diff --git a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/common/JsonUtils.java b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/common/JsonUtils.java
index 60e1d5a27f48b..5a33f288a4bb3 100644
--- a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/common/JsonUtils.java
+++ b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/common/JsonUtils.java
@@ -8,6 +8,7 @@
 package org.elasticsearch.xpack.inference.common;
 
 import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.xcontent.XContentBuilder;
 import org.elasticsearch.xcontent.json.JsonXContent;
 
@@ -23,7 +24,11 @@ public class JsonUtils {
     public static <T> String toJson(T value, String field) {
         try {
             XContentBuilder builder = JsonXContent.contentBuilder();
-            builder.value(value);
+            if (value instanceof SecureString secureString) {
+                builder.value(secureString.toString());
+            } else {
+                builder.value(value);
+            }
             return Strings.toString(builder);
         } catch (Exception e) {
             throw new IllegalStateException(
diff --git a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/ServiceUtils.java b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/ServiceUtils.java
index b12f5989e55ce..dfdabcab13a9c 100644
--- a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/ServiceUtils.java
+++ b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/ServiceUtils.java
@@ -22,7 +22,6 @@
 import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.xpack.core.ml.inference.assignment.AdaptiveAllocationsSettings;
 import org.elasticsearch.xpack.inference.services.settings.ApiKeySecrets;
-import org.elasticsearch.xpack.inference.services.settings.SerializableSecureString;
 
 import java.net.URI;
 import java.net.URISyntaxException;
@@ -652,7 +651,7 @@ public static void validateMapValues(
         }
     }
 
-    public static Map<String, SerializableSecureString> convertMapStringsToSecureString(
+    public static Map<String, SecureString> convertMapStringsToSecureString(
         Map<String, ?> map,
         String settingName,
         ValidationException validationException
@@ -661,11 +660,11 @@ public static Map<String, SerializableSecureString> convertMapStringsToSecureStr
             return Map.of();
         }
 
-        validateMapStringValues(map, settingName, validationException, true);
+        var validatedMap = validateMapStringValues(map, settingName, validationException, true);
 
-        return map.entrySet()
+        return validatedMap.entrySet()
             .stream()
-            .collect(Collectors.toMap(Map.Entry::getKey, e -> new SerializableSecureString((String) e.getValue())));
+            .collect(Collectors.toMap(Map.Entry::getKey, e -> new SecureString(e.getValue().toCharArray())));
     }
 
     /**
diff --git a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/custom/CustomSecretSettings.java b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/custom/CustomSecretSettings.java
index dadeb62f0215b..ac6b7ab10c8b3 100644
--- a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/custom/CustomSecretSettings.java
+++ b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/custom/CustomSecretSettings.java
@@ -12,10 +12,10 @@
 import org.elasticsearch.common.ValidationException;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.inference.SecretSettings;
 import org.elasticsearch.xcontent.XContentBuilder;
-import org.elasticsearch.xpack.inference.services.settings.SerializableSecureString;
 
 import java.io.IOException;
 import java.util.HashMap;
@@ -48,22 +48,22 @@ public static CustomSecretSettings fromMap(@Nullable Map<String, Object> map) {
         return new CustomSecretSettings(secureStringMap);
     }
 
-    private final Map<String, SerializableSecureString> secretParameters;
+    private final Map<String, SecureString> secretParameters;
 
     @Override
     public SecretSettings newSecretSettings(Map<String, Object> newSecrets) {
         return fromMap(new HashMap<>(newSecrets));
     }
 
-    public CustomSecretSettings(@Nullable Map<String, SerializableSecureString> secretParameters) {
+    public CustomSecretSettings(@Nullable Map<String, SecureString> secretParameters) {
         this.secretParameters = Objects.requireNonNullElse(secretParameters, Map.of());
     }
 
     public CustomSecretSettings(StreamInput in) throws IOException {
-        secretParameters = in.readImmutableMap(SerializableSecureString::new);
+        secretParameters = in.readImmutableMap(StreamInput::readSecureString);
     }
 
