@@ -280,7 +280,9 @@ java_library(
     ],
     deps = [
         ":base_proto_cel_value_converter",
+        ":optimized_selectable",
         ":preadapted_list",
+        ":select_field",
         ":values",
         "//:auto_value",
         "//common:options",
@@ -320,6 +322,7 @@ java_library(
         "ProtoLiteCelValueConverter.java",
         "ProtoMessageLiteValue.java",
         "RawProtoMessageLiteValue.java",
+        "WireMessageLite.java",
     ],
     tags = [
     ],
@@ -350,6 +353,7 @@ cel_android_library(
         "ProtoLiteCelValueConverter.java",
         "ProtoMessageLiteValue.java",
         "RawProtoMessageLiteValue.java",
+        "WireMessageLite.java",
     ],
     tags = [
     ],
 
@@ -21,12 +21,14 @@
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ImmutableMap;
 import com.google.errorprone.annotations.Immutable;
+import com.google.protobuf.ByteString;
 import com.google.protobuf.MessageLite;
 import dev.cel.common.types.CelType;
 import dev.cel.common.types.StructTypeReference;
 import dev.cel.common.values.ProtoLiteCelValueConverter.MessageFields;
 import dev.cel.protobuf.CelLiteDescriptor.FieldLiteDescriptor;
 import java.io.IOException;
+import java.util.Objects;
 import java.util.Optional;
 import org.jspecify.annotations.Nullable;
 
@@ -38,41 +40,72 @@
  * <p>If the codebase has access to full protobuf messages with descriptors, use {@code
  * ProtoMessageValue} instead.
  *
+ * <p>An instance is backed by either a materialized {@link #rawValue()} or unparsed {@link
+ * #wireBytes()} (exactly one is non-null). Wire-backed instances decode selected fields directly
+ * from {@link #wireBytes()} and lazily parse the full {@link MessageLite} only if {@link #value()}
+ * is invoked.
+ *
  * <p>Implements {@link OptimizedSelectable} so that select chains can address fields by number:
  *
  * <ul>
  *   <li><b>Field renames:</b> If a protobuf field is renamed in schema after an AST was compiled,
  *       resolving by {@link SelectField#fieldNumber()} maps the number to the runtime descriptor's
  *       current field name, preventing {@code CelAttributeNotFoundException}.
  *   <li><b>Version skew / unknown fields:</b> When evaluating payloads serialized by a newer binary
- *       containing fields absent from the local {@code CelLiteDescriptor}, the unknown wire bytes
- *       are preserved in {@link #unknownFields()} and decoded on demand using the compile-time wire
- *       type and default metadata in {@link SelectField}.
+ *       containing fields absent from the local {@code CelLiteDescriptor}, the unknown fields are
+ *       decoded on demand directly from the message's wire bytes using the compile-time wire type
+ *       and default metadata in {@link SelectField}.
  * </ul>
  */
 @AutoValue
 @Immutable
-public abstract class ProtoMessageLiteValue extends StructValue<String, MessageLite>
+abstract class ProtoMessageLiteValue extends StructValue<String, MessageLite>
     implements OptimizedSelectable {
 
-  @Override
-  public abstract MessageLite value();
+  // Populated when wrapping an already-materialized root MessageLite (e.g., from activation).
+  abstract @Nullable MessageLite rawValue();
+
+  // Populated when slicing a nested submessage from parent wire bytes to avoid deserializing and
+  // re-serializing intermediate hops; lazily parsed into a MessageLite only if value() is called.
+  abstract @Nullable ByteString wireBytes();
 
   @Override
   public abstract CelType celType();
 
   abstract ProtoLiteCelValueConverter protoLiteCelValueConverter();
 
+  @Memoized
+  @Override
+  public MessageLite value() {
+    MessageLite msg = rawValue();
+    if (msg != null) {
+      return msg;
+    }
+    return protoLiteCelValueConverter()
+        .parseMessageLite(checkNotNull(wireBytes()), celType().name());
+  }
+
+  @Memoized
+  ByteString serializedRawValue() {
+    return checkNotNull(rawValue()).toByteString();
+  }
+
+  ByteString toByteString() {
+    ByteString bytes = wireBytes();
+    return bytes != null ? bytes : serializedRawValue();
+  }
+
   @Memoized
   MessageFields messageFields() {
     try {
-      return protoLiteCelValueConverter().readMessageFields(value(), celType().name());
+      return protoLiteCelValueConverter().readAllFields(toByteString(), celType().name());
     } catch (IOException e) {
-      throw new IllegalStateException("Unable to read message fields for " + celType().name(), e);
+      throw new IllegalArgumentException(
+          "Failed to decode proto message of type: " + celType().name(), e);
     }
   }
 
-  ImmutableMap<String, Object> fieldValues() {
+  private ImmutableMap<String, Object> fieldValues() {
     return messageFields().values();
   }
 
@@ -82,9 +115,30 @@ ImmutableListMultimap<Integer, Object> unknownFields() {
 
   @Override
   public boolean isZeroValue() {
+    ByteString bytes = wireBytes();
+    if (bytes != null && bytes.isEmpty()) {
+      return true;
+    }
     return value().getDefaultInstanceForType().equals(value());
   }
 
