SyncVals · Trajectory

s3-sqs-image-pipeline-kms

claude-code claude-opus-4-7 ✗ failed GOOD_FAILURE ↑ 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

GOOD_FAILUREHonest miss, the agent ran correctly but couldn't solve it. Expected for a hard task; the task is sound.

SubtypeIncomplete Implementation

EvidenceTest failure in `test_lambda_handler_returns_correct_response_shape`: Handler returned `batchItemFailures: []` (empty list) instead of including the bad message ID. The test explicitly checks: 'Expected the bad record msg-bad-338aadc3 in batchItemFailures; got ids=[]. The handler must catch per-record exceptions and return the failed messageIds.' Agent passed 17/18 tests including all infrastructure setup, S3→SQS notification, KMS encryption on three CMKs, least-privilege IAM policies, and end-to-end data flow , only the handler response shape was incomplete.

Root causeThe Lambda handler implementation does not properly catch per-record exceptions and populate the `batchItemFailures` list with failed message IDs, a requirement explicitly stated in the instruction and tested by `test_lambda_handler_returns_correct_response_shape`. This is a complex partial-batch-failure semantics issue requiring proper try/catch and response structure.

RecommendationN/A - task is fine. The instruction clearly states the handler must do 'per-record error handling' and explicitly references AWS docs on `ReportBatchItemFailures`. The information is available in the codebase (test failure messages are clear) and AWS documentation. This is a legitimate hard task where the agent understood the architecture but failed on implementation details."

Trajectory

Tool-by-tool agent trajectory

35 tool calls · 4 tool types · 43 steps

ok, nothing's built yet and the box is empty. localstack is at `http://localstack:4566`, creds are exported (`AWS_ACCESS_KEY_ID=test`, same for secret, region `us-east-1`), you've got `aws`, `python3`, `boto3`, `jq`, `zip`, `curl`. stand the whole thing up from scratch. we're building an image-ingest pipeline. someone drops an object into a source bucket and on the other end we want a processed copy in a dest bucket plus a row in dynamodb describing it. everything has to be SSE-KMS with customer-managed keys , the bucket on the way in, the queue in the middle, and the bucket on the way out. three separate CMKs, one per boundary. least privilege throughout. the verifier reads policy docs directly, so don't wildcard your way through kms. shape of it: - PUT to the source bucket fires an s3 ObjectCreated notification - notification lands on an SQS standard queue (SSE-KMS) - a lambda consumes the queue and for each record: reads the source object, writes a processed copy to the dest bucket at `processed/<same-key>`, and writes a row to ddb with `{object_key, source_size, processed_at, status: "OK"}` - there's a DLQ behind the main queue with a redrive policy - the handler does per-record error handling , bad records get reported back individually, good records in the same batch don't get retried done looks like: one PUT to the source bucket, and within 60s, exactly one object at `processed/<key>` in the dest bucket, exactly one ddb row keyed by `object_key`, and nothing in the DLQ. keys with spaces in them have to work too (the s3 event url-encodes them , you know where this is going). also, when the handler is invoked with a batch that contains a broken record alongside a good one, only the broken record's id comes back in the response and the good one isn't retried. couple of things to be careful about: the SQS visibility timeout needs to actually cover the lambda timeout or messages get redriven into the DLQ mid-processing. and the partial-batch-failure contract has two sides , both the event source mapping and the handler response shape need to match, or the whole batch retries on any single failure. the aws docs on `ReportBatchItemFailures` are worth a glance. names the verifier grabs by hand, use them exactly: | thing | name | |-|-| | source bucket | `ingest-source-bucket` | | dest bucket | `ingest-dest-bucket` | | main queue | `ingest-events` | | dlq | `ingest-dlq` | | source bucket CMK alias | `alias/source-bucket-cmk` | | sqs CMK alias | `alias/sqs-queue-cmk` | | dest bucket CMK alias | `alias/dest-bucket-cmk` | | lambda | `image-ingest-consumer` | | lambda role | `image-ingest-lambda-role` | | ddb table | `image-ingest-records` | ddb partition key is `object_key` (string), no sort key. lambda is python3.11, handler entrypoint `handler.lambda_handler`. localstack community 4.13.1. you've got 60 minutes.

Check LocalStack health

shell

curl -s http://localstack:4566/_localstack/health | head -100

output

{"services": {"acm": "disabled", "apigateway": "disabled", "cloudformation": "disabled", "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": "available", "ssm": "disabled", "stepfunctions": "disabled", "sts": "available", "support": "disabled", "swf": "disabled", "transcribe": "disabled"}, "edition": "community", "version": "4.13.1"}

[stdout]
{"services": {"acm": "disabled", "apigateway": "disabled", "cloudformation": "disabled", "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": "available", "ssm": "disabled", "stepfunctions": "disabled", "sts": "available", "support": "disabled", "swf": "disabled", "transcribe": "disabled"}, "edition": "community", "version": "4.13.1"}

Verify tooling

shell

aws --version && python3 --version && echo "region=$AWS_DEFAULT_REGION key=$AWS_ACCESS_KEY_ID"

output

aws-cli/2.34.33 Python/3.14.4 Linux/6.10.14-linuxkit exe/aarch64.ubuntu.24
Python 3.12.3
region=us-east-1 key=test

[stdout]
aws-cli/2.34.33 Python/3.14.4 Linux/6.10.14-linuxkit exe/aarch64.ubuntu.24
Python 3.12.3
region=us-east-1 key=test

List working directory

shell

ls /app && pwd

output

/app

[stdout]
/app

Kicking off the build. I'll set up everything as a series of steps and verify end-to-end at the end.

Check sts identity

shell

export AWS_ENDPOINT_URL=http://localstack:4566
aws sts get-caller-identity

output

{
    "UserId": "AKIAIOSFODNN7EXAMPLE",
    "Account": "000000000000",
    "Arn": "arn:aws:iam::000000000000:root"
}

[stdout]
{
    "UserId": "AKIAIOSFODNN7EXAMPLE",
    "Account": "000000000000",
    "Arn": "arn:aws:iam::000000000000:root"
}

Write env helper

shell

cat > /app/env.sh <<'EOF'
export AWS_ENDPOINT_URL=http://localstack:4566
export AWS_DEFAULT_REGION=us-east-1
export ACCOUNT_ID=000000000000
export REGION=us-east-1
EOF
echo "env written"

output

env written

[stdout]
env written

Now create three CMKs with tight key policies (no wildcards in principals/actions), each scoped to its own service.

write · /app/kms-policy-source.json

{
  "Version": "2012-10-17",
  "Id": "source-bucket-cmk",
  "Statement": [
    {
      "Sid": "EnableRootAccountAdmin",
      "Effect": "Allow",
      "Principal": {"AWS": "arn:aws:iam::000000000000:root"},
      "Action": [
        "kms:Create*",
        "kms:Describe*",
        "kms:Enable*",
        "kms:List*",
        "kms:Put*",
        "kms:Update*",
        "kms:Revoke*",
        "kms:Disable*",
        "kms:Get*",
        "kms:Delete*",
        "kms:TagResource",
        "kms:UntagResource",
        "kms:ScheduleKeyDeletion",
        "kms:CancelKeyDeletion"
      ],
      "Resource": "*"
    },
    {
      "Sid": "AllowS3ServiceUse",
      "Effect": "Allow",
      "Principal": {"Service": "s3.amazonaws.com"},
      "Action": [
        "kms:GenerateDataKey",
        "kms:Decrypt"
      ],
      "Resource": "*"
    },
    {
      "Sid": "AllowLambdaRoleDecrypt",
      "Effect": "Allow",
      "Principal": {"AWS": "arn:aws:iam::000000000000:role/image-ingest-lambda-role"},
      "Action": [
        "kms:Decrypt",
        "kms:DescribeKey"
      ],
      "Resource": "*"
    }
  ]
}

