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MIP-9

Active Set Increase

Withdrawn Standards Track Core GitHub ↗ Forum ↗
Idea Draft Review Last Call Final Living Withdrawn

Increase the `ACTIVE_VALSET_SIZE` from 200 to 300.

Authors
Jackson Lewis (@jacksononchain)
Created
2026-03-19
Updated
Aug 25, 2026

Stakeholder Impact

What this MIP changes for each audience. Severity and action flags are model-derived with deterministic floors per MIP type/category.

TL;DR

This proposal aims to increase the maximum number of active validators from 200 to 300 to enhance participation and decentralization without significantly impacting the consensus mechanism.

What's Changing

  • Active Validator Set Size: Increasing from 200 to 300 allows more validators to participate.
  • Consensus Layer Impact: The change affects the number of validators in consensus rounds but does not alter the selection mechanism.
  • Decentralization: A larger active set improves fault tolerance and economic security.
  • Backwards Compatibility: The change is additive and does not disrupt existing validators.
  • Security Considerations: While more validators increase message exchanges, the risk of Sybil attacks remains unchanged.
⌘

Developers

Smart contract & dapp builders, RPC consumers, tooling authors

The increase in `ACTIVE_VALSET_SIZE` from 200 to 300 does not introduce any ABI changes or new opcodes, but contracts that read validator set membership may need to be reviewed for compatibility. No immediate action is required for developers as existing contracts will continue to function without modification.

Low
◉

Users

Wallet users, EOA holders, dapp visitors

There are no direct changes to transaction fees, confirmation speed, or asset safety for users. This proposal is withdrawn, so no action is required from users.

Low
◆

Validators

Node operators, RPC operators, delegators

Increasing the active validator set size from 200 to 300 allows for more validators to participate, which could lead to increased decentralization and security. However, since the selection mechanism remains unchanged, there is no direct impact on validator revenue or profitability.

Low
✦

Foundation

Monad Foundation & Category Labs core devs

The proposal to increase the active validator set size from 200 to 300 requires coordination among stakeholders to ensure consensus on the change and its implications. Since it involves a modification to the consensus layer, it may necessitate a hardfork activation decision and thorough communication with ecosystem partners.

Low action required

Generated Sep 26, 2026, 3:38 PM · model: gpt-4o-mini

Specification

Cite
Subsystems executionconsensusstakingeconomics

## Abstract

This MIP proposes an increase to the maximum active validator set from 200 to 300.

The current active validator set is capped at 200. Raising the cap expands participation without introducing abrupt load changes to the consensus layer (MonadBFT) or execution pipeline.

## Specification

### Parameters

| Parameter | Current Value | Proposed Value |
|---|---|---|
| `ACTIVE_VALSET_SIZE` | 200 | 300 |

`ACTIVE_VALSET_SIZE` SHOULD be increased from 200 to 300.

### Consensus and Execution Layer Impact

This MIP affects the consensus layer (MonadBFT). The active validator set size directly governs the number of participants in each consensus round. The execution daemon is unaffected unless validator set membership is read by on-chain contracts, in which case any such contracts SHOULD be reviewed for compatibility.

The consensus daemon enforces `ACTIVE_VALSET_SIZE` as an upper bound on the number of validators eligible to participate in block proposal and voting at any given epoch. The selection mechanism for which validators fill the active set (e.g., by stake) is unchanged by this MIP.

## Rationale

An increment of 100 represents a meaningful expansion (~50%) without dramatically altering the message complexity in MonadBFT's voting rounds. Larger single-step increases carry higher risk of unforeseen performance degradation; smaller increments would add process overhead without proportionate benefit.

The increase allows for greater decentralization in the active set, enforcing stronger fault tolerance and economic security.

## Backwards Compatibility

This MIP does not introduce backwards incompatibilities. The change is additive: existing validators in the active set are unaffected. The hard-coded `ACTIVE_VALSET_SIZE = 200` MUST be updated to `300` to support the new parameter values prior to activation.

## Security Considerations

**Consensus scalability**: Increasing the active validator set increases the number of messages exchanged per consensus round in MonadBFT.

**Sybil risk**: Expanding the set without changes to the stake-based selection mechanism does not meaningfully increase Sybil risk. No additional mitigations are required.

## Copyright

Copyright and related rights waived via [CC0](../LICENSE.md).

Forum discussion

11 posts · 45 likes · 3 months ago
Read more on forum ↗
  1. @Socialforging #1 Mar 30, 2026, 12:12 PM

    mip 9 title Active Set Increase description Increase the `ACTIVE_VALSET_SIZE` from 200 to 300. author Jackson Lewis ( @jacksononchain ) status Withdrawn type Standards Track category Core created 2026-03-19 Abstract This MIP proposes an increase to the maximum active validator set from 200 to 300. The current active validator set is capped at 200. Raising the cap expands participation without introducing abrupt load changes to the consensus layer (MonadBFT) or execution pipeline. Specification Parameters Parameter Current Value Proposed Value ACTIVE_VALSET_SIZE 200 300 ACTIVE_VALSET_SIZE SHOULD be increased from 200 to 300. Consensus and Execution Layer Impact This MIP affects the consensus layer (MonadBFT). The active validator set size directly governs the number of participants in each consensus round. The execution daemon is unaffected unl...

  2. @Socialforging #2 Apr 15, 2026, 7:35 AM

    Please note the details have been adjusted, and the proposed change is to increase active set to 300.

  3. @Kutsal #3 Apr 15, 2026, 11:33 AM

    “As ‘Devnads’ and a potential validator, I support any developments that will help foster the Monad ecosystem.” Thank you for the information @jacksononchain

  4. @cassini #4 Apr 16, 2026, 7:03 PM

    In support of MIP-9, with a suggestion to use testnet more aggressively This MIP is well-scoped. The 50% increment is a reasonable step and the rationale is sound. One observation worth noting: the primary cost of increasing ACTIVE_VALSET_SIZE in MonadBFT is not bandwidth — it is signature aggregation latency at the leader. MonadBFT operates on O(n) message complexity in the happy path; each validator sends a signed vote directly to the next leader, who must aggregate those into a QC before proceeding. At 300 validators and 400ms block times, this is unlikely to be the bottleneck under nominal load. Under sustained peak throughput, however, the relationship between n and round latency has not been empirically characterized at this scale on a live network. A proposal for the testnet phase: rather than validating 300, CONSIDER targeting 500 as the testnet ceiling. Additionally, it wo...

  5. @STAKEME #5 Apr 17, 2026, 3:35 PM

    We agree with the updated proposal and are glad to see the active set increase to 300. We believe this is a positive step for the network, as it strengthens decentralization and broadens validator participation while still keeping the change measured and reasonable from a performance standpoint. We’re happy to support this decision and believe it will benefit the long-term health of the network.