diff --git a/packages/core/package.json b/packages/core/package.json
index a53185d2adab1..b19600b67eb49 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -91,7 +91,6 @@
     "@smithy/smithy-client": "^4.6.4",
     "@smithy/types": "^4.5.0",
     "@smithy/util-base64": "^4.1.0",
-    "@smithy/util-body-length-browser": "^4.1.0",
     "@smithy/util-middleware": "^4.1.1",
     "@smithy/util-utf8": "^4.1.0",
     "tslib": "^2.6.2"
diff --git a/packages/core/src/submodules/protocols/ProtocolLib.ts b/packages/core/src/submodules/protocols/ProtocolLib.ts
index f378606fc4f9a..01c688ee7d9a4 100644
--- a/packages/core/src/submodules/protocols/ProtocolLib.ts
+++ b/packages/core/src/submodules/protocols/ProtocolLib.ts
@@ -1,12 +1,5 @@
 import { ErrorSchema, NormalizedSchema, TypeRegistry } from "@smithy/core/schema";
-import type {
-  BodyLengthCalculator,
-  HttpResponse as IHttpResponse,
-  MetadataBearer,
-  ResponseMetadata,
-  SerdeFunctions,
-} from "@smithy/types";
-import { calculateBodyLength } from "@smithy/util-body-length-browser";
+import type { HttpResponse as IHttpResponse, MetadataBearer, ResponseMetadata } from "@smithy/types";
 
 /**
  * @internal
@@ -22,23 +15,6 @@ type ErrorMetadataBearer = MetadataBearer & {
  * @internal
  */
 export class ProtocolLib {
-  /**
-   * @param body - to be inspected.
-   * @param serdeContext - this is a subset type but in practice is the client.config having a property called bodyLengthChecker.
-   *
-   * @returns content-length value for the body if possible.
-   * @throws Error and should be caught and handled if not possible to determine length.
-   */
-  public calculateContentLength(body: any, serdeContext?: SerdeFunctions) {
-    const bodyLengthCalculator: BodyLengthCalculator =
-      (
-        serdeContext as SerdeFunctions & {
-          bodyLengthChecker?: BodyLengthCalculator;
-        }
-      )?.bodyLengthChecker ?? calculateBodyLength;
-    return String(bodyLengthCalculator(body));
-  }
-
   /**
    * This is only for REST protocols.
    *
@@ -108,9 +84,7 @@ export class ProtocolLib {
       const errorSchema = getErrorSchema?.(registry, errorName) ?? (registry.getSchema(errorIdentifier) as ErrorSchema);
       return { errorSchema, errorMetadata };
     } catch (e) {
-      if (dataObject.Message) {
-        dataObject.message = dataObject.Message;
-      }
+      dataObject.message = dataObject.message ?? dataObject.Message ?? "UnknownError";
       const baseExceptionSchema = TypeRegistry.for("smithy.ts.sdk.synthetic." + namespace).getBaseException();
       if (baseExceptionSchema) {
         const ErrorCtor = baseExceptionSchema.ctor;
diff --git a/packages/core/src/submodules/protocols/json/AwsJson1_0Protocol.spec.ts b/packages/core/src/submodules/protocols/json/AwsJson1_0Protocol.spec.ts
index 2fbf124344889..16d7c227bba55 100644
--- a/packages/core/src/submodules/protocols/json/AwsJson1_0Protocol.spec.ts
+++ b/packages/core/src/submodules/protocols/json/AwsJson1_0Protocol.spec.ts
@@ -115,7 +115,6 @@ describe(AwsJson1_0Protocol.name, () => {
       );
 
