diff --git a/csharp/src/Google.Protobuf.Test/testprotos.pb b/csharp/src/Google.Protobuf.Test/testprotos.pb
index 9ecd4afc68..0f39b3822d 100644
Binary files a/csharp/src/Google.Protobuf.Test/testprotos.pb and b/csharp/src/Google.Protobuf.Test/testprotos.pb differ
diff --git a/csharp/src/Google.Protobuf/Reflection/Descriptor.pb.cs b/csharp/src/Google.Protobuf/Reflection/Descriptor.pb.cs
index 2b91751a18..a3b2dae49c 100644
--- a/csharp/src/Google.Protobuf/Reflection/Descriptor.pb.cs
+++ b/csharp/src/Google.Protobuf/Reflection/Descriptor.pb.cs
@@ -236,16 +236,17 @@ namespace Google.Protobuf.Reflection {
             "Cgtzb3VyY2VfZmlsZRgCIAEoCRINCgViZWdpbhgDIAEoBRILCgNlbmQYBCAB",
             "KAUSSAoIc2VtYW50aWMYBSABKA4yNi5nb29nbGUucHJvdG9idWYuR2VuZXJh",
             "dGVkQ29kZUluZm8uQW5ub3RhdGlvbi5TZW1hbnRpYyIoCghTZW1hbnRpYxII",
-            "CgROT05FEAASBwoDU0VUEAESCQoFQUxJQVMQAiqSAgoHRWRpdGlvbhITCg9F",
-            "RElUSU9OX1VOS05PV04QABITCg5FRElUSU9OX1BST1RPMhDmBxITCg5FRElU",
-            "SU9OX1BST1RPMxDnBxIRCgxFRElUSU9OXzIwMjMQ6AcSEQoMRURJVElPTl8y",
-            "MDI0EOkHEhcKE0VESVRJT05fMV9URVNUX09OTFkQARIXChNFRElUSU9OXzJf",
-            "VEVTVF9PTkxZEAISHQoXRURJVElPTl85OTk5N19URVNUX09OTFkQnY0GEh0K",
-            "F0VESVRJT05fOTk5OThfVEVTVF9PTkxZEJ6NBhIdChdFRElUSU9OXzk5OTk5",
-            "X1RFU1RfT05MWRCfjQYSEwoLRURJVElPTl9NQVgQ/////wdCfgoTY29tLmdv",
-            "b2dsZS5wcm90b2J1ZkIQRGVzY3JpcHRvclByb3Rvc0gBWi1nb29nbGUuZ29s",
-            "YW5nLm9yZy9wcm90b2J1Zi90eXBlcy9kZXNjcmlwdG9ycGL4AQGiAgNHUEKq",
-            "AhpHb29nbGUuUHJvdG9idWYuUmVmbGVjdGlvbg=="));
+            "CgROT05FEAASBwoDU0VUEAESCQoFQUxJQVMQAiqnAgoHRWRpdGlvbhITCg9F",
+            "RElUSU9OX1VOS05PV04QABITCg5FRElUSU9OX0xFR0FDWRCEBxITCg5FRElU",
+            "SU9OX1BST1RPMhDmBxITCg5FRElUSU9OX1BST1RPMxDnBxIRCgxFRElUSU9O",
+            "XzIwMjMQ6AcSEQoMRURJVElPTl8yMDI0EOkHEhcKE0VESVRJT05fMV9URVNU",
+            "X09OTFkQARIXChNFRElUSU9OXzJfVEVTVF9PTkxZEAISHQoXRURJVElPTl85",
+            "OTk5N19URVNUX09OTFkQnY0GEh0KF0VESVRJT05fOTk5OThfVEVTVF9PTkxZ",
+            "EJ6NBhIdChdFRElUSU9OXzk5OTk5X1RFU1RfT05MWRCfjQYSEwoLRURJVElP",
+            "Tl9NQVgQ/////wdCfgoTY29tLmdvb2dsZS5wcm90b2J1ZkIQRGVzY3JpcHRv",
+            "clByb3Rvc0gBWi1nb29nbGUuZ29sYW5nLm9yZy9wcm90b2J1Zi90eXBlcy9k",
+            "ZXNjcmlwdG9ycGL4AQGiAgNHUEKqAhpHb29nbGUuUHJvdG9idWYuUmVmbGVj",
+            "dGlvbg=="));
       descriptor = pbr::FileDescriptor.FromGeneratedCode(descriptorData,
           new pbr::FileDescriptor[] { },
           new pbr::GeneratedClrTypeInfo(new[] {typeof(global::Google.Protobuf.Reflection.Edition), }, null, new pbr::GeneratedClrTypeInfo[] {
@@ -289,6 +290,11 @@ namespace Google.Protobuf.Reflection {
     /// </summary>
     [pbr::OriginalName("EDITION_UNKNOWN")] Unknown = 0,
     /// <summary>
+    /// A placeholder edition for specifying default behaviors *before* a feature
+    /// was first introduced.  This is effectively an "infinite past".
