elastic · elasticsearchmachine · Jun 18, 2025 · Jun 18, 2025
diff --git a/server/src/main/java/org/elasticsearch/TransportVersions.java b/server/src/main/java/org/elasticsearch/TransportVersions.java
@@ -242,6 +242,7 @@ static TransportVersion def(int id) {
     public static final TransportVersion NONE_CHUNKING_STRATEGY_8_19 = def(8_841_0_49);
     public static final TransportVersion IDP_CUSTOM_SAML_ATTRIBUTES_ALLOW_LIST_8_19 = def(8_841_0_50);
     public static final TransportVersion SETTINGS_IN_DATA_STREAMS_8_19 = def(8_841_0_51);
+    public static final TransportVersion ML_INFERENCE_CUSTOM_SERVICE_REMOVE_ERROR_PARSING_8_19 = def(8_841_0_52);
 
     /*
      * STOP! READ THIS FIRST! No, really,

diff --git a/...src/main/java/org/elasticsearch/xpack/inference/services/custom/CustomRequestManager.java b/...src/main/java/org/elasticsearch/xpack/inference/services/custom/CustomRequestManager.java
@@ -41,8 +41,8 @@ public static RateLimitGrouping of(CustomModel model) {
         }
     }
 
-    private static ResponseHandler createCustomHandler(CustomModel model) {
-        return new CustomResponseHandler("custom model", CustomResponseEntity::fromResponse, model.getServiceSettings().getErrorParser());
+    private static ResponseHandler createCustomHandler() {
+        return new CustomResponseHandler("custom model", CustomResponseEntity::fromResponse);
     }
 
     public static CustomRequestManager of(CustomModel model, ThreadPool threadPool) {
@@ -55,7 +55,7 @@ public static CustomRequestManager of(CustomModel model, ThreadPool threadPool)
     private CustomRequestManager(CustomModel model, ThreadPool threadPool) {
         super(threadPool, model.getInferenceEntityId(), RateLimitGrouping.of(model), model.rateLimitServiceSettings().rateLimitSettings());
         this.model = model;
-        this.handler = createCustomHandler(model);
+        this.handler = createCustomHandler();
     }
 
     @Override

diff --git a/...rc/main/java/org/elasticsearch/xpack/inference/services/custom/CustomResponseHandler.java b/...rc/main/java/org/elasticsearch/xpack/inference/services/custom/CustomResponseHandler.java
@@ -8,21 +8,34 @@
 package org.elasticsearch.xpack.inference.services.custom;
 
 import org.elasticsearch.ElasticsearchStatusException;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.inference.InferenceServiceResults;
 import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.xpack.inference.external.http.HttpResult;
 import org.elasticsearch.xpack.inference.external.http.retry.BaseResponseHandler;
+import org.elasticsearch.xpack.inference.external.http.retry.ErrorResponse;
 import org.elasticsearch.xpack.inference.external.http.retry.ResponseParser;
 import org.elasticsearch.xpack.inference.external.http.retry.RetryException;
 import org.elasticsearch.xpack.inference.external.request.Request;
-import org.elasticsearch.xpack.inference.services.custom.response.ErrorResponseParser;
+
+import java.nio.charset.StandardCharsets;
+import java.util.function.Function;
 
 /**
  * Defines how to handle various response types returned from the custom integration.
  */
 public class CustomResponseHandler extends BaseResponseHandler {
-    public CustomResponseHandler(String requestType, ResponseParser parseFunction, ErrorResponseParser errorParser) {
-        super(requestType, parseFunction, errorParser);
+    // default for testing
+    static final Function<HttpResult, ErrorResponse> ERROR_PARSER = (httpResult) -> {
+        try {
+            return new ErrorResponse(new String(httpResult.body(), StandardCharsets.UTF_8));
+        } catch (Exception e) {
+            return new ErrorResponse(Strings.format("Failed to parse error response body: %s", e.getMessage()));
+        }
+    };
+
+    public CustomResponseHandler(String requestType, ResponseParser parseFunction) {
+        super(requestType, parseFunction, ERROR_PARSER);
     }
 
