Are there any open source examples of good context engineering or agent systems?

Any of the "design patterns" listed in the article will have a ton of popular open source implementations. For structured generation, I think outlines is a particularly cool library, especially if you want to poke around at how constrained decoding works under the hood: https://github.com/dottxt-ai/outlines

I‘d consider DSPy to be one. While the prompts it is using are not the most elaborate, they are well tested and reliable