+    /// </summary>
+    [pbr::OriginalName("EDITION_LEGACY")] Legacy = 900,
+    /// <summary>
     /// Legacy syntax "editions".  These pre-date editions, but behave much like
     /// distinct editions.  These can't be used to specify the edition of proto
     /// files, but feature definitions must supply proto2/proto3 defaults for
diff --git a/php/ext/google/protobuf/php-upb.c b/php/ext/google/protobuf/php-upb.c
index 142344cf5a..88f11bc2bd 100644
--- a/php/ext/google/protobuf/php-upb.c
+++ b/php/ext/google/protobuf/php-upb.c
@@ -1569,10 +1569,11 @@ static const upb_MiniTable *messages_layout[33] = {
 
 const upb_MiniTableEnum google_protobuf_Edition_enum_init = {
     64,
-    8,
+    9,
     {
         0x7,
         0x0,
+        0x384,
         0x3e6,
         0x3e7,
         0x3e8,
@@ -1766,7 +1767,7 @@ const upb_MiniTableFile google_protobuf_descriptor_proto_upb_file_layout = {
  * regenerated. */
 
 
-static const char descriptor[12154] = {'\n', ' ', 'g', 'o', 'o', 'g', 'l', 'e', '/', 'p', 'r', 'o', 't', 'o', 'b', 'u', 'f', '/', 'd', 'e', 's', 'c', 'r', 'i', 'p', 
+static const char descriptor[12175] = {'\n', ' ', 'g', 'o', 'o', 'g', 'l', 'e', '/', 'p', 'r', 'o', 't', 'o', 'b', 'u', 'f', '/', 'd', 'e', 's', 'c', 'r', 'i', 'p', 
 't', 'o', 'r', '.', 'p', 'r', 'o', 't', 'o', '\022', '\017', 'g', 'o', 'o', 'g', 'l', 'e', '.', 'p', 'r', 'o', 't', 'o', 'b', 'u', 
 'f', '\"', 'M', '\n', '\021', 'F', 'i', 'l', 'e', 'D', 'e', 's', 'c', 'r', 'i', 'p', 't', 'o', 'r', 'S', 'e', 't', '\022', '8', '\n', 
 '\004', 'f', 'i', 'l', 'e', '\030', '\001', ' ', '\003', '(', '\013', '2', '$', '.', 'g', 'o', 'o', 'g', 'l', 'e', '.', 'p', 'r', 'o', 't', 
@@ -2236,23 +2237,23 @@ static const char descriptor[12154] = {'\n', ' ', 'g', 'o', 'o', 'g', 'l', 'e',
 'f', 'o', '.', 'A', 'n', 'n', 'o', 't', 'a', 't', 'i', 'o', 'n', '.', 'S', 'e', 'm', 'a', 'n', 't', 'i', 'c', 'R', '\010', 's', 
 'e', 'm', 'a', 'n', 't', 'i', 'c', '\"', '(', '\n', '\010', 'S', 'e', 'm', 'a', 'n', 't', 'i', 'c', '\022', '\010', '\n', '\004', 'N', 'O', 
 'N', 'E', '\020', '\000', '\022', '\007', '\n', '\003', 'S', 'E', 'T', '\020', '\001', '\022', '\t', '\n', '\005', 'A', 'L', 'I', 'A', 'S', '\020', '\002', '*', 
-'\222', '\002', '\n', '\007', 'E', 'd', 'i', 't', 'i', 'o', 'n', '\022', '\023', '\n', '\017', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', 'U', 'N', 
-'K', 'N', 'O', 'W', 'N', '\020', '\000', '\022', '\023', '\n', '\016', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', 'P', 'R', 'O', 'T', 'O', '2', 
-'\020', '\346', '\007', '\022', '\023', '\n', '\016', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', 'P', 'R', 'O', 'T', 'O', '3', '\020', '\347', '\007', '\022', 
-'\021', '\n', '\014', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', '2', '0', '2', '3', '\020', '\350', '\007', '\022', '\021', '\n', '\014', 'E', 'D', 'I', 