-    public Map<String, SerializableSecureString> getSecretParameters() {
+    public Map<String, SecureString> getSecretParameters() {
         return secretParameters;
     }
 
@@ -74,7 +74,7 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
             builder.startObject(SECRET_PARAMETERS);
             {
                 for (var entry : secretParameters.entrySet()) {
-                    builder.field(entry.getKey(), entry.getValue());
+                    builder.field(entry.getKey(), entry.getValue().toString());
                 }
             }
             builder.endObject();
@@ -95,7 +95,7 @@ public TransportVersion getMinimalSupportedVersion() {
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
-        out.writeMap(secretParameters, (streamOutput, v) -> { v.writeTo(streamOutput); });
+        out.writeMap(secretParameters, StreamOutput::writeSecureString);
     }
 
     @Override
diff --git a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/custom/request/CustomRequest.java b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/custom/request/CustomRequest.java
index eaabdfea472af..1ea73f336bebb 100644
--- a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/custom/request/CustomRequest.java
+++ b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/custom/request/CustomRequest.java
@@ -21,7 +21,6 @@
 import org.elasticsearch.xpack.inference.external.request.Request;
 import org.elasticsearch.xpack.inference.services.custom.CustomModel;
 import org.elasticsearch.xpack.inference.services.custom.CustomServiceSettings;
-import org.elasticsearch.xpack.inference.services.settings.SerializableSecureString;
 
 import java.net.URI;
 import java.net.URISyntaxException;
@@ -70,8 +69,6 @@ private static void addStringParams(Map<String, String> stringParams, Map<String
         for (var entry : paramsToAdd.entrySet()) {
             if (entry.getValue() instanceof String str) {
                 stringParams.put(entry.getKey(), str);
-            } else if (entry.getValue() instanceof SerializableSecureString serializableSecureString) {
-                stringParams.put(entry.getKey(), serializableSecureString.getSecureString().toString());
             } else if (entry.getValue() instanceof SecureString secureString) {
                 stringParams.put(entry.getKey(), secureString.toString());
             }
diff --git a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/settings/SerializableSecureString.java b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/settings/SerializableSecureString.java
deleted file mode 100644
index 0ebd4cc0cad81..0000000000000
--- a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/settings/SerializableSecureString.java
+++ /dev/null
@@ -1,62 +0,0 @@
-/*
- * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
- * or more contributor license agreements. Licensed under the Elastic License
- * 2.0; you may not use this file except in compliance with the Elastic License
- * 2.0.
- */
-
-package org.elasticsearch.xpack.inference.services.settings;
-
-import org.elasticsearch.common.io.stream.StreamInput;
-import org.elasticsearch.common.io.stream.StreamOutput;
-import org.elasticsearch.common.io.stream.Writeable;
-import org.elasticsearch.common.settings.SecureString;
-import org.elasticsearch.xcontent.ToXContentFragment;
-import org.elasticsearch.xcontent.XContentBuilder;
-
-import java.io.IOException;
-import java.util.Objects;
-
-public class SerializableSecureString implements ToXContentFragment, Writeable {
-
-    private final SecureString secureString;
-
-    public SerializableSecureString(StreamInput in) throws IOException {
-        secureString = in.readSecureString();
-    }
-
-    public SerializableSecureString(SecureString secureString) {
-        this.secureString = Objects.requireNonNull(secureString);
-    }
-
-    public SerializableSecureString(String value) {
-        secureString = new SecureString(value.toCharArray());
-    }
-
-    public SecureString getSecureString() {
-        return secureString;
-    }
-
-    @Override
-    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
-        builder.value(secureString.toString());
-        return null;
-    }
-
-    @Override
-    public void writeTo(StreamOutput out) throws IOException {
-        out.writeSecureString(secureString);
-    }
-
-    @Override
-    public boolean equals(Object o) {
-        if (o == null || getClass() != o.getClass()) return false;
-        SerializableSecureString that = (SerializableSecureString) o;
-        return Objects.equals(secureString, that.secureString);
-    }
-
-    @Override
-    public int hashCode() {
-        return Objects.hashCode(secureString);
-    }
-}
diff --git a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/common/JsonUtilsTests.java b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/common/JsonUtilsTests.java
index 7f1003c6723a0..22fa955b6916b 100644
--- a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/common/JsonUtilsTests.java
+++ b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/common/JsonUtilsTests.java
@@ -13,7 +13,6 @@
 import org.elasticsearch.xcontent.ToXContent;
 import org.elasticsearch.xcontent.ToXContentFragment;
 import org.elasticsearch.xcontent.XContentBuilder;
-import org.elasticsearch.xpack.inference.services.settings.SerializableSecureString;
 