+  @Override
+  public final boolean equals(Object other) {
+    if (other == this) {
+      return true;
+    }
+    if (!(other instanceof ProtoMessageLiteValue)) {
+      return false;
+    }
+    ProtoMessageLiteValue that = (ProtoMessageLiteValue) other;
+    return this.celType().equals(that.celType()) && this.value().equals(that.value());
+  }
+
+  @Override
+  public final int hashCode() {
+    return Objects.hash(value(), celType());
+  }
+
   @Override
   public Object select(String field) {
     return find(field)
@@ -93,16 +147,15 @@ public Object select(String field) {
 
   @Override
   public Optional<Object> find(String field) {
-    Object fieldValue = fieldValues().get(field);
-    return Optional.ofNullable(fieldValue)
-        .map(value -> protoLiteCelValueConverter().toRuntimeValue(fieldValue));
+    return Optional.ofNullable(fieldValues().get(field))
+        .map(protoLiteCelValueConverter()::toRuntimeValue);
   }
 
   @Override
   public Object selectByFieldNumber(SelectField field) {
     FieldLiteDescriptor fd = findFieldDescriptor(field);
     if (fd != null) {
-      Object known = fieldValues().get(fd.getFieldName());
+      Object known = readField(fd);
       if (known != null) {
         return protoLiteCelValueConverter().toRuntimeValue(known);
       }
@@ -112,28 +165,48 @@ public Object selectByFieldNumber(SelectField field) {
       return protoLiteCelValueConverter().getDefaultCelValue(fd);
     }
     return RawProtoMessageLiteValue.selectWireOrDefault(
-        field, unknownFields().get(field.fieldNumber()), protoLiteCelValueConverter());
+        field,
+        RawProtoMessageLiteValue.readWireField(toByteString(), field.fieldNumber()),
+        protoLiteCelValueConverter());
   }
 
   @Override
   public boolean hasFieldByNumber(SelectField field) {
     FieldLiteDescriptor fd = findFieldDescriptor(field);
     if (fd != null) {
-      return fieldValues().containsKey(fd.getFieldName());
+      return hasField(fd);
     }
-    return RawProtoMessageLiteValue.isPresentInWire(
-        field, unknownFields().get(field.fieldNumber()));
+    return RawProtoMessageLiteValue.isPresentInWire(toByteString(), field);
   }
 
   @Override
   public Optional<Object> findByFieldNumber(SelectField field) {
     FieldLiteDescriptor fd = findFieldDescriptor(field);
     if (fd != null) {
-      return Optional.ofNullable(fieldValues().get(fd.getFieldName()))
-          .map(value -> protoLiteCelValueConverter().toRuntimeValue(value));
+      return Optional.ofNullable(readField(fd)).map(protoLiteCelValueConverter()::toRuntimeValue);
     }
     return RawProtoMessageLiteValue.navigateWire(
-        field, unknownFields().get(field.fieldNumber()), protoLiteCelValueConverter());
+        field,
+        RawProtoMessageLiteValue.readWireField(toByteString(), field.fieldNumber()),
+        protoLiteCelValueConverter());
+  }
+
+  private @Nullable Object readField(FieldLiteDescriptor fd) {
+    try {
+      return protoLiteCelValueConverter().readSingleField(toByteString(), fd);
+    } catch (IOException e) {
+      throw new IllegalArgumentException(
+          "Failed to decode proto message of type: " + celType().name(), e);
+    }
+  }
+
+  private boolean hasField(FieldLiteDescriptor fd) {
+    try {
+      return protoLiteCelValueConverter().hasSingleField(toByteString(), fd);
+    } catch (IOException e) {
+      throw new IllegalArgumentException(
+          "Failed to decode proto message of type: " + celType().name(), e);
+    }
   }
 
   private @Nullable FieldLiteDescriptor findFieldDescriptor(SelectField field) {
@@ -142,13 +215,30 @@ public Optional<Object> findByFieldNumber(SelectField field) {
         .orElse(null);
   }
 
-  public static ProtoMessageLiteValue create(
+  static ProtoMessageLiteValue create(
       MessageLite value, String typeName, ProtoLiteCelValueConverter protoLiteCelValueConverter) {
     checkNotNull(value);
     checkNotNull(typeName);
     checkNotNull(protoLiteCelValueConverter);
     return new AutoValue_ProtoMessageLiteValue(
-        value, StructTypeReference.create(typeName), protoLiteCelValueConverter);
+        value,
+        /* wireBytes= */ null,
+        StructTypeReference.create(typeName),
+        protoLiteCelValueConverter);
+  }
+
+  static ProtoMessageLiteValue create(
+      ByteString wireBytes,
+      String typeName,
+      ProtoLiteCelValueConverter protoLiteCelValueConverter) {
+    checkNotNull(wireBytes);
+    checkNotNull(typeName);
+    checkNotNull(protoLiteCelValueConverter);
+    return new AutoValue_ProtoMessageLiteValue(
+        /* rawValue= */ null,
+        wireBytes,
+        StructTypeReference.create(typeName),
+        protoLiteCelValueConverter);
   }
 