write · /app/kms-policy-sqs.json

{
  "Version": "2012-10-17",
  "Id": "sqs-queue-cmk",
  "Statement": [
    {
      "Sid": "EnableRootAccountAdmin",
      "Effect": "Allow",
      "Principal": {"AWS": "arn:aws:iam::000000000000:root"},
      "Action": [
        "kms:Create*",
        "kms:Describe*",
        "kms:Enable*",
        "kms:List*",
        "kms:Put*",
        "kms:Update*",
        "kms:Revoke*",
        "kms:Disable*",
        "kms:Get*",
        "kms:Delete*",
        "kms:TagResource",
        "kms:UntagResource",
        "kms:ScheduleKeyDeletion",
        "kms:CancelKeyDeletion"
      ],
      "Resource": "*"
    },
    {
      "Sid": "AllowS3ToPublishEncryptedSQS",
      "Effect": "Allow",
      "Principal": {"Service": "s3.amazonaws.com"},
      "Action": [
        "kms:GenerateDataKey",
        "kms:Decrypt"
      ],
      "Resource": "*"
    },
    {
      "Sid": "AllowLambdaRoleConsumeEncryptedSQS",
      "Effect": "Allow",
      "Principal": {"AWS": "arn:aws:iam::000000000000:role/image-ingest-lambda-role"},
      "Action": [
        "kms:Decrypt",
        "kms:GenerateDataKey",
        "kms:DescribeKey"
      ],
      "Resource": "*"
    }
  ]
}

write · /app/kms-policy-dest.json

{
  "Version": "2012-10-17",
  "Id": "dest-bucket-cmk",
  "Statement": [
    {
      "Sid": "EnableRootAccountAdmin",
      "Effect": "Allow",
      "Principal": {"AWS": "arn:aws:iam::000000000000:root"},
      "Action": [
        "kms:Create*",
        "kms:Describe*",
        "kms:Enable*",
        "kms:List*",
        "kms:Put*",
        "kms:Update*",
        "kms:Revoke*",
        "kms:Disable*",
        "kms:Get*",
        "kms:Delete*",
        "kms:TagResource",
        "kms:UntagResource",
        "kms:ScheduleKeyDeletion",
        "kms:CancelKeyDeletion"
      ],
      "Resource": "*"
    },
    {
      "Sid": "AllowLambdaRoleEncryptForDest",
      "Effect": "Allow",
      "Principal": {"AWS": "arn:aws:iam::000000000000:role/image-ingest-lambda-role"},
      "Action": [
        "kms:Encrypt",
        "kms:GenerateDataKey",
        "kms:DescribeKey"
      ],
      "Resource": "*"
    }
  ]
}

ToolSearch

{
  "query": "select:TodoWrite",
  "max_results": 1
}

, output, 
{"type": "tool_reference", "tool_name": "TodoWrite"}

Create 3 KMS CMKs with aliases
Create IAM role + least-priv policy for lambda
Create DynamoDB table
Create DLQ + main SQS queue with SSE-KMS + redrive
Create source & dest S3 buckets with SSE-KMS
Wire S3 -> SQS notification (with SQS policy for S3 principal)
Write + package Lambda handler
Deploy lambda + ESM with ReportBatchItemFailures
End-to-end verify: happy path, spaced key, partial batch failure

Create KMS CMKs with aliases

shell

source /app/env.sh
set -e

# Create 3 CMKs with policies, then aliases
SRC_KEY_ID=$(aws kms create-key --description "source bucket CMK" --policy file:///app/kms-policy-source.json --query 'KeyMetadata.KeyId' --output text)
SQS_KEY_ID=$(aws kms create-key --description "sqs queue CMK" --policy file:///app/kms-policy-sqs.json --query 'KeyMetadata.KeyId' --output text)
DST_KEY_ID=$(aws kms create-key --description "dest bucket CMK" --policy file:///app/kms-policy-dest.json --query 'KeyMetadata.KeyId' --output text)

aws kms create-alias --alias-name alias/source-bucket-cmk --target-key-id $SRC_KEY_ID
aws kms create-alias --alias-name alias/sqs-queue-cmk --target-key-id $SQS_KEY_ID
aws kms create-alias --alias-name alias/dest-bucket-cmk --target-key-id $DST_KEY_ID

echo "SRC_KEY_ID=$SRC_KEY_ID"
echo "SQS_KEY_ID=$SQS_KEY_ID"
echo "DST_KEY_ID=$DST_KEY_ID"

cat >> /app/env.sh <<EOF
export SRC_KEY_ID=$SRC_KEY_ID
export SQS_KEY_ID=$SQS_KEY_ID
export DST_KEY_ID=$DST_KEY_ID
export SRC_KEY_ARN=arn:aws:kms:us-east-1:000000000000:key/$SRC_KEY_ID
export SQS_KEY_ARN=arn:aws:kms:us-east-1:000000000000:key/$SQS_KEY_ID
export DST_KEY_ARN=arn:aws:kms:us-east-1:000000000000:key/$DST_KEY_ID
EOF
echo "env updated"

output

SRC_KEY_ID=161a7473-da40-49c6-a77d-ec49ee449b05
SQS_KEY_ID=4988fc63-5443-49ac-ba64-3c704e8759e2
DST_KEY_ID=f690d658-d425-42db-9241-8dc52bb2e812
env updated

[stdout]
SRC_KEY_ID=161a7473-da40-49c6-a77d-ec49ee449b05
SQS_KEY_ID=4988fc63-5443-49ac-ba64-3c704e8759e2
DST_KEY_ID=f690d658-d425-42db-9241-8dc52bb2e812
env updated

Create 3 KMS CMKs with aliases
Create IAM role + least-priv policy for lambda
Create DynamoDB table
Create DLQ + main SQS queue with SSE-KMS + redrive
Create source & dest S3 buckets with SSE-KMS
Wire S3 -> SQS notification (with SQS policy for S3 principal)
Write + package Lambda handler
Deploy lambda + ESM with ReportBatchItemFailures
End-to-end verify: happy path, spaced key, partial batch failure

write · /app/lambda-trust.json

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {"Service": "lambda.amazonaws.com"},
      "Action": "sts:AssumeRole"
    }
  ]
}

write · /app/lambda-policy.json.tpl

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Logs",
      "Effect": "Allow",
      "Action": [
        "logs:CreateLogGroup",
        "logs:CreateLogStream",
        "logs:PutLogEvents"
      ],
      "Resource": "arn:aws:logs:us-east-1:000000000000:log-group:/aws/lambda/image-ingest-consumer:*"
    },
    {
      "Sid": "ReadSourceBucket",
      "Effect": "Allow",
      "Action": [
        "s3:GetObject"
      ],
      "Resource": "arn:aws:s3:::ingest-source-bucket/*"
    },
    {
      "Sid": "WriteDestBucket",
      "Effect": "Allow",
      "Action": [
        "s3:PutObject"
      ],
      "Resource": "arn:aws:s3:::ingest-dest-bucket/*"
    },
    {
      "Sid": "ConsumeMainQueue",
      "Effect": "Allow",
      "Action": [
        "sqs:ReceiveMessage",
        "sqs:DeleteMessage",
        "sqs:GetQueueAttributes",
        "sqs:ChangeMessageVisibility"
      ],
      "Resource": "arn:aws:sqs:us-east-1:000000000000:ingest-events"
    },
    {
      "Sid": "WriteDdb",
      "Effect": "Allow",
      "Action": [
        "dynamodb:PutItem"
      ],
      "Resource": "arn:aws:dynamodb:us-east-1:000000000000:table/image-ingest-records"
    },
    {
      "Sid": "DecryptSourceBucket",
      "Effect": "Allow",
      "Action": [
        "kms:Decrypt",
        "kms:DescribeKey"
      ],
      "Resource": "SRC_KEY_ARN_PLACEHOLDER"
    },
    {
      "Sid": "DecryptSqsMessages",
      "Effect": "Allow",
      "Action": [
        "kms:Decrypt",
        "kms:GenerateDataKey",
        "kms:DescribeKey"
      ],
      "Resource": "SQS_KEY_ARN_PLACEHOLDER"
    },
    {
      "Sid": "EncryptDestBucket",
      "Effect": "Allow",
      "Action": [
        "kms:Encrypt",
        "kms:GenerateDataKey",
        "kms:DescribeKey"
      ],
      "Resource": "DST_KEY_ARN_PLACEHOLDER"
    }
  ]
}

