Bedrock runtime error when using prompt caching

[glc-froussel]

Checkboxes for prior research

• I've gone through Developer Guide and API reference
• I've checked AWS Forums and StackOverflow.
• I've searched for previous similar issues and didn't find any solution.

Describe the bug

With AWS Lambda, using the ConverseCommand with a cache point causes the following runtime error :

{
  "errorType": "TypeError",
  "errorMessage": "Cannot read properties of undefined (reading '0')",
  "trace": [
    "TypeError: Cannot read properties of undefined (reading '0')",
    "    at Object.visit (/var/runtime/node_modules/@aws-sdk/client-bedrock-runtime/dist-cjs/index.js:717:36)",
    "    at se_SystemContentBlock (/var/runtime/node_modules/@aws-sdk/client-bedrock-runtime/dist-cjs/index.js:1904:29)",
    "    at /var/runtime/node_modules/@aws-sdk/client-bedrock-runtime/dist-cjs/index.js:1912:12",
    "    at Array.map (<anonymous>)",
    "    at se_SystemContentBlocks (/var/runtime/node_modules/@aws-sdk/client-bedrock-runtime/dist-cjs/index.js:1911:41)",
    "    at system (/var/runtime/node_modules/@aws-sdk/client-bedrock-runtime/dist-cjs/index.js:1138:45)",
    "    at applyInstruction (/var/runtime/node_modules/@aws-sdk/node_modules/@smithy/smithy-client/dist-cjs/index.js:1115:27)",
    "    at take (/var/runtime/node_modules/@aws-sdk/node_modules/@smithy/smithy-client/dist-cjs/index.js:1083:5)",
    "    at se_ConverseCommand (/var/runtime/node_modules/@aws-sdk/client-bedrock-runtime/dist-cjs/index.js:1129:35)",
    "    at /var/runtime/node_modules/@aws-sdk/node_modules/@smithy/middleware-serde/dist-cjs/index.js:71:25"
  ]
}

Without cache point, everything is working fine.

Regression Issue

• Select this option if this issue appears to be a regression.

SDK version number

@aws-sdk/package-name@version, ...

Which JavaScript Runtime is this issue in?

Node.js

Details of the browser/Node.js/ReactNative version

NodeJS 22.X

Reproduction Steps

package.json :

  "dependencies": {
    "@aws-sdk/client-bedrock": "^3.816.0",
    "@aws-sdk/client-bedrock-runtime": "^3.816.0",
    "@smithy/node-http-handler": "^4.0.5"
  },
  "devDependencies": {
    "@tsconfig/node22": "^22.0.1",
    "@tsconfig/strictest": "^2.0.5",
    "@types/aws-lambda": "^8.10.149",
    "@types/node": "^22",
    "aws-cdk": "^2.1016.0",
    "aws-cdk-lib": "^2.196.0",
    "constructs": "^10.4.2",
    "esbuild": "^0.25.4",
    "tsx": "^4.19.4",
    "typescript": "^5.8.3"
  }

hello-bedrock-handler.ts :

import { BedrockRuntimeClient, ConverseCommand, ConverseCommandInput } from '@aws-sdk/client-bedrock-runtime';

const client = new BedrockRuntimeClient({
  region: 'us-east-1',
});

export const handler = async (): Promise<any> => {
  const input: ConverseCommandInput = {
    modelId: 'amazon.nova-lite-v1:0',
    system: [
      {
        text: 'Tu es un assistant utile qui aide les utilisateurs à obtenir des informations sur la météo actuelle dans une ville',
      },
      {
        cachePoint: {
          type: 'default',
        },
      },
    ],
    messages: [
      {
        role: 'user',
        content: [
          {
            text: 'Salut, ca va ?',
          },
        ],
      },
    ],
  };

  const response = await client.send(new ConverseCommand(input));

  return response.output;
};

cdk construct :

import { join, resolve } from 'path';

