diff --git a/server/sim/content/kits/tier5.js b/server/sim/content/kits/tier5.js
index f2beb571..9116b5a0 100644
--- a/server/sim/content/kits/tier5.js
+++ b/server/sim/content/kits/tier5.js
@@ -1985,6 +1985,10 @@ const KITS = {
       skills: lazySkills({
         skchr_thorn2_1: () => ({
           kind: instantKind(chess, def),
+          // an AUTO skill (skill_table 自动触发) that throws at an ally: it fires as soon as its SP is full, with or
+          // without an enemy — the basic DEFAULT rule waited for an attack, so with no enemy around it sat at 7/7
+          // (GitHub #124 「引星棘刺一技能不会在满技力时自动释放」)
+          trigger: { rule: 'SP_FULL' },
           onStart({ battle, unit }) {
             const t = battle.alliesInGrid(unit).filter((a) => a.hp > 0).sort((a, b) => a.hpRatio - b.hpRatio || b.blocking.length - a.blocking.length || dist(a, unit) - dist(b, unit) || a.id - b.id)[0];
             if (!t) return;
diff --git a/test/content/kits_alt_t5.test.js b/test/content/kits_alt_t5.test.js
index 58221883..12d0b54e 100644
--- a/test/content/kits_alt_t5.test.js
+++ b/test/content/kits_alt_t5.test.js
@@ -1028,6 +1028,23 @@ test('引星棘刺 S1 度算浪波: an alchemy unit on the lowest-HP ally: DEF +
   }
 });
 
+test('引星棘刺 S1 度算浪波 (AUTO): fires as soon as its SP is full, no enemy needed (GitHub #124)', () => {
+  for (const id of pair('15')) {
+    const h = run({
+      defs: { chess: { t_low: ally('t_low') } },
+      units: [entry(id, 'skchr_thorn2_1', { row: 10, col: 3 }), { chessId: 't_low', row: 10, col: 5 }],
+      enemies: [],
+    });
+    const u = sel(h, id, 'skchr_thorn2_1');
+    h.step();
+    assert.equal(h.b.enemies.length, 0, 'no enemy on the field');
+    const need = u.skill.spCost - u.skill.sp;
+    h.run(need + 0.5);
+    assert.ok((u.mem.zones || []).some((z) => z.type === 'guard'), `cast within ${need.toFixed(1)} s of SP filling, no enemy around`);
+    done(h);
+  }
+});
+
 test('引星棘刺 S3 “我的海疆”: passive skill range; alchemy units on the 3 lowest-block ops debuff (不叠加) and burn enemies around them, ramping to the max after 15 s', () => {
   for (const id of pair('15')) {
     const h = run({