     @Override

diff --git a/...erence/src/main/java/org/elasticsearch/xpack/inference/services/custom/CustomService.java b/...erence/src/main/java/org/elasticsearch/xpack/inference/services/custom/CustomService.java
@@ -249,8 +249,7 @@ private static CustomServiceSettings getCustomServiceSettings(CustomModel custom
             serviceSettings.getQueryParameters(),
             serviceSettings.getRequestContentString(),
             serviceSettings.getResponseJsonParser(),
-            serviceSettings.rateLimitSettings(),
-            serviceSettings.getErrorParser()
+            serviceSettings.rateLimitSettings()
         );
     }
 

diff --git a/...rc/main/java/org/elasticsearch/xpack/inference/services/custom/CustomServiceSettings.java b/...rc/main/java/org/elasticsearch/xpack/inference/services/custom/CustomServiceSettings.java
@@ -26,7 +26,6 @@
 import org.elasticsearch.xpack.inference.services.ConfigurationParseContext;
 import org.elasticsearch.xpack.inference.services.custom.response.CompletionResponseParser;
 import org.elasticsearch.xpack.inference.services.custom.response.CustomResponseParser;
-import org.elasticsearch.xpack.inference.services.custom.response.ErrorResponseParser;
 import org.elasticsearch.xpack.inference.services.custom.response.NoopResponseParser;
 import org.elasticsearch.xpack.inference.services.custom.response.RerankResponseParser;
 import org.elasticsearch.xpack.inference.services.custom.response.SparseEmbeddingResponseParser;
@@ -59,7 +58,6 @@ public class CustomServiceSettings extends FilteredXContentObject implements Ser
     public static final String REQUEST = "request";
     public static final String RESPONSE = "response";
     public static final String JSON_PARSER = "json_parser";
-    public static final String ERROR_PARSER = "error_parser";
 
     private static final RateLimitSettings DEFAULT_RATE_LIMIT_SETTINGS = new RateLimitSettings(10_000);
     private static final String RESPONSE_SCOPE = String.join(".", ModelConfigurations.SERVICE_SETTINGS, RESPONSE);
@@ -100,15 +98,6 @@ public static CustomServiceSettings fromMap(
 
         var responseJsonParser = extractResponseParser(taskType, jsonParserMap, validationException);
 
-        Map<String, Object> errorParserMap = extractRequiredMap(
-            Objects.requireNonNullElse(responseParserMap, new HashMap<>()),
-            ERROR_PARSER,
-            RESPONSE_SCOPE,
-            validationException
-        );
-
-        var errorParser = ErrorResponseParser.fromMap(errorParserMap, RESPONSE_SCOPE, inferenceId, validationException);
-
         RateLimitSettings rateLimitSettings = RateLimitSettings.of(
             map,
             DEFAULT_RATE_LIMIT_SETTINGS,
@@ -117,13 +106,12 @@ public static CustomServiceSettings fromMap(
             context
         );
 
-        if (responseParserMap == null || jsonParserMap == null || errorParserMap == null) {
+        if (responseParserMap == null || jsonParserMap == null) {
             throw validationException;
         }
 
         throwIfNotEmptyMap(jsonParserMap, JSON_PARSER, NAME);
         throwIfNotEmptyMap(responseParserMap, RESPONSE, NAME);
-        throwIfNotEmptyMap(errorParserMap, ERROR_PARSER, NAME);
 
         if (validationException.validationErrors().isEmpty() == false) {
             throw validationException;
@@ -136,8 +124,7 @@ public static CustomServiceSettings fromMap(
             queryParams,
             requestContentString,
             responseJsonParser,
-            rateLimitSettings,
-            errorParser
+            rateLimitSettings
         );
     }
 
@@ -209,7 +196,6 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
     private final String requestContentString;
     private final CustomResponseParser responseJsonParser;
     private final RateLimitSettings rateLimitSettings;
-    private final ErrorResponseParser errorParser;
 
     public CustomServiceSettings(
         TextEmbeddingSettings textEmbeddingSettings,
@@ -218,8 +204,7 @@ public CustomServiceSettings(
         @Nullable QueryParameters queryParameters,
         String requestContentString,
         CustomResponseParser responseJsonParser,
-        @Nullable RateLimitSettings rateLimitSettings,
-        ErrorResponseParser errorParser
+        @Nullable RateLimitSettings rateLimitSettings
     ) {
         this.textEmbeddingSettings = Objects.requireNonNull(textEmbeddingSettings);
         this.url = Objects.requireNonNull(url);
@@ -228,7 +213,6 @@ public CustomServiceSettings(
         this.requestContentString = Objects.requireNonNull(requestContentString);
         this.responseJsonParser = Objects.requireNonNull(responseJsonParser);
         this.rateLimitSettings = Objects.requireNonNullElse(rateLimitSettings, DEFAULT_RATE_LIMIT_SETTINGS);
-        this.errorParser = Objects.requireNonNull(errorParser);
     }
 
