diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cbd361f3..2387b416 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -62,6 +62,8 @@ jobs:
       - name: Bootstrap
         run: ./scripts/bootstrap
 
-      - name: Run tests
-        run: ./scripts/test
+      - name: Build
+        run: ./scripts/build-all
 
+      - name: Run tests
+        run: ./scripts/test-all
diff --git a/jest.config.ts b/jest.config.ts
index 00231b16..ded740d2 100644
--- a/jest.config.ts
+++ b/jest.config.ts
@@ -16,6 +16,7 @@ const config: JestConfigWithTsJest = {
     '<rootDir>/dist/',
     '<rootDir>/deno/',
     '<rootDir>/deno_tests/',
+    '<rootDir>/packages/',
   ],
   testPathIgnorePatterns: ['scripts'],
 };
diff --git a/package.json b/package.json
index 62c71965..e24d24cb 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,7 @@
   ],
   "private": false,
   "scripts": {
-    "test": "./scripts/test",
+    "test": "./scripts/test-all",
     "build": "./scripts/build-all",
     "prepublishOnly": "echo 'to publish, run yarn build && (cd dist; yarn publish)' && exit 1",
     "format": "prettier --write --cache --cache-strategy metadata . !dist",
diff --git a/packages/bedrock-sdk/jest.config.ts b/packages/bedrock-sdk/jest.config.ts
new file mode 100644
index 00000000..d9157e8e
--- /dev/null
+++ b/packages/bedrock-sdk/jest.config.ts
@@ -0,0 +1,17 @@
+import type { JestConfigWithTsJest } from 'ts-jest';
+
+const config: JestConfigWithTsJest = {
+  preset: 'ts-jest/presets/default-esm',
+  testEnvironment: 'node',
+  transform: {
+    '^.+\\.(t|j)sx?$': ['@swc/jest', { sourceMaps: 'inline' }],
+  },
+  moduleNameMapper: {
+    '^@anthropic-ai/bedrock-sdk$': '<rootDir>/src/index.ts',
+    '^@anthropic-ai/bedrock-sdk/(.*)$': '<rootDir>/src/$1',
+  },
+  modulePathIgnorePatterns: ['<rootDir>/dist/', '<rootDir>/deno/', '<rootDir>/deno_tests/'],
+  testPathIgnorePatterns: ['scripts'],
+};
+
+export default config;
diff --git a/packages/bedrock-sdk/package.json b/packages/bedrock-sdk/package.json
index 3d6a1c73..ee74d49f 100644
--- a/packages/bedrock-sdk/package.json
+++ b/packages/bedrock-sdk/package.json
@@ -11,7 +11,7 @@
   "packageManager": "yarn@1.22.21",
   "private": false,
   "scripts": {
-    "test": "echo 'no tests defined yet' && exit 1",
+    "test": "jest",
     "build": "bash ./build",
     "prepack": "echo 'to pack, run yarn build && (cd dist; yarn pack)' && exit 1",
     "prepublishOnly": "echo 'to publish, run yarn build && (cd dist; yarn publish)' && exit 1",
diff --git a/packages/bedrock-sdk/scripts/test b/packages/bedrock-sdk/scripts/test
new file mode 100755
index 00000000..73c44144
--- /dev/null
+++ b/packages/bedrock-sdk/scripts/test
@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+
+set -e
+
+cd "$(dirname "$0")/.."
+
+./node_modules/.bin/jest "$@"
diff --git a/packages/bedrock-sdk/src/client.ts b/packages/bedrock-sdk/src/client.ts
index cf2f7cac..523df8ba 100644
--- a/packages/bedrock-sdk/src/client.ts
+++ b/packages/bedrock-sdk/src/client.ts
@@ -117,6 +117,12 @@ export class AnthropicBedrock extends Core.APIClient {
   } {
     options.__streamClass = Stream;
 
