SyncVals · Trajectory

s3-lambda-ddb-pipeline

claude-code claude-opus-4-7 ✗ failed HARNESS_ERROR ↑ View task

Solved from the instruction alone, tests/ and solution/ were withheld from the agent's workspace and restored only for grading.

Reward = tests/test.sh exit code (0 → resolved); the classification below is post-hoc and cannot change it.

Classification , post-hoc; cannot change the reward

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Trajectory

Tool-by-tool agent trajectory

6 tool calls · 2 tool types · 11 steps

# S3 -> Lambda -> DynamoDB event pipeline ## Environment - **AWS endpoint:** LocalStack at `http://localstack:4566`. All AWS SDKs and CLIs in this environment already honour the pre-exported `AWS_ENDPOINT_URL=http://localstack:4566`. - **Credentials & region:** `AWS_ACCESS_KEY_ID=test`, `AWS_SECRET_ACCESS_KEY=test`, `AWS_DEFAULT_REGION=us-east-1`. Account ID is `000000000000` (LocalStack's default), which is the value to use when constructing ARNs. - **Installed tools:** `aws` (AWS CLI v2), `awslocal` (pre-configured for LocalStack), `python3`, `boto3`, `curl`, `jq`, `git`, `unzip`, `zip`. A Python venv at `/opt/venv` with `boto3` and `awscli-local` is already on `PATH`. - **Lambda networking:** Lambda functions created in this environment run in Docker containers on the same Compose network as LocalStack and can reach it at `http://localstack:4566`. The function's own `AWS_ENDPOINT_URL` must be set to that value for SDK calls from inside the function to hit LocalStack rather than real AWS. - **Working directory:** `/app`. It is empty , there are no starter files, templates, handlers, hints, or secrets. Everything the pipeline needs must be authored by you. ## Task Build the pipeline described below from scratch and deploy it via **CloudFormation** , the grader rejects solutions built imperatively with the CLI or SDK. The end state must be produced by at least one CloudFormation stack named **`pipeline-stack`** that owns the S3 bucket, the DynamoDB table, and the Lambda function. You are free to split into multiple stacks, add custom resources, choose any logical IDs, and use either `Code.ZipFile` or `Code.S3Bucket` for the Lambda code. ## Required outcome After you finish, the following must all be true in the LocalStack account: 1. A CloudFormation stack named **`pipeline-stack`** exists in `CREATE_COMPLETE` or `UPDATE_COMPLETE` and its stack resources include the S3 bucket `pipeline-source`, the DynamoDB table `pipeline-events`, and the Lambda function `pipeline-processor`. 2. An S3 bucket named **`pipeline-source`** exists. 3. A DynamoDB table named **`pipeline-events`** exists with a single string partition key `object_key`. 4. A Lambda function named **`pipeline-processor`** exists (runtime `python3.11`) and is invoked whenever an object is created in `pipeline-source`. 5. When a new object is put into `pipeline-source`, the Lambda must write one item to `pipeline-events` with these attributes: - `object_key` (S) , the S3 object key - `bucket` (S) , the source bucket name - `size` (N) , the object size in bytes - `event_time` (S) , the S3 event timestamp (non-empty) 6. The Lambda must have permission to be invoked by the S3 service (`Principal: s3.amazonaws.com`) for events from `pipeline-source`. 7. The Lambda execution role must have `dynamodb:PutItem` permission on the `pipeline-events` table. 8. The `pipeline-events` table must be encrypted at rest with a **customer-managed** KMS CMK that is itself created by the `pipeline-stack` CloudFormation stack (not the AWS-managed `alias/aws/dynamodb` key). 9. The Lambda execution role must be able to use that CMK , its policy set must grant `kms:Decrypt` and `kms:GenerateDataKey` on the CMK's ARN (or with `Resource: "*"`). Without these, the Lambda's `PutItem` would fail against an encrypted table even though `dynamodb:PutItem` is granted. ## End-to-end grading The grader uploads a fresh object to `pipeline-source` with a key it chooses, then polls `pipeline-events` for an item whose `object_key` equals that same key. If the item does not appear within a reasonable timeout, the task fails. The grader does not trust any agent-written tests; all assertions run out-of-band against the live LocalStack account.

