diff --git a/MODULE.bazel b/MODULE.bazel
index 545e714..0b34e51 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -71,7 +71,7 @@ bazel_dep(
 
 git_override(
     module_name = "protobuf",
-    commit = "12922359447fba435b8727796ced22b1c453cf0b",
+    commit = "6d03e4f090d809c87a8274b56d609ccc067632f1",
     remote = "https://github.com/protocolbuffers/protobuf",
 )
 
diff --git a/cel-c/internal/BUILD b/cel-c/internal/BUILD
index c35cb69..1ab272d 100644
--- a/cel-c/internal/BUILD
+++ b/cel-c/internal/BUILD
@@ -613,9 +613,8 @@ cc_library(
         "//cel-c:well_known_types",
         "@protobuf//upb/base",
         "@protobuf//upb/message",
+        "@protobuf//upb/message:compare",
         "@protobuf//upb/reflection",
-        "@protobuf//upb/wire:eps_copy_input_stream",
-        "@protobuf//upb/wire:reader",
     ],
 )
 
@@ -635,6 +634,10 @@ cc_test(
         "@abseil-cpp//absl/log:die_if_null",
         "@abseil-cpp//absl/strings:string_view",
         "@abseil-cpp//absl/types:variant",
+        "@cel-spec//proto/cel/expr/conformance/proto2:test_all_types_cc_proto",
+        "@cel-spec//proto/cel/expr/conformance/proto2:test_all_types_upb_proto",
+        "@cel-spec//proto/cel/expr/conformance/proto2:test_all_types_upb_proto_minitable",
+        "@cel-spec//proto/cel/expr/conformance/proto2:test_all_types_upb_proto_reflection",
         "@cel-spec//proto/cel/expr/conformance/proto3:test_all_types_cc_proto",
         "@cel-spec//proto/cel/expr/conformance/proto3:test_all_types_upb_proto",
         "@cel-spec//proto/cel/expr/conformance/proto3:test_all_types_upb_proto_reflection",
@@ -654,6 +657,8 @@ cc_test(
         "@protobuf//:wrappers_upb_reflection_proto",
         "@protobuf//upb/base",
         "@protobuf//upb/message",
+        "@protobuf//upb/message:message_unknowns_testonly",
+        "@protobuf//upb/mini_table",
         "@protobuf//upb/reflection",
         "@protobuf//upb/wire",
     ],
@@ -986,10 +991,8 @@ cc_library(
         ":any",
         ":array",
         ":bit",
-        ":bitset",
         ":ckdint",
         ":config",
-        ":malloc",
         ":message_equality",
         ":sort",
         "//cel-c:alloc",
@@ -1006,13 +1009,9 @@ cc_library(
         "//cel-c:type",
         "//cel-c:value_headers",
         "//cel-c:value_kind",
-        "//cel-c:well_known_types",
-        "@googleapis//google/rpc:code_upb_proto",
-        "@googleapis//google/rpc:status_upb_proto",
         "@protobuf//upb/base",
         "@protobuf//upb/message",
         "@protobuf//upb/reflection",
-        "@protobuf//upb/wire",
     ],
 )
 
diff --git a/cel-c/internal/message_equality.cc b/cel-c/internal/message_equality.cc
index 8d3f0a7..2b35336 100644
--- a/cel-c/internal/message_equality.cc
+++ b/cel-c/internal/message_equality.cc
@@ -30,54 +30,17 @@
 #include "upb/base/descriptor_constants.h"
 #include "upb/base/string_view.h"
 #include "upb/message/array.h"
+#include "upb/message/compare.h"
 #include "upb/message/map.h"
 #include "upb/message/message.h"
 #include "upb/reflection/def.h"
 #include "upb/reflection/message.h"
-#include "upb/wire/eps_copy_input_stream.h"
-#include "upb/wire/reader.h"
-#include "upb/wire/types.h"
-
-typedef struct _cel_UnknownField _cel_UnknownField;
-typedef struct _cel_UnknownFields _cel_UnknownFields;
-
-struct _cel_UnknownFields {
-  _cel_UnknownField* cel_nullable head;
