aws · kuhe · Nov 14, 2025 · Nov 14, 2025
@@ -1,10 +1,10 @@
 import "@aws-sdk/signature-v4-crt";
 
+import { getE2eTestResources } from "@aws-sdk/aws-util-test/src";
 import { ChecksumAlgorithm, S3 } from "@aws-sdk/client-s3";
 import { afterAll, afterEach, beforeAll, describe, expect, test as it } from "vitest";
 
 import { createBuffer } from "./helpers";
-import { getE2eTestResources } from "@aws-sdk/aws-util-test/src";
 
 let Key = `${Date.now()}`;
 
@@ -246,5 +246,19 @@ describe("@aws-sdk/client-s3", () => {
       expect(result.$metadata.httpStatusCode).toEqual(200);
       expect(result.Contents).toBeInstanceOf(Array);
     });
+
+    describe("error handling", () => {
+      it("should decorate exceptions with unmodeled error fields", async () => {
+        const error = await client
+          .abortMultipartUpload({
+            Bucket,
+            Key: "nonexistent-key",
+            UploadId: "uploadId",
+          })
+          .catch((e) => e);
+
+        expect((error as any).UploadId).toEqual("uploadId");
+      });
+    });
   });
 }, 60_000);
@@ -1,11 +1,12 @@
 import { NormalizedSchema, TypeRegistry } from "@smithy/core/schema";
+import { decorateServiceException, ServiceException as SDKBaseServiceException } from "@smithy/smithy-client";
 import type { HttpResponse as IHttpResponse, MetadataBearer, ResponseMetadata, StaticErrorSchema } from "@smithy/types";
 
 /**
  * @internal
  */
 type ErrorMetadataBearer = MetadataBearer & {
-  $response: IHttpResponse;
+  // $response is set by the deserializer middleware, not Protocol.
   $fault: "client" | "server";
 };
 
@@ -15,6 +16,8 @@ type ErrorMetadataBearer = MetadataBearer & {
  * @internal
  */
 export class ProtocolLib {
+  public constructor(private queryCompat = false) {}
+
   /**
    * This is only for REST protocols.
    *
@@ -74,7 +77,6 @@ export class ProtocolLib {
 
     const errorMetadata: ErrorMetadataBearer = {
       $metadata: metadata,
-      $response: response,
       $fault: response.statusCode < 500 ? ("client" as const) : ("server" as const),
     };
 
@@ -90,10 +92,32 @@ export class ProtocolLib {
       const baseExceptionSchema = synthetic.getBaseException();
       if (baseExceptionSchema) {
         const ErrorCtor = synthetic.getErrorCtor(baseExceptionSchema) ?? Error;
-        throw Object.assign(new ErrorCtor({ name: errorName }), errorMetadata, dataObject);
+        throw this.decorateServiceException(
+          Object.assign(new ErrorCtor({ name: errorName }), errorMetadata),
+          dataObject
+        );
+      }
+      throw this.decorateServiceException(Object.assign(new Error(errorName), errorMetadata), dataObject);
+    }
+  }
+
+  /**
+   * Assigns additions onto exception if not already present.
+   */
+  public decorateServiceException<E extends SDKBaseServiceException>(
+    exception: E,
+    additions: Record<string, any> = {}
+  ): E {
+    if (this.queryCompat) {
+      const msg = (exception as any).Message ?? additions.Message;
+      const error = decorateServiceException(exception, additions);
+      if (msg) {
+        (error as any).Message = msg;
+        (error as any).message = msg;
       }
-      throw Object.assign(new Error(errorName), errorMetadata, dataObject);
+      return error;
     }
+    return decorateServiceException(exception, additions);
   }
 
   /**

@@ -4,6 +4,7 @@ import { HttpResponse } from "@smithy/protocol-http";
 import type { NumericSchema, StringSchema } from "@smithy/types";
 import { describe, expect, test as it } from "vitest";
 
+import { context } from "../test-schema.spec";
 import { AwsSmithyRpcV2CborProtocol } from "./AwsSmithyRpcV2CborProtocol";
 
 describe(AwsSmithyRpcV2CborProtocol.name, () => {
@@ -56,16 +57,8 @@ describe(AwsSmithyRpcV2CborProtocol.name, () => {
       requestId: undefined,
     });
 