     public CustomServiceSettings(StreamInput in) throws IOException {
@@ -239,7 +223,11 @@ public CustomServiceSettings(StreamInput in) throws IOException {
         requestContentString = in.readString();
         responseJsonParser = in.readNamedWriteable(CustomResponseParser.class);
         rateLimitSettings = new RateLimitSettings(in);
-        errorParser = new ErrorResponseParser(in);
+        if (in.getTransportVersion().before(TransportVersions.ML_INFERENCE_CUSTOM_SERVICE_REMOVE_ERROR_PARSING_8_19)) {
+            // Read the error parsing fields for backwards compatibility
+            in.readString();
+            in.readString();
+        }
     }
 
     @Override
@@ -287,10 +275,6 @@ public CustomResponseParser getResponseJsonParser() {
         return responseJsonParser;
     }
 
-    public ErrorResponseParser getErrorParser() {
-        return errorParser;
-    }
-
     @Override
     public RateLimitSettings rateLimitSettings() {
         return rateLimitSettings;
@@ -331,7 +315,6 @@ public XContentBuilder toXContentFragmentOfExposedFields(XContentBuilder builder
         builder.startObject(RESPONSE);
         {
             responseJsonParser.toXContent(builder, params);
-            errorParser.toXContent(builder, params);
         }
         builder.endObject();
 
@@ -359,7 +342,11 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeString(requestContentString);
         out.writeNamedWriteable(responseJsonParser);
         rateLimitSettings.writeTo(out);
-        errorParser.writeTo(out);
+        if (out.getTransportVersion().before(TransportVersions.ML_INFERENCE_CUSTOM_SERVICE_REMOVE_ERROR_PARSING_8_19)) {
+            // Write empty strings for backwards compatibility for the error parsing fields
+            out.writeString("");
+            out.writeString("");
+        }
     }
 
     @Override
@@ -373,8 +360,7 @@ public boolean equals(Object o) {
             && Objects.equals(queryParameters, that.queryParameters)
             && Objects.equals(requestContentString, that.requestContentString)
             && Objects.equals(responseJsonParser, that.responseJsonParser)
-            && Objects.equals(rateLimitSettings, that.rateLimitSettings)
-            && Objects.equals(errorParser, that.errorParser);
+            && Objects.equals(rateLimitSettings, that.rateLimitSettings);
     }
 
     @Override
@@ -386,8 +372,7 @@ public int hashCode() {
             queryParameters,
             requestContentString,
             responseJsonParser,
-            rateLimitSettings,
-            errorParser
+            rateLimitSettings
         );
     }
 

diff --git a/.../java/org/elasticsearch/xpack/inference/services/custom/response/ErrorResponseParser.java b/.../java/org/elasticsearch/xpack/inference/services/custom/response/ErrorResponseParser.java
diff --git a/...nce/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomModelTests.java b/...nce/src/test/java/org/elasticsearch/xpack/inference/services/custom/CustomModelTests.java
@@ -15,7 +15,6 @@
 import org.elasticsearch.inference.TaskType;
 import org.elasticsearch.test.ESTestCase;
 import org.elasticsearch.xpack.inference.services.custom.response.CustomResponseParser;
-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.hamcrest.MatcherAssert;
@@ -120,8 +119,7 @@ public static CustomModel getTestModel(TaskType taskType, CustomResponseParser r
             QueryParameters.EMPTY,
             requestContentString,
             responseParser,
-            new RateLimitSettings(10_000),
-            new ErrorResponseParser("$.error.message", inferenceId)
+            new RateLimitSettings(10_000)
         );
 
         CustomTaskSettings taskSettings = new CustomTaskSettings(Map.of(taskSettingsKey, taskSettingsValue));

diff --git a/...est/java/org/elasticsearch/xpack/inference/services/custom/CustomRequestManagerTests.java b/...est/java/org/elasticsearch/xpack/inference/services/custom/CustomRequestManagerTests.java
@@ -17,7 +17,6 @@
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.xpack.inference.external.http.retry.RequestSender;
 import org.elasticsearch.xpack.inference.external.http.sender.EmbeddingsInput;
-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.junit.After;
@@ -64,8 +63,7 @@ public void testCreateRequest_ThrowsException_ForInvalidUrl() {
             null,
             requestContentString,
             new RerankResponseParser("$.result.score"),
-            new RateLimitSettings(10_000),
-            new ErrorResponseParser("$.error.message", inferenceId)
+            new RateLimitSettings(10_000)
         );
 
         var model = CustomModelTests.createModel(