       expect(request.headers).toEqual({
-        "content-length": "60",
         "content-type": "application/x-amz-json-1.0",
         "x-amz-target": "JsonRpc10.MyOperation",
       });
diff --git a/packages/core/src/submodules/protocols/json/AwsJsonRpcProtocol.ts b/packages/core/src/submodules/protocols/json/AwsJsonRpcProtocol.ts
index 115796935327e..34eecbb6a9a9e 100644
--- a/packages/core/src/submodules/protocols/json/AwsJsonRpcProtocol.ts
+++ b/packages/core/src/submodules/protocols/json/AwsJsonRpcProtocol.ts
@@ -71,9 +71,9 @@ export abstract class AwsJsonRpcProtocol extends RpcProtocol {
     if (deref(operationSchema.input) === "unit" || !request.body) {
       request.body = "{}";
     }
-    try {
-      request.headers["content-length"] = this.mixin.calculateContentLength(request.body, this.serdeContext);
-    } catch (e) {}
+
+    // content-length header is set by the contentLengthMiddleware.
+
     return request;
   }
 
diff --git a/packages/core/src/submodules/protocols/json/AwsRestJsonProtocol.spec.ts b/packages/core/src/submodules/protocols/json/AwsRestJsonProtocol.spec.ts
index 1f152e70e9a5a..ead21b9da5d79 100644
--- a/packages/core/src/submodules/protocols/json/AwsRestJsonProtocol.spec.ts
+++ b/packages/core/src/submodules/protocols/json/AwsRestJsonProtocol.spec.ts
@@ -161,7 +161,6 @@ describe(AwsRestJsonProtocol.name, () => {
       );
 
       expect(request.headers).toEqual({
-        "content-length": "25",
         "content-type": "application/json",
         header: "hello",
         a: "1",
@@ -265,7 +264,6 @@ describe(AwsRestJsonProtocol.name, () => {
 
       expect(request.headers).toEqual({
         "content-type": "application/json",
-        "content-length": "24",
         "header-default-date": "Thu, 01 Jan 1970 00:00:00 GMT",
         "header-member-trait-date": "1970-01-01T00:00:00Z",
         "header-epoch-seconds": "0",
diff --git a/packages/core/src/submodules/protocols/json/AwsRestJsonProtocol.ts b/packages/core/src/submodules/protocols/json/AwsRestJsonProtocol.ts
index 63fb7354a7cd3..695d9a50aac4f 100644
--- a/packages/core/src/submodules/protocols/json/AwsRestJsonProtocol.ts
+++ b/packages/core/src/submodules/protocols/json/AwsRestJsonProtocol.ts
@@ -78,11 +78,7 @@ export class AwsRestJsonProtocol extends HttpBindingProtocol {
       request.body = "{}";
     }
 
-    if (request.body) {
-      try {
-        request.headers["content-length"] = this.mixin.calculateContentLength(request.body, this.serdeContext);
-      } catch (e) {}
-    }
+    // content-length header is set by the contentLengthMiddleware.
 
     return request;
   }
diff --git a/packages/core/src/submodules/protocols/json/JsonShapeSerializer.ts b/packages/core/src/submodules/protocols/json/JsonShapeSerializer.ts
index 4ef83d947b276..38c4a210099d1 100644
--- a/packages/core/src/submodules/protocols/json/JsonShapeSerializer.ts
+++ b/packages/core/src/submodules/protocols/json/JsonShapeSerializer.ts
@@ -130,7 +130,7 @@ export class JsonShapeSerializer extends SerdeContextConfig implements ShapeSeri
 
       const mediaType = ns.getMergedTraits().mediaType;
 
-      if (typeof value === "string" && mediaType) {
+      if (value != null && mediaType) {
         const isJson = mediaType === "application/json" || mediaType.endsWith("+json");
         if (isJson) {
           return LazyJsonString.from(value);
diff --git a/packages/core/src/submodules/protocols/query/AwsQueryProtocol.ts b/packages/core/src/submodules/protocols/query/AwsQueryProtocol.ts
index 30d1fe3d67ee0..31e088f73e4e0 100644
--- a/packages/core/src/submodules/protocols/query/AwsQueryProtocol.ts
+++ b/packages/core/src/submodules/protocols/query/AwsQueryProtocol.ts
@@ -82,9 +82,8 @@ export class AwsQueryProtocol extends RpcProtocol {
       request.body = request.body.slice(-1);
     }
 
