Index: test/thread-crawl.test.js
===================================================================
--- test/thread-crawl.test.js	(revision dc41bef1bc3ebefe5d5dc1cfd1be3316e09cfc26)
+++ test/thread-crawl.test.js	(revision dc41bef1bc3ebefe5d5dc1cfd1be3316e09cfc26)
@@ -0,0 +1,31 @@
+// Remote thread crawl — the stale-while-revalidate guard. The BFS itself is network-bound
+// (verified live), so here we only cover that the entry point exists, is safe with no cached
+// replies (no seeds → no crawl), and is TTL-gated. In-memory SQLite. Run: npm test
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+
+process.env.DATABASE_PATH = ':memory:';
+process.env.PUBLIC_BASE_URL = 'https://test.example';
+
+const dbMod = await import('../src/config/database.js');
+const db = dbMod.default;
+dbMod.initializeDatabase();
+const AP = (await import('../src/services/ActivityPubService.js')).default;
+
+test('maybeCrawlThread is exported and safe with no cached replies', () => {
+  assert.equal(typeof AP.maybeCrawlThread, 'function');
+  // No ap_interactions rows for this post → the crawl finds no seeds and does nothing.
+  AP.maybeCrawlThread('no-replies-post');
+  assert.ok(true, 'did not throw');
+});
+
+test('a second call within the TTL is gated (timestamp recorded)', () => {
+  AP.maybeCrawlThread('ttl-post');
+  const row = db.prepare('SELECT value FROM app_settings WHERE key = ?').get('thread_crawl:ttl-post');
+  assert.ok(row && Number(row.value) > 0, 'crawl timestamp recorded');
+  // Immediately calling again must not reset/refire (still gated by the fresh timestamp).
+  const before = row.value;
+  AP.maybeCrawlThread('ttl-post');
+  const after = db.prepare('SELECT value FROM app_settings WHERE key = ?').get('thread_crawl:ttl-post').value;
+  assert.equal(after, before, 'timestamp unchanged within TTL');
+});