Check working directory and LocalStack connectivity

shell

ls -la /app && echo "---" && which aws awslocal python3 && echo "---" && curl -s http://localstack:4566/_localstack/health | head -50

output

total 8
drwxr-xr-x 2 root root 4096 Apr 21 17:23 .
drwxr-xr-x 1 root root 4096 Apr 21 18:38 ..
---
/usr/local/bin/aws
/opt/venv/bin/awslocal
/opt/venv/bin/python3
---
{"services": {"acm": "disabled", "apigateway": "disabled", "cloudformation": "available", "cloudwatch": "disabled", "config": "disabled", "dynamodb": "available", "dynamodbstreams": "available", "ec2": "disabled", "es": "disabled", "events": "available", "firehose": "disabled", "iam": "available", "kinesis": "available", "kms": "available", "lambda": "available", "logs": "available", "opensearch": "disabled", "redshift": "disabled", "resource-groups": "disabled", "resourcegroupstaggingapi": "disabled", "route53": "disabled", "route53resolver": "disabled", "s3": "available", "s3control": "disabled", "scheduler": "disabled", "secretsmanager": "disabled", "ses": "disabled", "sns": "disabled", "sqs": "disabled", "ssm": "disabled", "stepfunctions": "disabled", "sts": "available", "support": "disabled", "swf": "disabled", "transcribe": "disabled"}, "edition": "community", "version": "4.13.1"}

[stdout]
total 8
drwxr-xr-x 2 root root 4096 Apr 21 17:23 .
drwxr-xr-x 1 root root 4096 Apr 21 18:38 ..
---
/usr/local/bin/aws
/opt/venv/bin/awslocal
/opt/venv/bin/python3
---
{"services": {"acm": "disabled", "apigateway": "disabled", "cloudformation": "available", "cloudwatch": "disabled", "config": "disabled", "dynamodb": "available", "dynamodbstreams": "available", "ec2": "disabled", "es": "disabled", "events": "available", "firehose": "disabled", "iam": "available", "kinesis": "available", "kms": "available", "lambda": "available", "logs": "available", "opensearch": "disabled", "redshift": "disabled", "resource-groups": "disabled", "resourcegroupstaggingapi": "disabled", "route53": "disabled", "route53resolver": "disabled", "s3": "available", "s3control": "disabled", "scheduler": "disabled", "secretsmanager": "disabled", "ses": "disabled", "sns": "disabled", "sqs": "disabled", "ssm": "disabled", "stepfunctions": "disabled", "sts": "available", "support": "disabled", "swf": "disabled", "transcribe": "disabled"}, "edition": "community", "version": "4.13.1"}

I'll build this pipeline as a CloudFormation stack. Let me create the template and deploy it.

write · /app/pipeline-stack.yaml

AWSTemplateFormatVersion: "2010-09-09"
Description: S3 -> Lambda -> DynamoDB event pipeline

Resources:

  PipelineKey:
    Type: AWS::KMS::Key
    Properties:
      Description: CMK for pipeline-events table encryption
      KeyPolicy:
        Version: "2012-10-17"
        Statement:
          - Sid: EnableRoot
            Effect: Allow
            Principal:
              AWS: arn:aws:iam::000000000000:root
            Action: "kms:*"
            Resource: "*"

  PipelineTable:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: pipeline-events
      BillingMode: PAY_PER_REQUEST
      AttributeDefinitions:
        - AttributeName: object_key
          AttributeType: S
      KeySchema:
        - AttributeName: object_key
          KeyType: HASH
      SSESpecification:
        SSEEnabled: true
        SSEType: KMS
        KMSMasterKeyId: !Ref PipelineKey

  PipelineRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
          - Effect: Allow
            Principal:
              Service: lambda.amazonaws.com
            Action: sts:AssumeRole
      Policies:
        - PolicyName: pipeline-inline
          PolicyDocument:
            Version: "2012-10-17"
            Statement:
              - Effect: Allow
                Action: dynamodb:PutItem
                Resource: !GetAtt PipelineTable.Arn
              - Effect: Allow
                Action:
                  - kms:Decrypt
                  - kms:GenerateDataKey
                  - kms:DescribeKey
                Resource: !GetAtt PipelineKey.Arn
              - Effect: Allow
                Action:
                  - logs:CreateLogGroup
                  - logs:CreateLogStream
                  - logs:PutLogEvents
                Resource: "*"

  PipelineFunction:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: pipeline-processor
      Runtime: python3.11
      Handler: index.handler
      Role: !GetAtt PipelineRole.Arn
      Timeout: 30
      Environment:
        Variables:
          LOCALSTACK_ENDPOINT: http://localstack:4566
          TABLE_NAME: pipeline-events
      Code:
        ZipFile: |
          import json
          import os
          import boto3

          TABLE = os.environ["TABLE_NAME"]
          ENDPOINT = os.environ.get("LOCALSTACK_ENDPOINT") or os.environ.get("AWS_ENDPOINT_URL")

          ddb = boto3.client("dynamodb", endpoint_url=ENDPOINT)

          def handler(event, context):
              print("event:", json.dumps(event))
              for rec in event.get("Records", []):
                  s3 = rec.get("s3", {})
                  obj = s3.get("object", {})
                  bucket = s3.get("bucket", {})
                  key = obj.get("key", "")
                  size = int(obj.get("size") or 0)
                  bucket_name = bucket.get("name", "")
                  event_time = rec.get("eventTime", "")
                  ddb.put_item(
                      TableName=TABLE,
                      Item={
                          "object_key": {"S": key},
                          "bucket": {"S": bucket_name},
                          "size": {"N": str(size)},
                          "event_time": {"S": event_time},
                      },
                  )
              return {"ok": True}

  PipelineInvokePermission:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !GetAtt PipelineFunction.Arn
      Action: lambda:InvokeFunction
      Principal: s3.amazonaws.com
      SourceAccount: "000000000000"
      SourceArn: arn:aws:s3:::pipeline-source

  PipelineBucket:
    Type: AWS::S3::Bucket
    DependsOn: PipelineInvokePermission
    Properties:
      BucketName: pipeline-source
      NotificationConfiguration:
        LambdaConfigurations:
          - Event: s3:ObjectCreated:*
            Function: !GetAtt PipelineFunction.Arn

Outputs:
  BucketName:
    Value: !Ref PipelineBucket
  TableName:
    Value: !Ref PipelineTable
  FunctionName:
    Value: !Ref PipelineFunction
  KeyArn:
    Value: !GetAtt PipelineKey.Arn

Create pipeline-stack CloudFormation stack

shell

awslocal cloudformation create-stack --stack-name pipeline-stack --template-body file:///app/pipeline-stack.yaml --capabilities CAPABILITY_IAM 2>&1

output

{
    "StackId": "arn:aws:cloudformation:us-east-1:000000000000:stack/pipeline-stack/24faf9fa-95fd-40c5-968a-06339456483c"
}

[stdout]
{
    "StackId": "arn:aws:cloudformation:us-east-1:000000000000:stack/pipeline-stack/24faf9fa-95fd-40c5-968a-06339456483c"
}

Wait for stack creation

shell

for i in 1 2 3 4 5 6 7 8 9 10; do
  status=$(awslocal cloudformation describe-stacks --stack-name pipeline-stack --query 'Stacks[0].StackStatus' --output text 2>&1)
  echo "[$i] $status"
  case "$status" in
    CREATE_COMPLETE|UPDATE_COMPLETE|ROLLBACK_COMPLETE|CREATE_FAILED|ROLLBACK_FAILED) break ;;
  esac
  sleep 3
done

output

[1] CREATE_IN_PROGRESS
[2] CREATE_COMPLETE

[stdout]
[1] CREATE_IN_PROGRESS
[2] CREATE_COMPLETE

Stack is created. Let me verify each required resource and test end-to-end.

