Decompose modernization by capability and responsibility before technology

The decision

Analyze business capabilities and responsibilities before deriving target domains, services, and work packages.

Why it mattered

Decomposing directly by technical component can reproduce accidental legacy boundaries in the target state.

The trade-off

Capability analysis requires more discovery up front, but reduces the risk of carrying architectural contamination into the target and supports future core replacement.

What changed

Target decomposition was oriented around responsibilities and capabilities rather than reproducing the accidental shape of the legacy estate.

The outcome

Implementation is not claimed; architecture analysis and design remain in progress.

Summary of a documented architecture decision. Method, mechanism and supporting evidence are not published.