# Optimism challenger release requires explicit configuration to retain Cannon coverage

> Upgrading operators must explicitly retain Cannon when required; otherwise their challenger stops playing those games.

- URL: https://riadefi.com/on-chain/2026-09-04-optimism-op-challenger-1-9-5-default-game-types/
- Type: Upgrade or migration
- Stage: Confirmed
- Evidence: confirmed
- Materiality: material
- Event date: 2026-09-04
- Version: 1, published 2026-09-15 (first published 2026-09-15)
- Follow-up: 2026-09-07
- Advisor-relevant: no
- Affects: Optimism canonical bridge (protocol)

## What happened

Optimism published challenger software whose default supported game set drops legacy Cannon.

## What changed

Upgrading operators must explicitly retain Cannon when required; otherwise their challenger stops playing those games.

## What did not change

The release does not establish a mainnet contract upgrade, shortened withdrawal period, or actual loss of challenger coverage.

## Confirmed

- Version 1.9.5 defaults to cannon-kona alone.
- The release warns that legacy Cannon participation stops without explicit configuration.
- Super and ZK game changes described in the release prepare for future upgrades.

## Still open

- Which relevant production challengers have upgraded and their configured game types.
- Whether any OP Mainnet game currently depends on an operator affected by this default.

## What it means for an advisor

- Review the bridge diligence file's challenger-coverage assumptions and obtain configuration evidence before treating operator upgrades as complete.

## Sources

1. [op-challenger/v1.9.5](https://github.com/ethereum-optimism/optimism/releases/tag/op-challenger/v1.9.5) · Optimism official repository · 2026-09-04


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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.