 import java.io.IOException;
 import java.util.List;
@@ -53,16 +52,16 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         assertThat(toJson(1.1f, "field"), is("1.1"));
         assertThat(toJson(true, "field"), is("true"));
         assertThat(toJson(false, "field"), is("false"));
-        assertThat(toJson(new SerializableSecureString("api_key"), "field"), is("\"api_key\""));
+        assertThat(toJson(new SecureString("api_key".toCharArray()), "field"), is("\"api_key\""));
     }
 
     public void testToJson_ThrowsException_WhenUnableToSerialize() {
-        var exception = expectThrows(IllegalStateException.class, () -> toJson(new SecureString("string".toCharArray()), "field"));
+        var exception = expectThrows(IllegalStateException.class, () -> toJson(new Object(), "field"));
         assertThat(
             exception.getMessage(),
             is(
                 "Failed to serialize value as JSON, field: field, error: "
-                    + "cannot write xcontent for unknown value of type class org.elasticsearch.common.settings.SecureString"
+                    + "cannot write xcontent for unknown value of type class java.lang.Object"
             )
         );
     }
diff --git a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/ServiceUtilsTests.java b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/ServiceUtilsTests.java
index 770f85c866ba7..8ffdca90ef2d5 100644
--- a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/ServiceUtilsTests.java
+++ b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/ServiceUtilsTests.java
@@ -9,13 +9,13 @@
 
 import org.elasticsearch.ElasticsearchStatusException;
 import org.elasticsearch.common.ValidationException;
+import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.core.Booleans;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.core.Tuple;
 import org.elasticsearch.inference.InputType;
 import org.elasticsearch.test.ESTestCase;
 import org.elasticsearch.xpack.core.ml.inference.assignment.AdaptiveAllocationsSettings;
-import org.elasticsearch.xpack.inference.services.settings.SerializableSecureString;
 
 import java.util.EnumSet;
 import java.util.HashMap;
@@ -1116,7 +1116,7 @@ public void testConvertMapStringsToSecureString() {
         var validation = new ValidationException();
         assertThat(
             convertMapStringsToSecureString(Map.of("key", "value", "key2", "abc"), "setting", validation),
-            is(Map.of("key", new SerializableSecureString("value"), "key2", new SerializableSecureString("abc")))
+            is(Map.of("key", new SecureString("value".toCharArray()), "key2", new SecureString("abc".toCharArray())))
         );
     }
 
diff --git a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomModelTests.java b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomModelTests.java
index c3c4a44bcab07..412066cb3bdd5 100644
--- a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomModelTests.java
+++ b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomModelTests.java
@@ -8,6 +8,7 @@
 package org.elasticsearch.xpack.inference.services.custom;
 
