diff --git a/packages/core/src/submodules/account-id-endpoint/account-id-endpoint.integ.spec.ts b/packages/core/integ/account-id-endpoint.integ.spec.ts
similarity index 100%
rename from packages/core/src/submodules/account-id-endpoint/account-id-endpoint.integ.spec.ts
rename to packages/core/integ/account-id-endpoint.integ.spec.ts
diff --git a/packages/core/integ/configuration-file/aws-config-file.integ.spec.ts b/packages/core/integ/configuration-file/aws-config-file.integ.spec.ts
new file mode 100644
index 0000000000000..1b1ee2c59c4bd
--- /dev/null
+++ b/packages/core/integ/configuration-file/aws-config-file.integ.spec.ts
@@ -0,0 +1,45 @@
+import { afterAll, beforeEach, describe, expect, test as it } from "vitest";
+import { S3 } from "@aws-sdk/client-s3";
+import path from "node:path";
+import type { Provider } from "@smithy/types";
+
+describe("defaults mode", () => {
+  const snapshot = {
+    ...process.env,
+  };
+
+  beforeEach(async () => {
+    process.env = {};
+  });
+
+  afterAll(async () => {
+    process.env = snapshot;
+  });
+
+  it("should load various client configuration options from file with default profile", async () => {
+    process.env.AWS_CONFIG_FILE = path.join(__dirname, "mock-aws-config");
+
+    const client = new S3({});
+
+    expect(await client.config.region()).toEqual("us-west-2");
+  });
+
+  it("should load various client configuration options from specific profile", async () => {
+    process.env.AWS_CONFIG_FILE = path.join(__dirname, "mock-aws-config");
+
+    const client = new S3({
+      profile: "abc",
+    });
+
+    expect(await client.config.region()).toEqual("ap-northeast-1");
+    expect(await (client.config.retryMode as Provider<string>)()).toEqual("adaptive");
+    expect(await (client.config.disableS3ExpressSessionAuth as Provider<boolean>)()).toEqual(true);
+    expect(await client.config.maxAttempts()).toEqual(33);
+    expect(await client.config.requestChecksumCalculation()).toEqual("WHEN_REQUIRED");
+    expect(await client.config.sigv4aSigningRegionSet()).toEqual(["*", "*", "us-west-2"]);
+    expect(await client.config.useFipsEndpoint()).toEqual(true);
+    expect(await (client.config.useArnRegion as Provider<boolean>)()).toEqual(true);
+    expect(await client.config.useDualstackEndpoint()).toEqual(true);
+    expect(await client.config.userAgentAppId()).toEqual("blargh");
+  });
+});
diff --git a/packages/core/integ/configuration-file/mock-aws-config b/packages/core/integ/configuration-file/mock-aws-config
new file mode 100644
index 0000000000000..1f77f160eaea8
--- /dev/null
+++ b/packages/core/integ/configuration-file/mock-aws-config
@@ -0,0 +1,17 @@
+[profile empty]
+
+[default]
+region = us-west-2
+output = json
+
+[profile abc]
+region = ap-northeast-1
+retry_mode = adaptive
+s3_disable_express_session_auth = true
+max_attempts = 33
+request_checksum_calculation = when_required
+sigv4a_signing_region_set = *,*,us-west-2
+use_fips_endpoint = true
+s3_use_arn_region = true
+use_dualstack_endpoint = true
+sdk-ua-app-id = blargh
diff --git a/packages/core/integ/defaults-mode.integ.spec.ts b/packages/core/integ/defaults-mode.integ.spec.ts
new file mode 100644
index 0000000000000..6175a0d458720
--- /dev/null
+++ b/packages/core/integ/defaults-mode.integ.spec.ts
@@ -0,0 +1,94 @@
+import { describe, test as it, expect, beforeEach, afterAll } from "vitest";
+
+import { CloudWatch } from "@aws-sdk/client-cloudwatch";
+import type { DefaultsMode } from "@smithy/smithy-client";
+import type { NodeHttpHandlerOptions, Provider } from "@smithy/types";
+import type { Agent as hAgent } from "http";
+import type { Agent as hsAgent } from "https";
+
+describe("defaults mode", () => {
