Code health is the maintainability and internal quality that let a codebase evolve safely, efficiently, and over the long term. Shortcuts that damage it reduce the rate of change and become expensive later. section 10.3.1 section 10.1.1
Code health is socio-technical: architecture and domain boundaries reduce coupling, while team organization creates incentives to keep systems evolvable. Long-lived teams are more likely to maintain the code they must continue supporting. section 10.3.1 section 11.1.2
Strategic and decisive domains
In strategic IT and a decisive core, code health receives high investment because the business needs differentiating features to keep moving quickly, with lower cost and fewer risks. Advanced architecture and richer domain modeling may be justified when they sustain that rate of change. section 10.1.1 section 10.3.1
Team continuity
A stable, long-lived team remains responsible for part of a product and therefore has reason to improve its code continuously. Legacy code illustrates the opposite condition: poor flow and expensive remediation. section 11.1.2
