I take the idea of “design defense” from Pyramid (Python Web Framework) [0], and have incorporated it into documentation on my projects.

Basically, it’s a narrative discussion of how this solution came to be, the trade offs involved, and perhaps its relationships with prior art.

[0] https://docs.pylonsproject.org/projects/pyramid/en/1.10-bran...

Do you know if this is called something else? (perhaps in other disciplines)

Googling "Design defen{c,s}e" just got me a whole lot of military contractors.

http://enwp.org/Design_document is the commonly used term of art.

Very cool. Thank you. Seems like it would be a useful exercise. Added to the todo list.