major [Stability & Availability]
→ ]8;;vscode://file//work/apps/alp-dex/src/inventory/maintain.ts:283apps/alp-dex/src/inventory/maintain.ts:283-288]8;;

Reserve slush sats for postage before funding XEC inventory.

remaining is derived from the full slush spendable balance. The loop
then funds XEC inventory batches until remaining reaches 0 or the batch
cap is hit. This drains the slush pool. Step 4 computes
postageFundBatchCount(postage.length, spendableSats) from what is left,
so postage funding can become 0 stamps and seller postage starves. The
comment on Line 267-268 states the opposite intent.

Subtract a postage reserve from the sat total before converting to XEC
inventory units.


♻️ Proposed fix

-            let remaining = inventoryUnitCount(
-                slush
-                    .spendableSatsOnlyUtxos()
-                    .reduce((sum, utxo) => sum + utxo.sats, 0n),
-                xecToken.utxoAtoms,
-            );
+            const slushSatsAvailableForXec = (): bigint => {
+                const total = slush
+                    .spendableSatsOnlyUtxos()
+                    .reduce((sum, utxo) => sum + utxo.sats, 0n);
+                const reserve = POSTAGE_RESERVE_SATS;
+                return total > reserve ? total - reserve : 0n;
+            };
+            let remaining = inventoryUnitCount(
+                slushSatsAvailableForXec(),
+                xecToken.utxoAtoms,
+            );

Apply the same helper at Line 303-308 for nextRemaining.

minor [Security & Privacy]
→ ]8;;vscode://file//work/apps/alp-dex/src/settle/parseSwap.ts:522apps/alp-dex/src/settle/parseSwap.ts:522-530]8;;

Reject zero-sat non-token outputs on the ALP–XEC path.

An output with no ALP amount and sats === 0n is skipped here, so it
never enters mids. validatePartiallySignedTx then never sees it, and
the rest.length > 2 limits do not count it. The ALP–ALP path rejects
this case explicitly (Line 272-276).

A taker can therefore append arbitrary zero-sat outputs. The node pays for
the added transaction size through postage fuel.


🛡️ Proposed fix

         if (out.sats > 0n) {
             mids.push({
                 idx: outIdx,
                 script: out.script.toHex(),
                 sats: out.sats,
                 tokenId: XEC_ASSET_ID,
                 atoms: out.sats,
             });
+            continue;
         }
+        throw new ValidationError(
+            `Invalid swap: non-token output ${outIdx} must have sats`,
+        );