diff --git a/upb/mini_table/file.h b/upb/mini_table/file.h
index 590164f72f..db8d22cf76 100644
--- a/upb/mini_table/file.h
+++ b/upb/mini_table/file.h
@@ -12,4 +12,45 @@
 
 typedef struct upb_MiniTableFile upb_MiniTableFile;
 
+// Must be last.
+#include "upb/port/def.inc"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+UPB_API_INLINE const struct upb_MiniTableEnum* upb_MiniTableFile_Enum(
+    const upb_MiniTableFile* f, int i) {
+  return UPB_PRIVATE(_upb_MiniTableFile_Enum)(f, i);
+}
+
+UPB_API_INLINE int upb_MiniTableFile_EnumCount(const upb_MiniTableFile* f) {
+  return UPB_PRIVATE(_upb_MiniTableFile_EnumCount)(f);
+}
+
+UPB_API_INLINE const struct upb_MiniTableExtension* upb_MiniTableFile_Extension(
+    const upb_MiniTableFile* f, int i) {
+  return UPB_PRIVATE(_upb_MiniTableFile_Extension)(f, i);
+}
+
+UPB_API_INLINE int upb_MiniTableFile_ExtensionCount(
+    const upb_MiniTableFile* f) {
+  return UPB_PRIVATE(_upb_MiniTableFile_ExtensionCount)(f);
+}
+
+UPB_API_INLINE const struct upb_MiniTable* upb_MiniTableFile_Message(
+    const upb_MiniTableFile* f, int i) {
+  return UPB_PRIVATE(_upb_MiniTableFile_Message)(f, i);
+}
+
+UPB_API_INLINE int upb_MiniTableFile_MessageCount(const upb_MiniTableFile* f) {
+  return UPB_PRIVATE(_upb_MiniTableFile_MessageCount)(f);
+}
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#include "upb/port/undef.inc"
+
 #endif /* UPB_MINI_TABLE_FILE_H_ */
diff --git a/upb/mini_table/internal/file.h b/upb/mini_table/internal/file.h
index a8a3343197..0afabcf1b3 100644
--- a/upb/mini_table/internal/file.h
+++ b/upb/mini_table/internal/file.h
@@ -12,14 +12,55 @@
 #include "upb/port/def.inc"
 
 struct upb_MiniTableFile {
-  const struct upb_MiniTable** msgs;
-  const struct upb_MiniTableEnum** enums;
-  const struct upb_MiniTableExtension** exts;
-  int msg_count;
-  int enum_count;
-  int ext_count;
+  const struct upb_MiniTable** UPB_PRIVATE(msgs);
+  const struct upb_MiniTableEnum** UPB_PRIVATE(enums);
+  const struct upb_MiniTableExtension** UPB_PRIVATE(exts);
+  int UPB_PRIVATE(msg_count);
+  int UPB_PRIVATE(enum_count);
+  int UPB_PRIVATE(ext_count);
 };
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+UPB_INLINE int UPB_PRIVATE(_upb_MiniTableFile_EnumCount)(
+    const struct upb_MiniTableFile* f) {
+  return f->UPB_PRIVATE(enum_count);
+}
+
+UPB_INLINE int UPB_PRIVATE(_upb_MiniTableFile_ExtensionCount)(
+    const struct upb_MiniTableFile* f) {
+  return f->UPB_PRIVATE(ext_count);
+}
+
+UPB_INLINE int UPB_PRIVATE(_upb_MiniTableFile_MessageCount)(
+    const struct upb_MiniTableFile* f) {
+  return f->UPB_PRIVATE(msg_count);
+}
+
+UPB_INLINE const struct upb_MiniTableEnum* UPB_PRIVATE(_upb_MiniTableFile_Enum)(
+    const struct upb_MiniTableFile* f, int i) {
+  UPB_ASSERT(i < f->UPB_PRIVATE(enum_count));
+  return f->UPB_PRIVATE(enums)[i];
+}
+
+UPB_INLINE const struct upb_MiniTableExtension* UPB_PRIVATE(
+    _upb_MiniTableFile_Extension)(const struct upb_MiniTableFile* f, int i) {
+  UPB_ASSERT(i < f->UPB_PRIVATE(ext_count));
+  return f->UPB_PRIVATE(exts)[i];
+}
+
+UPB_INLINE const struct upb_MiniTable* UPB_PRIVATE(_upb_MiniTableFile_Message)(
+    const struct upb_MiniTableFile* f, int i) {
+  UPB_ASSERT(i < f->UPB_PRIVATE(msg_count));
+  return f->UPB_PRIVATE(msgs)[i];
+}
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
 #include "upb/port/undef.inc"
 
 #endif /* UPB_MINI_TABLE_INTERNAL_FILE_H_ */
diff --git a/upb/reflection/BUILD b/upb/reflection/BUILD
index f6ea369d06..4880c23727 100644
--- a/upb/reflection/BUILD
+++ b/upb/reflection/BUILD
@@ -140,6 +140,7 @@ bootstrap_cc_library(
         "//upb:mini_descriptor",
         "//upb:mini_descriptor_internal",
         "//upb:mini_table",
+        "//upb:mini_table_internal",
         "//upb:port",
         "//upb/base:internal",
     ],
diff --git a/upb/reflection/enum_def.c b/upb/reflection/enum_def.c
index 2b44fd05fc..de85cbd9b1 100644
--- a/upb/reflection/enum_def.c
+++ b/upb/reflection/enum_def.c
@@ -7,16 +7,27 @@
 