-  _cel_UnknownField* cel_nullable tail;
-  _cel_UnknownField* cel_nullable mid;
-  uint32_t size;
-  int32_t balance;
-};
-
-struct _cel_UnknownField {
-  _cel_UnknownField* cel_nullable prev;
-  _cel_UnknownField* cel_nullable next;
-#ifdef _MSC_VER
-#pragma pack(push, 4)
-#endif
-  union CEL_ATTRIBUTE_PACKED(4) {
-    uint64_t varint;
-    uint64_t fixed64;
-    uint32_t fixed32;
-    struct CEL_ATTRIBUTE_PACKED(4) {
-      const char* cel_nullability_unknown data;
-      uint32_t size;
-    } delimited;
-    _cel_UnknownFields* cel_nullable group;
-  } data;
-#ifdef _MSC_VER
-#pragma pack(pop)
-#endif
-  uint32_t field_num : 29;
-  uint8_t wire_type : 3;
-};
 
 typedef struct {
   const upb_DefPool* const cel_nonnull def_pool;
   const cel_WellKnownTypes* const cel_nonnull wkts;
   cel_Allocator* const cel_nonnull alloc;
   cel_Arena* cel_nullable arena;
-  upb_EpsCopyInputStream stream;
   _cel_MessageEquality result;
   int depth;
   _cel_jmp_buf jmp;
@@ -106,262 +69,25 @@ _cel_MessageEqualityState_Arena(_cel_MessageEqualityState* cel_nonnull state) {
   return arena;
 }
 
-CEL_ATTRIBUTE_NODISCARD
-static _cel_UnknownFields* cel_nonnull
-_cel_UnknownFields_New(_cel_MessageEqualityState* cel_nonnull state) {
-  _cel_UnknownFields* fields = reinterpret_cast<_cel_UnknownFields*>(
-      cel_Arena_Malloc(_cel_MessageEqualityState_Arena(state),
-                       sizeof(_cel_UnknownFields), cel_nullptr));
-  if (CEL_UNLIKELY(fields == cel_nullptr)) {
-    _cel_MessageEqualityState_Throw(state, _cel_MessageEquality_kOutOfMemory);
-  }
-  fields->head = cel_nullptr;
-  fields->tail = cel_nullptr;
-  fields->mid = cel_nullptr;
-  fields->size = 0;
-  fields->balance = 0;
-  return fields;
-}
-
-CEL_ATTRIBUTE_NODISCARD
-static _cel_UnknownField* cel_nonnull _cel_UnknownField_New(
-    _cel_MessageEqualityState* cel_nonnull state, uint32_t tag) {
-  _cel_UnknownField* field = reinterpret_cast<_cel_UnknownField*>(
-      cel_Arena_Malloc(_cel_MessageEqualityState_Arena(state),
-                       sizeof(_cel_UnknownField), cel_nullptr));
-  if (CEL_UNLIKELY(field == cel_nullptr)) {
-    _cel_MessageEqualityState_Throw(state, _cel_MessageEquality_kOutOfMemory);
-  }
-  field->prev = cel_nullptr;
-  field->next = cel_nullptr;
-  field->field_num = upb_WireReader_GetFieldNumber(tag);
-  field->wire_type = upb_WireReader_GetWireType(tag);
-  return field;
-}
-
-CEL_ATTRIBUTE_NODISCARD
-static int _cel_UnknownField_Compare(const _cel_UnknownField* cel_nonnull lhs,
-                                     const _cel_UnknownField* cel_nonnull rhs) {
-  const uint32_t lhs_field_num = lhs->field_num;
-  const uint32_t rhs_field_num = rhs->field_num;
-  if (lhs_field_num < rhs_field_num) {
-    return -1;
-  }
-  if (lhs_field_num > rhs_field_num) {
-    return 1;
-  }
-  const uint8_t lhs_wire_type = lhs->wire_type;
-  const uint8_t rhs_wire_type = rhs->wire_type;
-  return lhs_wire_type < rhs_wire_type   ? -1
-         : lhs_wire_type > rhs_wire_type ? 1
-                                         : 0;
-}
-
-static void _cel_UnknownFields_Add(_cel_UnknownFields* cel_nonnull fields,
-                                   _cel_UnknownField* cel_nonnull field) {
-  if (fields->tail != cel_nullptr) {
-    _cel_UnknownField* tail = fields->tail;
-    if (_cel_UnknownField_Compare(field, tail) >= 0) {
-      // Fast path. Fields are in order already.