 import org.apache.http.HttpHeaders;
+import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapper;
 import org.elasticsearch.inference.SimilarityMeasure;
@@ -17,7 +18,6 @@
 import org.elasticsearch.xpack.inference.services.custom.response.ErrorResponseParser;
 import org.elasticsearch.xpack.inference.services.custom.response.TextEmbeddingResponseParser;
 import org.elasticsearch.xpack.inference.services.settings.RateLimitSettings;
-import org.elasticsearch.xpack.inference.services.settings.SerializableSecureString;
 import org.hamcrest.MatcherAssert;
 
 import java.util.HashMap;
@@ -30,7 +30,7 @@ public class CustomModelTests extends ESTestCase {
     private static final String taskSettingsValue = "test_taskSettings_value";
 
     private static final String secretSettingsKey = "test_secret_key";
-    private static final SerializableSecureString secretSettingsValue = new SerializableSecureString("test_secret_value");
+    private static final SecureString secretSettingsValue = new SecureString("test_secret_value".toCharArray());
     private static final String url = "http://www.abc.com";
 
     public void testOverride_DoesNotModifiedFields_TaskSettingsIsEmpty() {
diff --git a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomRequestManagerTests.java b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomRequestManagerTests.java
index 16c058b3e0115..484585bdff68d 100644
--- a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomRequestManagerTests.java
+++ b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomRequestManagerTests.java
@@ -9,6 +9,7 @@
 
 import org.elasticsearch.ElasticsearchStatusException;
 import org.elasticsearch.action.support.PlainActionFuture;
+import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.inference.InferenceServiceResults;
 import org.elasticsearch.inference.TaskType;
@@ -19,7 +20,6 @@
 import org.elasticsearch.xpack.inference.services.custom.response.ErrorResponseParser;
 import org.elasticsearch.xpack.inference.services.custom.response.RerankResponseParser;
 import org.elasticsearch.xpack.inference.services.settings.RateLimitSettings;
-import org.elasticsearch.xpack.inference.services.settings.SerializableSecureString;
 import org.junit.After;
 import org.junit.Before;
 
@@ -73,7 +73,7 @@ public void testCreateRequest_ThrowsException_ForInvalidUrl() {
             TaskType.RERANK,
             serviceSettings,
             new CustomTaskSettings(Map.of("url", "^")),
-            new CustomSecretSettings(Map.of("api_key", new SerializableSecureString("my-secret-key")))
+            new CustomSecretSettings(Map.of("api_key", new SecureString("my-secret-key".toCharArray())))
         );
 
         var listener = new PlainActionFuture<InferenceServiceResults>();
diff --git a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomSecretSettingsTests.java b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomSecretSettingsTests.java
index a29992cd7f9fd..d8c6c8faf02ae 100644
--- a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomSecretSettingsTests.java
+++ b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomSecretSettingsTests.java
@@ -11,12 +11,12 @@
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.ValidationException;
 import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.xcontent.XContentBuilder;
 import org.elasticsearch.xcontent.XContentFactory;
 import org.elasticsearch.xcontent.XContentType;
 import org.elasticsearch.xpack.core.ml.AbstractBWCWireSerializationTestCase;
-import org.elasticsearch.xpack.inference.services.settings.SerializableSecureString;
 
 import java.io.IOException;
 import java.util.HashMap;
@@ -28,10 +28,10 @@
 
 public class CustomSecretSettingsTests extends AbstractBWCWireSerializationTestCase<CustomSecretSettings> {
     public static CustomSecretSettings createRandom() {
-        Map<String, SerializableSecureString> secretParameters = randomMap(
+        Map<String, SecureString> secretParameters = randomMap(
             0,
             5,
-            () -> tuple(randomAlphaOfLength(5), new SerializableSecureString(randomAlphaOfLength(5)))
+            () -> tuple(randomAlphaOfLength(5), new SecureString(randomAlphaOfLength(5).toCharArray()))
         );
 
         return new CustomSecretSettings(secretParameters);
@@ -44,7 +44,7 @@ public void testFromMap() {
 
         assertThat(
             CustomSecretSettings.fromMap(secretParameters),
-            is(new CustomSecretSettings(Map.of("test_key", new SerializableSecureString("test_value"))))
+            is(new CustomSecretSettings(Map.of("test_key", new SecureString("test_value".toCharArray()))))
         );
     }
 
