Summary

• ChainTransformer: Generators are now consumed between each step of the chain. Each yielded item is passed individually to the next transformer (flatMap semantics), instead of passing the Generator object itself.
• EtlExecutor: A TransformEvent is now dispatched per transformed item instead of once for the entire batch. SkipRequest in a listener only skips the individual item, not all items from the generator.
• Scalar/array return values are unaffected — only Generator instances trigger fan-out.

Breaking changes

Example

$etl = (new EtlExecutor())
    ->transformWith(
        fn (string $item): string => strrev($item),
        function (string $item): Generator {
            yield $item;
            yield strtoupper($item);
        },
        fn (string $item): string => "({$item})",
    );

$report = $etl->process(['foo', 'bar']);
// Output: ['(oof)', '(OOF)', '(rab)', '(RAB)']

Test plan

• All 129 tests pass (237 assertions)
• PHPStan clean
• 100% code coverage maintained

🤖 Generated with Claude Code