Polkadot Details JAM Migration Plan but Sets No Mainnet Date

Polkadot’s developers have outlined four workstreams for moving parachain finality to the Join-Accumulate Machine, advancing a major network redesign while leaving the mainnet activation date unspecified.

The Relay Chain currently coordinates parachains and provides their shared security and finality. JAM is designed to support a broader range of computing services, with parachains among the services that could run on it.

The Sept. 10 plan divides the work among PolkaJAM, Minimal Relay (AHM v2), Offchain Messaging and Parachain Service. PolkaJAM is the planned production node, while the Parachain Service would run on JAM and handle finality for existing parachains. Minimal Relay would reduce the Relay Chain’s role, and Offchain Messaging is a separate part of the transition.

The migration plan would move parachain registration, channel management and on-demand coretime ordering to the Coretime chain. Deposits connected to those functions would move with them, while remaining free balances would go to Asset Hub. The intended end state leaves no Polkadot (DOT) on the Relay Chain and no user transactions there.

The planned production PolkaJAM node targets Gray Paper v1.0 and is meant to withstand malicious peers, denial-of-service attacks, overload and unscheduled restarts. The plan also includes an in-browser light-node library.

An Oct. 8 development update showed earlier-stage progress. PolkaJAM supported Gray Paper v0.8, with work on v0.8.1 underway. A stress-test network had expanded from 78 to 255 validators, and typical runs reported no errors over 24 hours. Multiple validators ran on each machine, so the test setup did not place each validator on a separate machine.

The update also described a working browser light-client proof of concept and a Parachain Service proof of concept running on JAM; conversion of the service toward production code had begun. The public Parachain Service remains a proof of concept. The broader transition still requires implementation, integration, benchmarking, ecosystem testing, security review and audits.

The planned network transition is expected to culminate in a hard fork. The work plan and development updates do not set a date for the mainnet switch.