-    try {
-      request.headers["content-length"] = this.mixin.calculateContentLength(request.body, this.serdeContext);
-    } catch (e) {}
+    // content-length header is set by the contentLengthMiddleware.
+
     return request;
   }
 
@@ -142,6 +141,13 @@ export class AwsQueryProtocol extends RpcProtocol {
   ): Promise<never> {
     const errorIdentifier = this.loadQueryErrorCode(response, dataObject) ?? "Unknown";
     const errorData = this.loadQueryError(dataObject);
+    const message = this.loadQueryErrorMessage(dataObject);
+    errorData.message = message;
+    errorData.Error = {
+      Type: errorData.Type,
+      Code: errorData.Code,
+      Message: message,
+    };
 
     const { errorSchema, errorMetadata } = await this.mixin.getErrorSchemaOrThrowBaseException(
       errorIdentifier,
@@ -156,10 +162,11 @@ export class AwsQueryProtocol extends RpcProtocol {
     );
 
     const ns = NormalizedSchema.of(errorSchema);
-    const message = this.loadQueryErrorMessage(dataObject);
     const exception = new errorSchema.ctor(message);
 
-    const output = {} as any;
+    const output = {
+      Error: errorData.Error,
+    } as any;
 
     for (const [name, member] of ns.structIterator()) {
       const target = member.getMergedTraits().xmlName ?? name;
diff --git a/packages/core/src/submodules/protocols/xml/AwsRestXmlProtocol.spec.ts b/packages/core/src/submodules/protocols/xml/AwsRestXmlProtocol.spec.ts
index 5fdbd8863c381..ded37f44705a1 100644
--- a/packages/core/src/submodules/protocols/xml/AwsRestXmlProtocol.spec.ts
+++ b/packages/core/src/submodules/protocols/xml/AwsRestXmlProtocol.spec.ts
@@ -37,7 +37,6 @@ describe(AwsRestXmlProtocol.name, () => {
             method: "POST",
             headers: {
               "content-type": "application/xml",
-              "content-length": "167",
             },
             query: {
               delete: "",
diff --git a/packages/core/src/submodules/protocols/xml/AwsRestXmlProtocol.ts b/packages/core/src/submodules/protocols/xml/AwsRestXmlProtocol.ts
index b915d2ba6700c..de759d5e685e6 100644
--- a/packages/core/src/submodules/protocols/xml/AwsRestXmlProtocol.ts
+++ b/packages/core/src/submodules/protocols/xml/AwsRestXmlProtocol.ts
@@ -74,11 +74,7 @@ export class AwsRestXmlProtocol extends HttpBindingProtocol {
       }
     }
 
-    if (request.body) {
-      try {
-        request.headers["content-length"] = this.mixin.calculateContentLength(request.body, this.serdeContext);
-      } catch (e) {}
-    }
+    // content-length header is set by the contentLengthMiddleware.
 
     return request;
   }
diff --git a/packages/core/src/submodules/protocols/xml/XmlShapeDeserializer.ts b/packages/core/src/submodules/protocols/xml/XmlShapeDeserializer.ts
index 212ab2da183bc..992a408151cbd 100644
--- a/packages/core/src/submodules/protocols/xml/XmlShapeDeserializer.ts
+++ b/packages/core/src/submodules/protocols/xml/XmlShapeDeserializer.ts
@@ -58,6 +58,11 @@ export class XmlShapeDeserializer extends SerdeContextConfig implements ShapeDes
 
   public readSchema(_schema: Schema, value: any): any {
     const ns = NormalizedSchema.of(_schema);
+
+    if (ns.isUnitSchema()) {
+      return;
+    }
+
     const traits = ns.getMergedTraits();
 