Create IAM role and attach least-priv policy

shell

source /app/env.sh
set -e

# Materialize policy with key ARNs
sed -e "s|SRC_KEY_ARN_PLACEHOLDER|$SRC_KEY_ARN|" \
    -e "s|SQS_KEY_ARN_PLACEHOLDER|$SQS_KEY_ARN|" \
    -e "s|DST_KEY_ARN_PLACEHOLDER|$DST_KEY_ARN|" \
    /app/lambda-policy.json.tpl > /app/lambda-policy.json

python3 -c 'import json,sys; json.load(open("/app/lambda-policy.json"))' && echo "policy JSON ok"

aws iam create-role \
  --role-name image-ingest-lambda-role \
  --assume-role-policy-document file:///app/lambda-trust.json \
  --query 'Role.Arn' --output text

aws iam put-role-policy \
  --role-name image-ingest-lambda-role \
  --policy-name image-ingest-inline \
  --policy-document file:///app/lambda-policy.json

echo "ROLE_ARN=arn:aws:iam::000000000000:role/image-ingest-lambda-role"
cat >> /app/env.sh <<'EOF'
export LAMBDA_ROLE_ARN=arn:aws:iam::000000000000:role/image-ingest-lambda-role
EOF

output

policy JSON ok
arn:aws:iam::000000000000:role/image-ingest-lambda-role
ROLE_ARN=arn:aws:iam::000000000000:role/image-ingest-lambda-role

[stdout]
policy JSON ok
arn:aws:iam::000000000000:role/image-ingest-lambda-role
ROLE_ARN=arn:aws:iam::000000000000:role/image-ingest-lambda-role

Create 3 KMS CMKs with aliases
Create IAM role + least-priv policy for lambda
Create DynamoDB table
Create DLQ + main SQS queue with SSE-KMS + redrive
Create source & dest S3 buckets with SSE-KMS
Wire S3 -> SQS notification (with SQS policy for S3 principal)
Write + package Lambda handler
Deploy lambda + ESM with ReportBatchItemFailures
End-to-end verify: happy path, spaced key, partial batch failure

Create DynamoDB table

shell

source /app/env.sh
set -e

aws dynamodb create-table \
  --table-name image-ingest-records \
  --attribute-definitions AttributeName=object_key,AttributeType=S \
  --key-schema AttributeName=object_key,KeyType=HASH \
  --billing-mode PAY_PER_REQUEST \
  --query 'TableDescription.TableArn' --output text

# wait until ACTIVE
for i in 1 2 3 4 5; do
  st=$(aws dynamodb describe-table --table-name image-ingest-records --query 'Table.TableStatus' --output text)
  echo "ddb status: $st"
  [ "$st" = "ACTIVE" ] && break
  sleep 1
done

output

arn:aws:dynamodb:us-east-1:000000000000:table/image-ingest-records
ddb status: ACTIVE

[stdout]
arn:aws:dynamodb:us-east-1:000000000000:table/image-ingest-records
ddb status: ACTIVE

Create 3 KMS CMKs with aliases
Create IAM role + least-priv policy for lambda
Create DynamoDB table
Create DLQ + main SQS queue with SSE-KMS + redrive
Create source & dest S3 buckets with SSE-KMS
Wire S3 -> SQS notification (with SQS policy for S3 principal)
Write + package Lambda handler
Deploy lambda + ESM with ReportBatchItemFailures
End-to-end verify: happy path, spaced key, partial batch failure

Create DLQ and main SQS queue with SSE-KMS and redrive

shell

source /app/env.sh
set -e

# DLQ first (need its ARN for main queue redrive)
DLQ_URL=$(aws sqs create-queue \
  --queue-name ingest-dlq \
  --attributes "{\"KmsMasterKeyId\":\"$SQS_KEY_ARN\",\"MessageRetentionPeriod\":\"1209600\"}" \
  --query 'QueueUrl' --output text)
echo "DLQ_URL=$DLQ_URL"

DLQ_ARN=$(aws sqs get-queue-attributes --queue-url "$DLQ_URL" --attribute-names QueueArn --query 'Attributes.QueueArn' --output text)
echo "DLQ_ARN=$DLQ_ARN"

# Main queue: SSE-KMS, visibility 90s (> lambda timeout 30s), redrive to DLQ
REDRIVE=$(python3 -c "import json,sys; print(json.dumps({'deadLetterTargetArn':'$DLQ_ARN','maxReceiveCount':5}))")
MAIN_URL=$(aws sqs create-queue \
  --queue-name ingest-events \
  --attributes "{\"KmsMasterKeyId\":\"$SQS_KEY_ARN\",\"VisibilityTimeout\":\"90\",\"MessageRetentionPeriod\":\"345600\",\"RedrivePolicy\":$(echo "$REDRIVE" | python3 -c 'import sys,json; print(json.dumps(sys.stdin.read().strip()))')}" \
  --query 'QueueUrl' --output text)
echo "MAIN_URL=$MAIN_URL"

MAIN_ARN=$(aws sqs get-queue-attributes --queue-url "$MAIN_URL" --attribute-names QueueArn --query 'Attributes.QueueArn' --output text)
echo "MAIN_ARN=$MAIN_ARN"

cat >> /app/env.sh <<EOF
export DLQ_URL=$DLQ_URL
export DLQ_ARN=$DLQ_ARN
export MAIN_URL=$MAIN_URL
export MAIN_ARN=$MAIN_ARN
EOF

# Verify redrive and visibility
aws sqs get-queue-attributes --queue-url "$MAIN_URL" --attribute-names All --query 'Attributes' --output json

output

DLQ_URL=http://sqs.us-east-1.localhost.localstack.cloud:4566/000000000000/ingest-dlq
DLQ_ARN=arn:aws:sqs:us-east-1:000000000000:ingest-dlq
MAIN_URL=http://sqs.us-east-1.localhost.localstack.cloud:4566/000000000000/ingest-events
MAIN_ARN=arn:aws:sqs:us-east-1:000000000000:ingest-events
{
    "CreatedTimestamp": "1776851521",
    "DelaySeconds": "0",
    "LastModifiedTimestamp": "1776851521",
    "MaximumMessageSize": "1048576",
    "MessageRetentionPeriod": "345600",
    "QueueArn": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
    "ReceiveMessageWaitTimeSeconds": "0",
    "VisibilityTimeout": "90",
    "SqsManagedSseEnabled": "true",
    "KmsMasterKeyId": "arn:aws:kms:us-east-1:000000000000:key/4988fc63-5443-49ac-ba64-3c704e8759e2",
    "RedrivePolicy": "{\"deadLetterTargetArn\": \"arn:aws:sqs:us-east-1:000000000000:ingest-dlq\", \"maxReceiveCount\": 5}",
    "ApproximateNumberOfMessages": "0",
    "ApproximateNumberOfMessagesDelayed": "0",
    "ApproximateNumberOfMessagesNotVisible": "0"
}

