diff --git a/Makefile b/Makefile
index a949b50bc231..3995659765a6 100644
--- a/Makefile
+++ b/Makefile
@@ -34,6 +34,7 @@ test-schema: bundles
 
 test-integration: bundles
 	rm -rf ./clients/client-sso/node_modules/\@smithy # todo(yarn) incompatible redundant nesting.
+	node ./scripts/validation/no-generic-byte-arrays.js
 	yarn g:vitest run -c vitest.config.integ.mts
 	make test-protocols
 	make test-types
diff --git a/packages/crc64-nvme-crt/src/CrtCrc64Nvme.ts b/packages/crc64-nvme-crt/src/CrtCrc64Nvme.ts
index 0bcff3ccc3cf..5717e65216a7 100644
--- a/packages/crc64-nvme-crt/src/CrtCrc64Nvme.ts
+++ b/packages/crc64-nvme-crt/src/CrtCrc64Nvme.ts
@@ -9,7 +9,7 @@ export class CrtCrc64Nvme implements Checksum {
     this.checksum = checksums.crc64nvme(data, this.checksum);
   }
 
-  async digest() {
+  async digest(): Promise<Uint8Array> {
     return toUint8Array(this.checksum);
   }
 
diff --git a/packages/middleware-flexible-checksums/src/getCrc32ChecksumAlgorithmFunction.ts b/packages/middleware-flexible-checksums/src/getCrc32ChecksumAlgorithmFunction.ts
index 92046dfdd7a1..5ee421b46000 100644
--- a/packages/middleware-flexible-checksums/src/getCrc32ChecksumAlgorithmFunction.ts
+++ b/packages/middleware-flexible-checksums/src/getCrc32ChecksumAlgorithmFunction.ts
@@ -11,7 +11,7 @@ class NodeCrc32 implements Checksum {
     this.checksum = zlib.crc32(data, this.checksum);
   }
 
-  async digest() {
+  async digest(): Promise<Uint8Array> {
     return numToUint8(this.checksum);
   }
 
diff --git a/packages/middleware-flexible-checksums/src/stringHasher.ts b/packages/middleware-flexible-checksums/src/stringHasher.ts
index dbaa471037fe..bf21abe8d22c 100644
--- a/packages/middleware-flexible-checksums/src/stringHasher.ts
+++ b/packages/middleware-flexible-checksums/src/stringHasher.ts
@@ -4,7 +4,10 @@ import { toUint8Array } from "@smithy/util-utf8";
 /**
  * A function that, given a hash constructor and a string, calculates the hash of the string.
  */
-export const stringHasher = (checksumAlgorithmFn: ChecksumConstructor | HashConstructor, body: any) => {
+export const stringHasher = (
+  checksumAlgorithmFn: ChecksumConstructor | HashConstructor,
+  body: any
+): Promise<Uint8Array> => {
   const hash = new checksumAlgorithmFn();
   hash.update(toUint8Array(body || ""));
   return hash.digest();
diff --git a/packages/middleware-sdk-ec2/src/fixture.ts b/packages/middleware-sdk-ec2/src/fixture.spec.ts
similarity index 75%
rename from packages/middleware-sdk-ec2/src/fixture.ts
rename to packages/middleware-sdk-ec2/src/fixture.spec.ts
index 565eda165a61..529291fac52c 100644
--- a/packages/middleware-sdk-ec2/src/fixture.ts
+++ b/packages/middleware-sdk-ec2/src/fixture.spec.ts
@@ -1,11 +1,14 @@
 import { SourceData } from "@smithy/types";
+import { describe, test as it } from "vitest";
 
 export class MockSha256 {
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
   constructor(secret?: string | ArrayBuffer | ArrayBufferView) {}
+
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
   update(data?: SourceData) {}
-  digest() {
+
+  digest(): Promise<Uint8Array> {
     return Promise.resolve(new Uint8Array(5));
   }
 }
@@ -18,3 +21,7 @@ export const credentials = () =>
     secretAccessKey: "secret",
     sessionToken: "session",
   });
+
+describe("placeholder", () => {
+  it("placeholder for exports of testing constructs", () => {});
+});
diff --git a/packages/middleware-sdk-ec2/src/index.spec.ts b/packages/middleware-sdk-ec2/src/index.spec.ts
index 55f2a76f7d67..7d2f2a79360e 100755
--- a/packages/middleware-sdk-ec2/src/index.spec.ts
+++ b/packages/middleware-sdk-ec2/src/index.spec.ts
@@ -2,7 +2,7 @@ import { HttpRequest } from "@smithy/protocol-http";
 import { EndpointV2 } from "@smithy/types";
 import { beforeEach, describe, expect, test as it, vi } from "vitest";
 