     if (ns.isListSchema() && !Array.isArray(value)) {
diff --git a/packages/middleware-sdk-ec2/src/index.ts b/packages/middleware-sdk-ec2/src/index.ts
index bbb861974daa5..a3063fa9c3971 100755
--- a/packages/middleware-sdk-ec2/src/index.ts
+++ b/packages/middleware-sdk-ec2/src/index.ts
@@ -3,7 +3,7 @@ import { getEndpointFromInstructions, toEndpointV1 } from "@smithy/middleware-en
 import { HttpRequest } from "@smithy/protocol-http";
 import { SignatureV4 } from "@smithy/signature-v4";
 import { extendedEncodeURIComponent } from "@smithy/smithy-client";
-import {
+import type {
   AwsCredentialIdentity,
   ChecksumConstructor,
   Endpoint,
@@ -113,8 +113,8 @@ export function copySnapshotPresignedUrlMiddleware(options: PreviouslyResolved):
           },
         };
 
-        // we also double-check the work of the serialzier here
-        // because this middleware may be placed after the regular serialzier.
+        // we also double-check the work of the serializer here
+        // because this middleware may be placed after the regular serializer.
         if (HttpRequest.isInstance(args.request)) {
           const { request } = args;
           if (!(request.body ?? "").includes("DestinationRegion=")) {
diff --git a/packages/middleware-sdk-ec2/src/middleware-sdk-ec2.e2e.spec.ts b/packages/middleware-sdk-ec2/src/middleware-sdk-ec2.e2e.spec.ts
index 8e919b573469e..df46e022c8b81 100644
--- a/packages/middleware-sdk-ec2/src/middleware-sdk-ec2.e2e.spec.ts
+++ b/packages/middleware-sdk-ec2/src/middleware-sdk-ec2.e2e.spec.ts
@@ -1,5 +1,6 @@
 import { EC2, EC2ServiceException, waitUntilSnapshotCompleted, waitUntilVolumeAvailable } from "@aws-sdk/client-ec2";
 import { KMS } from "@aws-sdk/client-kms";
+import { getHttpDebugLogPlugin } from "@aws-sdk/middleware-http-debug-log";
 import { afterAll, beforeAll, describe, expect, onTestFailed, test as it } from "vitest";
 
 const errors = [] as any[];
@@ -108,6 +109,14 @@ describe("EC2 feature test", () => {
     const sourceKms = new KMS({ region: sourceRegion, logger });
     const destinationKms = new KMS({ region: destRegion, logger });
 
+    for (const client of [sourceEc2, destinationEc2, sourceKms, destinationKms]) {
+      // I'm leaving this debug call in the test because it's so slow that
+      // you will want to see active request progress.
+      void getHttpDebugLogPlugin;
+      void client;
+      // client.middlewareStack.use(getHttpDebugLogPlugin("line"));
+    }
+
     async function teardown() {
       if (volumeId) {
         await sourceEc2.deleteVolume({ VolumeId: volumeId });
diff --git a/private/aws-client-retry-test/src/ClientRetryTest.spec.ts b/private/aws-client-retry-test/src/ClientRetryTest.spec.ts
index c9c38a8726064..e218b5fc8328e 100644
--- a/private/aws-client-retry-test/src/ClientRetryTest.spec.ts
+++ b/private/aws-client-retry-test/src/ClientRetryTest.spec.ts
@@ -1,4 +1,4 @@
-import { ListFunctionsCommand, Lambda, LambdaClient, LambdaServiceException } from "@aws-sdk/client-lambda";
+import { Lambda, LambdaClient, LambdaServiceException, ListFunctionsCommand } from "@aws-sdk/client-lambda";
 import { HttpHandler, HttpResponse } from "@smithy/protocol-http";
 import { AwsCredentialIdentity, RequestHandlerOutput } from "@smithy/types";
 import { ConfiguredRetryStrategy, StandardRetryStrategy } from "@smithy/util-retry";
diff --git a/private/aws-middleware-test/src/middleware-content-length.spec.ts b/private/aws-middleware-test/src/middleware-content-length.spec.ts
index 34aaeed347779..84fb882847a34 100644
--- a/private/aws-middleware-test/src/middleware-content-length.spec.ts
+++ b/private/aws-middleware-test/src/middleware-content-length.spec.ts
@@ -1,10 +1,9 @@
+import { requireRequestsFrom } from "@aws-sdk/aws-util-test/src";
 import { AccessAnalyzer } from "@aws-sdk/client-accessanalyzer";
 import { S3 } from "@aws-sdk/client-s3";
 import { XRay } from "@aws-sdk/client-xray";
 import { describe, expect, test as it } from "vitest";
 