 #include "upb/reflection/internal/enum_def.h"
 
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "upb/base/status.h"
+#include "upb/base/string_view.h"
+#include "upb/hash/common.h"
 #include "upb/hash/int_table.h"
 #include "upb/hash/str_table.h"
+#include "upb/mem/arena.h"
 #include "upb/mini_descriptor/decode.h"
+#include "upb/mini_descriptor/internal/encode.h"
+#include "upb/mini_table/enum.h"
+#include "upb/mini_table/file.h"
+#include "upb/reflection/def.h"
 #include "upb/reflection/def_type.h"
 #include "upb/reflection/internal/def_builder.h"
 #include "upb/reflection/internal/desc_state.h"
 #include "upb/reflection/internal/enum_reserved_range.h"
 #include "upb/reflection/internal/enum_value_def.h"
 #include "upb/reflection/internal/file_def.h"
-#include "upb/reflection/internal/message_def.h"
 #include "upb/reflection/internal/strdup2.h"
 
 // Must be last.
@@ -274,8 +285,7 @@ static void create_enumdef(upb_DefBuilder* ctx, const char* prefix,
 
   if (upb_EnumDef_IsClosed(e)) {
     if (ctx->layout) {
-      UPB_ASSERT(ctx->enum_count < ctx->layout->enum_count);
-      e->layout = ctx->layout->enums[ctx->enum_count++];
+      e->layout = upb_MiniTableFile_Enum(ctx->layout, ctx->enum_count++);
     } else {
       e->layout = create_enumlayout(ctx, e);
     }
diff --git a/upb/reflection/file_def.c b/upb/reflection/file_def.c
index 6b836f83a6..e287d7efa3 100644
--- a/upb/reflection/file_def.c
+++ b/upb/reflection/file_def.c
@@ -8,9 +8,16 @@
 #include "upb/reflection/internal/file_def.h"
 
 #include <stddef.h>
-
-#include "upb/reflection/def_pool.h"
+#include <stdint.h>
+#include <string.h>
+
+#include "upb/base/string_view.h"
+#include "upb/mini_table/extension.h"
+#include "upb/mini_table/extension_registry.h"
+#include "upb/mini_table/file.h"
+#include "upb/reflection/def.h"
 #include "upb/reflection/internal/def_builder.h"
+#include "upb/reflection/internal/def_pool.h"
 #include "upb/reflection/internal/enum_def.h"
 #include "upb/reflection/internal/field_def.h"
 #include "upb/reflection/internal/message_def.h"
@@ -258,11 +265,12 @@ void _upb_FileDef_Create(upb_DefBuilder* ctx,
 
   if (ctx->layout) {
     // We are using the ext layouts that were passed in.
-    file->ext_layouts = ctx->layout->exts;
-    if (ctx->layout->ext_count != file->ext_count) {
+    file->ext_layouts = ctx->layout->UPB_PRIVATE(exts);
+    const int mt_ext_count = upb_MiniTableFile_ExtensionCount(ctx->layout);
+    if (mt_ext_count != file->ext_count) {
       _upb_DefBuilder_Errf(ctx,
                            "Extension count did not match layout (%d vs %d)",
-                           ctx->layout->ext_count, file->ext_count);
+                           mt_ext_count, file->ext_count);
     }
   } else {
     // We are building ext layouts from scratch.
diff --git a/upb/reflection/message_def.c b/upb/reflection/message_def.c
index a51481a76b..2d5497acab 100644
--- a/upb/reflection/message_def.c
+++ b/upb/reflection/message_def.c
@@ -7,13 +7,22 @@
 
 #include "upb/reflection/internal/message_def.h"
 
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
 #include "upb/base/descriptor_constants.h"
+#include "upb/base/string_view.h"
+#include "upb/hash/common.h"
 #include "upb/hash/int_table.h"
 #include "upb/hash/str_table.h"
+#include "upb/mem/arena.h"
 #include "upb/mini_descriptor/decode.h"
+#include "upb/mini_descriptor/internal/encode.h"
 #include "upb/mini_descriptor/internal/modifiers.h"
+#include "upb/mini_table/file.h"
+#include "upb/mini_table/message.h"
 #include "upb/reflection/def.h"
-#include "upb/reflection/def_type.h"
 #include "upb/reflection/internal/def_builder.h"
 #include "upb/reflection/internal/desc_state.h"
 #include "upb/reflection/internal/enum_def.h"
@@ -436,8 +445,7 @@ void _upb_MessageDef_CreateMiniTable(upb_DefBuilder* ctx, upb_MessageDef* m) {
   if (ctx->layout == NULL) {
     m->layout = _upb_MessageDef_MakeMiniTable(ctx, m);
   } else {
-    UPB_ASSERT(ctx->msg_count < ctx->layout->msg_count);
-    m->layout = ctx->layout->msgs[ctx->msg_count++];
+    m->layout = upb_MiniTableFile_Message(ctx->layout, ctx->msg_count++);
     UPB_ASSERT(m->field_count == m->layout->field_count);
 
     // We don't need the result of this call, but it will assign layout_index