-import { credentials, MockSha256, region } from "./fixture";
+import { credentials, MockSha256, region } from "./fixture.spec";
 import { copySnapshotPresignedUrlMiddleware } from "./index";
 
 const nextHandler = vi.fn();
diff --git a/packages/middleware-sdk-rds/src/fixture.ts b/packages/middleware-sdk-rds/src/fixture.spec.ts
similarity index 79%
rename from packages/middleware-sdk-rds/src/fixture.ts
rename to packages/middleware-sdk-rds/src/fixture.spec.ts
index b9c171a26292..c923e67e1b9d 100644
--- a/packages/middleware-sdk-rds/src/fixture.ts
+++ b/packages/middleware-sdk-rds/src/fixture.spec.ts
@@ -1,11 +1,12 @@
 import { SourceData } from "@smithy/types";
+import { describe, test as it } from "vitest";
 
 export class MockSha256 {
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
   constructor(secret?: string | ArrayBuffer | ArrayBufferView) {}
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
   update(data?: SourceData) {}
-  digest() {
+  digest(): Promise<Uint8Array> {
     return Promise.resolve(new Uint8Array(5));
   }
   reset() {}
@@ -26,3 +27,7 @@ export const credentials = () =>
     secretAccessKey: "secret",
     sessionToken: "session",
   });
+
+describe("placeholder", () => {
+  it("placeholder for exports of testing constructs", () => {});
+});
diff --git a/packages/middleware-sdk-rds/src/index.spec.ts b/packages/middleware-sdk-rds/src/index.spec.ts
index b82d683cecb5..b770cfa1179e 100644
--- a/packages/middleware-sdk-rds/src/index.spec.ts
+++ b/packages/middleware-sdk-rds/src/index.spec.ts
@@ -1,7 +1,7 @@
 import { beforeEach, describe, expect, test as it, vi } from "vitest";
 
 import { crossRegionPresignedUrlMiddleware } from "./";
-import { credentials, endpoint, MockSha256, region } from "./fixture";
+import { credentials, endpoint, MockSha256, region } from "./fixture.spec";
 
 const nextHandler = vi.fn();
 const arn = "arn:aws:rds:src-region:000000000000:src-snapshot:dist-snapshot";
diff --git a/packages/middleware-signing/src/awsAuthConfiguration.spec.ts b/packages/middleware-signing/src/awsAuthConfiguration.spec.ts
index aa10fe8c3969..87a972730c13 100644
--- a/packages/middleware-signing/src/awsAuthConfiguration.spec.ts
+++ b/packages/middleware-signing/src/awsAuthConfiguration.spec.ts
@@ -118,7 +118,10 @@ describe("AuthConfig", () => {
       for (let i = 0; i < repeats; i++) {
         await signer.sign(request);
       }
-      console.log("what is credentials", credentials);
+      expect(await credentials()).toEqual({
+        accessKeyId: "key",
+        secretAccessKey: "secret",
+      });
       expect(spy).toBeCalledTimes(2);
     });
   });
diff --git a/scripts/validation/no-generic-byte-arrays.js b/scripts/validation/no-generic-byte-arrays.js
new file mode 100644
index 000000000000..8e6c8e5f0b5a
--- /dev/null
+++ b/scripts/validation/no-generic-byte-arrays.js
@@ -0,0 +1,44 @@
+#!/usr/bin/env node
+
+/**
+ * Runs after a full build to assert that Uint8Array was not generated with a type parameter
+ * by TypeScript, which is only compatible with TypeScript 5.7.
+ */
+
+const walk = require("../utils/walk");
+const fs = require("node:fs");
+const path = require("node:path");
+
+const root = path.join(__dirname, "..", "..");
+
+const clients = path.join(root, "clients");
+const lib = path.join(root, "lib");
+const packages = path.join(root, "packages");
+const private = path.join(root, "private");
+
+(async () => {
+  const errors = [];
+  for (const group of [clients, lib, packages, private]) {
+    for (const folder of fs.readdirSync(group)) {
+      const packagePath = path.join(group, folder);
+      const distTypes = path.join(packagePath, "dist-types");
+      if (fs.existsSync(distTypes)) {
+        for await (const file of walk(distTypes)) {
+          const contents = fs.readFileSync(file, "utf-8");
+          if (contents.includes("Uint8Array<")) {
+            errors.push(file);
+          }
+        }
+      }
+    }
+  }
+  if (errors.length > 0) {
+    throw new Error(
+      `The following files used Uint8Array in a generic way, only compatible with TypeScript 5.7:\n\t${errors.join(
+        "\n\t"
+      )}`
+    );
+  } else {
+    console.log(`✅ No Uint8Arrays with type parameters.`);
+  }
+})();