+    if (Core.isObj(options.body)) {
+      // create a shallow copy of the request body so that code that mutates it later
+      // doesn't mutate the original user-provided object
+      options.body = { ...options.body };
+    }
+
     if (Core.isObj(options.body)) {
       if (!options.body['anthropic_version']) {
         options.body['anthropic_version'] = DEFAULT_VERSION;
diff --git a/packages/bedrock-sdk/tests/client.test.ts b/packages/bedrock-sdk/tests/client.test.ts
new file mode 100644
index 00000000..d9c42bf2
--- /dev/null
+++ b/packages/bedrock-sdk/tests/client.test.ts
@@ -0,0 +1,29 @@
+import { AnthropicBedrock } from '@anthropic-ai/bedrock-sdk';
+import Anthropic from '@anthropic-ai/sdk';
+
+test('body params are not mutated', async () => {
+  const client = new AnthropicBedrock({
+    baseURL: 'http://localhost:5000/',
+    awsRegion: 'us-east-1',
+    awsAccessKey: 'placeholder',
+    awsSecretKey: 'placeholder',
+    fetch: (url) => {
+      return Promise.resolve(
+        new Response(JSON.stringify({ url, custom: true }), {
+          headers: { 'Content-Type': 'application/json' },
+        }),
+      );
+    },
+  });
+
+  const params: Anthropic.MessageCreateParamsNonStreaming = {
+    model: 'claude-3-opus-latest',
+    messages: [],
+    max_tokens: 100,
+  };
+  const original = JSON.stringify(params);
+
+  await client.messages.create(params);
+
+  expect(JSON.stringify(params)).toEqual(original);
+});
diff --git a/packages/vertex-sdk/jest.config.ts b/packages/vertex-sdk/jest.config.ts
new file mode 100644
index 00000000..e3f740e4
--- /dev/null
+++ b/packages/vertex-sdk/jest.config.ts
@@ -0,0 +1,17 @@
+import type { JestConfigWithTsJest } from 'ts-jest';
+
+const config: JestConfigWithTsJest = {
+  preset: 'ts-jest/presets/default-esm',
+  testEnvironment: 'node',
+  transform: {
+    '^.+\\.(t|j)sx?$': ['@swc/jest', { sourceMaps: 'inline' }],
+  },
+  moduleNameMapper: {
+    '^@anthropic-ai/vertex-sdk$': '<rootDir>/src/index.ts',
+    '^@anthropic-ai/vertex-sdk/(.*)$': '<rootDir>/src/$1',
+  },
+  modulePathIgnorePatterns: ['<rootDir>/dist/', '<rootDir>/deno/', '<rootDir>/deno_tests/'],
+  testPathIgnorePatterns: ['scripts'],
+};
+
+export default config;
diff --git a/packages/vertex-sdk/package.json b/packages/vertex-sdk/package.json
index ed7c7f84..288a81a8 100644
--- a/packages/vertex-sdk/package.json
+++ b/packages/vertex-sdk/package.json
@@ -11,7 +11,7 @@
   "packageManager": "yarn@1.22.21",
   "private": false,
   "scripts": {
-    "test": "echo 'no tests defined yet' && exit 1",
+    "test": "jest",
     "build": "bash ./build",
     "prepack": "echo 'to pack, run yarn build && (cd dist; yarn pack)' && exit 1",
     "prepublishOnly": "echo 'to publish, run yarn build && (cd dist; yarn publish)' && exit 1",
diff --git a/packages/vertex-sdk/scripts/test b/packages/vertex-sdk/scripts/test
new file mode 100755
index 00000000..73c44144
--- /dev/null
+++ b/packages/vertex-sdk/scripts/test
@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+
+set -e
+
+cd "$(dirname "$0")/.."
+
+./node_modules/.bin/jest "$@"
diff --git a/packages/vertex-sdk/src/client.ts b/packages/vertex-sdk/src/client.ts
index 61f67582..06231649 100644
--- a/packages/vertex-sdk/src/client.ts
+++ b/packages/vertex-sdk/src/client.ts
@@ -114,6 +114,12 @@ export class AnthropicVertex extends Core.APIClient {
     url: string;
     timeout: number;
   } {
+    if (Core.isObj(options.body)) {
+      // create a shallow copy of the request body so that code that mutates it later
+      // doesn't mutate the original user-provided object
+      options.body = { ...options.body };
+    }
+
     if (Core.isObj(options.body)) {
       if (!options.body['anthropic_version']) {
         options.body['anthropic_version'] = DEFAULT_VERSION;
diff --git a/packages/vertex-sdk/tests/client.test.ts b/packages/vertex-sdk/tests/client.test.ts
new file mode 100644
index 00000000..1f9a500a
--- /dev/null
+++ b/packages/vertex-sdk/tests/client.test.ts
@@ -0,0 +1,29 @@
+import { AnthropicVertex } from '@anthropic-ai/vertex-sdk';
+import Anthropic from '@anthropic-ai/sdk';
+
+test('body params are not mutated', async () => {
+  const client = new AnthropicVertex({
+    baseURL: 'http://localhost:5000/',
+    accessToken: 'placeholder',
+    region: 'us-east-2',
+    projectId: 'placeholder',
+    fetch: (url) => {
+      return Promise.resolve(
+        new Response(JSON.stringify({ url, custom: true }), {
+          headers: { 'Content-Type': 'application/json' },
+        }),
+      );
+    },
+  });
+
+  const params: Anthropic.MessageCreateParamsNonStreaming = {
+    model: 'claude-3-opus-latest',
+    messages: [],
+    max_tokens: 100,
+  };
+  const original = JSON.stringify(params);
+
+  await client.messages.create(params);
+
+  expect(JSON.stringify(params)).toEqual(original);
+});
diff --git a/scripts/test-all b/scripts/test-all
new file mode 100755
index 00000000..4da421bb
--- /dev/null
+++ b/scripts/test-all
@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+set -e
+
+bash ./scripts/test
+
+for dir in packages/*; do
+    if [ -f "$dir/scripts/test" ]; then
+        echo "==> Running tests in $dir"
+        (cd "$dir" && bash scripts/test)
+    fi
+done