Verify resources exist

shell

echo "=== Stack resources ==="
awslocal cloudformation list-stack-resources --stack-name pipeline-stack --query 'StackResourceSummaries[*].[LogicalResourceId,ResourceType,PhysicalResourceId,ResourceStatus]' --output table
echo
echo "=== S3 bucket ==="
awslocal s3 ls | grep pipeline-source
echo
echo "=== DynamoDB table ==="
awslocal dynamodb describe-table --table-name pipeline-events --query 'Table.[TableName,KeySchema,SSEDescription]' --output json
echo
echo "=== Lambda ==="
awslocal lambda get-function --function-name pipeline-processor --query 'Configuration.[FunctionName,Runtime,Handler,Role]' --output json
echo
echo "=== Notifications ==="
awslocal s3api get-bucket-notification-configuration --bucket pipeline-source

output

=== Stack resources ===
--------------------------------------------------------------------------------------------------------------------------------
|                                                      ListStackResources                                                      |
+--------------------------+--------------------------+----------------------------------------------------+-------------------+
|  PipelineKey             |  AWS::KMS::Key           |  eb337b11-49d7-4b58-bcd5-bf2b130e03f8              |  CREATE_COMPLETE  |
|  PipelineTable           |  AWS::DynamoDB::Table    |  pipeline-events                                   |  CREATE_COMPLETE  |
|  PipelineRole            |  AWS::IAM::Role          |  pipeline-stack-PipelineRole-bec10995              |  CREATE_COMPLETE  |
|  PipelineFunction        |  AWS::Lambda::Function   |  pipeline-processor                                |  CREATE_COMPLETE  |
|  PipelineInvokePermission|  AWS::Lambda::Permission |  pipeline-stack-PipelineInvokePermission-76320c7e  |  CREATE_COMPLETE  |
|  PipelineBucket          |  AWS::S3::Bucket         |  pipeline-source                                   |  CREATE_COMPLETE  |
+--------------------------+--------------------------+----------------------------------------------------+-------------------+

=== S3 bucket ===
2026-04-21 18:40:38 pipeline-source

=== DynamoDB table ===
[
    "pipeline-events",
    [
        {
            "AttributeName": "object_key",
            "KeyType": "HASH"
        }
    ],
    {
        "Status": "ENABLED",
        "SSEType": "KMS",
        "KMSMasterKeyArn": "arn:aws:kms:us-east-1:000000000000:key/eb337b11-49d7-4b58-bcd5-bf2b130e03f8"
    }
]

=== Lambda ===
[
    "pipeline-processor",
    "python3.11",
    "index.handler",
    "arn:aws:iam::000000000000:role/pipeline-stack-PipelineRole-bec10995"
]

=== Notifications ===
{
    "LambdaFunctionConfigurations": [
        {
            "Id": "8c730c58",
            "LambdaFunctionArn": "arn:aws:lambda:us-east-1:000000000000:function:pipeline-processor",
            "Events": [
                "s3:ObjectCreated:*"
            ]
        }
    ]
}

[stdout]
=== Stack resources ===
--------------------------------------------------------------------------------------------------------------------------------
|                                                      ListStackResources                                                      |
+--------------------------+--------------------------+----------------------------------------------------+-------------------+
|  PipelineKey             |  AWS::KMS::Key           |  eb337b11-49d7-4b58-bcd5-bf2b130e03f8              |  CREATE_COMPLETE  |
|  PipelineTable           |  AWS::DynamoDB::Table    |  pipeline-events                                   |  CREATE_COMPLETE  |
|  PipelineRole            |  AWS::IAM::Role          |  pipeline-stack-PipelineRole-bec10995              |  CREATE_COMPLETE  |
|  PipelineFunction        |  AWS::Lambda::Function   |  pipeline-processor                                |  CREATE_COMPLETE  |
|  PipelineInvokePermission|  AWS::Lambda::Permission |  pipeline-stack-PipelineInvokePermission-76320c7e  |  CREATE_COMPLETE  |
|  PipelineBucket          |  AWS::S3::Bucket         |  pipeline-source                                   |  CREATE_COMPLETE  |
+--------------------------+--------------------------+----------------------------------------------------+-------------------+

