Parachain Service PoC

The parachain service lets you run Polkadot parachains on JAM. It:

• Replaces the candidate inclusion with an implementation of JAM accumulate.
• Replaces the off-chain validation of candidate backing with an implementation of JAM refine.
• Offloads approval checking, availability and backing to JAM.
• Exposes a new Cumulus interface for collators to author parachain blocks as Work Packages.

There is no longer a relay chain runtime; the former relay chain logic is implemented without FRAME directly as an accumulate hook.

Project Structure

.
├── authorizer          # JAM authorizer for the service
│   └── bin             # Blob builder for the authorizer
├── cumulus             # Re-exports for candidate authorship
├── runtimes            # Parachain runtimes
│   └── frameless       # One mock runtime for both Coretime and Asset Hub
├── scripts             # Justfile modules
├── service             # The parachain service (refine + accumulate)
│   └── bin             # Blob builder for the service
├── support             # Code shared across the crates above
└── tools
    └── executor        # PolkaJAM test adapter

Notable Code Locations

• is_authorized.rs and its tests
• refine.rs and its tests
• accumulate.rs and its tests
• frameless, the mock runtime whose Config picks Coretime or Asset Hub
• PolkaJAM in-memory execution wrapper

Executor

The blob integration tests use PolkaJAM's in-memory executor with real PVM blobs and host calls.

Building

Fetch the vendored submodules once, then build and test with cargo:

git submodule update --init # only needed once
cargo test

There are just recipes for the other operations (just --list).