Unilateral exit: put vtxos on-chain without the server

The trustless backstop behind the Ark card's promise. The vtxo's
genesis chain reconstructs to fully-signed txs (keyspend sigs for
cosigned/arkoor transitions, preimage script-path for hark leaves);
they are zero-fee v3 with P2A anchors, so each hop broadcasts as a
[parent, CPFP child] package via esplora POST /txs/package, one
confirmed hop at a time (TRUC allows a single unconfirmed parent).
After the vtxo tx confirms and the CSV exit delta passes, the claim
spends the delayed_sign leaf with only the user key into the wallet's
own receive address.

Settings gains 'Exit on-chain without the server' with live per-exit
status lines; the claim tx is labeled 'Ark exit' in History. Probing
uses /tx/:txid (definitive 404), never /tx/:txid/status, which answers
confirmed:false for unknown txids.

Also: a fresh visitor opening an ark gift link now adopts the gift's
network automatically instead of being sent to Settings.

Co-Authored-By: Claude Fable 5 <[email protected]>

1 files changed, 10 insertions, 5 deletions

diff --git a/src/ark/send.js b/src/ark/send.js
index 39cd1fb..a959b22 100644
--- a/src/ark/send.js
+++ b/src/ark/send.js
@@ -84,14 +84,19 @@ export function taprootOneLeaf(userPub, serverPub, leafScript) {
   // lift internal x-only, add tweak*G
   const internalPoint = P.fromHex(concatBytes(Uint8Array.of(0x02), internalXOnly));
   const outputPoint = internalPoint.add(P.BASE.multiply(BigInt('0x' + hex.encode(tapTweak))));
-  const outputXOnly = outputPoint.toRawBytes(true).slice(1);
+  const outputCompressed = outputPoint.toRawBytes(true);
+  const outputXOnly = outputCompressed.slice(1);
   const scriptPubKey = concatBytes(hex.decode('5120'), outputXOnly);
-  return { sortedKeys, internalXOnly, merkleRoot, tapTweak, outputXOnly, scriptPubKey };
+  const outputParity = outputCompressed[0] === 0x03 ? 1 : 0; // for script-path control blocks
+  return { sortedKeys, internalXOnly, merkleRoot, tapTweak, outputXOnly, outputParity, scriptPubKey };
 }
 
-// PubkeyVtxoPolicy: keyspend musig(user,server); leaf = delayed_sign(exit_delta, user)
-export const pubkeyPolicyTaproot = (userPub, serverPub, exitDelta) =>
-  taprootOneLeaf(userPub, serverPub, delayedSignScript(exitDelta, xonly(userPub)));
+// PubkeyVtxoPolicy: keyspend musig(user,server); leaf = delayed_sign(exit_delta, user).
+// leafScript is returned so a unilateral exit can claim through it after the CSV.
+export const pubkeyPolicyTaproot = (userPub, serverPub, exitDelta) => {
+  const leafScript = delayedSignScript(exitDelta, xonly(userPub));
+  return { ...taprootOneLeaf(userPub, serverPub, leafScript), leafScript };
+};
 
 // CheckpointVtxoPolicy: keyspend musig(user,server); leaf = timelock_sign(expiry, server)
 export const checkpointPolicyTaproot = (userPub, serverPub, expiryHeight) =>