I’m currently working on an canister that should react to incoming ckBTC transfers. I’m exploring whether I can use the transfer + notify pattern.
While inspecting the March 26, 2025 release of the ICP Ledger Suite, I noticed a file named ledger-canister_notify-method.wasm.gz, which suggests the ledger includes a notify method. However, the ledger.did file from the release does not reference any notify method.
Could anybody please clarify? Any clarifications or pointers (source code, interface examples, upgrade notes, etc.) would be greatly appreciated.
Hi @deucalion!
The notify method you’re referring to in the ICP ledger is for a deprecated legacy workflow regarding cycles minting (see more information in this post). I’ve pinged the ckBTC team internally to clarify regarding the ckBTC transfer+notify.
Thanks for following up, @deucalion! Maybe @THLO would know if there is something in the ckBTC-specific flow that could be utilized (e.g., in the minter?), but if you’re looking for something specifically in the ckBTC ledger, then there’s nothing available, and due to the reasons outlined in the other post I linked to, I don’t see anything like that being introduced in the near or mid term. If you would like to implement something similar to the new CMC flow (in your own canister), then the current ckBTC ledger functionality should be enough, unless there are details regarding the transaction IDs or similar that I am missing?
The ckBTC minter is not aware of ckBTC transfers. As @mathiasb pointed out (and as you can see here), the ckBTC ledger does not have any notify functionality.