Glossary coding Term Page
env_nested_delimiter
Separator (such as __) that lets environment variables populate nested configuration objects.
Core Idea
env_nested_delimiter tells pydantic-settings how to interpret nested field names. With a delimiter of __, a variable like APP_FEATURE__BETA=true feeds into Settings(feature=FeatureFlags(beta=True)). This keeps related knobs grouped without inventing long flat names.
Why It Matters Here
In the FastAPI series, nested delimiters help readers manage complex toggles (feature flags, database clusters, service endpoints) in .env files while keeping names predictable alongside the chosen env_prefix.