“A valid $0.01 sandbox purchase failed in the sponsor layer”

I tested the Modal via Tempo MPP integration on July 17, 2026 by trying to create a small, realistic CPU sandbox for 60 seconds using a Python 3.13 slim image. The dynamic live challenge quoted exactly $0.01.

POST https://modal.mpp.tempo.xyz/sandbox/create
{"image":"python:3.13-slim","cpu":1,"memory":512,"timeout":60}

The documented request reached the payment step, but the sponsored transaction failed before Modal returned a sandbox.

Sponsored transaction from this sender is already in flight.

No sandbox ID, status, connection details, runtime output, debit, or cleanup handle arrived. This is a review of the Tempo MPP integration rather than Modal's normal platform. The failure made even a minimal one-minute compute purchase impossible.