Add regtest address support to address_to_script_pubkey

[jimmysong]

Summary

• address_to_script_pubkey() now handles regtest bech32 addresses (bcrt1q for P2WPKH/P2WSH, bcrt1p for P2TR)
• TxFetcher.get_url() raises a clear ValueError for regtest instead of an unhelpful KeyError
• Added tests for regtest address roundtrips and TxFetcher error handling

Network parameter audit

Every function/method that takes network as a parameter was reviewed. Here is the full analysis:

Dict lookup (regtest key exists in dict)

File:Line	Function	How network is used	Regtest?
bech32.py:172	encode_bech32_checksum()	PREFIX.get(network)	Yes — PREFIX has "regtest": "bcrt"
network.py:43	GenericMessage.__init__()	Stored, not branched	Yes
network.py:52	GenericMessage.parse()	MAGIC[network]	Yes — MAGIC has regtest
network.py:306	SimpleNode.__init__()	PORT[network]	Yes — PORT has regtest
hd.py:141	HDPrivateKey.from_seed()	XPRV[network]	Yes — XPRV has regtest
tx.py:53	TxFetcher.get_url()	URL[network]	Fixed — now raises clear ValueError
tx.py:62	TxFetcher.fetch()	Calls get_url(network)	Fixed via get_url
tx.py:97	TxFetcher.sendrawtransaction()	Calls get_url(network)	Fixed via get_url

Passthrough (stores or forwards network, no branching)

File:Line	Function	How network is used
cecc.py:368	PrivateKey.__init__()	Stores self.network
pecc.py:538	PrivateKey.__init__()	Stores self.network
cecc.py:215	S256Point.address()	Forwards to p2pkh_script().address(network)
cecc.py:219	S256Point.p2wpkh_address()	Forwards to p2wpkh_script().address(network)
cecc.py:223	S256Point.p2sh_p2wpkh_address()	Forwards to p2wpkh_script().p2sh_address(network)
cecc.py:227	S256Point.p2tr_address()	Forwards to p2tr_script().address(network)
pecc.py:339-351	Same 4 methods on S256Point	Same as cecc.py
script.py:428	RedeemScript.address()	Forwards to script_pubkey().address(network)
script.py:511	P2WPKHScriptPubKey.p2sh_address()	Forwards to redeem_script().address(network)
script.py:579	WitnessScript.p2sh_address()	Forwards to redeem_script().address(network)
tx.py:164-237	Tx.parse_hex/parse/parse_legacy/parse_segwit	Stores self.network
tx.py:864-878	TxIn.fetch_tx/value/script_pubkey	Forwards to TxFetcher.fetch(network)
psbt.py (6 methods)	Various parse() methods	Stores or forwards, uses path_network() as fallback
hd.py:273,695	raw_parse()	Infers from xpub/xprv version bytes, override via param

Branching on network == "mainnet" (else = all non-mainnet including regtest)

File:Line	Function	Logic	Regtest?
script.py:386	P2PKHScriptPubKey.address()	mainnet → 0x00, else → 0x6f	Yes — regtest uses 0x6f
script.py:405	P2SHScriptPubKey.address()	mainnet → 0x05, else → 0xc4	Yes — regtest uses 0xc4
script.py:504	P2WPKHScriptPubKey.address()	Calls encode_bech32_checksum(network)	Yes
script.py:545	P2WSHScriptPubKey.address()	Calls encode_bech32_checksum(network)	Yes
script.py:572	P2TRScriptPubKey.address()	Calls encode_bech32_checksum(network)	Yes

All mainnet-vs-else branches are correct for regtest because regtest shares testnet's base58 version bytes, and bech32 functions use the PREFIX dict which already includes regtest.

Inherent protocol limitations (not bugs)

• WIF parse (cecc.py:493, pecc.py:693): WIF prefix 0xEF is shared by testnet/signet/regtest — the format cannot distinguish them. pecc.py documents this explicitly.
• path_network() (helper.py:360): BIP32 paths use coin 1' for all non-mainnet networks — cannot distinguish testnet/signet/regtest. PSBT callers allow explicit network override.

Test plan

• Regtest P2WPKH address (bcrt1q..., len 44) parses and roundtrips
• Regtest P2WSH address (bcrt1q..., len 64) parses and roundtrips
• Regtest P2TR address (bcrt1p..., len 64) parses and roundtrips
• TxFetcher.get_url("regtest") raises ValueError with clear message
• All existing tests still pass

🤖 Generated with Claude Code

[jimmysong]

takes care of #162 and #163