[Core Protocol] Are there system transactions in Optimism mainnet?

[alecalve]

Did you check the documentation and specs?

• Yes

Was there anything unclear or missing?

In this document, it says:

A deposit has the following fields (rlp encoded in the order they appear here):
...
bool isSystemTx: If true, the transaction does not interact with the L2 block gas pool.
Note: boolean is disabled (enforced to be false) starting from the Regolith upgrade.

However it seems to me that the isSystemTx flag was added during the Regolith upgrade fork to Optimism mainnet (see this commit).

Therefore, there would never be transactions where isSystemTx would be true for Optimism mainnet, is that correct?

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• Yes

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[hash1go]

Hello!
It’s not correct that there were never any transactions with isSystemTx = true on OP mainnet.
The field was introduced with the Bedrock upgrade and was used by L1 attributes transactions until the Regolith upgrade, at which point isSystemTx became permanently enforced to false.
https://specs.optimism.io/protocol/deposits.html#l1-attributes-deposited-transaction

Also, the commit you referenced is actually a Bedrock commit, not a Regolith commit.

[alecalve]

The field was introduced with the Bedrock upgrade and was used by L1 attributes transactions until the Regolith upgrade, at which point isSystemTx became permanently enforced to false.

Didn't they both activate on mainnet at the same time?

[hash1go]

Thank you for pointing that out!
Indeed, on mainnet, the Bedrock release included the Regolith changes at the same time in June 2023, so they effectively activated together. From a specification perspective, isSystemTx was introduced with Bedrock, and Regolith enforced it to always be false. On testnet, there was a brief window between March and June where isSystemTx could be true.
I appreciate the clarification!

https://x.com/Optimism/status/1634234542809554944
https://x.com/Optimism/status/1665790663516909568