The protocol layer and everything technical around it: the CKB protocol, CKB-VM, consensus, RFCs, Layer 2 (Fiber, Axon, Godwoken), SDKs, scripts, and dev tooling.
The question this category answers is “how the chain works, and how it should work” — and building is only one way to engage with that question. Proposing a protocol change or releasing an SDK belongs here; so does reading the code and asking why it does what it does, analyzing a security assumption, measuring real network behavior, or writing up what you dug out of an RFC’s history. You don’t need to ship anything to post here — a sharp technical question or a careful analysis moves this category as much as a pull request does.
If your topic is about the economics and incentives behind the design rather than its mechanics, Cryptoeconomics & Mechanism Design is next door.
Old technical threads stay open in this category on purpose. They are the knowledge base this forum has accumulated over the years; a seven-year-old thread that answers your question is a feature, not a bug.