[General] Questions about historical stalled cross-chain transactions in the OP Mainnet Standard Bridge

[iLifetruth]

Discussion Topic

Hi Optimism team,

We are currently studying cross-chain transactions that remain incomplete beyond their expected completion time and the assets left in unresolved states, including their possible effects on users, liquidity, and asset transparency. We refer to these incomplete lifecycles as stalled transactions and to the associated unresolved value as stranded assets.

Our broader goal is to better understand transaction reliability, recovery, and financial transparency across the bridge ecosystem. Because public records may not capture protocol-specific handling or subsequent resolution, we are contacting bridge teams to check our interpretation and learn how these states are managed in practice. We are not seeking to assign fault or characterize the observations as vulnerabilities.

While looking through public OP Mainnet Standard Bridge records, we came across historical L2-to-L1 withdrawals whose elapsed time exceeded the eight-day operational waiting threshold measured from L2 initiation and used in our analysis, but for which we did not observe L1 finalization at the measurement cutoff. We also noticed a small number of token-recording anomalies and L1-to-L2 deposits involving token pairs for which we did not observe successful completion through the standard bridge flow. Some transactions may have been resolved since our review, and we may be missing relevant protocol or operational context.

Until finalization, the associated value may remain unavailable to the user, while the corresponding locked assets may also represent outstanding withdrawal obligations. We would be grateful for any guidance on how OP Mainnet handles and accounts for these states.

Reference records

The following three L2 source transactions and their corresponding protocol withdrawal identifiers (the MessagePassed.withdrawalHash event field) are included to make the observed finalization states concrete. A fresh finalizedWithdrawals check on August 24, 2026 returned false for all three:

• Source transaction 0x42c34b884dadaf54b0d489f5ea6dd0c21eb84339fbc2facde34a4f46aafa0b8b; 43.7 ETH; protocol withdrawal identifier 0x59669ff0b0b6efc24ec1eb6a3a0887f07224db0bc35af081283c0029234aaeaa; initiated 2024-08-05 05:24:23 UTC.
• Source transaction 0x74a7d4146815a14e6a37575337267638f259b2b0bdb1e423d95526e655b9c687; 5.4 ETH; protocol withdrawal identifier 0xdd0b3ead3422787570828e9fa704ecc9d4cd17b0f9d11b987a4104790c8668ad; initiated 2023-12-28 22:15:15 UTC.
• Source transaction 0x5b4eb1965320367bed347bbf6a78fb049cc9948875338524bdac2954be785353; 3.996083460129702119 ETH; protocol withdrawal identifier 0x5ba70c8d0751de0cabee8ed077aa559453dac831f1f3bc84a34395f3b085ce60; initiated 2023-07-31 20:27:45 UTC.

If possible, could you help us understand the following?

Withdrawal and recovery

1. Can an older L2-to-L1 withdrawal that remains unfinalized still be proven, re-proven where necessary, and finalized by its user or another relayer once the protocol conditions are satisfied? Are there any expiry, protocol-version, or migration conditions that may affect historical withdrawals?

2. What mechanisms currently help users complete withdrawals after they become eligible for finalization, such as user reminders, permissionless third-party finalization, or simplified finalization workflows?

Other observed states

3. Which team would be the appropriate contact for reviewing the token-recording cases and the L1-to-L2 deposits that did not complete through the standard bridge flow? Any guidance on their expected interpretation or recovery path would be helpful.

PoR and reserve transparency

Regular or real-time reconciliation can give users clearer information about which locked assets remain available as backing and which are already committed to unresolved withdrawal obligations, thereby improving transparency and confidence.

A simple example illustrates why this matters: if 100 BTC remains locked after 50 of the original 100 WBTC has been burned for a withdrawal that has not completed, the gross reserve ratio is 100 BTC / 50 WBTC = 200%. Treating the 50 BTC committed to that unresolved withdrawal as unavailable backing gives an adjusted ratio of (100 BTC - 50 BTC) / 50 WBTC = 100%.

4. Does OP Mainnet conduct or recommend any periodic or real-time inventory, reconciliation, or audit of assets locked in the L1 Standard Bridge against the corresponding bridge-issued supply on L2 and outstanding withdrawal obligations through PoR or an equivalent process? If so, how frequently is it updated, what information is made available to users, and are assets associated with withdrawals awaiting L1 finalization treated as stranded assets and excluded from available backing or disclosed separately? If OP Mainnet does not publish such reporting, a pointer to the recommended accounting source would also be helpful.

If useful, we would be glad to provide the token-recording transaction identifiers, additional withdrawal records, storage-check evidence, or event comparisons and to help investigate particular cases. A brief reply or guidance on the appropriate technical contact would already be very helpful.

Thank you for considering the questions.

Best regards,

Wenlong Zhang
Zhejiang University
wlzhang_edu@zju.edu.cn