This article introduces the concept of bundle as a new powerful tool in the study of party reforms. The intensive and intricate nature of the engineering political parties undertake to preserve the status quo amidst a challenging environment tends to be obscured by the focus on their so-called ‘conservative nature’. Applied to the process tracing of a large sequence of reforms implemented by the Belgian French-Speaking liberal party (MR) between 2019 and 2022, the bundle concept provides the opportunity to go beyond the narrow vision of party reforms only defined and empirically studied so far through their type, size and success. I triangulate a variety of sources to uncover mechanisms through which a handful of key party actors - as powerful steering agents - perceive and translate environmental factors into specific reforms. The bundle analysis brings notably to light a key sequencing mechanism – a snowball effect – explaining how the sequence actually unfolded and fed on itself, challenging our hitherto accepted understanding of party engineering. This study also offers a transferable conceptual framework with valuable insights for wider use in the field, providing an avenue for theory building through causal analysis.