-import { requireRequestsFrom } from "@aws-sdk/aws-util-test/src";
-
 describe("middleware-content-length", () => {
   describe(AccessAnalyzer.name, () => {
     it("should not add content-length if no body", async () => {
@@ -40,6 +39,7 @@ describe("middleware-content-length", () => {
         headers: {
           "content-length": /106/,
         },
+        body: /clientToken/, // must include idempotencyToken.
       });
 
       await client.createAccessPreview({
@@ -47,7 +47,7 @@ describe("middleware-content-length", () => {
         analyzerArn: "my-analyzer-arn",
       });
 
-      expect.assertions(1);
+      expect.assertions(2);
     });
   });
 
diff --git a/private/aws-middleware-test/src/middleware-serde.spec.ts b/private/aws-middleware-test/src/middleware-serde.spec.ts
index ebe2cc3fe8511..58ec7b3777abd 100644
--- a/private/aws-middleware-test/src/middleware-serde.spec.ts
+++ b/private/aws-middleware-test/src/middleware-serde.spec.ts
@@ -1,11 +1,10 @@
+import { requireRequestsFrom } from "@aws-sdk/aws-util-test/src";
 import { EC2 } from "@aws-sdk/client-ec2";
 import { S3 } from "@aws-sdk/client-s3";
 import { SageMaker } from "@aws-sdk/client-sagemaker";
 import { SageMakerRuntime } from "@aws-sdk/client-sagemaker-runtime";
 import { describe, test as it } from "vitest";
 
-import { requireRequestsFrom } from "@aws-sdk/aws-util-test/src";
-
 describe("middleware-serde", () => {
   describe(S3.name, () => {
     it("should serialize xml", async () => {
@@ -75,7 +74,15 @@ describe("middleware-serde", () => {
           "content-type": "application/x-www-form-urlencoded",
           host: "ec2.us-west-2.amazonaws.com",
         },
-        body: /ClientCidrBlock=ClientCidrBlock&ServerCertificateArn=ServerCertificateArn(.*?)&Action=CreateClientVpnEndpoint&Version=2016-11-15/,
+        body(body: any) {
+          const params = Object.fromEntries(new URLSearchParams(body).entries());
+          expect(params).toMatchObject({
+            Action: "CreateClientVpnEndpoint",
+            Version: "2016-11-15",
+            ClientCidrBlock: "ClientCidrBlock",
+            ServerCertificateArn: "ServerCertificateArn",
+          });
+        },
         protocol: "https:",
         path: "/",
       });
diff --git a/yarn.lock b/yarn.lock
index 81aeafa89902a..62242bd39107a 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -23355,7 +23355,6 @@ __metadata:
     "@smithy/smithy-client": "npm:^4.6.4"
     "@smithy/types": "npm:^4.5.0"
     "@smithy/util-base64": "npm:^4.1.0"
-    "@smithy/util-body-length-browser": "npm:^4.1.0"
     "@smithy/util-middleware": "npm:^4.1.1"
     "@smithy/util-utf8": "npm:^4.1.0"
     "@tsconfig/recommended": "npm:1.0.1"