Bug Report: Incompatibility and Missing Documentation for OptimismPortal2.sol in Interop Rollup Updates

📌 Summary
After the recent Optimism Bedrock/Interop updates, including the deployment of OptimismPortal2.sol, there is insufficient documentation and tooling support for developers implementing custom bridges or sequencers. The current version of [Viem](https://viem.sh/) does not support the updated ABI or event structure of OptimismPortal2, causing compatibility issues and runtime errors. This makes it impossible to implement a fully functional native bridge on custom OP Stack chains relying on updated rollup contracts.

🔧 Environment
Client library: viem@latest

Optimism repo: ethereum-optimism/monorepo (or relevant fork)

OS: macOS/Linux/Ubuntu (Dev Machine + Containerized L2 Infra)

Chain: Custom OP Stack L2 with Interop rollup config

Portal Contract Version: OptimismPortal2.sol (post-interop update)

⚠️ Expected Behavior
ABI compatibility with viem

Ability to decode logs/events like WithdrawalProven, WithdrawalFinalized, WithdrawalHalted, etc.

Clear migration and usage guidelines for OptimismPortal2.sol

Consistent behavior with prior OptimismPortal (v1)

💥 Actual Behavior
ABI parsing fails for events with custom struct arguments and new storage access patterns

Event decoding throws:

vbnet
Copy
Edit
Error: Decoding error: unable to decode log for event "WithdrawalProven"
Incompatibility with:

Updated withdrawal finalization logic

Custom calldata formats

New state access pattern (anchorStateRegistry, disputeGameFactory references)

No clear documentation on:

OptimismPortal2.sol deployment procedure

Canonical ABI or address assignment

Required challenger/attester interactions

Portal upgrade path

🔍 Steps to Reproduce
Set up a custom OP Stack chain using the interop rollup configuration

Deploy the latest OptimismPortal2.sol

Attempt to:

Listen for events using Viem

Parse withdrawal logs from L2 → L1 messages

Observe parsing errors and decoding failures

Check optimism monorepo/docs for guidelines (none found)

🧩 Related Components
[OptimismPortal2.sol](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/contracts/L1/OptimismPortal2.sol)

OP Challenger (dispute game dependencies)

L2 withdraw-prove-finalize lifecycle

AnchorStateRegistry & GameProxy support