The Reactor Upgrade

Over the past months, our team has been working on a major upgrade to Initia's core L1 blockchain, appchain stack, and interoperability systems. The Reactor Upgrade is a significant milestone that improves appchain performance and liveness through faster block times, lower latency, and higher throughput. It also introduces a new instant interoperability system that uses subsets of the Initia L1 validator set for security attestations.

The Reactor Upgrade is already live on the Initia testnet, with significant testing completed and audits from Zellic concluded. It combines the following ICUPs into one network hard fork.

• ICUP 2: Attested IBC
• ICUP 3: Sequencing Reactor
• ICUP 4: Forwarding Accounts w/ Memos
• ICUP 5: Community Pool Supply

ICUP 2: Attested IBC (Fast and Secure Interop)

Currently, appchains built with Initia's interwoven stack use both a native Optimistic Bridge and IBC for asset bridging and interoperability. Appchain operators choose which bridging standard to use for each asset on their network. These two options offer different tradeoffs: the OP Bridge is highly secure but requires a withdrawal period to bridge assets out, while IBC is fast but can leave assets at risk if an appchain operator is compromised.

The team has developed a system that combines speed with safety, made possible by Initia's unique architecture: Attested IBC. This system uses subsets of the Initia L1 validator set to verify withdrawals from appchains without slowing down block production.

Once a block is confirmed valid, attesters sign the proposed block with a commit and propagate the signed commit to other peers. Full nodes collect these commits and offer them to relayers when queried during IBC relaying.

This is uniquely powerful in Initia's network of appchains: through the LayerZero endpoint on the Initia L1 and Attested IBC, every appchain gets fast and secure interoperability for free.

As part of ICUP 2, a bridge replacement mechanism is also included which allows for seamless transition from OP Bridge backend to an IBC transport layer while preserving the familiar OP Bridge interface. This will allow appchains to migrate from the OP Bridge to Attested IBC with no impact to users.

Additional Patch Notes for ICUP 2

L1

• x/ophost
  • Users and developers can continue using the existing MsgInitiateTokenDeposit and MsgInitiateTokenWithdrawal messages and still receive OP tokens (not IBC vouchers), even though the underlying transport now uses IBC. The system automatically handles IBC → OP conversion via middleware and preserves bridge hooks through IBC transfer memos.
  • https://github.com/initia-labs/OPinit/pull/159, https://github.com/initia-labs/OPinit/pull/163, https://github.com/initia-labs/OPinit/pull/164, https://github.com/initia-labs/OPinit/pull/173
  • GitHub Docs

Appchain

• x/opchild:
  • Users and developers can continue using the existing MsgInitiateTokenDeposit  and MsgInitiateTokenWithdrawal messages and still receive OP tokens (not IBC vouchers), even though the underlying transport now relies on IBC. The system automatically handles IBC → OP conversion via middleware and supports bridge hook preservation through IBC transfer memos.
  • https://github.com/initia-labs/OPinit/pull/159, https://github.com/initia-labs/OPinit/pull/163, https://github.com/initia-labs/OPinit/pull/164, https://github.com/initia-labs/OPinit/pull/173
  • GitHub Docs
• x/opchild
  • Attester registration interfaces
  • https://github.com/initia-labs/OPinit/pull/165

ICUP 3: Sequencing Reactor (Faster Blocks, Lower Latency)

The Sequencing Reactor is a vastly improved consensus engine designed for appchains to enable rapid block propagation. This upgrade increases block speed by 5x from 500 ms to 100 ms per block.

The reactor uses a deterministic leader sequencer that publishes blocks without interruption. Blocks advance immediately when the sequencer signs them. All other work, including consensus rounds, block synchronization, and attestation for bridging, happens asynchronously. Previously, appchains used the full Comet BFT consensus reactor. Initia's sequencing reactor now replaces it.

For ICUP 2 and other light clients, attester quorum is still required to verify blocks externally. However, it no longer blocks execution.

Additional Patch Notes for ICUP 3

Appchain

• cometbft
• https://github.com/initia-labs/cometbft/pull/50
• GitHub Docs

ICUP 4: Forwarding Accounts w/ Memos

This update allows forwarding accounts to include memos in their relayed messages.

• x/forwarding
  • Allows creation of forwarding accounts with static memos
  • https://github.com/initia-labs/forwarding/pull/1

ICUP 5: Community Pool Supply

This update allows governance to redirect tokens from the existing rewards module account to the Community Pool, from where governance may vote to use those tokens with strong reasoning.

• x/reward
  • Introduces FundCommunityPoolMsg to allow governance to redirect preallocated tokens to the community pool
  • https://github.com/initia-labs/initia/pull/445

More Performance

Outside of the upgrades mentioned above, developers are working on further performance enhancements to the Interwoven Stack. Two such examples currently in progress are memIAVL, which has led to 3-5 times faster state reads in testing, and cometKMS, a custom KMS for high liveness guarantees.

Release Binary & Upgrade Resources

• Release Name/Version: v1.2.2
• GitHub Release: https://github.com/initia-labs/initia/releases/tag/v1.2.2
• Binary Download: binaries in https://github.com/initia-labs/initia/releases/tag/v1.2.2
• Upgrade Name: v1.2.2
• Upgrade Height: Block #11,270,000
• Estimated Time: 2025-12-22T12:00:00.000000000Z
• Validator Upgrade Guide:

git clone https://github.com/initia-labs/initia && cd initia
git checkout v1.2.2
make install

# locate the binary to proper location like ~/.initia/cosmovisor/upgrades/v1.2.2/bin
#
# mkdir -p ~/.initia/cosmovisor/upgrades/v1.2.2/bin
# cp ~/go/bin/initia ~/.initia/cosmovisor/upgrades/v1.2.2/bin

# restart binary with new version
sudo systemctl restart initiad

Timeline

• Dec 10th - This forum post
• Dec 12th - Proposal moves onchain for a 7 day vote
• Dec 22nd - Target upgrade date