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

# Remote eval runner environment variable size limit

> Diagnose and fix `Argument list too long` errors caused by the Linux per-environment-variable size cap (~128 KB) in the eval runner.

export const plans_0 = "Any"

export const deployments_0 = "Any"

export const data_plane_version_0 = undefined

export const use_case_0 = "Use case - Running remote evals"

<Note>
  **Applies to:**

  * Plan - {plans_0}
  * Deployment - {deployments_0}
  * {data_plane_version_0}
  * {use_case_0}
</Note>

## Summary

Runs can fail with `Argument list too long` when the CLI passes the entire remote eval request to a fresh runner via a single environment variable.

## What is happening

The `bt eval` launcher hands the full remote eval request to a fresh runner process in one environment variable. Linux imposes a per-environment-variable size cap of roughly 128 KB. If your request or config exceeds that cap, the runner process fails to start and the run shows `Argument list too long` or a similar error.

## Fix or suggestion

### Use the braintrust SDK (fastest workaround)

1. Run your remote eval with the `braintrust eval --dev` command
2. Verify runs complete without the startup error

## How to confirm it worked

* Run the same remote eval that previously failed and confirm it completes without `Argument list too long` errors.
* Verify the process exit code is zero and results are produced as expected.