> ## Documentation Index
> Fetch the complete documentation index at: https://docs.valkyrie.vals.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Invoke a post-run Lambda

> Run an AWS Lambda function after a benchmark finishes.

The `--lambda` flag on [`valkyrie run start`](/reference/cli/run#start) invokes an AWS Lambda function after a run completes.

```bash theme={null}
valkyrie run start \
  --agent agents/claude_code \
  --benchmark swebench \
  --lambda my-post-benchmark-handler
```

The lambda is invoked once after all tasks finish and results are uploaded. If the lambda fails (uncaught exception or `statusCode >= 400`), the run will be marked as `ERROR`.

## Payload

The tracker invokes your lambda with the full `BenchmarkArguments` plus the persisted benchmark ID and name:

```json theme={null}
{
  "contract": {
    "name": "claude_code",
    "install_cmd": "bash setup.sh",
    "run_cmd": "cat /tmp/problem_statement | claude -p ...",
    "final_output": "/logs",
    "secrets": {
      "ANTHROPIC_API_KEY": "AnthropicApiKey"
    }
  },
  "concurrency": 5,
  "task_ids": ["astropy__astropy-12907"],
  "slice_str": null,
  "lambda_function": "my-post-benchmark-handler",
  "benchmark_id": "e532551e-d51b-4912-983d-47695bd24174",
  "benchmark_name": "swebench"
}
```

| Field             | Type           | Description                               |
| ----------------- | -------------- | ----------------------------------------- |
| `contract`        | object         | The agent contract used for the run       |
| `concurrency`     | int            | Concurrency level                         |
| `task_ids`        | list or null   | Task IDs that were run (null = all)       |
| `slice_str`       | string or null | Dataset slice if provided                 |
| `lambda_function` | string         | Name of this lambda function              |
| `benchmark_id`    | string         | UUID of the completed run                 |
| `benchmark_name`  | string         | Persisted name of the completed benchmark |

## Format required by AWS

AWS Lambda expects a `lambda_function.py` with a `lambda_handler` entry point

Example method:

```python theme={null}
def lambda_handler(event, context):
    benchmark_id = event["benchmark_id"]
    agent_name = event["contract"]["name"]

    # Your post-run logic here
    # e.g. send a Slack notification, trigger evaluation, etc.

    return {"statusCode": 200, "body": f"Processed {agent_name} run {benchmark_id}"}
```

## Deployment

The lambda is invoked using the user's AWS credentials (from `valkyrie config init`). It must be deployed in the user's AWS account and region defined by the user.