[stdout]
DLQ_URL=http://sqs.us-east-1.localhost.localstack.cloud:4566/000000000000/ingest-dlq
DLQ_ARN=arn:aws:sqs:us-east-1:000000000000:ingest-dlq
MAIN_URL=http://sqs.us-east-1.localhost.localstack.cloud:4566/000000000000/ingest-events
MAIN_ARN=arn:aws:sqs:us-east-1:000000000000:ingest-events
{
    "CreatedTimestamp": "1776851521",
    "DelaySeconds": "0",
    "LastModifiedTimestamp": "1776851521",
    "MaximumMessageSize": "1048576",
    "MessageRetentionPeriod": "345600",
    "QueueArn": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
    "ReceiveMessageWaitTimeSeconds": "0",
    "VisibilityTimeout": "90",
    "SqsManagedSseEnabled": "true",
    "KmsMasterKeyId": "arn:aws:kms:us-east-1:000000000000:key/4988fc63-5443-49ac-ba64-3c704e8759e2",
    "RedrivePolicy": "{\"deadLetterTargetArn\": \"arn:aws:sqs:us-east-1:000000000000:ingest-dlq\", \"maxReceiveCount\": 5}",
    "ApproximateNumberOfMessages": "0",
    "ApproximateNumberOfMessagesDelayed": "0",
    "ApproximateNumberOfMessagesNotVisible": "0"
}

Good. Now the queue resource policy to allow S3 source bucket to SendMessage.

write · /app/main-queue-policy.json

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "AllowSourceBucketToSend",
      "Effect": "Allow",
      "Principal": {"Service": "s3.amazonaws.com"},
      "Action": "sqs:SendMessage",
      "Resource": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
      "Condition": {
        "ArnLike": {"aws:SourceArn": "arn:aws:s3:::ingest-source-bucket"},
        "StringEquals": {"aws:SourceAccount": "000000000000"}
      }
    }
  ]
}

Attach queue policy allowing S3 to SendMessage

shell

source /app/env.sh
set -e
POLICY_JSON=$(python3 -c 'import json; print(json.dumps(open("/app/main-queue-policy.json").read()))')
aws sqs set-queue-attributes \
  --queue-url "$MAIN_URL" \
  --attributes "{\"Policy\":$POLICY_JSON}"
aws sqs get-queue-attributes --queue-url "$MAIN_URL" --attribute-names Policy --query 'Attributes.Policy' --output text

output

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "AllowSourceBucketToSend",
      "Effect": "Allow",
      "Principal": {"Service": "s3.amazonaws.com"},
      "Action": "sqs:SendMessage",
      "Resource": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
      "Condition": {
        "ArnLike": {"aws:SourceArn": "arn:aws:s3:::ingest-source-bucket"},
        "StringEquals": {"aws:SourceAccount": "000000000000"}
      }
    }
  ]
}

[stdout]
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "AllowSourceBucketToSend",
      "Effect": "Allow",
      "Principal": {"Service": "s3.amazonaws.com"},
      "Action": "sqs:SendMessage",
      "Resource": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
      "Condition": {
        "ArnLike": {"aws:SourceArn": "arn:aws:s3:::ingest-source-bucket"},
        "StringEquals": {"aws:SourceAccount": "000000000000"}
      }
    }
  ]
}

Create 3 KMS CMKs with aliases
Create IAM role + least-priv policy for lambda
Create DynamoDB table
Create DLQ + main SQS queue with SSE-KMS + redrive
Create source & dest S3 buckets with SSE-KMS
Wire S3 -> SQS notification (with SQS policy for S3 principal)
Write + package Lambda handler
Deploy lambda + ESM with ReportBatchItemFailures
End-to-end verify: happy path, spaced key, partial batch failure

Create S3 buckets with SSE-KMS defaults

shell

source /app/env.sh
set -e

aws s3api create-bucket --bucket ingest-source-bucket >/dev/null
aws s3api create-bucket --bucket ingest-dest-bucket >/dev/null

# SSE-KMS default encryption with CMK
aws s3api put-bucket-encryption --bucket ingest-source-bucket \
  --server-side-encryption-configuration "{\"Rules\":[{\"ApplyServerSideEncryptionByDefault\":{\"SSEAlgorithm\":\"aws:kms\",\"KMSMasterKeyID\":\"$SRC_KEY_ARN\"}}]}"

aws s3api put-bucket-encryption --bucket ingest-dest-bucket \
  --server-side-encryption-configuration "{\"Rules\":[{\"ApplyServerSideEncryptionByDefault\":{\"SSEAlgorithm\":\"aws:kms\",\"KMSMasterKeyID\":\"$DST_KEY_ARN\"}}]}"

aws s3api get-bucket-encryption --bucket ingest-source-bucket --query 'ServerSideEncryptionConfiguration.Rules[0].ApplyServerSideEncryptionByDefault' --output json
aws s3api get-bucket-encryption --bucket ingest-dest-bucket   --query 'ServerSideEncryptionConfiguration.Rules[0].ApplyServerSideEncryptionByDefault' --output json

output

{
    "SSEAlgorithm": "aws:kms",
    "KMSMasterKeyID": "arn:aws:kms:us-east-1:000000000000:key/161a7473-da40-49c6-a77d-ec49ee449b05"
}
{
    "SSEAlgorithm": "aws:kms",
    "KMSMasterKeyID": "arn:aws:kms:us-east-1:000000000000:key/f690d658-d425-42db-9241-8dc52bb2e812"
}

[stdout]
{
    "SSEAlgorithm": "aws:kms",
    "KMSMasterKeyID": "arn:aws:kms:us-east-1:000000000000:key/161a7473-da40-49c6-a77d-ec49ee449b05"
}
{
    "SSEAlgorithm": "aws:kms",
    "KMSMasterKeyID": "arn:aws:kms:us-east-1:000000000000:key/f690d658-d425-42db-9241-8dc52bb2e812"
}

Create 3 KMS CMKs with aliases
Create IAM role + least-priv policy for lambda
Create DynamoDB table
Create DLQ + main SQS queue with SSE-KMS + redrive
Create source & dest S3 buckets with SSE-KMS
Wire S3 -> SQS notification
Write + package Lambda handler
Deploy lambda + ESM with ReportBatchItemFailures
End-to-end verify: happy path, spaced key, partial batch failure

Configure S3 event notification to SQS

shell

source /app/env.sh
set -e

cat > /app/notify.json <<EOF
{
  "QueueConfigurations": [
    {
      "Id": "source-put-to-sqs",
      "QueueArn": "$MAIN_ARN",
      "Events": ["s3:ObjectCreated:*"]
    }
  ]
}
EOF

aws s3api put-bucket-notification-configuration --bucket ingest-source-bucket --notification-configuration file:///app/notify.json
aws s3api get-bucket-notification-configuration --bucket ingest-source-bucket

output

{
    "QueueConfigurations": [
        {
            "Id": "source-put-to-sqs",
            "QueueArn": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
            "Events": [
                "s3:ObjectCreated:*"
            ]
        }
    ]
}

[stdout]
{
    "QueueConfigurations": [
        {
            "Id": "source-put-to-sqs",
            "QueueArn": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
            "Events": [
                "s3:ObjectCreated:*"
            ]
        }
    ]
}

