diff --git a/task-unified-service.mjs b/task-unified-service.mjs
index ba85fca..e6d7779 100644
--- a/task-unified-service.mjs
+++ b/task-unified-service.mjs
@@ -37,6 +37,17 @@ function legacyKey(ref) {
   return `${ref.table}:${ref.id}`;
 }
 
+/** MySQL JSON column key order is not stable; match by extracted fields. */
+function legacyRefMatchSql(column = 'legacy_ref_json') {
+  return `${column} IS NOT NULL
+    AND JSON_UNQUOTE(JSON_EXTRACT(${column}, '$.table')) = ?
+    AND JSON_UNQUOTE(JSON_EXTRACT(${column}, '$.id')) = ?`;
+}
+
+function legacyRefMatchParams(legacyRef) {
+  return [legacyRef.table, legacyRef.id];
+}
+
 function formatTriggerLabel(task, timezone = DEFAULT_TIMEZONE) {
   const trigger = task.trigger ?? {};
   if (trigger.at) return trigger.at;
@@ -352,9 +363,9 @@ export function createTaskUnifiedService(pool, { clock = { now: () => Date.now()
     if (mapped.legacyRef?.table && mapped.legacyRef?.id) {
       const [existing] = await pool.query(
         `SELECT * FROM h5_tasks
-         WHERE user_id = ? AND legacy_ref_json = ?
+         WHERE user_id = ? AND ${legacyRefMatchSql()}
          LIMIT 1`,
-        [mapped.userId, JSON.stringify(mapped.legacyRef)],
+        [mapped.userId, ...legacyRefMatchParams(mapped.legacyRef)],
       );
       if (existing?.[0]) return rowToUnifiedTask(existing[0]);
     }
@@ -373,8 +384,8 @@ export function createTaskUnifiedService(pool, { clock = { now: () => Date.now()
     const [result] = await pool.query(
       `UPDATE h5_tasks
        SET status = 'cancelled', updated_at = ?
-       WHERE user_id = ? AND legacy_ref_json = ?`,
-      [clock.now(), userId, JSON.stringify(legacyRef)],
+       WHERE user_id = ? AND ${legacyRefMatchSql()}`,
+      [clock.now(), userId, ...legacyRefMatchParams(legacyRef)],
     );
     return Number(result?.affectedRows ?? 0);
   };
@@ -400,17 +411,17 @@ export function createTaskUnifiedService(pool, { clock = { now: () => Date.now()
     }
     if (lastError !== undefined) {
       const [rows] = await pool.query(
-        `SELECT spec_json FROM h5_tasks WHERE user_id = ? AND legacy_ref_json = ? LIMIT 1`,
-        [userId, JSON.stringify(legacyRef)],
+        `SELECT spec_json FROM h5_tasks WHERE user_id = ? AND ${legacyRefMatchSql()} LIMIT 1`,
+        [userId, ...legacyRefMatchParams(legacyRef)],
       );
       const spec = parseJson(rows?.[0]?.spec_json) ?? {};
       spec.lastError = lastError ?? null;
       sets.push('spec_json = ?');
       params.push(JSON.stringify(spec));
     }
-    params.push(userId, JSON.stringify(legacyRef));
+    params.push(userId, ...legacyRefMatchParams(legacyRef));
     const [result] = await pool.query(
-      `UPDATE h5_tasks SET ${sets.join(', ')} WHERE user_id = ? AND legacy_ref_json = ?`,
+      `UPDATE h5_tasks SET ${sets.join(', ')} WHERE user_id = ? AND ${legacyRefMatchSql()}`,
       params,
     );
     return Number(result?.affectedRows ?? 0);
@@ -568,8 +579,8 @@ export function createTaskUnifiedService(pool, { clock = { now: () => Date.now()
     for (const candidate of candidates) {
       try {
         const before = await pool.query(
-          `SELECT id FROM h5_tasks WHERE user_id = ? AND legacy_ref_json = ? LIMIT 1`,
-          [candidate.userId, JSON.stringify(candidate.legacyRef)],
+          `SELECT id FROM h5_tasks WHERE user_id = ? AND ${legacyRefMatchSql()} LIMIT 1`,
+          [candidate.userId, ...legacyRefMatchParams(candidate.legacyRef)],
         );
         if (before?.[0]?.[0]) {
           stats.skipped += 1;