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0xPolygon/heimdall-v2 - v0.4.0 New

Published: Sep 24, 2025

MAINNET Deadline: Jul 24, 2024

Release Summary

Heimdall v0.4.0 has been released, centered around the mandatory Rio hardfork. This update will activate on the mainnet at Bor block height 77414656.

The Rio Hardfork & VEBloP

The primary purpose of this release is to enable the Validator-Elected Block Producer (VEBloP) mechanism via the Rio hardfork. This fundamentally changes how block producers are selected:

Producer Voting: A new message type, MsgVoteProducers, allows validators to cast votes for a ranked list of their preferred block producer candidates.
New Selection Process: A fixed number of block producers (initially set to 3) are selected based on aggregated voting power. This new method replaces the previous span proposal and voting system.
Dynamic Span Rotation: If a current producer fails to create blocks that get finalized within a set time window, the system automatically triggers a span rotation to ensure network liveness.

Breaking Change for Bridge Operators

This release introduces a critical change for all nodes running the bridge service. The bridge can no longer be run as a separate process.

Validators must now run the bridge as a child process embedded within `heimdalld` using the --bridge and --rest-server flags. The required command is now: heimdalld start --bridge --all --rest-server.

Other Key Highlights and Improvements

Stateless Sync: A major new feature, stateless sync, has been introduced. This will enable nodes to synchronize with the network significantly faster.
Node Stability and Resiliency:
- Heimdall will no longer crash if its rest-server becomes unresponsive. Instead, it will wait and log warnings, giving operators time to investigate.
- The span rotation logic was improved to avoid unnecessary rotations when milestone consensus is between 33% and 67%, enhancing stability.
- The bridge initialization process is now more robust and will no longer panic if a new validator joins while the node is still syncing.
Corrections and Fixes:
- A bug was fixed where new spans created under VEBloP were one block shorter than the intended duration.
- The generate-keystore command was fixed to correctly use a provided private key. A new --generate-new flag was added to create a random keystore.
- A check has been re-enabled to verify the voting power in tally votes against the validator set, improving consensus security.
Configuration and Security:
- The list of mainnet seed nodes has been updated to improve peer discovery.
- Security updates have been applied, including new default configurations to manage access to consensus-related endpoints in CometBFT.

Release Notes

## Description

This release introduces Rio hardfork at bor's block height [77414656](https://polygonscan.com/block/countdown/77414656) on mainnet.
The hardfork will enable validator-elected block producer ([VEBloP](https://github.com/0xPolygon/Polygon-Improvement-Proposals/blob/main/PIPs/PIP-64.md)).

For more details about producer election process, see the migration plan in https://github.com/0xPolygon/heimdall-v2/pull/283 .

## What's Changed
* Improve span rotation logic by @cffls in https://github.com/0xPolygon/heimdall-v2/pull/392
* chore: remove validator test case and bump kurtosis by @kamuikatsurgi in https://github.com/0xPolygon/heimdall-v2/pull/413
* chore: side msg and abci handler metrics by @kamuikatsurgi in https://github.com/0xPolygon/heimdall-v2/pull/410
* Delete spans backfill by @avalkov in https://github.com/0xPolygon/heimdall-v2/pull/344
* misc: migrated from maticnetwork to 0xPolygon by @pratikspatil024 in https://github.com/0xPolygon/heimdall-v2/pull/420
* chore: bump kurtosis by @kamuikatsurgi in https://github.com/0xPolygon/heimdall-v2/pull/422
* Re-enable voting power check in tally votes by @Raneet10 in https://github.com/0xPolygon/heimdall-v2/pull/409
* fix: build by @kamuikatsurgi in https://github.com/0xPolygon/heimdall-v2/pull/423
* Fix generate-keystore command by @Raneet10 in https://github.com/0xPolygon/heimdall-v2/pull/424
* update: cosmos-sdk by @kamuikatsurgi in https://github.com/0xPolygon/heimdall-v2/pull/425
* feat: bump kurtosis and migrate to pos-workflows by @kamuikatsurgi in https://github.com/0xPolygon/heimdall-v2/pull/431
* Set initial number of block producers by @cffls in https://github.com/0xPolygon/heimdall-v2/pull/429
* Resolve main-develop conflicts by @Raneet10 in https://github.com/0xPolygon/heimdall-v2/pull/430
* Back merge main->develop by @Raneet10 in https://github.com/0xPolygon/heimdall-v2/pull/428
* feat: remove matic-cli e2e-tests by @kamuikatsurgi in https://github.com/0xPolygon/heimdall-v2/pull/432
* bridge: improvements / app: improvements by @marcello33 in https://github.com/0xPolygon/heimdall-v2/pull/427
* [bugfix] make the length of a new span strictly equal to SpanDuration by @cffls in https://github.com/0xPolygon/heimdall-v2/pull/433
* feat(ci): kurtosis stateless sync e2e tests by @kamuikatsurgi in https://github.com/0xPolygon/heimdall-v2/pull/434
* Set voting power and valset check heights for amoy by @Raneet10 in https://github.com/0xPolygon/heimdall-v2/pull/435
* Add penultimate valset to genesis export by @Raneet10 in https://github.com/0xPolygon/heimdall-v2/pull/436
* Updated mainnet seeds by @sanketsaagar in https://github.com/0xPolygon/heimdall-v2/pull/439
* Stateless sync by @cffls in https://github.com/0xPolygon/heimdall-v2/pull/440
* fix: update lastSeqNo if less than account sequence by @kamuikatsurgi in https://github.com/0xPolygon/heimdall-v2/pull/437
* ci: post merge chores by @kamuikatsurgi in https://github.com/0xPolygon/heimdall-v2/pull/442
* sec fixes by @marcello33 in https://github.com/0xPolygon/heimdall-v2/pull/443
* Change HF name from veblop to rio by @cffls in https://github.com/0xPolygon/heimdall-v2/pull/447
* V0.4.0 candidate merge by @cffls in https://github.com/0xPolygon/heimdall-v2/pull/473
* V0.4.0 candidate by @cffls in https://github.com/0xPolygon/heimdall-v2/pull/474
* Update Rio HF block number by @cffls in https://github.com/0xPolygon/heimdall-v2/pull/475

## New Contributors
* @sanketsaagar made their first contribution in https://github.com/0xPolygon/heimdall-v2/pull/439

**Full Changelog**: https://github.com/0xPolygon/heimdall-v2/compare/v0.3.1...v0.4.0

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