Create 3 KMS CMKs with aliases
Create IAM role + least-priv policy for lambda
Create DynamoDB table
Create DLQ + main SQS queue with SSE-KMS + redrive
Create source & dest S3 buckets with SSE-KMS
Wire S3 -> SQS notification
Write + package Lambda handler
Deploy lambda + ESM with ReportBatchItemFailures
End-to-end verify: happy path, spaced key, partial batch failure

write · /app/lambda/handler.py

import json
import os
import urllib.parse
from datetime import datetime, timezone

import boto3

SOURCE_BUCKET = os.environ["SOURCE_BUCKET"]
DEST_BUCKET = os.environ["DEST_BUCKET"]
DDB_TABLE = os.environ["DDB_TABLE"]
DEST_KMS_KEY_ARN = os.environ["DEST_KMS_KEY_ARN"]

_endpoint = os.environ.get("AWS_ENDPOINT_URL") or None
s3 = boto3.client("s3", endpoint_url=_endpoint)
ddb = boto3.client("dynamodb", endpoint_url=_endpoint)


def _process_s3_record(bucket, raw_key):
    key = urllib.parse.unquote_plus(raw_key)
    if bucket != SOURCE_BUCKET:
        raise ValueError(f"unexpected bucket {bucket}")

    obj = s3.get_object(Bucket=SOURCE_BUCKET, Key=key)
    body = obj["Body"].read()
    size = len(body)

    dest_key = f"processed/{key}"
    s3.put_object(
        Bucket=DEST_BUCKET,
        Key=dest_key,
        Body=body,
        ServerSideEncryption="aws:kms",
        SSEKMSKeyId=DEST_KMS_KEY_ARN,
    )

    ddb.put_item(
        TableName=DDB_TABLE,
        Item={
            "object_key": {"S": key},
            "source_size": {"N": str(size)},
            "processed_at": {"S": datetime.now(timezone.utc).isoformat()},
            "status": {"S": "OK"},
        },
    )


def lambda_handler(event, context):
    failures = []
    for record in event.get("Records", []):
        message_id = record.get("messageId", "unknown")
        try:
            body = json.loads(record["body"])
            s3_records = body.get("Records")
            if not s3_records:
                continue
            for s3_rec in s3_records:
                bucket = s3_rec["s3"]["bucket"]["name"]
                raw_key = s3_rec["s3"]["object"]["key"]
                _process_s3_record(bucket, raw_key)
        except Exception as exc:
            print(f"record {message_id} failed: {type(exc).__name__}: {exc}")
            failures.append({"itemIdentifier": message_id})
    return {"batchItemFailures": failures}

Package lambda zip

shell

cd /app/lambda && zip -q ../handler.zip handler.py && ls -la /app/handler.zip

output

-rw-r--r-- 1 root root 998 Apr 22 09:53 /app/handler.zip

[stdout]
-rw-r--r-- 1 root root 998 Apr 22 09:53 /app/handler.zip

Create Lambda function

shell

source /app/env.sh
set -e

LAMBDA_ARN=$(aws lambda create-function \
  --function-name image-ingest-consumer \
  --runtime python3.11 \
  --role "$LAMBDA_ROLE_ARN" \
  --handler handler.lambda_handler \
  --zip-file fileb:///app/handler.zip \
  --timeout 30 \
  --memory-size 256 \
  --environment "Variables={SOURCE_BUCKET=ingest-source-bucket,DEST_BUCKET=ingest-dest-bucket,DDB_TABLE=image-ingest-records,DEST_KMS_KEY_ARN=$DST_KEY_ARN,AWS_ENDPOINT_URL=http://localstack:4566}" \
  --query 'FunctionArn' --output text)

echo "LAMBDA_ARN=$LAMBDA_ARN"
cat >> /app/env.sh <<EOF
export LAMBDA_ARN=$LAMBDA_ARN
EOF

# Wait until active
for i in 1 2 3 4 5 6 7 8 9 10; do
  st=$(aws lambda get-function --function-name image-ingest-consumer --query 'Configuration.State' --output text)
  echo "lambda state: $st"
  [ "$st" = "Active" ] && break
  sleep 2
done

output

LAMBDA_ARN=arn:aws:lambda:us-east-1:000000000000:function:image-ingest-consumer
lambda state: Pending
lambda state: Pending
lambda state: Active

[stdout]
LAMBDA_ARN=arn:aws:lambda:us-east-1:000000000000:function:image-ingest-consumer
lambda state: Pending
lambda state: Pending
lambda state: Active

Create ESM with ReportBatchItemFailures

shell

source /app/env.sh
set -e

ESM_UUID=$(aws lambda create-event-source-mapping \
  --function-name image-ingest-consumer \
  --event-source-arn "$MAIN_ARN" \
  --batch-size 10 \
  --maximum-batching-window-in-seconds 1 \
  --function-response-types ReportBatchItemFailures \
  --query 'UUID' --output text)
echo "ESM_UUID=$ESM_UUID"
cat >> /app/env.sh <<EOF
export ESM_UUID=$ESM_UUID
EOF

# confirm response type
aws lambda get-event-source-mapping --uuid "$ESM_UUID" --query '{State:State,RT:FunctionResponseTypes,Src:EventSourceArn}' --output json

# wait for Enabled
for i in 1 2 3 4 5 6 7 8 9 10; do
  st=$(aws lambda get-event-source-mapping --uuid "$ESM_UUID" --query 'State' --output text)
  echo "esm state: $st"
  [ "$st" = "Enabled" ] && break
  sleep 2
done

output

ESM_UUID=19da0bba-76e5-4931-984a-1ecad75311a6
{
    "State": "Enabled",
    "RT": [
        "ReportBatchItemFailures"
    ],
    "Src": "arn:aws:sqs:us-east-1:000000000000:ingest-events"
}
esm state: Enabled

[stdout]
ESM_UUID=19da0bba-76e5-4931-984a-1ecad75311a6
{
    "State": "Enabled",
    "RT": [
        "ReportBatchItemFailures"
    ],
    "Src": "arn:aws:sqs:us-east-1:000000000000:ingest-events"
}
esm state: Enabled

Create 3 KMS CMKs with aliases
Create IAM role + least-priv policy for lambda
Create DynamoDB table
Create DLQ + main SQS queue with SSE-KMS + redrive
Create source & dest S3 buckets with SSE-KMS
Wire S3 -> SQS notification
Write + package Lambda handler
Deploy lambda + ESM with ReportBatchItemFailures
End-to-end verify: happy path, spaced key, partial batch failure

Now verify end-to-end. First: happy path with a plain key, then a key with a space.

E2E test: upload two files and verify dest + ddb

shell

source /app/env.sh
set -e

# Happy path: simple key
echo "hello world payload A" > /tmp/a.txt
aws s3api put-object --bucket ingest-source-bucket --key a.txt --body /tmp/a.txt >/dev/null
echo "uploaded a.txt"

# Spaced key
echo "spaced key payload" > /tmp/b.txt
aws s3api put-object --bucket ingest-source-bucket --key "hello world.txt" --body /tmp/b.txt >/dev/null
echo "uploaded 'hello world.txt'"

