[remote signing]: walletrpc.ImportTapscript behaves differently in remote-signer vs. normal signing mode

[BetweenBits]

Dear Lightning Labs team,

We are currently testing the Taproot Assets functionality in the Integrated mode of lightning-terminal, where lnd is embedded and running in watch-only mode, configured to use an external remote signer (via accounts-signer.json).

During our testing, we encountered two critical issues:

1. On-Chain Asset Send Fails Due to Input Not Being Locked
   When attempting to send Taproot assets on-chain using tapcli, the following error is returned:

tapcli --tlscertpath ~/.lit/tls.cert --rpcserver=localhost:8443 --network=regtest assets send
--addr taprt1qqqszqspqqzzp[...]
--sat_per_vbyte 25

[tapcli] unable to send assets: rpc error: code = Unknown desc = unable to anchor virtual transactions:
unable to fund psbt: unable to fund psbt:
rpc error: code = Unknown desc = input c01a0ac316135366e848801573edbac4d8cfdab14bb415cbcf7355314ca7668d:0 is not locked
2. Asset Channel Creation Fails with the Same Input Locking Error
Similarly, when attempting to open a Lightning channel with a Taproot Asset via litcli ln fundchannel, we receive this error:

[litcli] error funding channel: rpc error: code = Unknown desc = error funding channel:
unable to fund PSBT: unable to fund psbt:
rpc error: code = Unknown desc = input c01a0ac316135366e848801573edbac4d8cfdab14bb415cbcf7355314ca7668d:0 is not locked
Question
Is this a known limitation or bug when using Taproot Assets with lnd in watch-only mode and an external remote signer in Integrated mode of Lightning Terminal?

Does the current remote signing implementation support signing transactions involving Taproot Assets (especially PSBT anchoring inputs), or is this functionality still under development?

We would appreciate your clarification on whether:

Taproot Assets are supported with remote signers in this configuration, and

Any known workarounds or upcoming releases will address this input locking/signing issue.

Thank you for your support.

[guggero]

Thanks for the report.
While in theory there should be nothing preventing Taproot Assets to work in a remote signing scenario, we haven't really tested that particular feature combination yet.
So it's possible there's a small bug that leads to the error you've described.
I'll try to take a look some time soon. I assume you're using the latest version of litd? v0.15.1-alpha?

[guggero]

Okay I was able to reproduce the behavior, going to look into a fix.

[guggero]

Was able to track it down to a btcwallet issue. Somehow importing Tapscript addresses behaves differently in remote-signing mode.
I'm going to rename the issue and transfer it to the lnd repository.

The integration tests in lightningnetwork/lnd#10119 demonstrates the issue.

[guggero]

Ah, actually, I can't transfer the issue since it's not the same organization. Going to re-open it in lnd.

[guggero]

Will be tracked here: lightningnetwork/lnd#10120