-      field->prev = tail;
-      tail->next = field;
-      fields->tail = field;
-      ++fields->balance;
-    } else {
-      // Slow path.
-      _cel_UnknownField* node = fields->mid;
-      CEL_ASSERT_NOT_NULL(node);
-      while (_cel_UnknownField_Compare(field, node) < 0) {
-        node = node->prev;
-        if (node == cel_nullptr) {
-          field->next = fields->head;
-          fields->head->prev = field;
-          fields->head = field;
-          goto inserted;
-        }
-        CEL_ASSERT_NOT_NULL(node);
-      }
-      CEL_ASSERT_NOT_NULL(node);
-      while (_cel_UnknownField_Compare(field, node) >= 0) {
-        node = node->next;
-        CEL_ASSERT_NOT_NULL(node);
-      }
-      field->next = node;
-      field->prev = node->prev;
-      if (node->prev != cel_nullptr) {
-        node->prev->next = field;
-        node->prev = field;
-      } else {
-        fields->head = field;
-      }
-    }
-  inserted:
-    fields->balance += _cel_UnknownField_Compare(field, fields->mid);
-  } else {
-    fields->head = fields->mid = fields->tail = field;
-  }
-  ++fields->size;
-  if (fields->size > 2 && (fields->size & 1) == 1) {
-    if (fields->balance < 0) {
-      fields->mid = fields->mid->prev;
-    } else if (fields->balance > 0) {
-      fields->mid = fields->mid->next;
-    }
-    fields->balance = 0;
-  }
-}
-
-CEL_ATTRIBUTE_NODISCARD
-static _cel_UnknownFields* cel_nullable
-_cel_UnknownFields_Read(_cel_MessageEqualityState* cel_nonnull state,
-                        _cel_UnknownFields* fields, const char** buf) {
-  const char* ptr = *buf;
-  while (!upb_EpsCopyInputStream_IsDone(&state->stream, &ptr)) {
-    uint32_t tag;
-    ptr = upb_WireReader_ReadTag(ptr, &tag, &state->stream);
-    uint8_t wire_type = upb_WireReader_GetWireType(tag);
-    if (wire_type == kUpb_WireType_EndGroup) {
-      break;
-    }
-    if (CEL_UNLIKELY(fields == cel_nullptr)) {
-      fields = _cel_UnknownFields_New(state);
-    }
-    _cel_UnknownField* field = _cel_UnknownField_New(state, tag);
-    switch (wire_type) {
-      case kUpb_WireType_Varint:
-        ptr =
-            upb_WireReader_ReadVarint(ptr, &field->data.varint, &state->stream);
-        break;
-      case kUpb_WireType_64Bit:
-        ptr = upb_WireReader_ReadFixed64(ptr, &field->data.fixed64,
-                                         &state->stream);
-        break;
-      case kUpb_WireType_32Bit:
-        ptr = upb_WireReader_ReadFixed32(ptr, &field->data.fixed32,
-                                         &state->stream);
-        break;
-      case kUpb_WireType_Delimited: {
-        int size;
-        upb_StringView sv;
-        ptr = upb_WireReader_ReadSize(ptr, &size, &state->stream);
-        ptr = upb_EpsCopyInputStream_ReadStringAlwaysAlias(&state->stream, ptr,
-                                                           size, &sv);
-        field->data.delimited.data = sv.data;
-        field->data.delimited.size = sv.size;
-      } break;
-      case kUpb_WireType_StartGroup:
-        CEL_ASSERT_GT(state->depth, 0);
-        if (--state->depth == 0) {
-          _cel_MessageEqualityState_Throw(
-              state, _cel_MessageEquality_kMaxDepthExceeded);
-        }
