reghandlerset() below for an example.
+typedef void upb_onmsgreg(void *closure, upb_mhandlers *mh, upb_msgdef *m);
+typedef void upb_onfieldreg(void *closure, upb_fhandlers *mh, upb_fielddef *m);
+upb_mhandlers *upb_handlers_regmsgdef(upb_handlers *h, upb_msgdef *m,
+                                      upb_onmsgreg *msgreg_cb,
+                                      upb_onfieldreg *fieldreg_cb,
+                                      void *closure);
+
+// Convenience function for registering a set of handlers for all messages and
+// fields in a msgdef and its children, with the fval bound to the upb_fielddef.
+// Any of the handlers may be NULL, in which case no callback will be set and
+// the nop callback will be used.
+typedef struct {
+  upb_startmsg_handler *startmsg;
+  upb_endmsg_handler *endmsg;
+  upb_value_handler *value;
+  upb_startsubmsg_handler *startsubmsg;
+  upb_endsubmsg_handler *endsubmsg;
+} upb_handlerset;
+
+INLINE void upb_onmreg_hset(void *c, upb_mhandlers *mh, upb_msgdef *m) {
+  (void)m;
+  upb_handlerset *hs = (upb_handlerset*)c;
+  if (hs->startmsg) upb_mhandlers_setstartmsg(mh, hs->startmsg);
+  if (hs->endmsg) upb_mhandlers_setendmsg(mh, hs->endmsg);
+}
+INLINE void upb_onfreg_hset(void *c, upb_fhandlers *fh, upb_fielddef *f) {
+  upb_handlerset *hs = (upb_handlerset*)c;
+  if (hs->value) upb_fhandlers_setvalue(fh, hs->value);
+  if (hs->startsubmsg) upb_fhandlers_setstartsubmsg(fh, hs->startsubmsg);
+  if (hs->endsubmsg) upb_fhandlers_setendsubmsg(fh, hs->endsubmsg);
+  upb_value val;
+  upb_value_setfielddef(&val, f);
+  upb_fhandlers_setfval(fh, val);
+}
+INLINE upb_mhandlers *upb_handlers_reghandlerset(upb_handlers *h, upb_msgdef *m,
+                                                 upb_handlerset *hs) {
+  return upb_handlers_regmsgdef(h, m, &upb_onmreg_hset, &upb_onfreg_hset, hs);
 }
-upb_fhandlers *upb_handlers_lookup(upb_inttable *dispatch_table, upb_field_number_t fieldnum);
 
 
 /* upb_dispatcher *************************************************************/
@@ -338,7 +334,7 @@ upb_flow_t upb_dispatch_endsubmsg(upb_dispatcher *d);
 INLINE upb_flow_t upb_dispatch_value(upb_dispatcher *d, upb_fhandlers *f,
                                      upb_value val) {
   if (upb_dispatcher_skipping(d)) return UPB_SKIPSUBMSG;
-  upb_flow_t flow = f->cb.value(d->top->closure, f->fval, val);
+  upb_flow_t flow = f->value(d->top->closure, f->fval, val);
   if (flow != UPB_CONTINUE) {
     d->noframe_depth = d->current_depth + 1;
     d->skip_depth = (flow == UPB_BREAK) ? d->delegated_depth : d->current_depth;
diff --git a/src/upb_msg.c b/src/upb_msg.c
index 98147c8543..1115673801 100644
--- a/src/upb_msg.c
+++ b/src/upb_msg.c
@@ -461,55 +461,49 @@ upb_sflow_t upb_msgsink_startsubmsg_r(void *_m, upb_value _fval) {
   return UPB_CONTINUE_WITH(upb_msg_appendmsg(m, &f, &md));
 }
 
