World models
The rebuild tax has no invoice
Every stack change, the team rebuilds the context that made the last setup work. The cost is real, and it never shows up as a line item.
A team moves from one harness to the next and quietly pays for the same context a second time. The agent was never the hard part. The context was, and it gets left behind every time the stack moves.
Build is cheaper, until it isn't
Build-is-cheaper is true for one rule and one repo. It stops being true at the fifth teammate and the third migration, where the maintenance tax exceeds the value and someone senior spends their week on it. Buying the plumbing is not about whether you can build it. It is about what the rebuild is displacing.
The world model that survives the stack change is a company asset. It stays worth more in month twelve than in month one, because nothing re-onboards.