-    expect(error.$response).toEqual(
-      new HttpResponse({
-        body,
-        headers: {
-          "x-amzn-query-error": "MyQueryError;Client",
-        },
-        reason: undefined,
-        statusCode: 400,
-      })
-    );
+    // set by deserializer middleware, not Protocol.
+    expect(error.$response).toEqual(undefined);
 
     expect(error.Code).toEqual(MyQueryError.name);
     expect(error.Error.Code).toEqual(MyQueryError.name);
@@ -91,4 +84,41 @@ describe(AwsSmithyRpcV2CborProtocol.name, () => {
       Code: "MyQueryError",
     });
   });
+
+  it("decorates service exceptions with unmodeled fields", async () => {
+    const httpResponse = new HttpResponse({
+      statusCode: 400,
+      headers: {},
+      body: cbor.serialize({
+        UnmodeledField: "Oh no",
+      }),
+    });
+
+    const protocol = new AwsSmithyRpcV2CborProtocol({
+      defaultNamespace: "",
+    });
+
+    const output = await protocol
+      .deserializeResponse(
+        {
+          namespace: "ns",
+          name: "Empty",
+          traits: 0,
+          input: "unit" as const,
+          output: [3, "ns", "EmptyOutput", 0, [], []],
+        },
+        context,
+        httpResponse
+      )
+      .catch((e) => {
+        return e;
+      });
+
+    expect(output).toMatchObject({
+      UnmodeledField: "Oh no",
+      $metadata: {
+        httpStatusCode: 400,
+      },
+    });
+  });
 });
@@ -19,7 +19,7 @@ import { ProtocolLib } from "../ProtocolLib";
  */
 export class AwsSmithyRpcV2CborProtocol extends SmithyRpcV2CborProtocol {
   private readonly awsQueryCompatible: boolean;
-  private readonly mixin = new ProtocolLib();
+  private readonly mixin: ProtocolLib;
 
   public constructor({
     defaultNamespace,
@@ -30,6 +30,7 @@ export class AwsSmithyRpcV2CborProtocol extends SmithyRpcV2CborProtocol {
   }) {
     super({ defaultNamespace });
     this.awsQueryCompatible = !!awsQueryCompatible;
+    this.mixin = new ProtocolLib(this.awsQueryCompatible);
   }
 
   /**
@@ -84,14 +85,17 @@ export class AwsSmithyRpcV2CborProtocol extends SmithyRpcV2CborProtocol {
       this.mixin.queryCompatOutput(dataObject, output);
     }
 
-    throw Object.assign(
-      exception,
-      errorMetadata,
-      {
-        $fault: ns.getMergedTraits().error,
-        message,
-      },
-      output
+    throw this.mixin.decorateServiceException(
+      Object.assign(
+        exception,
+        errorMetadata,
+        {
+          $fault: ns.getMergedTraits().error,
+          message,
+        },
+        output
+      ),
+      dataObject
     );
   }
 }
@@ -86,4 +86,40 @@ describe(AwsJson1_1Protocol, () => {
       },
     });
   });
+
+  it("decorates service exceptions with unmodeled fields", async () => {
+    const httpResponse = new HttpResponse({
+      statusCode: 400,
+      headers: {},
+      body: Buffer.from(`{"UnmodeledField":"Oh no"}`),
+    });
+
+    const protocol = new AwsJson1_1Protocol({
+      defaultNamespace: "",
+      serviceTarget: "JsonRpc11",
+    });
+
+    const output = await protocol
+      .deserializeResponse(
+        {
+          namespace: "ns",
+          name: "Empty",
+          traits: 0,
+          input: "unit" as const,
+          output: [3, "ns", "EmptyOutput", 0, [], []],
+        },
+        context,
+        httpResponse
+      )
+      .catch((e) => {
+        return e;
+      });
+
+    expect(output).toMatchObject({
+      UnmodeledField: "Oh no",
+      $metadata: {
+        httpStatusCode: 400,
+      },
+    });
+  });
 });
@@ -80,16 +80,8 @@ describe(AwsJsonRpcProtocol.name, () => {
       requestId: undefined,
     });
 