@@ -59,7 +59,7 @@ public void testFromMap_RemovesNullValues() {
 
         assertThat(
             CustomSecretSettings.fromMap(modifiableMap(Map.of(CustomSecretSettings.SECRET_PARAMETERS, mapWithNulls))),
-            is(new CustomSecretSettings(Map.of("value", new SerializableSecureString("abc"))))
+            is(new CustomSecretSettings(Map.of("value", new SecureString("abc".toCharArray()))))
         );
     }
 
@@ -87,7 +87,7 @@ public void testFromMap_DefaultsToEmptyMap_WhenSecretParametersField_DoesNotExis
     }
 
     public void testXContent() throws IOException {
-        var entity = new CustomSecretSettings(Map.of("test_key", new SerializableSecureString("test_value")));
+        var entity = new CustomSecretSettings(Map.of("test_key", new SecureString("test_value".toCharArray())));
 
         XContentBuilder builder = XContentFactory.contentBuilder(XContentType.JSON);
         entity.toXContent(builder, null);
diff --git a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomServiceTests.java b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomServiceTests.java
index b9a94e0124183..420bf52ce113b 100644
--- a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomServiceTests.java
+++ b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomServiceTests.java
@@ -8,6 +8,7 @@
 package org.elasticsearch.xpack.inference.services.custom;
 
 import org.elasticsearch.action.support.PlainActionFuture;
+import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapper;
 import org.elasticsearch.inference.InferenceServiceResults;
@@ -35,7 +36,6 @@
 import org.elasticsearch.xpack.inference.services.custom.response.SparseEmbeddingResponseParser;
 import org.elasticsearch.xpack.inference.services.custom.response.TextEmbeddingResponseParser;
 import org.elasticsearch.xpack.inference.services.settings.RateLimitSettings;
-import org.elasticsearch.xpack.inference.services.settings.SerializableSecureString;
 
 import java.io.IOException;
 import java.util.EnumSet;
@@ -123,7 +123,7 @@ private static CustomModel assertCommonModelFields(Model model) {
         assertThat(customModel.getTaskSettings().getParameters(), is(Map.of("test_key", "test_value")));
         assertThat(
             customModel.getSecretSettings().getSecretParameters(),
-            is(Map.of("test_key", new SerializableSecureString("test_value")))
+            is(Map.of("test_key", new SecureString("test_value".toCharArray())))
         );
 
         return customModel;
@@ -249,7 +249,7 @@ private static CustomModel createInternalEmbeddingModel(
                 new ErrorResponseParser("$.error.message", inferenceId)
             ),
             new CustomTaskSettings(Map.of("key", "test_value")),
-            new CustomSecretSettings(Map.of("test_key", new SerializableSecureString("test_value")))
+            new CustomSecretSettings(Map.of("test_key", new SecureString("test_value".toCharArray())))
         );
     }
 
@@ -271,7 +271,7 @@ private static CustomModel createCustomModel(TaskType taskType, CustomResponsePa
                 new ErrorResponseParser("$.error.message", inferenceId)
             ),
             new CustomTaskSettings(Map.of("key", "test_value")),
-            new CustomSecretSettings(Map.of("test_key", new SerializableSecureString("test_value")))
+            new CustomSecretSettings(Map.of("test_key", new SecureString("test_value".toCharArray())))
         );
     }
 