-'T', 'I', 'O', 'N', '_', '2', '0', '2', '4', '\020', '\351', '\007', '\022', '\027', '\n', '\023', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', '1', 
-'_', 'T', 'E', 'S', 'T', '_', 'O', 'N', 'L', 'Y', '\020', '\001', '\022', '\027', '\n', '\023', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', '2', 
-'_', 'T', 'E', 'S', 'T', '_', 'O', 'N', 'L', 'Y', '\020', '\002', '\022', '\035', '\n', '\027', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', '9', 
-'9', '9', '9', '7', '_', 'T', 'E', 'S', 'T', '_', 'O', 'N', 'L', 'Y', '\020', '\235', '\215', '\006', '\022', '\035', '\n', '\027', 'E', 'D', 'I', 
-'T', 'I', 'O', 'N', '_', '9', '9', '9', '9', '8', '_', 'T', 'E', 'S', 'T', '_', 'O', 'N', 'L', 'Y', '\020', '\236', '\215', '\006', '\022', 
-'\035', '\n', '\027', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', '9', '9', '9', '9', '9', '_', 'T', 'E', 'S', 'T', '_', 'O', 'N', 'L', 
-'Y', '\020', '\237', '\215', '\006', '\022', '\023', '\n', '\013', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', 'M', 'A', 'X', '\020', '\377', '\377', '\377', '\377', 
-'\007', 'B', '~', '\n', '\023', 'c', 'o', 'm', '.', 'g', 'o', 'o', 'g', 'l', 'e', '.', 'p', 'r', 'o', 't', 'o', 'b', 'u', 'f', 'B', 
-'\020', 'D', 'e', 's', 'c', 'r', 'i', 'p', 't', 'o', 'r', 'P', 'r', 'o', 't', 'o', 's', 'H', '\001', 'Z', '-', 'g', 'o', 'o', 'g', 
-'l', 'e', '.', 'g', 'o', 'l', 'a', 'n', 'g', '.', 'o', 'r', 'g', '/', 'p', 'r', 'o', 't', 'o', 'b', 'u', 'f', '/', 't', 'y', 
-'p', 'e', 's', '/', 'd', 'e', 's', 'c', 'r', 'i', 'p', 't', 'o', 'r', 'p', 'b', '\370', '\001', '\001', '\242', '\002', '\003', 'G', 'P', 'B', 
-'\252', '\002', '\032', 'G', 'o', 'o', 'g', 'l', 'e', '.', 'P', 'r', 'o', 't', 'o', 'b', 'u', 'f', '.', 'R', 'e', 'f', 'l', 'e', 'c', 
-'t', 'i', 'o', 'n', 
+'\247', '\002', '\n', '\007', 'E', 'd', 'i', 't', 'i', 'o', 'n', '\022', '\023', '\n', '\017', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', 'U', 'N', 
+'K', 'N', 'O', 'W', 'N', '\020', '\000', '\022', '\023', '\n', '\016', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', 'L', 'E', 'G', 'A', 'C', 'Y', 
+'\020', '\204', '\007', '\022', '\023', '\n', '\016', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', 'P', 'R', 'O', 'T', 'O', '2', '\020', '\346', '\007', '\022', 
+'\023', '\n', '\016', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', 'P', 'R', 'O', 'T', 'O', '3', '\020', '\347', '\007', '\022', '\021', '\n', '\014', 'E', 
+'D', 'I', 'T', 'I', 'O', 'N', '_', '2', '0', '2', '3', '\020', '\350', '\007', '\022', '\021', '\n', '\014', 'E', 'D', 'I', 'T', 'I', 'O', 'N', 
+'_', '2', '0', '2', '4', '\020', '\351', '\007', '\022', '\027', '\n', '\023', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', '1', '_', 'T', 'E', 'S', 
