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/E120.md.
mfeflow

    MFEFLOW_E120

    A PUBLIC_ variable would be baked into the bundle.

    Rsbuild inlines every PUBLIC_* variable into the JavaScript at build time. A value that differs per environment would tie one build to one environment, which breaks build once, deploy many. Only constants (PUBLIC_APP_NAME, PUBLIC_BUILD_VERSION) are accepted.

    Fix

    Move the value to runtime config: mfeflow add env-key KEY --scope runtime --schema "…", then read it with getRuntimeConfig().