Thread Safety¶

Kompoz combinators are lightweight and mostly stateless, but a few attributes are mutated during execution. If you share a combinator instance across threads or async tasks, use the pure alternatives listed below.

Mutable Attributes¶

Mutable attribute	On class	Pure alternative
`last_error`	`Transform` / `AsyncTransform`	`run_with_error()` -> `(ok, ctx, error)`
`last_error`	`Retry` / `AsyncRetry`	`run_with_info()` -> `RetryResult`
`attempts_made`	`Retry` / `AsyncRetry`	`run_with_info()` -> `RetryResult`

Context Mutation in OR Chains¶

When transforms are combined with |, the left-hand side may modify the context before the right-hand side sees it. If your context is a mutable object (e.g. a dataclass), the fallback branch receives the already-mutated value. To avoid surprises, return new objects from each transform rather than mutating in place:

from dataclasses import replace

@pipe
def enrich(user: User) -> User:
    # Safe: returns a new object instead of mutating
    return replace(user, enriched=True)