testnet4 support

[embetrix]

does specter desktop support testnet4 ?

I get in this case addresses with prefix ert1 which bitcoin core cannot deal with:

Jan 03 22:05:45 raspberrypi5-c8-bf-64 specter[601]: [2026-01-03 22:05:45,816] ERROR in specter_error: Request error for method getreceivedbyaddress('ert1q7eppjgvgfupx5vhycatpglrh709cgkn6p3y3uq', 0): Invalid Bitcoin address
Jan 03 22:05:45 raspberrypi5-c8-bf-64 specter[601]: Traceback (most recent call last):
Jan 03 22:05:45 raspberrypi5-c8-bf-64 specter[601]:   File "/usr/lib/python3.12/site-packages/cryptoadvance/specter/wallet/wallet.py", line 764, in getdata
Jan 03 22:05:45 raspberrypi5-c8-bf-64 specter[601]:     value_on_address = self.rpc.getreceivedbyaddress(self.change_address, 0)
Jan 03 22:05:45 raspberrypi5-c8-bf-64 specter[601]:                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Jan 03 22:05:45 raspberrypi5-c8-bf-64 specter[601]:   File "/usr/lib/python3.12/site-packages/cryptoadvance/specter/rpc.py", line 509, in fn
Jan 03 22:05:45 raspberrypi5-c8-bf-64 specter[601]:     raise RpcError(
Jan 03 22:05:45 raspberrypi5-c8-bf-64 specter[601]: cryptoadvance.specter.rpc.RpcError: Request error for method getreceivedbyaddress('ert1q7eppjgvgfupx5vhycatpglrh709cgkn6p3y3uq', 0): Invalid Bitcoin address

[embetrix]

tested with testnet3 the addresses prefix is: tb1

where should I look to make it working for testnet4 ?

[al-munazzim]

Triage Assessment

Valid enhancement request. The ert1 prefix suggests Specter is detecting the network as Elements/Liquid regtest rather than testnet4.

Root cause: Bitcoin Core 28.0+ introduced testnet4 (BIP-???), but Specter's network detection likely predates this and doesn't recognize the new chain parameters.

Where to look:

• src/cryptoadvance/specter/util/common.py — network detection logic
• src/cryptoadvance/specter/helpers.py — address validation
• Check how chain is determined from Bitcoin Core's getblockchaininfo

testnet4 specifics:

• Chain name: testnet4
• Address prefix: tb1 (same as testnet3 for bech32)
• P2PKH prefix: different from testnet3

I can investigate the codebase and propose a fix if someone can confirm which Bitcoin Core version + config they're using for testnet4.

[embetrix]

any recent bitcoin core version .i.e:

# bitcoind --version
Bitcoin Core daemon version v30.2.0 bitcoind
Copyright (C) 2009-2026 The Bitcoin Core developers

Please contribute if you find Bitcoin Core useful. Visit
<https://bitcoincore.org/> for further information about the software.
The source code is available from <https://github.com/bitcoin/bitcoin>.

This is experimental software.
Distributed under the MIT software license, see the accompanying file COPYING
or <https://opensource.org/license/MIT>

[k9ert]

I'm not sure whether it's worth supporting testnet4 before we have reasonable support for signet.

[embetrix]

at least the chain should be detected correctly and and error message for example "not supported" displayed instead of generating wrong addresses

[al-munazzim]

Related: I've submitted embit PR #109 adding testnet4 network support to embit. Once merged, Specter can properly detect the chain.

In the meantime, PR #2537 provides a workaround by aliasing testnet4 to testnet3 parameters (which are identical for address generation).

[al-munazzim]

Triage Assessment

Type: Compatibility/Network Support
Verdict: VALID-BUG
Priority: MEDIUM (affects testnet4 users)

Assessment: User reports Specter generates testnet4 addresses with ert1 prefix which Bitcoin Core rejects as "Invalid Bitcoin address". This indicates testnet4 address format incompatibility.

Root Cause: Testnet4 (BIP 94) uses different address prefixes than testnet3. Specter likely still uses testnet3 address generation when connected to testnet4 node.

Fix Strategy: Update address generation logic to detect testnet4 network and use correct address format:

• Testnet4 uses tb1 prefix (same as testnet3), but different network parameters
• Need to properly detect testnet4 vs testnet3 via getblockchaininfo RPC
• Update address validation to accept testnet4 format

Implementation: Moderate complexity - requires network detection + address format updates across wallet creation and validation code.

Workaround: Use testnet3 until fixed, or manually patch address generation.