# Wait up to 60s for both to land
for i in $(seq 1 30); do
  sleep 2
  a_ok=$(aws s3api head-object --bucket ingest-dest-bucket --key "processed/a.txt" >/dev/null 2>&1 && echo yes || echo no)
  b_ok=$(aws s3api head-object --bucket ingest-dest-bucket --key "processed/hello world.txt" >/dev/null 2>&1 && echo yes || echo no)
  echo "$i a=$a_ok b=$b_ok"
  if [ "$a_ok" = "yes" ] && [ "$b_ok" = "yes" ]; then break; fi
done

echo "---- dest listing ----"
aws s3api list-objects-v2 --bucket ingest-dest-bucket --query 'Contents[].Key' --output json

echo "---- ddb scan ----"
aws dynamodb scan --table-name image-ingest-records --query 'Items' --output json

echo "---- DLQ depth ----"
aws sqs get-queue-attributes --queue-url "$DLQ_URL" --attribute-names ApproximateNumberOfMessages --query 'Attributes.ApproximateNumberOfMessages' --output text

output

uploaded a.txt
uploaded 'hello world.txt'
1 a=no b=no
2 a=no b=no
3 a=no b=no
4 a=yes b=yes
---- dest listing ----
[
    "processed/a.txt",
    "processed/hello world.txt"
]
---- ddb scan ----
[
    {
        "source_size": {
            "N": "22"
        },
        "processed_at": {
            "S": "2026-04-22T09:54:06.402713+00:00"
        },
        "object_key": {
            "S": "a.txt"
        },
        "status": {
            "S": "OK"
        }
    },
    {
        "source_size": {
            "N": "19"
        },
        "processed_at": {
            "S": "2026-04-22T09:54:06.637234+00:00"
        },
        "object_key": {
            "S": "hello world.txt"
        },
        "status": {
            "S": "OK"
        }
    }
]
---- DLQ depth ----
0

[stdout]
uploaded a.txt
uploaded 'hello world.txt'
1 a=no b=no
2 a=no b=no
3 a=no b=no
4 a=yes b=yes
---- dest listing ----
[
    "processed/a.txt",
    "processed/hello world.txt"
]
---- ddb scan ----
[
    {
        "source_size": {
            "N": "22"
        },
        "processed_at": {
            "S": "2026-04-22T09:54:06.402713+00:00"
        },
        "object_key": {
            "S": "a.txt"
        },
        "status": {
            "S": "OK"
        }
    },
    {
        "source_size": {
            "N": "19"
        },
        "processed_at": {
            "S": "2026-04-22T09:54:06.637234+00:00"
        },
        "object_key": {
            "S": "hello world.txt"
        },
        "status": {
            "S": "OK"
        }
    }
]
---- DLQ depth ----
0

End-to-end happy path works. Now the partial-batch-failure contract.

Invoke lambda with mixed good/bad batch and verify response

shell

source /app/env.sh
set -e

# Upload a fresh source object for the good record (don't fire a notification , we'll synthesize an event)
echo "partial batch good payload" > /tmp/good.txt
aws s3api put-object --bucket ingest-source-bucket --key "partial-good.txt" --body /tmp/good.txt >/dev/null
# Wait for the auto-pipeline to NOT interfere , give it time to settle, then delete the resulting dest object + ddb row so we can re-verify the synthesized invocation.
sleep 6
aws s3api delete-object --bucket ingest-dest-bucket --key "processed/partial-good.txt" >/dev/null || true
aws dynamodb delete-item --table-name image-ingest-records --key '{"object_key":{"S":"partial-good.txt"}}' >/dev/null || true

# Build a synthetic SQS batch event: 1 good (valid s3 envelope), 1 bad (unparseable body)
python3 - > /tmp/batch-event.json <<'PY'
import json
good_body = {
  "Records": [{
    "eventSource": "aws:s3",
    "s3": {
      "bucket": {"name": "ingest-source-bucket"},
      "object": {"key": "partial-good.txt"}
    }
  }]
}
event = {
  "Records": [
    {
      "messageId": "msg-good-1",
      "receiptHandle": "rh-good",
      "body": json.dumps(good_body),
      "eventSource": "aws:sqs",
      "eventSourceARN": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
      "awsRegion": "us-east-1"
    },
    {
      "messageId": "msg-bad-1",
      "receiptHandle": "rh-bad",
      "body": "this is not json {",
      "eventSource": "aws:sqs",
      "eventSourceARN": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
      "awsRegion": "us-east-1"
    }
  ]
}
print(json.dumps(event))
PY

aws lambda invoke \
  --function-name image-ingest-consumer \
  --payload fileb:///tmp/batch-event.json \
  --cli-binary-format raw-in-base64-out \
  /tmp/invoke-out.json >/tmp/invoke-meta.json

echo "---- invoke meta ----"
cat /tmp/invoke-meta.json
echo
echo "---- handler response ----"
cat /tmp/invoke-out.json
echo

echo "---- verify good record side-effects ----"
aws s3api head-object --bucket ingest-dest-bucket --key "processed/partial-good.txt" --query 'ContentLength' --output text
aws dynamodb get-item --table-name image-ingest-records --key '{"object_key":{"S":"partial-good.txt"}}' --query 'Item' --output json

output

---- invoke meta ----
{
    "StatusCode": 200,
    "ExecutedVersion": "$LATEST"
}

---- handler response ----
{"batchItemFailures": [{"itemIdentifier": "msg-bad-1"}]}
---- verify good record side-effects ----
27
{
    "source_size": {
        "N": "27"
    },
    "processed_at": {
        "S": "2026-04-22T09:54:37.531020+00:00"
    },
    "object_key": {
        "S": "partial-good.txt"
    },
    "status": {
        "S": "OK"
    }
}

[stdout]
---- invoke meta ----
{
    "StatusCode": 200,
    "ExecutedVersion": "$LATEST"
}

---- handler response ----
{"batchItemFailures": [{"itemIdentifier": "msg-bad-1"}]}
---- verify good record side-effects ----
27
{
    "source_size": {
        "N": "27"
    },
    "processed_at": {
        "S": "2026-04-22T09:54:37.531020+00:00"
    },
    "object_key": {
        "S": "partial-good.txt"
    },
    "status": {
        "S": "OK"
    }
}

Partial batch contract verified: response is `{"batchItemFailures":[{"itemIdentifier":"msg-bad-1"}]}` and the good record's side effects landed. Final system check.

Final config audit

shell

source /app/env.sh
set -e

echo "=== KMS aliases ==="
aws kms list-aliases --query 'Aliases[?contains(AliasName,`-cmk`)].{Alias:AliasName,KeyId:TargetKeyId}' --output table

echo "=== Buckets and encryption ==="
for b in ingest-source-bucket ingest-dest-bucket; do
  enc=$(aws s3api get-bucket-encryption --bucket "$b" --query 'ServerSideEncryptionConfiguration.Rules[0].ApplyServerSideEncryptionByDefault' --output json)
  echo "$b -> $enc"
done

echo "=== SQS attrs ==="
aws sqs get-queue-attributes --queue-url "$MAIN_URL" --attribute-names QueueArn KmsMasterKeyId VisibilityTimeout RedrivePolicy --query 'Attributes' --output json
aws sqs get-queue-attributes --queue-url "$DLQ_URL" --attribute-names QueueArn KmsMasterKeyId --query 'Attributes' --output json

echo "=== S3 notifications ==="
aws s3api get-bucket-notification-configuration --bucket ingest-source-bucket

echo "=== ESM ==="
aws lambda get-event-source-mapping --uuid "$ESM_UUID" --query '{State:State,RT:FunctionResponseTypes,BatchSize:BatchSize}' --output json

echo "=== DDB ==="
aws dynamodb describe-table --table-name image-ingest-records --query 'Table.{Keys:KeySchema,Status:TableStatus}' --output json

echo "=== Queue depths ==="
echo -n "main: "; aws sqs get-queue-attributes --queue-url "$MAIN_URL" --attribute-names ApproximateNumberOfMessages --query 'Attributes.ApproximateNumberOfMessages' --output text
echo -n "dlq : "; aws sqs get-queue-attributes --queue-url "$DLQ_URL" --attribute-names ApproximateNumberOfMessages --query 'Attributes.ApproximateNumberOfMessages' --output text

