# catchCause

Constructs a Match AST complete-cause boundary.

## Signatures

```ts
export declare const catchCause: (matches: ReadonlyArray<MatchAst>, f: (cause: RefSubject<Cause<any>>) => Fx<any, any, any>) => MatchAst.Catch;
```

## Why

Fallback Fx output can observe full Effect causes without erasing defects or interruption.

## Ownership and lifetime

`catchCause` returns a fresh plain AST node immediately and retains any supplied child nodes or arrays by reference; it acquires no external resource.