-    expect(error.$response).toEqual(
-      new HttpResponse({
-        body,
-        headers: {
-          "x-amzn-query-error": "MyQueryError;Client",
-        },
-        reason: undefined,
-        statusCode: 400,
-      })
-    );
+    // set by deserializer middleware, not protocol
+    expect(error.$response).toEqual(undefined);
 
     expect(error.Code).toEqual(MyQueryError.name);
     expect(error.Error.Code).toEqual(MyQueryError.name);

@@ -25,7 +25,7 @@ export abstract class AwsJsonRpcProtocol extends RpcProtocol {
   protected deserializer: ShapeDeserializer<string | Uint8Array>;
   protected serviceTarget: string;
   private readonly codec: JsonCodec;
-  private readonly mixin = new ProtocolLib();
+  private readonly mixin: ProtocolLib;
   private readonly awsQueryCompatible: boolean;
 
   protected constructor({
@@ -51,6 +51,7 @@ export abstract class AwsJsonRpcProtocol extends RpcProtocol {
     this.serializer = this.codec.createSerializer();
     this.deserializer = this.codec.createDeserializer();
     this.awsQueryCompatible = !!awsQueryCompatible;
+    this.mixin = new ProtocolLib(this.awsQueryCompatible);
   }
 
   public async serializeRequest<Input extends object>(
@@ -84,6 +85,9 @@ export abstract class AwsJsonRpcProtocol extends RpcProtocol {
 
   protected abstract getJsonRpcVersion(): "1.1" | "1.0";
 
+  /**
+   * @override
+   */
   protected async handleError(
     operationSchema: OperationSchema,
     context: HandlerExecutionContext & SerdeFunctions,
@@ -120,14 +124,17 @@ export abstract class AwsJsonRpcProtocol extends RpcProtocol {
       this.mixin.queryCompatOutput(dataObject, output);
     }
 
-    throw Object.assign(
-      exception,
-      errorMetadata,
-      {
-        $fault: ns.getMergedTraits().error,
-        message,
-      },
-      output
+    throw this.mixin.decorateServiceException(
+      Object.assign(
+        exception,
+        errorMetadata,
+        {
+          $fault: ns.getMergedTraits().error,
+          message,
+        },
+        output
+      ),
+      dataObject
     );
   }
 }
@@ -410,5 +410,40 @@ describe(AwsRestJsonProtocol.name, () => {
         payload: null,
       });
     });
+
+    it("decorates service exceptions with unmodeled fields", async () => {
+      const httpResponse = new HttpResponse({
+        statusCode: 400,
+        headers: {},
+        body: Buffer.from(`{"UnmodeledField":"Oh no"}`),
+      });
+
+      const protocol = new AwsRestJsonProtocol({
+        defaultNamespace: "",
+      });
+
+      const output = await protocol
+        .deserializeResponse(
+          {
+            namespace: "ns",
+            name: "Empty",
+            traits: 0,
+            input: "unit" as const,
+            output: [3, "ns", "EmptyOutput", 0, [], []],
+          },
+          context,
+          httpResponse
+        )
+        .catch((e) => {
+          return e;
+        });
+
+      expect(output).toMatchObject({
+        UnmodeledField: "Oh no",
+        $metadata: {
+          httpStatusCode: 400,
+        },
+      });
+    });
   });
 });
@@ -139,14 +139,17 @@ export class AwsRestJsonProtocol extends HttpBindingProtocol {
       output[name] = this.codec.createDeserializer().readObject(member, dataObject[target]);
     }
 
-    throw Object.assign(
-      exception,
-      errorMetadata,
-      {
-        $fault: ns.getMergedTraits().error,
-        message,
-      },
-      output
+    throw this.mixin.decorateServiceException(
+      Object.assign(
+        exception,
+        errorMetadata,
+        {
+          $fault: ns.getMergedTraits().error,
+          message,
+        },
+        output
+      ),
+      dataObject
     );
   }