-void upb_msg_regdhandlers(upb_handlers *h) {
-  upb_register_all(h, NULL, NULL, NULL, NULL, NULL);
-  for (int i = 0; i < h->msgs_len; i++) {
-    upb_mhandlers *m = &h->msgs[i];
-    upb_inttable_iter iter = upb_inttable_begin(&m->fieldtab);
-    for(; !upb_inttable_done(iter);
-        iter = upb_inttable_next(&m->fieldtab, iter)) {
-      upb_fhandlers *fe = upb_inttable_iter_value(iter);
-      if (fe->type == UPB_TYPE_ENDGROUP) continue;
-      upb_fielddef *f = upb_value_getfielddef(fe->fval);
-      uint16_t msg_size = 0;
-      uint8_t set_flags_bytes = 0;
-      if (upb_issubmsg(f)) {
-        upb_msgdef *md = upb_downcast_msgdef(f->def);
-        msg_size = md->size;
-        set_flags_bytes = md->set_flags_bytes;
-      }
-      upb_value_setuint64(&fe->fval,
-          upb_msgsink_packfval(f->set_bit_offset, f->set_bit_mask,
-                               f->byte_offset, msg_size, set_flags_bytes));
+INLINE void upb_msg_onfreg(void *c, upb_fhandlers *fh, upb_fielddef *f) {
+  (void)c;
+  uint16_t msg_size = 0;
+  uint8_t set_flags_bytes = 0;
+  if (upb_issubmsg(f)) {
+    upb_msgdef *md = upb_downcast_msgdef(f->def);
+    msg_size = md->size;
+    set_flags_bytes = md->set_flags_bytes;
+  }
+  upb_value_setuint64(&fh->fval,
+      upb_msgsink_packfval(f->set_bit_offset, f->set_bit_mask,
+                           f->byte_offset, msg_size, set_flags_bytes));
 #define CASE(upb_type, type) \
-    case UPB_TYPE(upb_type): \
-        fe->cb.value = upb_isarray(f) ? \
-            upb_msgsink_ ## type ## value_r : upb_msgsink_ ## type ## value; \
-        break;
-      switch (f->type) {
-        CASE(DOUBLE,   double)
-        CASE(FLOAT,    float)
-        CASE(INT32,    int32)
-        CASE(INT64,    int64)
-        CASE(UINT32,   uint32)
-        CASE(UINT64,   uint64)
-        CASE(SINT32,   int32)
-        CASE(SINT64,   int64)
-        CASE(FIXED32,  uint32)
-        CASE(FIXED64,  uint64)
-        CASE(SFIXED32, int32)
-        CASE(SFIXED64, int64)
-        CASE(BOOL,     bool)
-        CASE(ENUM,     int32)
-        CASE(STRING,   str)
-        CASE(BYTES,    str)
+case UPB_TYPE(upb_type): \
+    fh->value = upb_isarray(f) ? \
+        upb_msgsink_ ## type ## value_r : upb_msgsink_ ## type ## value; \
+    break;
+  switch (f->type) {
+    CASE(DOUBLE,   double)
+    CASE(FLOAT,    float)
+    CASE(INT32,    int32)
+    CASE(INT64,    int64)
+    CASE(UINT32,   uint32)
+    CASE(UINT64,   uint64)
+    CASE(SINT32,   int32)
+    CASE(SINT64,   int64)
+    CASE(FIXED32,  uint32)
+    CASE(FIXED64,  uint64)
+    CASE(SFIXED32, int32)
+    CASE(SFIXED64, int64)
+    CASE(BOOL,     bool)
+    CASE(ENUM,     int32)
+    CASE(STRING,   str)
+    CASE(BYTES,    str)
 #undef CASE
-        case UPB_TYPE(MESSAGE):
-        case UPB_TYPE(GROUP):
-          fe->cb.startsubmsg =
-              upb_isarray(f) ? upb_msgsink_startsubmsg_r : upb_msgsink_startsubmsg;
-          break;
-      }
-    }
+    case UPB_TYPE(MESSAGE):
+    case UPB_TYPE(GROUP):
+      fh->startsubmsg =
+          upb_isarray(f) ? upb_msgsink_startsubmsg_r : upb_msgsink_startsubmsg;
+      break;
   }
 }
+
+upb_mhandlers *upb_msg_reghandlers(upb_handlers *h, upb_msgdef *m) {
+  return upb_handlers_regmsgdef(h, m, NULL, &upb_msg_onfreg, NULL);
+}
diff --git a/src/upb_msg.h b/src/upb_msg.h
index 68ba13ae4b..33f5d1cc4d 100644
--- a/src/upb_msg.h
+++ b/src/upb_msg.h
@@ -277,11 +277,7 @@ INLINE void upb_msg_clear(upb_msg *msg, upb_msgdef *md) {
 
