Context isolation¶

Var stores its active value in contextvars.ContextVar. An override therefore belongs to the current execution context, not to the config singleton itself. Nested overrides unwind in reverse order even when the block raises.

New async tasks inherit the context that exists when they are created. Later changes do not retroactively update existing tasks, and threads have separate contexts. This makes a cached BaseConfig suitable for request-, test-, or operation-local settings as long as callers do not share mutable values by manually setting the same object.