diff --git a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/request/CustomRequestTests.java b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/request/CustomRequestTests.java
index 06bfc0b1f6956..0f5daaf13af43 100644
--- a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/request/CustomRequestTests.java
+++ b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/services/custom/request/CustomRequestTests.java
@@ -11,6 +11,7 @@
 import org.apache.http.client.methods.HttpPost;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.Streams;
+import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapper;
 import org.elasticsearch.inference.SimilarityMeasure;
@@ -26,7 +27,6 @@
 import org.elasticsearch.xpack.inference.services.custom.response.RerankResponseParser;
 import org.elasticsearch.xpack.inference.services.custom.response.TextEmbeddingResponseParser;
 import org.elasticsearch.xpack.inference.services.settings.RateLimitSettings;
-import org.elasticsearch.xpack.inference.services.settings.SerializableSecureString;
 
 import java.io.IOException;
 import java.io.InputStream;
@@ -72,7 +72,7 @@ public void testCreateRequest() throws IOException {
             TaskType.TEXT_EMBEDDING,
             serviceSettings,
             new CustomTaskSettings(Map.of("url", "https://www.elastic.com")),
-            new CustomSecretSettings(Map.of("api_key", new SerializableSecureString("my-secret-key")))
+            new CustomSecretSettings(Map.of("api_key", new SecureString("my-secret-key".toCharArray())))
         );
 
         var request = new CustomRequest(null, List.of("abc", "123"), model);
@@ -126,7 +126,7 @@ public void testCreateRequest_QueryParametersAreEscaped_AndEncoded() {
             TaskType.TEXT_EMBEDDING,
             serviceSettings,
             new CustomTaskSettings(Map.of("url", "https://www.elastic.com")),
-            new CustomSecretSettings(Map.of("api_key", new SerializableSecureString("my-secret-key")))
+            new CustomSecretSettings(Map.of("api_key", new SecureString("my-secret-key".toCharArray())))
         );
 
         var request = new CustomRequest(null, List.of("abc", "123"), model);
@@ -174,7 +174,7 @@ public void testCreateRequest_SecretsInTheJsonBody_AreEncodedCorrectly() throws
             TaskType.TEXT_EMBEDDING,
             serviceSettings,
             new CustomTaskSettings(Map.of("url", "https://www.elastic.com")),
-            new CustomSecretSettings(Map.of("api_key", new SerializableSecureString("my-secret-key")))
+            new CustomSecretSettings(Map.of("api_key", new SecureString("my-secret-key".toCharArray())))
         );
 
         var request = new CustomRequest(null, List.of("abc", "123"), model);
@@ -222,7 +222,7 @@ public void testCreateRequest_HandlesQuery() throws IOException {
             TaskType.RERANK,
             serviceSettings,
             new CustomTaskSettings(Map.of()),
-            new CustomSecretSettings(Map.of("api_key", new SerializableSecureString("my-secret-key")))
+            new CustomSecretSettings(Map.of("api_key", new SecureString("my-secret-key".toCharArray())))
         );
 
         var request = new CustomRequest("query string", List.of("abc", "123"), model);
@@ -265,7 +265,7 @@ public void testCreateRequest_IgnoresNonStringFields_ForStringParams() throws IO
             TaskType.RERANK,
             serviceSettings,
             new CustomTaskSettings(Map.of("task.key", 100)),
-            new CustomSecretSettings(Map.of("api_key", new SerializableSecureString("my-secret-key")))
+            new CustomSecretSettings(Map.of("api_key", new SecureString("my-secret-key".toCharArray())))
         );
 
         var request = new CustomRequest(null, List.of("abc", "123"), model);
@@ -297,7 +297,7 @@ public void testCreateRequest_ThrowsException_ForInvalidUrl() {
             TaskType.RERANK,
             serviceSettings,
             new CustomTaskSettings(Map.of("url", "^")),
-            new CustomSecretSettings(Map.of("api_key", new SerializableSecureString("my-secret-key")))
+            new CustomSecretSettings(Map.of("api_key", new SecureString("my-secret-key".toCharArray())))
         );
 
         var exception = expectThrows(IllegalStateException.class, () -> new CustomRequest(null, List.of("abc", "123"), model));