That's super interesting, thanks for sharing the Yelp/PayPal lineage. You're right: there's probably a lot of prior art in internal release engineering systems that never got much written up publicly.

The angle we took in the blog post focused on what was widely documented and accessible to the community (open-source tools like Bors, Homu, Bulldozer, Zuul, etc.), because those left a public footprint that other teams could adopt or build on.

It's a great reminder that many companies were solving the "keep main green" problem in parallel (some with pretty sophisticated tooling), even if it didn't make it into OSS or blog posts at the time.

Gotta be honest: the AI-ness of both the images and the text in this blog post (as well as your response) leaves a bad taste.