+'T', '_', 'O', 'N', 'L', 'Y', '\020', '\001', '\022', '\027', '\n', '\023', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', '2', '_', 'T', 'E', 'S', 
+'T', '_', 'O', 'N', 'L', 'Y', '\020', '\002', '\022', '\035', '\n', '\027', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', '9', '9', '9', '9', '7', 
+'_', 'T', 'E', 'S', 'T', '_', 'O', 'N', 'L', 'Y', '\020', '\235', '\215', '\006', '\022', '\035', '\n', '\027', 'E', 'D', 'I', 'T', 'I', 'O', 'N', 
+'_', '9', '9', '9', '9', '8', '_', 'T', 'E', 'S', 'T', '_', 'O', 'N', 'L', 'Y', '\020', '\236', '\215', '\006', '\022', '\035', '\n', '\027', 'E', 
+'D', 'I', 'T', 'I', 'O', 'N', '_', '9', '9', '9', '9', '9', '_', 'T', 'E', 'S', 'T', '_', 'O', 'N', 'L', 'Y', '\020', '\237', '\215', 
+'\006', '\022', '\023', '\n', '\013', 'E', 'D', 'I', 'T', 'I', 'O', 'N', '_', 'M', 'A', 'X', '\020', '\377', '\377', '\377', '\377', '\007', 'B', '~', '\n', 
+'\023', 'c', 'o', 'm', '.', 'g', 'o', 'o', 'g', 'l', 'e', '.', 'p', 'r', 'o', 't', 'o', 'b', 'u', 'f', 'B', '\020', 'D', 'e', 's', 
+'c', 'r', 'i', 'p', 't', 'o', 'r', 'P', 'r', 'o', 't', 'o', 's', 'H', '\001', 'Z', '-', 'g', 'o', 'o', 'g', 'l', 'e', '.', 'g', 
+'o', 'l', 'a', 'n', 'g', '.', 'o', 'r', 'g', '/', 'p', 'r', 'o', 't', 'o', 'b', 'u', 'f', '/', 't', 'y', 'p', 'e', 's', '/', 
+'d', 'e', 's', 'c', 'r', 'i', 'p', 't', 'o', 'r', 'p', 'b', '\370', '\001', '\001', '\242', '\002', '\003', 'G', 'P', 'B', '\252', '\002', '\032', 'G', 
+'o', 'o', 'g', 'l', 'e', '.', 'P', 'r', 'o', 't', 'o', 'b', 'u', 'f', '.', 'R', 'e', 'f', 'l', 'e', 'c', 't', 'i', 'o', 'n', 
 };
 
 static _upb_DefPool_Init *deps[1] = {
@@ -2263,7 +2264,7 @@ _upb_DefPool_Init google_protobuf_descriptor_proto_upbdefinit = {
   deps,
   &google_protobuf_descriptor_proto_upb_file_layout,
   "google/protobuf/descriptor.proto",
-  UPB_STRINGVIEW_INIT(descriptor, 12154)
+  UPB_STRINGVIEW_INIT(descriptor, 12175)
 };
 
 
diff --git a/php/ext/google/protobuf/php-upb.h b/php/ext/google/protobuf/php-upb.h
index 74a77ba658..820add1527 100644
--- a/php/ext/google/protobuf/php-upb.h
+++ b/php/ext/google/protobuf/php-upb.h
@@ -4545,6 +4545,7 @@ typedef enum {
   google_protobuf_EDITION_UNKNOWN = 0,
   google_protobuf_EDITION_1_TEST_ONLY = 1,
   google_protobuf_EDITION_2_TEST_ONLY = 2,
+  google_protobuf_EDITION_LEGACY = 900,
   google_protobuf_EDITION_PROTO2 = 998,
   google_protobuf_EDITION_PROTO3 = 999,
   google_protobuf_EDITION_2023 = 1000,
diff --git a/ruby/ext/google/protobuf_c/ruby-upb.c b/ruby/ext/google/protobuf_c/ruby-upb.c
index a34b081ef8..626d988fdb 100644
--- a/ruby/ext/google/protobuf_c/ruby-upb.c
+++ b/ruby/ext/google/protobuf_c/ruby-upb.c
@@ -1569,10 +1569,11 @@ static const upb_MiniTable *messages_layout[33] = {
 
 const upb_MiniTableEnum google_protobuf_Edition_enum_init = {
     64,
-    8,
+    9,
     {
         0x7,
         0x0,
+        0x384,
         0x3e6,
         0x3e7,
