Blog
JAVM Capability System
JAVM (Join-Accumulate Virtual Machine) is JAR’s VM system based on PVM. As some of you may recall, JAR is an experiment we started a month ago to test the limit of agentic development process. JAR itself has gradually evolved to its own protocol, but here we still want to introduce everyone to our newly developed capability system which I think is still relevant to Polkadot. Background As you may know, with the JAR development ongoing, we aren’t really happy with PVM’s design. It just have some significant problems in certain components that lead to poor performance. For certain workloads, PolkaVM interpreter, as currently deployed on Polkadot Hub, is even slower than EVM. We were able to fix certain things in code, and now we have something that consistently beat PVM on benchmarks. Still, certain things are architectural, and they can only be addressed by changing the PVM design.
April 8, 2026
Grey / JAR Update: Lean 4 specification, linear memory model, faster than PolkaVM
Grey is an experiment for an LLM agent to write a JAM node implementation. You can read the initial announcement here. Here are some updates I would like to report on behalf of Grey. Lean 4 formalization We created the project JAR. JAR is a Lean 4 formalization of the JAM protocol. Doing this would allow us to cross-check Grey’s implementation with JAR, and vice versa. JAR also contains its own testing framework, fuzzing framework, as well as a “variant” system to support multiple specifications.
March 22, 2026
Announcing Grey 0.1: LLM tries to build a JAM node implementation
How long does it take for an LLM to write a JAM node implementation? The constraints are simple: I’m allowed to occasionally guide it, but that’s it – the LLM must write all the code. The process (written by me, the human) This was an experiment I started last week, called Grey. The LLM I worked with is Claude Code. So we started building. The intial process is really straightforward. I fed it the Gray Paper (v0.7.2 version). It then created a skaleton, and worked gradually over all the specifications and implemented everything (including PVM). This part was mostly autonomous.
March 9, 2026