+  const snapshot = {
+    AWS_EXECUTION_ENV: process.env.AWS_EXECUTION_ENV,
+    AWS_REGION: process.env.AWS_REGION,
+    AWS_DEFAULT_REGION: process.env.AWS_DEFAULT_REGION,
+    AWS_DEFAULTS_MODE: process.env.AWS_DEFAULTS_MODE,
+  };
+
+  beforeEach(async () => {
+    delete process.env.AWS_EXECUTION_ENV;
+    delete process.env.AWS_REGION;
+    delete process.env.AWS_DEFAULT_REGION;
+    delete process.env.AWS_DEFAULTS_MODE;
+  });
+
+  afterAll(async () => {
+    Object.assign(process.env, snapshot);
+  });
+
+  const sharedConfig = {
+    credentials: {
+      accessKeyId: "INTEG",
+      secretAccessKey: "INTEG",
+    },
+    region: "ap-northeast-1",
+  };
+
+  async function assertCrossRegion(client: CloudWatch) {
+    expect(await (client.config.defaultsMode as Provider<DefaultsMode>)()).toEqual("cross-region");
+    const handler = client.config.requestHandler;
+
+    type ResolvedNodeHttpHandlerConfig = Omit<NodeHttpHandlerOptions, "httpAgent" | "httpsAgent"> & {
+      httpAgent: hAgent;
+      httpsAgent: hsAgent;
+    };
+
+    const config = await (
+      handler as unknown as {
+        configProvider: Promise<ResolvedNodeHttpHandlerConfig>;
+      }
+    ).configProvider;
+
+    expect(config).toMatchObject({
+      connectionTimeout: 3100,
+    });
+  }
+
+  it("should set a higher timeout due to cross-region defaults mode when auto-detected (ENV)", async () => {
+    process.env.AWS_DEFAULTS_MODE = "auto";
+    process.env.AWS_EXECUTION_ENV = "INTEGRATION_TEST";
+    process.env.AWS_DEFAULT_REGION = "us-east-1";
+
+    const client = new CloudWatch(sharedConfig);
+
+    await assertCrossRegion(client);
+  });
+
+  it("should set a higher timeout due to cross-region defaults mode when auto-detected (client-config)", async () => {
+    process.env.AWS_EXECUTION_ENV = "INTEGRATION_TEST";
+    process.env.AWS_DEFAULT_REGION = "us-east-1";
+
+    const client = new CloudWatch({
+      ...sharedConfig,
+      defaultsMode: "auto",
+    });
+
+    await assertCrossRegion(client);
+  });
+
+  it("should set a higher timeout when cross region defaults-mode is set (ENV)", async () => {
+    process.env.AWS_DEFAULTS_MODE = "cross-region";
+
+    const client = new CloudWatch(sharedConfig);
+
+    await assertCrossRegion(client);
+  });
+
+  it("should set a higher timeout when cross region defaults-mode is set (client-config)", async () => {
+    const client = new CloudWatch({
+      ...sharedConfig,
+      defaultsMode: "cross-region",
+    });
+
+    await assertCrossRegion(client);
+  });
+});
diff --git a/packages/core/src/submodules/protocols/lazy-json-string.integ.spec.ts b/packages/core/integ/lazy-json-string.integ.spec.ts
similarity index 100%
rename from packages/core/src/submodules/protocols/lazy-json-string.integ.spec.ts
rename to packages/core/integ/lazy-json-string.integ.spec.ts
diff --git a/packages/core/src/submodules/client/pagination.integ.spec.ts b/packages/core/integ/pagination.integ.spec.ts
similarity index 100%
rename from packages/core/src/submodules/client/pagination.integ.spec.ts
rename to packages/core/integ/pagination.integ.spec.ts
diff --git a/packages/core/src/submodules/protocols/request-compression.integ.spec.ts b/packages/core/integ/request-compression.integ.spec.ts
similarity index 100%
rename from packages/core/src/submodules/protocols/request-compression.integ.spec.ts
rename to packages/core/integ/request-compression.integ.spec.ts
diff --git a/packages/core/src/submodules/client/waiters.integ.spec.ts b/packages/core/integ/waiters.integ.spec.ts
similarity index 100%
rename from packages/core/src/submodules/client/waiters.integ.spec.ts
rename to packages/core/integ/waiters.integ.spec.ts