import { Construct } from 'constructs';
import { RemovalPolicy, Duration, Stack, StackProps } from 'aws-cdk-lib';
import { LogGroup, RetentionDays } from 'aws-cdk-lib/aws-logs';
import { NodejsFunction, OutputFormat, SourceMapMode } from 'aws-cdk-lib/aws-lambda-nodejs';
import { Role, ServicePrincipal, ManagedPolicy, PolicyStatement, Effect } from 'aws-cdk-lib/aws-iam';
import { Function, Code, Runtime, Architecture } from 'aws-cdk-lib/aws-lambda';

export class BedrockCachingStack extends Stack {
  constructor(scope: Construct, id: string, props: StackProps) {
    super(scope, id, props);

    const app = 'bedrock-caching';
    const env = 'dev';

    const role = new Role(this, 'Role', {
      roleName: `${app}-function-${env}`,
      assumedBy: new ServicePrincipal('lambda.amazonaws.com'),
      managedPolicies: [ManagedPolicy.fromAwsManagedPolicyName('service-role/AWSLambdaVPCAccessExecutionRole')],
    });

    role.addToPolicy(
      new PolicyStatement({
        effect: Effect.ALLOW,
        actions: ['bedrock:*'],
        resources: ['*'],
      })
    );

    const functionName = `${app}-hello-${env}`;

    const logGroup = new LogGroup(this, 'LogGroup', {
      logGroupName: `/aws/lambda/${functionName}`,
      retention: RetentionDays.ONE_MONTH,
      removalPolicy: RemovalPolicy.DESTROY,
    });

    const function1 = new NodejsFunction(this, 'Function', {
      runtime: Runtime.NODEJS_22_X,
      memorySize: 512,
      timeout: Duration.seconds(10),
      architecture: Architecture.ARM_64,
      entry: resolve(join(process.cwd(), 'src/handlers', 'hello-bedrock-handler.ts')),
      handler: 'handler',
      functionName,
      logGroup,
      role,
      bundling: {
        platform: 'node',
        format: OutputFormat.CJS,
        forceDockerBundling: false,
        minify: true,
        sourceMap: true,
        sourcesContent: true,
        sourceMapMode: SourceMapMode.INLINE,
        metafile: false,
      },
      awsSdkConnectionReuse: false,
    });

    function1.node.addDependency(logGroup);
  }
}

Then manually trigger the function on AWS Console.

Observed Behavior

With cache point set in the request the error is thrown, without the cache point it's working.

If I execute manually the handler locally (outside Lambda), no error, even with the cache point.

• This is apparently not a permission error because without the cache point it's working
• I first though of a packaging issue of the Lambda, but again, without cache point it's working and I tried different packaging setup without luck
• Behavior happens for nova-lite but also claude 3.5 haiku

Expected Behavior

No error.

Possible Solution

No response

Additional Information/Context

Exactly same error than #6404 (comment)

But the root cause seems different as I am using last versions of aws-sdk.

[glc-froussel]

Allright I think I found the root cause and it's CDK not the SDK.

Using NodejsFunction comes with externalModules that contains by default the aws-sdk which means that the aws-sdk will not be packaged with the code, but the version provided by the Lambda container will be used instead.

My guess is that the version provided by the Lambda container is prior to 3.779.0 (which supports cachePoint.

Configuration that works currently:

    const function1 = new NodejsFunction(this, 'Function', {
      ...
      bundling: {
        ...
        externalModules: [],  // override the default value set by CDK
      },
    });

[aBurmeseDev]

Hi @glc-froussel - appreciate you sharing the root cause and following up here. All supported Lambda Node.js runtimes include a specific minor version of the AWS SDK for JavaScript v3, not the latest version. Also just a quick tip that you can check Lambda provided SDK version like below:

import packageJson from '@aws-sdk/client-s3/package.json' with { type: 'json' };

export const handler = async () => ({ version: packageJson.version });

Hope that helps, let us know if you ran into any issues with JavaScript SDK here.