diff --git a/tools/keygen.mjs b/tools/keygen.mjs
index 43481d3..4089fc0 100644
--- a/tools/keygen.mjs
+++ b/tools/keygen.mjs
@@ -1,5 +1,6 @@
 // Mint PRO unlock keys for RecipesCam. Dev-side only — never bundled.
 //   node tools/keygen.mjs 5        mint 5 keys
+//   node tools/keygen.mjs --from MYCHOSEN12   key for a payload you pick
 //   node tools/keygen.mjs --check  mint 3 keys and verify them (parity guard)
 // The key is 12 payload chars + 4 checksum chars, so any 12-char payload works.
 // Keep KEY_ALPHABET / KEY_SECRET / checksum identical to
@@ -30,14 +31,27 @@ const keyIsValid = (raw) => {
   return true;
 };
 
-const mint = () => {
-  let payload = '';
-  for (let i = 0; i < 12; i++) payload += KEY_ALPHABET[randomInt(KEY_ALPHABET.length)];
+const format = (s) => s.replace(/(.{4})/g, '$1-').slice(0, -1);
+
+const checkOf = (payload) => {
   const bits = checksum(payload);
   let check = '';
   for (let i = 0; i < 4; i++) check += KEY_ALPHABET[(bits >>> (i * 5)) & 31];
-  const s = payload + check;
-  return s.replace(/(.{4})/g, '$1-').slice(0, -1);
+  return check;
+};
+
+const mint = () => {
+  let payload = '';
+  for (let i = 0; i < 12; i++) payload += KEY_ALPHABET[randomInt(KEY_ALPHABET.length)];
+  return format(payload + checkOf(payload));
+};
+
+// Mint the key for a payload you picked yourself — must be 12 chars, alphabet only.
+const from = (payload) => {
+  const p = (payload || '').toUpperCase().replace(/[^A-Z0-9]/g, '');
+  if (p.length !== 12) throw new Error(`payload must be 12 chars, got ${p.length}: ${p}`);
+  for (const ch of p) if (KEY_ALPHABET.indexOf(ch) < 0) throw new Error(`'${ch}' is not in ${KEY_ALPHABET}`);
+  return format(p + checkOf(p));
 };
 
 const args = process.argv.slice(2);
@@ -50,6 +64,8 @@ if (args[0] === '--check') {
     }
   }
   console.log('ok', keys.join(' '));
+} else if (args[0] === '--from') {
+  console.log(from(args[1]));
 } else {
   const n = Number(args[0]) || 1;
   for (let i = 0; i < n; i++) console.log(mint());