=== S3 bucket ===
2026-04-21 18:40:38 pipeline-source

=== DynamoDB table ===
[
    "pipeline-events",
    [
        {
            "AttributeName": "object_key",
            "KeyType": "HASH"
        }
    ],
    {
        "Status": "ENABLED",
        "SSEType": "KMS",
        "KMSMasterKeyArn": "arn:aws:kms:us-east-1:000000000000:key/eb337b11-49d7-4b58-bcd5-bf2b130e03f8"
    }
]

=== Lambda ===
[
    "pipeline-processor",
    "python3.11",
    "index.handler",
    "arn:aws:iam::000000000000:role/pipeline-stack-PipelineRole-bec10995"
]

=== Notifications ===
{
    "LambdaFunctionConfigurations": [
        {
            "Id": "8c730c58",
            "LambdaFunctionArn": "arn:aws:lambda:us-east-1:000000000000:function:pipeline-processor",
            "Events": [
                "s3:ObjectCreated:*"
            ]
        }
    ]
}

All resources look right. Now end-to-end test: upload an object and poll DynamoDB.

Upload object and poll for DynamoDB item

shell

KEY="test-$(date +%s).txt"
echo "Uploading $KEY"
echo "hello world" > /tmp/testobj.txt
awslocal s3 cp /tmp/testobj.txt s3://pipeline-source/$KEY
echo
echo "=== Polling DynamoDB ==="
for i in 1 2 3 4 5 6 7 8 9 10; do
  item=$(awslocal dynamodb get-item --table-name pipeline-events --key "{\"object_key\":{\"S\":\"$KEY\"}}" --output json 2>&1)
  if echo "$item" | grep -q '"Item"'; then
    echo "[$i] FOUND:"
    echo "$item"
    break
  fi
  echo "[$i] not yet"
  sleep 2
done

output

Uploading test-1776796856.txt
Completed 12 Bytes/12 Bytes (971 Bytes/s) with 1 file(s) remaining
upload: ../tmp/testobj.txt to s3://pipeline-source/test-1776796856.txt

=== Polling DynamoDB ===
[1] not yet
[2] FOUND:
{
    "Item": {
        "bucket": {
            "S": "pipeline-source"
        },
        "object_key": {
            "S": "test-1776796856.txt"
        },
        "size": {
            "N": "12"
        },
        "event_time": {
            "S": "2026-04-21T18:40:56.719Z"
        }
    }
}

[stdout]
Uploading test-1776796856.txt
Completed 12 Bytes/12 Bytes (971 Bytes/s) with 1 file(s) remaining
upload: ../tmp/testobj.txt to s3://pipeline-source/test-1776796856.txt

=== Polling DynamoDB ===
[1] not yet
[2] FOUND:
{
    "Item": {
        "bucket": {
            "S": "pipeline-source"
        },
        "object_key": {
            "S": "test-1776796856.txt"
        },
        "size": {
            "N": "12"
        },
        "event_time": {
            "S": "2026-04-21T18:40:56.719Z"
        }
    }
}

End-to-end works. The `pipeline-stack` is `CREATE_COMPLETE` with all six resources (KMS CMK, DynamoDB table encrypted with that CMK, IAM role with dynamodb+kms perms, Lambda `pipeline-processor` on python3.11, `lambda:InvokeFunction` permission for `s3.amazonaws.com` on bucket ARN, and the S3 bucket with an `s3:ObjectCreated:*` notification). Uploading an object produced a matching item with `object_key`, `bucket`, `size`, and `event_time` populated.

Final diff , what the agent changed

No file changes, the agent left the workspace untouched.

Verifier output , the proof behind the reward

tests/test.sh

============================= test session starts ==============================
platform linux -- Python 3.12.3, pytest-8.4.1, pluggy-1.6.0 -- /root/.cache/uv/archive-v0/AqG7T26iaeFSDpx2Hj7Yg/bin/python
cachedir: .pytest_cache
rootdir: /tests
plugins: json-ctrf-0.3.5
collecting ... collected 13 items

