Speed without a map
When building is cheap, responsibilities drift. Later work spends the saved time finding where the last change belonged.
The problem
The product has to stay understandable after the agent leaves the chat.
Coding agents changed how fast a feature can appear. They did not change the need to know what the product is, which part owns a change, and what must remain true. That picture was being rebuilt from scratch in every session.
A chat is not a record
The overview in a conversation ends when the conversation ends. The repository has to be able to say what is current.
A map that stays current
The contract graph records what each part of the product owns. The agent uses it to place the work, and updates it as the product changes.