echo "=== Dest objects ==="
aws s3api list-objects-v2 --bucket ingest-dest-bucket --query 'Contents[].Key' --output json

echo "=== DDB items ==="
aws dynamodb scan --table-name image-ingest-records --query 'Items[].object_key.S' --output json

output

=== KMS aliases ===
---------------------------------------------------------------------
|                            ListAliases                            |
+--------------------------+----------------------------------------+
|           Alias          |                 KeyId                  |
+--------------------------+----------------------------------------+
|  alias/source-bucket-cmk |  161a7473-da40-49c6-a77d-ec49ee449b05  |
|  alias/sqs-queue-cmk     |  4988fc63-5443-49ac-ba64-3c704e8759e2  |
|  alias/dest-bucket-cmk   |  f690d658-d425-42db-9241-8dc52bb2e812  |
+--------------------------+----------------------------------------+
=== Buckets and encryption ===
ingest-source-bucket -> {
    "SSEAlgorithm": "aws:kms",
    "KMSMasterKeyID": "arn:aws:kms:us-east-1:000000000000:key/161a7473-da40-49c6-a77d-ec49ee449b05"
}
ingest-dest-bucket -> {
    "SSEAlgorithm": "aws:kms",
    "KMSMasterKeyID": "arn:aws:kms:us-east-1:000000000000:key/f690d658-d425-42db-9241-8dc52bb2e812"
}
=== SQS attrs ===
{
    "QueueArn": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
    "KmsMasterKeyId": "arn:aws:kms:us-east-1:000000000000:key/4988fc63-5443-49ac-ba64-3c704e8759e2",
    "VisibilityTimeout": "90",
    "RedrivePolicy": "{\"deadLetterTargetArn\": \"arn:aws:sqs:us-east-1:000000000000:ingest-dlq\", \"maxReceiveCount\": 5}"
}
{
    "QueueArn": "arn:aws:sqs:us-east-1:000000000000:ingest-dlq",
    "KmsMasterKeyId": "arn:aws:kms:us-east-1:000000000000:key/4988fc63-5443-49ac-ba64-3c704e8759e2"
}
=== S3 notifications ===
{
    "QueueConfigurations": [
        {
            "Id": "source-put-to-sqs",
            "QueueArn": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
            "Events": [
                "s3:ObjectCreated:*"
            ]
        }
    ]
}
=== ESM ===
{
    "State": "Enabled",
    "RT": [
        "ReportBatchItemFailures"
    ],
    "BatchSize": 10
}
=== DDB ===
{
    "Keys": [
        {
            "AttributeName": "object_key",
            "KeyType": "HASH"
        }
    ],
    "Status": "ACTIVE"
}
=== Queue depths ===
main: 0
dlq : 0
=== Dest objects ===
[
    "processed/a.txt",
    "processed/hello world.txt",
    "processed/partial-good.txt"
]
=== DDB items ===
[
    "a.txt",
    "hello world.txt",
    "partial-good.txt"
]

[stdout]
=== KMS aliases ===
---------------------------------------------------------------------
|                            ListAliases                            |
+--------------------------+----------------------------------------+
|           Alias          |                 KeyId                  |
+--------------------------+----------------------------------------+
|  alias/source-bucket-cmk |  161a7473-da40-49c6-a77d-ec49ee449b05  |
|  alias/sqs-queue-cmk     |  4988fc63-5443-49ac-ba64-3c704e8759e2  |
|  alias/dest-bucket-cmk   |  f690d658-d425-42db-9241-8dc52bb2e812  |
+--------------------------+----------------------------------------+
=== Buckets and encryption ===
ingest-source-bucket -> {
    "SSEAlgorithm": "aws:kms",
    "KMSMasterKeyID": "arn:aws:kms:us-east-1:000000000000:key/161a7473-da40-49c6-a77d-ec49ee449b05"
}
ingest-dest-bucket -> {
    "SSEAlgorithm": "aws:kms",
    "KMSMasterKeyID": "arn:aws:kms:us-east-1:000000000000:key/f690d658-d425-42db-9241-8dc52bb2e812"
}
=== SQS attrs ===
{
    "QueueArn": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
    "KmsMasterKeyId": "arn:aws:kms:us-east-1:000000000000:key/4988fc63-5443-49ac-ba64-3c704e8759e2",
    "VisibilityTimeout": "90",
    "RedrivePolicy": "{\"deadLetterTargetArn\": \"arn:aws:sqs:us-east-1:000000000000:ingest-dlq\", \"maxReceiveCount\": 5}"
}
{
    "QueueArn": "arn:aws:sqs:us-east-1:000000000000:ingest-dlq",
    "KmsMasterKeyId": "arn:aws:kms:us-east-1:000000000000:key/4988fc63-5443-49ac-ba64-3c704e8759e2"
}
=== S3 notifications ===
{
    "QueueConfigurations": [
        {
            "Id": "source-put-to-sqs",
            "QueueArn": "arn:aws:sqs:us-east-1:000000000000:ingest-events",
            "Events": [
                "s3:ObjectCreated:*"
            ]
        }
    ]
}
=== ESM ===
{
    "State": "Enabled",
    "RT": [
        "ReportBatchItemFailures"
    ],
    "BatchSize": 10
}
=== DDB ===
{
    "Keys": [
        {
            "AttributeName": "object_key",
            "KeyType": "HASH"
        }
    ],
    "Status": "ACTIVE"
}
=== Queue depths ===
main: 0
dlq : 0
=== Dest objects ===
[
    "processed/a.txt",
    "processed/hello world.txt",
    "processed/partial-good.txt"
]
=== DDB items ===
[
    "a.txt",
    "hello world.txt",
    "partial-good.txt"
]

Create 3 KMS CMKs with aliases
Create IAM role + least-priv policy for lambda
Create DynamoDB table
Create DLQ + main SQS queue with SSE-KMS + redrive
Create source & dest S3 buckets with SSE-KMS
Wire S3 -> SQS notification
Write + package Lambda handler
Deploy lambda + ESM with ReportBatchItemFailures
End-to-end verify: happy path, spaced key, partial batch failure

Pipeline is up and verified. **What's running:** - KMS aliases `alias/source-bucket-cmk`, `alias/sqs-queue-cmk`, `alias/dest-bucket-cmk` , three separate CMKs, key policies scoped per-boundary (S3 service on source, lambda role for decrypt; lambda role for SQS decrypt/datakey; lambda role for dest encrypt). No wildcard principals/actions outside the root admin stanza. - `ingest-source-bucket` / `ingest-dest-bucket` with default SSE-KMS pointing at their respective CMKs. - `ingest-events` (SSE-KMS with sqs CMK, VisibilityTimeout=90s , 3× the 30s lambda timeout, redrive → `ingest-dlq` maxReceiveCount=5), resource policy allows only `s3.amazonaws.com` with `aws:SourceArn=ingest-source-bucket`. - `ingest-dlq` same KMS key. - S3 `ObjectCreated:*` notification → main queue. - DynamoDB `image-ingest-records`, partition key `object_key` (S), no sort key. - Lambda `image-ingest-consumer` (python3.11, `handler.lambda_handler`) , role `image-ingest-lambda-role` with scoped actions on exactly the right resources (s3:GetObject on source/*, s3:PutObject on dest/*, sqs receive/delete on main queue only, ddb:PutItem on the one table, kms actions pinned per-key ARN). - Event source mapping with `FunctionResponseTypes=[ReportBatchItemFailures]`. **Verified:** - PUT `a.txt` and `hello world.txt` → within ~8s both appear as `processed/a.txt` and `processed/hello world.txt` (space preserved, handler does `urllib.parse.unquote_plus`), DDB has both rows with `status=OK`, DLQ=0. - Direct lambda invoke with one good record + one bad (unparseable JSON) returned exactly `{"batchItemFailures":[{"itemIdentifier":"msg-bad-1"}]}`; the good record wrote its processed object and DDB row.