-        field->data.group = _cel_UnknownFields_Read(state, cel_nullptr, &ptr);
-        ++state->depth;
-        break;
-      default:
-        CEL_UNREACHABLE();
-    }
-    _cel_UnknownFields_Add(fields, field);
-  }
-  *buf = ptr;
-  return fields;
-}
-
-CEL_ATTRIBUTE_NODISCARD
-static _cel_UnknownFields* cel_nullable
-_cel_UnknownFields_FromMessage(_cel_MessageEqualityState* cel_nonnull state,
-                               const upb_Message* cel_nonnull msg) {
-  _cel_UnknownFields* fields = cel_nullptr;
-  cel_StringView unknown;
-  uintptr_t iter = kUpb_Message_UnknownBegin;
-  while (upb_Message_NextUnknown(msg, &unknown, &iter)) {
-    upb_EpsCopyInputStream_Init(&state->stream, &unknown.data,
-                                cel_StringView_Size(unknown));
-    fields = _cel_UnknownFields_Read(state, fields, &unknown.data);
-    CEL_ASSERT(upb_EpsCopyInputStream_IsDone(&state->stream, &unknown.data) &&
-               !upb_EpsCopyInputStream_IsError(&state->stream));
-  }
-  return fields;
-}
-
-CEL_ATTRIBUTE_NODISCARD
-static bool _cel_UnknownFields_Equals(
-    _cel_MessageEqualityState* cel_nonnull state,
-    const _cel_UnknownFields* cel_nullable lhs_fields,
-    const _cel_UnknownFields* cel_nullable rhs_fields) {
-  const size_t lhs_fields_size =
-      lhs_fields != cel_nullptr ? lhs_fields->size : 0;
-  const size_t rhs_fields_size =
-      rhs_fields != cel_nullptr ? rhs_fields->size : 0;
-  if (lhs_fields_size != rhs_fields_size) {
-    return false;
-  }
-  if (lhs_fields_size == 0) {
-    return true;
-  }
-
-  const _cel_UnknownField* lhs_field = lhs_fields->head;
-  const _cel_UnknownField* rhs_field = rhs_fields->head;
-  for (size_t i = 0; i < lhs_fields_size;
-       ++i, lhs_field = lhs_field->next, rhs_field = rhs_field->next) {
-    if (lhs_field->field_num != rhs_field->field_num ||
-        lhs_field->wire_type != rhs_field->wire_type) {
-      return false;
-    }
-    switch (lhs_field->wire_type) {
-      case kUpb_WireType_Varint:
-        if (lhs_field->data.varint != rhs_field->data.varint) {
-          return false;
-        }
-        break;
-      case kUpb_WireType_64Bit:
-        if (lhs_field->data.fixed64 != rhs_field->data.fixed64) {
-          return false;
-        }
-        break;
-      case kUpb_WireType_32Bit:
-        if (lhs_field->data.fixed32 != rhs_field->data.fixed32) {
-          return false;
-        }
-        break;
-      case kUpb_WireType_Delimited:
-        if (!cel_StringView_Equals(
-                cel_StringView_FromArray(lhs_field->data.delimited.data,
-                                         lhs_field->data.delimited.size),
-                cel_StringView_FromArray(rhs_field->data.delimited.data,
-                                         rhs_field->data.delimited.size))) {
-          return false;
-        }
-        break;
-      case kUpb_WireType_StartGroup:
-        if (!_cel_UnknownFields_Equals(state, lhs_field->data.group,
-                                       rhs_field->data.group)) {
-          return false;
-        }
-        break;
-      default:
-        CEL_UNREACHABLE();
-    }
-  }
-  return true;
-}
-
 CEL_ATTRIBUTE_NODISCARD
 static bool _cel_MessageEqualityState_UnknownEquals(
