Export JSON/PDF for single/multi signature omit change address branch

[tadeubas]

Describe the bug
When creating a single/multi signature with ambiguous XPUB (i.e. without branch/output address info), Specter export the wallet with branch/output address for receive only (branch /0/*).

To Reproduce
Example steps to reproduce the behavior:

"Add wallet > Single Signature > Add new device > SeedSigner > Scan QR Code [e0c595c5/84'/0'/0']zpub6qV6TyVkDQsoP6XnSgLJxoH7YunCwUKzPZq3FhccdoQT7uS9w5hDo45tLpRQxr6P3FJnwWaCnYJcZSQiXif5WnPQ5rN2yMRHAE5ZyTzQvre and give device a name > Continue > Create single key wallet > give wallet a name and Create wallet > Save Backup PDF"

The first page of the PDF has the QR Code with descriptor as /0/* without change address info:

{"label": "a name", "blockheight": 481824, "descriptor": "wpkh([669dce62/84h/0h/0h]xpub6Cygb51hbAxuxKQ4hwVV5z6YvhauXbhDexEuA7EoAq9DkejbuF2najEM3YdY2BvC39XYa9nHE3R9QWr2yYgTU58LTNQ7ipFQoj4TszqYVeS/0/*)#w0rtkcqe", "devices": [{"type": "other", "label": "gg"}]}

The second page of the PDF has the text with descriptor as /0/* without change address info:

{"label": "a name", "blockheight": 481824, "descriptor": "wp
kh([669dce62/84h/0h/0h]xpub6Cygb51hbAxuxKQ4hwVV5z6YvhauXbhDe
xEuA7EoAq9DkejbuF2najEM3YdY2BvC39XYa9nHE3R9QWr2yYgTU58LTNQ7i
pFQoj4TszqYVeS/0/*)#w0rtkcqe", "devices": [{"type": "other",
"label": "gg"}]}

The same thing happen if you go to "Settings > Export > Go to export details, descriptor as /0/* in the QR Code and the JSON Data:

{"label": "a name", "blockheight": 481824, "descriptor": "wpkh([669dce62/84h/0h/0h]xpub6Cygb51hbAxuxKQ4hwVV5z6YvhauXbhDexEuA7EoAq9DkejbuF2najEM3YdY2BvC39XYa9nHE3R9QWr2yYgTU58LTNQ7ipFQoj4TszqYVeS/0/*)#w0rtkcqe", "devices": [{"type": "other", "label": "gg"}]}

Expected behavior
It would be fine to return ONLY the [fingerprint/deriv/path]xpub... which would be an XPUB with origin-info rather than a complete descriptor... or since Specter Desktop is returning a descriptor that made some assumptions (script wrapper and checksum) to also assume the change path /<0;1>/* rather than assuming receive path only /0/*.

Screenshots

Desktop (please complete the following information):

• Where is your node running: public
• Where is your specter running: Binaries downloaded from Specter site
• If you're running a binary, which OS: Linux
• Browser N/A
• Specter v2.0.5 - May 30, 2024

Additional context
SeedSigner and Krux exports the ZPUB/XPUB without branch/output address info. Specter-DIY "Master public keys Single key/Multisig" also give values without branch/output address info. But Specter-DIY "Wallets > Default > Settings > Export wallet descriptor" gives values with /0/* with branch/output for receive address only.

[al-munazzim]

Triage Assessment

Category: Bug - Descriptor export
Priority: Medium
Complexity: Medium

Summary

When exporting wallet backups (PDF/JSON) for wallets created with ambiguous xpubs (no branch info in derivation), Specter exports descriptors with /0/* (receive-only path) instead of the expected /<0;1>/* (receive + change paths).

Impact

• Wallet backups may not properly restore change address capability
• Confusing for users who expect complete descriptors
• Interoperability concern when importing to other wallets

Root Cause (likely)

The export logic in wallet.py probably defaults to receive-only derivation when the source xpub doesn't specify branch info, rather than inferring both branches.

Suggested Fix

1. When exporting descriptors from wallets with ambiguous xpubs, use /<0;1>/* multipath notation
2. Or export the raw xpub with origin info without forcing a script type assumption

Files to investigate

• src/cryptoadvance/specter/wallet.py - export methods
• src/cryptoadvance/specter/util/descriptor.py - descriptor construction

Notes

• Good reproduction steps provided with SeedSigner
• Related to broader descriptor standardization (BIP-389 multipath descriptors)