Remote eval runner environment variable size limit

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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.

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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.

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Fix or suggestion

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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

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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.