     _cel_MessageEqualityState* cel_nonnull state,
     const upb_Message* cel_nonnull lhs, const upb_Message* cel_nonnull rhs) {
-  const bool lhs_has_unknown = upb_Message_HasUnknown(lhs);
-  const bool rhs_has_unknown = upb_Message_HasUnknown(rhs);
-  if (!lhs_has_unknown && !rhs_has_unknown) {
-    return true;
-  }
-  if (!(lhs_has_unknown && rhs_has_unknown)) {
-    return false;
+  upb_UnknownCompareResult result =
+      upb_Message_UnknownFieldsAreEqual(lhs, rhs, state->depth);
+  switch (result) {
+    case kUpb_UnknownCompareResult_Equal:
+      return true;
+    case kUpb_UnknownCompareResult_NotEqual:
+      return false;
+    case kUpb_UnknownCompareResult_OutOfMemory:
+      _cel_MessageEqualityState_Throw(state, _cel_MessageEquality_kOutOfMemory);
+    case kUpb_UnknownCompareResult_MaxDepthExceeded:
+      _cel_MessageEqualityState_Throw(state,
+                                      _cel_MessageEquality_kMaxDepthExceeded);
+    default:
+      CEL_UNREACHABLE();
   }
-
-  _cel_UnknownFields* lhs_fields = _cel_UnknownFields_FromMessage(state, lhs);
-  _cel_UnknownFields* rhs_fields = _cel_UnknownFields_FromMessage(state, rhs);
-  return _cel_UnknownFields_Equals(state, lhs_fields, rhs_fields);
 }
 
 CEL_ATTRIBUTE_NODISCARD
diff --git a/cel-c/internal/message_equality_test.cc b/cel-c/internal/message_equality_test.cc
index ace2d46..665e843 100644
--- a/cel-c/internal/message_equality_test.cc
+++ b/cel-c/internal/message_equality_test.cc
@@ -19,6 +19,7 @@
 #include <memory>
 #include <string>
 #include <utility>
+#include <variant>
 
 #include "google/protobuf/any.pb.h"
 #include "google/protobuf/any.upbdefs.h"
@@ -44,6 +45,8 @@
 #include "cel-c/internal/config.h"
 #include "cel-c/status.h"
 #include "cel-c/well_known_types.h"
+#include "cel/expr/conformance/proto2/test_all_types.upbdefs.h"
+#include "cel/expr/conformance/proto2/test_all_types_extensions.upb_minitable.h"
 #include "cel/expr/conformance/proto3/test_all_types.pb.h"
 #include "cel/expr/conformance/proto3/test_all_types.upbdefs.h"
 #include "google/protobuf/descriptor.h"
@@ -52,6 +55,8 @@
 #include "google/protobuf/unknown_field_set.h"
 #include "upb/message/array.h"
 #include "upb/message/message.h"
+#include "upb/message/unknown_fields_testonly.h"
+#include "upb/mini_table/message.h"
 #include "upb/reflection/def.h"
 #include "upb/reflection/message.h"
 #include "upb/wire/decode.h"
@@ -2543,4 +2548,114 @@ INSTANTIATE_TEST_SUITE_P(
             },
         }));
 
+class MessageEqualityTest_NonCanonical : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    arena_ = cel_Arena_New(cel_DefaultAllocator);
+    def_pool_ = upb_DefPool_New();
+    cel_Status_Construct(&status_);
+    msg_def_ = cel_expr_conformance_proto2_TestAllTypes_getmsgdef(def_pool_);
+    ASSERT_NE(msg_def_, nullptr);
+    ASSERT_TRUE(cel_WellKnownTypes_Initialize(&wkts_, def_pool_, &status_));
+    mt_ = upb_MessageDef_MiniTable(msg_def_);
+  }
+
+  void TearDown() override {
+    cel_Status_Destruct(&status_);
+    upb_DefPool_Free(def_pool_);
+    cel_Arena_Delete(arena_);
+  }
+
+  upb_Message* NewMessage() { return upb_Message_New(mt_, arena_); }
+
+  _cel_MessageEquality CheckEquals(const upb_Message* lhs,