   ProtoMessageLiteValue() {}
 
@@ -14,8 +14,9 @@
 
 package dev.cel.common.values;
 
+import static com.google.common.base.Preconditions.checkNotNull;
+
 import com.google.auto.value.AutoValue;
-import com.google.common.base.Preconditions;
 import com.google.errorprone.annotations.Immutable;
 import com.google.protobuf.Descriptors.Descriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
@@ -28,7 +29,8 @@
 /** ProtoMessageValue is a struct value with protobuf support. */
 @AutoValue
 @Immutable
-public abstract class ProtoMessageValue extends StructValue<String, Message> {
+public abstract class ProtoMessageValue extends StructValue<String, Message>
+    implements OptimizedSelectable {
 
   @Override
   public abstract Message value();
@@ -60,28 +62,38 @@ public Optional<Object> find(String field) {
     FieldDescriptor fieldDescriptor =
         findField(celDescriptorPool(), value().getDescriptorForType(), field);
 
-    // Selecting a field on a protobuf message yields a default value even if the field is not
-    // declared. Therefore, we must exhaustively test whether they are actually declared.
-    if (fieldDescriptor.isRepeated()) {
-      if (value().getRepeatedFieldCount(fieldDescriptor) == 0) {
-        return Optional.empty();
-      }
-    } else if (!value().hasField(fieldDescriptor)) {
-      return Optional.empty();
-    }
+    return findFieldValue(fieldDescriptor);
+  }
 
-    return Optional.of(
-        protoCelValueConverter().fromProtoMessageFieldToCelValue(value(), fieldDescriptor));
+  @Override
+  public Object selectByFieldNumber(SelectField field) {
+    FieldDescriptor fieldDescriptor = findFieldByNumber(value().getDescriptorForType(), field);
+
+    return protoCelValueConverter().fromProtoMessageFieldToCelValue(value(), fieldDescriptor);
+  }
+
+  @Override
+  public boolean hasFieldByNumber(SelectField field) {
+    FieldDescriptor fieldDescriptor = findFieldByNumber(value().getDescriptorForType(), field);
+
+    return isFieldPresent(fieldDescriptor);
+  }
+
+  @Override
+  public Optional<Object> findByFieldNumber(SelectField field) {
+    FieldDescriptor fieldDescriptor = findFieldByNumber(value().getDescriptorForType(), field);
+
+    return findFieldValue(fieldDescriptor);
   }
 
   public static ProtoMessageValue create(
       Message value,
       CelDescriptorPool celDescriptorPool,
       ProtoCelValueConverter protoCelValueConverter,
       boolean enableJsonFieldNames) {
-    Preconditions.checkNotNull(value);
-    Preconditions.checkNotNull(celDescriptorPool);
-    Preconditions.checkNotNull(protoCelValueConverter);
+    checkNotNull(value);
+    checkNotNull(celDescriptorPool);
+    checkNotNull(protoCelValueConverter);
     return new AutoValue_ProtoMessageValue(
         value,
         StructTypeReference.create(value.getDescriptorForType().getFullName()),
@@ -90,6 +102,36 @@ public static ProtoMessageValue create(
         enableJsonFieldNames);
   }
 
+  private Optional<Object> findFieldValue(FieldDescriptor fieldDescriptor) {
+    if (!isFieldPresent(fieldDescriptor)) {
+      return Optional.empty();
+    }
+
+    return Optional.of(
+        protoCelValueConverter().fromProtoMessageFieldToCelValue(value(), fieldDescriptor));
+  }
+
+  private boolean isFieldPresent(FieldDescriptor fieldDescriptor) {
+    // Selecting a field on a protobuf message yields a default value even if the field is not
+    // declared. Therefore, we must exhaustively test whether they are actually declared.
+    if (fieldDescriptor.isRepeated()) {
+      return value().getRepeatedFieldCount(fieldDescriptor) > 0;
+    }
+    return value().hasField(fieldDescriptor);
+  }
+
+  private static FieldDescriptor findFieldByNumber(Descriptor descriptor, SelectField field) {
+    FieldDescriptor fieldDescriptor = descriptor.findFieldByNumber(field.fieldNumber());
+    if (fieldDescriptor != null) {
+      return fieldDescriptor;
+    }
+
+    throw new IllegalArgumentException(
+        String.format(
+            "field '%s' (number %d) is not declared in message '%s'",
+            field.fieldName(), field.fieldNumber(), descriptor.getFullName()));
+  }
+
   private FieldDescriptor findField(
       CelDescriptorPool celDescriptorPool, Descriptor descriptor, String fieldName) {
     if (enableJsonFieldNames()) {
@@ -114,4 +156,6 @@ private FieldDescriptor findField(
                         "field '%s' is not declared in message '%s'",
                         fieldName, descriptor.getFullName())));
   }
+
+  ProtoMessageValue() {}
 }