wallet: Date a new wallet by this computer's clock

Bitcoin Core resolves an import timestamp of "now" to its tip's median
time. On an offline signer that never synced, that is the genesis block,
so every new wallet was born in 2009, and the watch-only copy Bails
exports from it asks the online node to rescan from genesis, which a
pruned node cannot do.

A new wallet now takes this computer's clock, a day early like a
recorded creation date, so a clock running up to a day fast cannot skip
its first payments. Restores keep the recorded date.

On a Core 32.1 regtest signer at genesis, the descriptors were dated
1296688602 (genesis) before and the clock less a day after; the signer
still found a payment from blocks it synced later.

Claude-Session: https://claude.ai/code/session_01N8jLK61uohaW6W7Y8AHnMb

Author: BenWestgate

src/codex32/_bitcoin_core.py

@@ -449,12 +449,16 @@ def initialize(
                     continue
                 # Checked last, after any wait above: a pruning node keeps pruning while it waits.
                 self.check_history(timestamp)
+                # Core's "now" is its tip's time: the genesis block's on an offline signer that never
+                # synced, and watch-only exports carry it. A new wallet takes this computer's clock,
+                # a day early like a record's date, so a fast clock cannot skip its first payments.
+                start = max(0, int(time.time()) - 86400) if timestamp == "now" else timestamp
                 records = core_descriptors(
                     secret,
                     account=account,
                     testnet=self.chain != "main",
                     private=True,
-                    timestamp=timestamp,
+                    timestamp=start,
                 )
                 imported = self._rpc(
                     "importdescriptors",

tests/test_bitcoin_core.py

@@ -391,6 +391,7 @@ def test_encrypted_import_retries_without_a_passphrase_verifies_and_relocks(
         "_rpc",
         lambda client, *args, wallet=None, stdin=None: rpc(client, *args, wallet=wallet, stdin=stdin),
     )
+    monkeypatch.setattr("codex32._bitcoin_core.time.time", lambda: 1_700_000_000.5)
     client = BitcoinCore("bitcoin-cli", "main", 300000)
     messages: list[str] = []
     delays: list[int] = []
@@ -411,7 +412,8 @@ def unlock(seconds: int) -> None:
     assert arguments == ("importdescriptors",) and wallet == "signer"
     assert private_stdin is not None and private_stdin.endswith("\n")
     records = json.loads(private_stdin)
-    assert len(records) == 4 and all(record["timestamp"] == "now" for record in records)
+    # A new wallet's "now" is this computer's clock less a day, not Core's tip (genesis offline).
+    assert len(records) == 4 and all(record["timestamp"] == 1_700_000_000 - 86400 for record in records)
     assert all("xprv" in record["desc"] for record in records)
     assert all("xprv" not in " ".join((*args, selected or "")) for args, selected, _data in rpc.calls)
     assert sum(args[:2] == ("-named", "derivehdkey") for args, _wallet, _stdin in rpc.calls) == 4