# Optimism proposes Upgrade 19 and the Karst hardfork

> If approved and executed, permissionless fault-proof chains would change their respected game type from CANNON to CANNON_KONA for withdrawal proving;

- URL: https://riadefi.com/on-chain/2026-06-15-optimism-bridge-upgrade-19-karst-hardfork/
- Type: Upgrade or migration
- Stage: Proposed
- Evidence: confirmed
- Materiality: material
- Event date: 2026-06-15
- Version: 1, published 2026-08-22 (first published 2026-08-22)
- Advisor-relevant: no
- Affects: Optimism canonical bridge (protocol)

## What happened

OP Labs submitted the off-cycle Upgrade 19 proposal, bundling the Karst execution-layer hardfork with new predeploy upgrade machinery, OP Contracts Manager v2, a new primary fault-proof implementation, and portal dispatch changes.

## What changed

If approved and executed, permissionless fault-proof chains would change their respected game type from CANNON to CANNON_KONA for withdrawal proving; L2CM and OPCMv2 would change upgrade execution; the portal would dispatch claims by game type; seven Fusaka EIPs and a lower BN256 pairing-input limit would become active; and op-geth and op-program support would end.

## What did not change

The proposal did not establish mainnet approval or activation during June. It stated that fee take, governor/servicer role separation, ossified gas limits, and direct fee-margin controls would not change, and it anticipated no downtime.

## Confirmed

- CANNON_KONA was proposed as the respected game type for permissionless fault-proof chains.
- The proposal would make kona-client on Cannon the primary fault-proof program used for withdrawals.
- L2CM would add deterministic predeploy upgrades through ProxyAdmin.
- OPCMv2 would replace five manager functions with unified deploy and upgrade calls.
- The mainnet activation was scheduled for July 8, 2026, pending governance approval, outside the permitted event-date boundary.

## Still open

- The governance outcome and mainnet execution after the June boundary.
- Final audit results, production contract addresses, upgrade transactions, and deployed component versions.
- Operator readiness for migration from op-geth and op-program to op-reth and kona-client.
- Whether the new fault-proof and portal-dispatch paths operated normally after activation.

## What it means for an advisor

- Review the Optimism bridge memo's withdrawal-proof, respected-game-type, and upgrade-execution assumptions before recognizing Upgrade 19 as operative.
- Verify governance approval, deployed contracts, upgrade transactions, audits, prestates, and operator migration evidence on-chain.
- Do not infer that deterministic tooling or completed testing makes the bridge safer or approved.

## Sources

1. [Upgrade 19b — Karst Hardfork](https://gov.optimism.io/t/upgrade-19b-karst-hardfork/10713) · OP Labs · 2026-06-15


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Published by Ketju Research on RIADeFi (https://riadefi.com). Educational research for financial professionals; not investment, legal, tax, or compliance advice.