AWS Batch: customize event - amazon-web-services

Question

I am running an AWS Batch array job with a few thousand children. When the parent job is complete, I'd like to trigger a lambda to do some cleanup on the output.
I can currently trigger an EventBridge rule when each child job finishes. How can we distinguish when the parent job completes?
EDIT: You can identify the parent job via
if ":" not in event["detail"]["jobId"]:
I'd also like to change the data included in the event signal, so I can tell my lambda what bucket the output went to, the name of the output file produced, etc. Can we customize the fields in an event created by Batch?
Currently, the events I'm getting look like this (account number removed):
{
"version": "0",
"id": "f6c74fc4-a943-9592-2be0-99df7b67f79f",
"detail-type": "Batch Job State Change",
"source": "aws.batch",
"account": "",
"time": "2022-12-07T22:51:38Z",
"region": "us-east-1",
"resources": [
"arn:aws:batch:us-east-1::job/138677dc-d684-4e39-b42f-6626515be7c7:2"
],
"detail": {
"jobArn": "arn:aws:batch:us-east-1::job/138677dc-d684-4e39-b42f-6626515be7c7:2",
"jobName": "event_test",
"jobId": "138677dc-d684-4e39-b42f-6626515be7c7:2",
"jobQueue": "arn:aws:batch:us-east-1::job-queue/HLM2",
"status": "SUCCEEDED",
"attempts": [
{
"container": {
"containerInstanceArn": "arn:aws:ecs:us-east-1::container-instance/AWSBatch-HLM2-c929f2e7-5cd9-3f96-8ad3-a2717fb4d2ec/6f1037214ed247aebe5ead4bf19e5929",
"taskArn": "arn:aws:ecs:us-east-1::task/AWSBatch-HLM2-c929f2e7-5cd9-3f96-8ad3-a2717fb4d2ec/5cb0c860da6a484ca6ba23a468a7f76c",
"exitCode": 0,
"logStreamName": "HLM2/default/5cb0c860da6a484ca6ba23a468a7f76c",
"networkInterfaces": []
},
"startedAt": 1670453438605,
"stoppedAt": 1670453497525,
"statusReason": "Essential container in task exited"
}
],
"statusReason": "Essential container in task exited",
"createdAt": 1670453294805,
"startedAt": 1670453438605,
"stoppedAt": 1670453497525,
"dependsOn": [],
"jobDefinition": "arn:aws:batch:us-east-1::job-definition/HLM2:8",
"parameters": {},
"container": {
"image": ".dkr.ecr.us-east-1.amazonaws.com/hlm:latest",
"command": [],
"jobRoleArn": "arn:aws:iam:::role/hlm-ec2-access-role",
"executionRoleArn": "arn:aws:iam:::role/hlm-ec2-access-role",
"volumes": [],
"environment": [],
"mountPoints": [],
"ulimits": [],
"exitCode": 0,
"containerInstanceArn": "arn:aws:ecs:us-east-1::container-instance/AWSBatch-HLM2-c929f2e7-5cd9-3f96-8ad3-a2717fb4d2ec/6f1037214ed247aebe5ead4bf19e5929",
"taskArn": "arn:aws:ecs:us-east-1::task/AWSBatch-HLM2-c929f2e7-5cd9-3f96-8ad3-a2717fb4d2ec/5cb0c860da6a484ca6ba23a468a7f76c",
"logStreamName": "HLM2/default/5cb0c860da6a484ca6ba23a468a7f76c",
"networkInterfaces": [],
"resourceRequirements": [
{
"value": "2",
"type": "VCPU"
},
{
"value": "8192",
"type": "MEMORY"
}
],
"secrets": []
},
"arrayProperties": {
"statusSummary": {},
"index": 2
},
"timeout": {
"attemptDurationSeconds": 1800
},
"tags": {
"resourceArn": "arn:aws:batch:us-east-1::job/138677dc-d684-4e39-b42f-6626515be7c7"
},
"platformCapabilities": [
"EC2"
],
"eksAttempts": []
}
}