         0x3e8,
diff --git a/ruby/ext/google/protobuf_c/ruby-upb.h b/ruby/ext/google/protobuf_c/ruby-upb.h
index 06bf3a9865..60196a0637 100755
--- a/ruby/ext/google/protobuf_c/ruby-upb.h
+++ b/ruby/ext/google/protobuf_c/ruby-upb.h
@@ -4947,6 +4947,7 @@ typedef enum {
   google_protobuf_EDITION_UNKNOWN = 0,
   google_protobuf_EDITION_1_TEST_ONLY = 1,
   google_protobuf_EDITION_2_TEST_ONLY = 2,
+  google_protobuf_EDITION_LEGACY = 900,
   google_protobuf_EDITION_PROTO2 = 998,
   google_protobuf_EDITION_PROTO3 = 999,
   google_protobuf_EDITION_2023 = 1000,
diff --git a/upb/cmake/google/protobuf/descriptor.upb.h b/upb/cmake/google/protobuf/descriptor.upb.h
index 8cbca671de..81d1d3d96f 100644
--- a/upb/cmake/google/protobuf/descriptor.upb.h
+++ b/upb/cmake/google/protobuf/descriptor.upb.h
@@ -57,6 +57,7 @@ typedef enum {
   google_protobuf_EDITION_UNKNOWN = 0,
   google_protobuf_EDITION_1_TEST_ONLY = 1,
   google_protobuf_EDITION_2_TEST_ONLY = 2,
+  google_protobuf_EDITION_LEGACY = 900,
   google_protobuf_EDITION_PROTO2 = 998,
   google_protobuf_EDITION_PROTO3 = 999,
   google_protobuf_EDITION_2023 = 1000,
diff --git a/upb/cmake/google/protobuf/descriptor.upb_minitable.c b/upb/cmake/google/protobuf/descriptor.upb_minitable.c
index d09c175145..1cc463de95 100644
--- a/upb/cmake/google/protobuf/descriptor.upb_minitable.c
+++ b/upb/cmake/google/protobuf/descriptor.upb_minitable.c
@@ -1171,10 +1171,11 @@ static const upb_MiniTable *messages_layout[33] = {
 
 const upb_MiniTableEnum google_protobuf_Edition_enum_init = {
     64,
-    8,
+    9,
     {
         0x7,
         0x0,
+        0x384,
         0x3e6,
         0x3e7,
         0x3e8,
diff --git a/upb/reflection/cmake/google/protobuf/descriptor.upb.h b/upb/reflection/cmake/google/protobuf/descriptor.upb.h
index 8cbca671de..81d1d3d96f 100644
--- a/upb/reflection/cmake/google/protobuf/descriptor.upb.h
+++ b/upb/reflection/cmake/google/protobuf/descriptor.upb.h
@@ -57,6 +57,7 @@ typedef enum {
   google_protobuf_EDITION_UNKNOWN = 0,
   google_protobuf_EDITION_1_TEST_ONLY = 1,
   google_protobuf_EDITION_2_TEST_ONLY = 2,
+  google_protobuf_EDITION_LEGACY = 900,
   google_protobuf_EDITION_PROTO2 = 998,
   google_protobuf_EDITION_PROTO3 = 999,
   google_protobuf_EDITION_2023 = 1000,
diff --git a/upb/reflection/cmake/google/protobuf/descriptor.upb_minitable.c b/upb/reflection/cmake/google/protobuf/descriptor.upb_minitable.c
index d09c175145..1cc463de95 100644
--- a/upb/reflection/cmake/google/protobuf/descriptor.upb_minitable.c
+++ b/upb/reflection/cmake/google/protobuf/descriptor.upb_minitable.c
@@ -1171,10 +1171,11 @@ static const upb_MiniTable *messages_layout[33] = {
 
 const upb_MiniTableEnum google_protobuf_Edition_enum_init = {
     64,
-    8,
+    9,
     {
         0x7,
         0x0,
+        0x384,
         0x3e6,
         0x3e7,
         0x3e8,