 // Registers handlers for populating a msg for the given upb_msgdef.
 // The upb_msg itself must be passed as the param to the src.
-void upb_msg_reghandlers(upb_handlers *h, upb_msgdef *md);
-
-// Registers handlers that are suitable for populating a msg of *any*
-// upb_msgdef ("dynamic" handlers).  May be slower than upb_msg_reghandlers().
-void upb_msg_regdhandlers(upb_handlers *h);
+upb_mhandlers *upb_msg_reghandlers(upb_handlers *h, upb_msgdef *md);
 
 void upb_msg_runhandlers(upb_msg *msg, upb_msgdef *md, upb_handlers *h,
                          void *closure, upb_status *status);
diff --git a/src/upb_textprinter.c b/src/upb_textprinter.c
index 2f3a6b5a4f..7d0a9dd21d 100644
--- a/src/upb_textprinter.c
+++ b/src/upb_textprinter.c
@@ -185,12 +185,13 @@ void upb_textprinter_reset(upb_textprinter *p, upb_bytesink *sink,
   p->indent_depth = 0;
 }
 
-void upb_textprinter_reghandlers(upb_handlers *h) {
-  upb_register_all(h,
+upb_mhandlers *upb_textprinter_reghandlers(upb_handlers *h, upb_msgdef *m) {
+  upb_handlerset hset = {
     NULL,  // startmsg
     NULL,  // endmsg
     upb_textprinter_value,
     upb_textprinter_startsubmsg,
     upb_textprinter_endsubmsg
-  );
+  };
+  return upb_handlers_reghandlerset(h, m, &hset);
 }
diff --git a/src/upb_textprinter.h b/src/upb_textprinter.h
index f8c7f782f5..2d70d2e124 100644
--- a/src/upb_textprinter.h
+++ b/src/upb_textprinter.h
@@ -22,7 +22,7 @@ upb_textprinter *upb_textprinter_new();
 void upb_textprinter_free(upb_textprinter *p);
 void upb_textprinter_reset(upb_textprinter *p, upb_bytesink *sink,
                            bool single_line);
-void upb_textprinter_reghandlers(upb_handlers *h);
+upb_mhandlers *upb_textprinter_reghandlers(upb_handlers *h, upb_msgdef *m);
 
 #ifdef __cplusplus
 }  /* extern "C" */
diff --git a/tests/tests.c b/tests/tests.c
index d07d495b3d..dea535c889 100644
--- a/tests/tests.c
+++ b/tests/tests.c
@@ -39,8 +39,9 @@ static void test_upb_jit() {
   ASSERT(def);
 
   upb_handlers h;
-  upb_handlers_init(&h, upb_downcast_msgdef(def));
-  upb_register_all(&h, NULL, NULL, &upb_test_onvalue, NULL, NULL);
+  upb_handlers_init(&h);
+  upb_handlerset hset = {NULL, NULL, &upb_test_onvalue, NULL, NULL};
+  upb_handlers_reghandlerset(&h, upb_downcast_msgdef(def), &hset);
   upb_decoder d;
   upb_decoder_init(&d, &h);
   upb_decoder_uninit(&d);