diff --git a/tests/game-engine.test.mjs b/tests/game-engine.test.mjs
index babe299..492842d 100644
--- a/tests/game-engine.test.mjs
+++ b/tests/game-engine.test.mjs
@@ -11,6 +11,7 @@ import {
   reset,
   validateLevel,
 } from '../game-engine.js';
+import { LEVELS } from '../levels.js';
 
 const ONE_RELAY = [
   '#########',
@@ -117,3 +118,18 @@ test('two independent echoes can sustain a staged two-gate extraction route', ()
   assert.equal(state.status, 'won');
   assert.deepEqual(state.player, { x: 11, y: 1 });
 });
+
+test('three independent echoes sustain the cathedral-null extraction route end-to-end', () => {
+  const tripleRelay = LEVELS.find((level) => level.id === 'cathedral-null');
+  let state = createGame(tripleRelay.map, { maxEchoes: 3 });
+
+  state = anchor(drive(state, 'DDRRRRR'));
+  state = anchor(drive(state, 'DDDDRRRRR'));
+  state = anchor(drive(state, 'RRR'));
+
+  assert.deepEqual(getActiveGateIds(state), ['A', 'B', 'C']);
+
+  state = drive(state, 'RRRRRRRRRRRR');
+  assert.equal(state.status, 'won');
+  assert.deepEqual(state.player, { x: 13, y: 1 });
+});
diff --git a/tests/shell.test.mjs b/tests/shell.test.mjs
index 69ea0c6..d9d1ff6 100644
--- a/tests/shell.test.mjs
+++ b/tests/shell.test.mjs
@@ -12,6 +12,8 @@ test('the playable shell uses a local canvas entry point and no external runtime
   assert.match(html, /<script\s+type="module"\s+src="\.\/app\.js"><\/script>/);
   assert.match(html, /data-action="anchor"/);
   assert.doesNotMatch(html, /<(?:script|link|img)\b[^>]+(?:src|href)\s*=\s*["']https?:\/\//i);
+  assert.doesNotMatch(html, /@import\s+(?:url\()?\s*["']?https?:\/\//i);
+  assert.doesNotMatch(html, /url\(\s*["']?https?:\/\//i);
 });
 
 test('the runtime exposes a narrow smoke-test surface without network calls', () => {