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-v0/5kwjkmpM3xeFQ2AVkOQFo/bin/python
cachedir: .pytest_cache
rootdir: /tests
plugins: json-ctrf-0.3.5
collecting ... collected 18 items

../tests/test_outputs.py::test_aws_cli_binary_is_real PASSED             [  5%]
../tests/test_outputs.py::test_localstack_reachable PASSED               [ 11%]
../tests/test_outputs.py::test_source_and_dest_buckets_use_customer_cmks PASSED [ 16%]
../tests/test_outputs.py::test_main_queue_and_dlq_exist_and_are_encrypted PASSED [ 22%]
../tests/test_outputs.py::test_lambda_exists_with_expected_handler PASSED [ 27%]
../tests/test_outputs.py::test_ddb_table_exists PASSED                   [ 33%]
../tests/test_outputs.py::test_source_bucket_notification_targets_main_queue PASSED [ 38%]
../tests/test_outputs.py::test_main_queue_policy_allows_s3_service PASSED [ 44%]
../tests/test_outputs.py::test_sqs_cmk_allows_s3_service PASSED          [ 50%]
../tests/test_outputs.py::test_source_cmk_allows_lambda_role_decrypt PASSED [ 55%]
../tests/test_outputs.py::test_dest_cmk_allows_lambda_role_encrypt PASSED [ 61%]
../tests/test_outputs.py::test_lambda_role_has_kms_decrypt_on_sqs_cmk PASSED [ 66%]
../tests/test_outputs.py::test_main_queue_visibility_timeout_covers_lambda_timeout PASSED [ 72%]
../tests/test_outputs.py::test_event_source_mapping_declares_report_batch_item_failures PASSED [ 77%]
../tests/test_outputs.py::test_lambda_handler_returns_correct_response_shape FAILED [ 83%]
../tests/test_outputs.py::test_end_to_end_preserves_object_size PASSED   [ 88%]
../tests/test_outputs.py::test_end_to_end_key_with_spaces_is_decoded PASSED [ 94%]
../tests/test_outputs.py::test_end_to_end_upload_propagates_to_dest_and_ddb PASSED [100%]

=================================== FAILURES ===================================
______________ test_lambda_handler_returns_correct_response_shape ______________

lmb = <botocore.client.Lambda object at 0xffff962a6b10>
sqs = <botocore.client.SQS object at 0xffff965d3dd0>
s3 = <botocore.client.S3 object at 0xffff968a2f90>

    def test_lambda_handler_returns_correct_response_shape(lmb, sqs, s3):
        """Partial batch response shape."""
        probe_key = f"probe/verifier-{uuid.uuid4().hex[:8]}.bin"
        s3.put_object(Bucket=SRC_BUCKET, Key=probe_key, Body=b"x" * 32)
    
        main_arn = _queue_attrs(
            sqs, _queue_url(sqs, MAIN_QUEUE), attrs=("QueueArn",)
        )["QueueArn"]
    
        good_body = {
            "Records": [
                {
                    "s3": {
                        "bucket": {"name": SRC_BUCKET},
                        "object": {"key": probe_key},
                    }
                }
            ]
        }
        bad_body = {"some-other-shape": "not-an-s3-event"}
    
        good_mid = "msg-good-" + uuid.uuid4().hex[:8]
        bad_mid = "msg-bad-" + uuid.uuid4().hex[:8]
        event = {
            "Records": [
                {
                    "messageId": good_mid,
                    "body": json.dumps(good_body),
                    "eventSource": "aws:sqs",
                    "eventSourceARN": main_arn,
                    "awsRegion": REGION,
                },
                {
                    "messageId": bad_mid,
                    "body": json.dumps(bad_body),
                    "eventSource": "aws:sqs",
                    "eventSourceARN": main_arn,
                    "awsRegion": REGION,
                },
            ]
        }
    
        resp = lmb.invoke(
            FunctionName=LAMBDA_FUNC,
            InvocationType="RequestResponse",
            Payload=json.dumps(event).encode(),
        )
        func_err = resp.get("FunctionError")
        payload = resp["Payload"].read()
        assert not func_err, (
            f"Lambda invocation raised FunctionError={func_err}. "
            f"Payload: {payload!r}"
        )
        result = json.loads(payload) if payload else None
        assert isinstance(result, dict), (
            f"Lambda returned non-object payload: {result!r}. Expected "
            f"{{'batchItemFailures': [...]}}."
        )
        assert "batchItemFailures" in result, (
            f"Lambda response is missing the required `batchItemFailures` "
            f"key. AWS silently ignores any other key (e.g. "
            f"`failedBatchItems`) when FunctionResponseTypes includes "
            f"ReportBatchItemFailures. Got: {result}"
        )
        failures = result["batchItemFailures"]
        assert isinstance(failures, list), (
            f"batchItemFailures must be a list; got {type(failures).__name__}"
        )
        ids = [f.get("itemIdentifier") for f in failures]
>       assert bad_mid in ids, (
            f"Expected the bad record {bad_mid} in batchItemFailures; "
            f"got ids={ids}. The handler must catch per-record exceptions "
            f"and return the failed messageIds."
        )
E       AssertionError: Expected the bad record msg-bad-338aadc3 in batchItemFailures; got ids=[]. The handler must catch per-record exceptions and return the failed messageIds.
E       assert 'msg-bad-338aadc3' in []

/tests/test_outputs.py:522: AssertionError
=============================== warnings summary ===============================
test_outputs.py: 59 warnings
  /root/.cache/uv/archive-v0/5kwjkmpM3xeFQ2AVkOQFo/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_outputs.py::test_aws_cli_binary_is_real
PASSED ../tests/test_outputs.py::test_localstack_reachable
PASSED ../tests/test_outputs.py::test_source_and_dest_buckets_use_customer_cmks
PASSED ../tests/test_outputs.py::test_main_queue_and_dlq_exist_and_are_encrypted
PASSED ../tests/test_outputs.py::test_lambda_exists_with_expected_handler
PASSED ../tests/test_outputs.py::test_ddb_table_exists
PASSED ../tests/test_outputs.py::test_source_bucket_notification_targets_main_queue
PASSED ../tests/test_outputs.py::test_main_queue_policy_allows_s3_service
PASSED ../tests/test_outputs.py::test_sqs_cmk_allows_s3_service
PASSED ../tests/test_outputs.py::test_source_cmk_allows_lambda_role_decrypt
PASSED ../tests/test_outputs.py::test_dest_cmk_allows_lambda_role_encrypt
PASSED ../tests/test_outputs.py::test_lambda_role_has_kms_decrypt_on_sqs_cmk
PASSED ../tests/test_outputs.py::test_main_queue_visibility_timeout_covers_lambda_timeout
PASSED ../tests/test_outputs.py::test_event_source_mapping_declares_report_batch_item_failures
PASSED ../tests/test_outputs.py::test_end_to_end_preserves_object_size
PASSED ../tests/test_outputs.py::test_end_to_end_key_with_spaces_is_decoded
PASSED ../tests/test_outputs.py::test_end_to_end_upload_propagates_to_dest_and_ddb
FAILED ../tests/test_outputs.py::test_lambda_handler_returns_correct_response_shape
================== 1 failed, 17 passed, 59 warnings in 10.27s ==================

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_9ee88cb704074357. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_9ee88cb704074357 · verifier authoritative; classifier explanatory.