[Runtime] RT4201 Schedule

Development Runtime upgrades
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We are planning to release Runtime 4201 in all network(s) following the schedule below:

  • Moonbase Alpha upgrade: Wednesday, February 11, 2026

  • Moonriver proposal: Wednesday, February 11, 2026

  • Moonbeam proposal: Wednesday, March 4, 2026

  • Moonriver upgrade authorized: Monday, March 2, 2026

  • Moonbeam upgrade authorized: Tuesday, March 24, 2026

This runtime upgrade includes several breaking changes.
See the release note for more details: Releases · moonbeam-foundation/moonbeam · GitHub

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Summary of Changes

Moonbeam Runtime 4201 — What it means for you

Runtime 4201 introduces major EVM protocol updates, XCM pricing refactors, and fee model adjustments, alongside important security and gas-limit changes.

:star: Ethereum Osaka Fork support
:backhand_index_pointing_right: Added support for EIP-7939 (CLZ opcode)
:backhand_index_pointing_right: Implemented EIP-7823 & EIP-7825

  • MODEXP precompile inputs now limited to 1024 bytes

  • Transaction gas limit capped at 2²⁴ (16,777,216)
    :backhand_index_pointing_right: Implemented EIP-7883

  • Significantly increases ModExp gas costs

These changes align Moonbeam with upcoming Ethereum protocol upgrades and improve DoS resistance.

:sparkles: XCM Fee & Weight Model Overhaul
:backhand_index_pointing_right: Refactored XCM Transactor to delegate fee pricing to the XcmWeightTrader

  • Removed setFeePerSecond and removeFeePerSecond extrinsics

  • Removed DestinationAssetFeePerSecond storage
    :backhand_index_pointing_right: Benchmarked XCM instructions (updated weights)
    :backhand_index_pointing_right: Improved get_units_per_second computation

Result: asset pricing now sourced exclusively from XcmWeightTrader.supportedAssets, simplifying fee management and improving consistency.

:money_bag: Fee Model Adjustments
:backhand_index_pointing_right: Improved WeightToFee calculation

  • Transactions dominated by proof_size may now cost more

  • Storage-heavy Substrate extrinsics are most impacted

:backhand_index_pointing_right: Many XCM instruction weights increased

  • Some cross-chain messages may become more expensive or fail if underfunded

:wrench: Additional Improvements
:full_moon: Improved multi-delegation request handling
:full_moon: Improved trace_filter RPC bounds & caching behavior
:full_moon: Multiple XCM logic fixes and refund handling improvements
:full_moon: Updated Frontier & dependency pins
:full_moon: New runtime weights generated

:warning: Breaking Changes

  • MODEXP inputs > 1024 bytes now fail and consume all gas

  • Transactions with gas limit > 16,777,216 are rejected at validation

  • EIP-7883 increases ModExp gas costs (may break contracts relying on previous pricing)

  • XCM instruction weights updated (fee impact)

  • pallet-xcm-transactor extrinsics setFeePerSecond and removeFeePerSecond removed

  • DestinationAssetFeePerSecond storage removed

:wrench: Client requirement
Minimum client version: v0.50.2

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Please note that the Moonbeam Foundation is proposing the cancelation of Referenda 95 (authorization to upgrade Moonriver to RT4201) due to an issue that has been identified with the release.

A runtime 4202 will be cut in the next week or so and the updated schedule will be announced at that time.