Heimdall v0.8.2-beta has been released, providing a security and liveness fix for Polygon. This is a recommended upgrade for all node operators.
This update resolves a critical issue where a block producer could stall under high transaction loads. The problem occurred because proposers were calculating the size of a transaction block using a method (raw length) that underestimated its actual size after being protobuf-encoded. This discrepancy could cause a proposer to create a block that passed its own size check but was then rejected by CometBFT for exceeding the maximum size, stalling that proposer and impacting block production.
The fix ensures the proposer now uses the correct method (ComputeProtoSizeForTxs) to calculate the block's size, matching the validation logic used by CometBFT and preventing proposal failures.
Important Notes for Node Operators:
This change is not consensus-affecting and does not require a hard fork, as it only alters how a proposer assembles a block, not how the block is processed or validated by the network.
While the network can tolerate mixed versions, any validator that has not upgraded remains at risk of stalling when it is their turn to propose a block. Therefore, all validators should upgrade to ensure network stability and liveness.
## Summary The heimdall `v0.8.2-beta` release contains a security/liveness fix for Polygon, mirroring the `v0.8.2-priv` private release. Upgrade is recommended for all node operators. ## Highlights Block-producer liveness fix in `PrepareProposal`. The proposer now sizes its proposal using the same protobuf-encoded unit CometBFT uses to validate it (`ComputeProtoSizeForTxs`) instead of raw `len(tx)`. Raw length undercounted per-tx protobuf overhead, so under high transaction load a proposer could assemble a batch that passed its own size check but exceeded `MaxTxBytes` once CometBFT re-measured it — failing proposal creation and stalling block production on that proposer. - Not consensus-affecting. Only changes which txs a proposer includes during `PrepareProposal`; `ProcessProposal`, the state transition, and block replay are untouched — no app-hash impact, no hardfork. - Backwards-compatible. Mixed-version networks are safe, but an un-upgraded validator can still stall itself while proposing, so all validators should upgrade. ## What's Changed - app/abci: size proto proposal by @marcello33 in https://github.com/0xPolygon/heimdall-v2/commit/31b356811767e4bdcd97f8c124e1f753b7eb77dd ## Full Changelog https://github.com/0xPolygon/heimdall-v2/compare/v0.8.1...v0.8.2-beta