For AI agents: the complete documentation index is available at https://mfeflow.github.io/mfeflow/llms.txt, the full documentation bundle is available at https://mfeflow.github.io/mfeflow/llms-full.txt, and this page is available as Markdown at https://mfeflow.github.io/mfeflow/errors/E301.md.
mfeflow

    MFEFLOW_E301

    A singleton resolves to more than one version.

    Fix

    Pin one version of the package in every app (the pnpm catalog is the place), then reinstall. Two copies of React break hooks.