../tests/test_state.py::test_aws_cli_binary_is_real PASSED               [  7%]
../tests/test_state.py::test_localstack_reachable PASSED                 [ 15%]
../tests/test_state.py::test_cfn_stack_is_deployed PASSED                [ 23%]
../tests/test_state.py::test_cfn_stack_owns_core_resources PASSED        [ 30%]
../tests/test_state.py::test_bucket_exists PASSED                        [ 38%]
../tests/test_state.py::test_table_exists_with_correct_schema PASSED     [ 46%]
../tests/test_state.py::test_lambda_exists_with_correct_runtime PASSED   [ 53%]
../tests/test_state.py::test_lambda_permission_allows_s3_invoke PASSED   [ 61%]
../tests/test_state.py::test_bucket_notification_points_at_lambda PASSED [ 69%]
../tests/test_state.py::test_stack_owns_customer_managed_kms_key PASSED  [ 76%]
../tests/test_state.py::test_ddb_encrypted_with_stack_cmk PASSED         [ 84%]
../tests/test_state.py::test_lambda_role_can_use_the_cmk PASSED          [ 92%]
../tests/test_state.py::test_end_to_end_put_creates_ddb_item FAILED      [100%]

=================================== FAILURES ===================================
_____________________ test_end_to_end_put_creates_ddb_item _____________________

s3 = <botocore.client.S3 object at 0xffff92a72d20>
ddb = <botocore.client.DynamoDB object at 0xffff9254eea0>

    def test_end_to_end_put_creates_ddb_item(s3, ddb):
        key = f"verifier/red flower-{uuid.uuid4().hex}.bin"
        body = struct.pack(">Q", int(time.time_ns())) + os.urandom(32)
        s3.put_object(Bucket=BUCKET, Key=key, Body=body)
    
        deadline = time.time() + 60
        last_err = None
        item = None
        while time.time() < deadline:
            try:
                resp = ddb.get_item(
                    TableName=TABLE,
                    Key={"object_key": {"S": key}},
                    ConsistentRead=True,
                )
                if "Item" in resp:
                    item = resp["Item"]
                    break
            except ClientError as e:
                last_err = e
            time.sleep(1)
    
>       assert item is not None, (
            f"Lambda never wrote item for key={key} within 60s; last_err={last_err}"
        )
E       AssertionError: Lambda never wrote item for key=verifier/red flower-2b689ace08f34b9faefac6838a681b3c.bin within 60s; last_err=None
E       assert None is not None

/tests/test_state.py:297: AssertionError
=============================== warnings summary ===============================
test_state.py: 75 warnings
  /root/.cache/uv/archive-v0/AqG7T26iaeFSDpx2Hj7Yg/lib/python3.12/site-packages/botocore/auth.py:424: DeprecationWarning: datetime.datetime.utcnow() is deprecated and scheduled for removal in a future version. Use timezone-aware objects to represent datetimes in UTC: datetime.datetime.now(datetime.UTC).
    datetime_now = datetime.datetime.utcnow()

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
==================================== PASSES ====================================
=========================== short test summary info ============================
PASSED ../tests/test_state.py::test_aws_cli_binary_is_real
PASSED ../tests/test_state.py::test_localstack_reachable
PASSED ../tests/test_state.py::test_cfn_stack_is_deployed
PASSED ../tests/test_state.py::test_cfn_stack_owns_core_resources
PASSED ../tests/test_state.py::test_bucket_exists
PASSED ../tests/test_state.py::test_table_exists_with_correct_schema
PASSED ../tests/test_state.py::test_lambda_exists_with_correct_runtime
PASSED ../tests/test_state.py::test_lambda_permission_allows_s3_invoke
PASSED ../tests/test_state.py::test_bucket_notification_points_at_lambda
PASSED ../tests/test_state.py::test_stack_owns_customer_managed_kms_key
PASSED ../tests/test_state.py::test_ddb_encrypted_with_stack_cmk
PASSED ../tests/test_state.py::test_lambda_role_can_use_the_cmk
FAILED ../tests/test_state.py::test_end_to_end_put_creates_ddb_item - Asserti...
============= 1 failed, 12 passed, 75 warnings in 60.65s (0:01:00) =============

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_97d195f9684b430a. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_97d195f9684b430a · verifier authoritative; classifier explanatory.