+                                   const upb_Message* rhs) {
+    return _cel_Message_Equals(lhs, rhs, msg_def_, def_pool_, &wkts_,
+                               cel_DefaultAllocator);
+  }
+
+  cel_Arena* arena_;
+  upb_DefPool* def_pool_;
+  cel_Status status_;
+  cel_WellKnownTypes wkts_;
+  const upb_MessageDef* msg_def_;
+  const upb_MiniTable* mt_;
+};
+
+TEST_F(MessageEqualityTest_NonCanonical, EqualSameExtensionAndValue) {
+  upb_Message* msg1 = NewMessage();
+  int32_t val1 = 42;
+  ASSERT_TRUE(upb_Message_SetNonCanonicalExtension(
+      msg1, cel_expr_conformance_proto2_int32_ext_ext, &val1, arena_));
+
+  upb_Message* msg2 = NewMessage();
+  int32_t val2 = 42;
+  ASSERT_TRUE(upb_Message_SetNonCanonicalExtension(
+      msg2, cel_expr_conformance_proto2_int32_ext_ext, &val2, arena_));
+
+  EXPECT_EQ(CheckEquals(msg1, msg2), _cel_MessageEquality_kEqual);
+}
+
+TEST_F(MessageEqualityTest_NonCanonical,
+       EqualUnknownStringViewAndNonCanonicalExtension) {
+  upb_Message* msg1 = NewMessage();
+  std::string bytes = UnknownFields{UnknownField::Varint(1000, 42)};
+  ASSERT_EQ(
+      upb_Decode(bytes.data(), bytes.size(), msg1, mt_, nullptr, 0, arena_),
+      kUpb_DecodeStatus_Ok);
+
+  upb_Message* msg2 = NewMessage();
+  int32_t val2 = 42;
+  ASSERT_TRUE(upb_Message_SetNonCanonicalExtension(
+      msg2, cel_expr_conformance_proto2_int32_ext_ext, &val2, arena_));
+
+  EXPECT_EQ(CheckEquals(msg1, msg2), _cel_MessageEquality_kEqual);
+}
+
+TEST_F(MessageEqualityTest_NonCanonical, NotEqualDifferentValue) {
+  upb_Message* msg1 = NewMessage();
+  int32_t val1 = 42;
+  ASSERT_TRUE(upb_Message_SetNonCanonicalExtension(
+      msg1, cel_expr_conformance_proto2_int32_ext_ext, &val1, arena_));
+
+  upb_Message* msg2 = NewMessage();
+  int32_t val2 = 43;
+  ASSERT_TRUE(upb_Message_SetNonCanonicalExtension(
+      msg2, cel_expr_conformance_proto2_int32_ext_ext, &val2, arena_));
+
+  EXPECT_EQ(CheckEquals(msg1, msg2), _cel_MessageEquality_kNotEqual);
+}
+
+TEST_F(MessageEqualityTest_NonCanonical, NotEqualDifferentExtension) {
+  upb_Message* msg1 = NewMessage();
+  int32_t val1 = 42;
+  ASSERT_TRUE(upb_Message_SetNonCanonicalExtension(
+      msg1, cel_expr_conformance_proto2_int32_ext_ext, &val1, arena_));
+
+  upb_Message* msg2 = NewMessage();
+  const upb_Message* nested_msg = NewMessage();
+  ASSERT_TRUE(upb_Message_SetNonCanonicalExtension(
+      msg2, cel_expr_conformance_proto2_nested_ext_ext, &nested_msg, arena_));
+
+  EXPECT_EQ(CheckEquals(msg1, msg2), _cel_MessageEquality_kNotEqual);
+}
+
+TEST_F(MessageEqualityTest_NonCanonical, EncodeFailureMaxDepth) {
+  upb_Message* msg1 = NewMessage();
+  upb_Message* current = msg1;
+  for (int i = 0; i < 105; ++i) {
+    upb_Message* next = NewMessage();
+    ASSERT_TRUE(upb_Message_SetNonCanonicalExtension(
+        current, cel_expr_conformance_proto2_nested_ext_ext, &next, arena_));
+    current = next;
+  }
+
+  upb_Message* msg2 = NewMessage();
+  int32_t val2 = 42;
+  ASSERT_TRUE(upb_Message_SetNonCanonicalExtension(
+      msg2, cel_expr_conformance_proto2_int32_ext_ext, &val2, arena_));
+
+  EXPECT_EQ(CheckEquals(msg1, msg2), _cel_MessageEquality_kMaxDepthExceeded);
+}
+
 }  // namespace