diff --git a/app/core.py b/app/core.py
index 93107de..71b2b3b 100644
--- a/app/core.py
+++ b/app/core.py
@@ -13,8 +13,12 @@ ROOT = Path(__file__).resolve().parent.parent
 
 def discover_themes():
     """Discover built-in themes from themes/*/manifest.json (single source of truth)."""
+    themes_dir = ROOT / 'themes'
+    if not themes_dir.is_dir():
+        raise RuntimeError(f'themes directory missing: {themes_dir}')
     found = []
-    for entry in sorted((ROOT / 'themes').iterdir()):
+    for entry in sorted(themes_dir.iterdir()):
+        # Underscore prefix marks non-theme assets (e.g. _professional_components.html).
         if not entry.is_dir() or entry.name.startswith('_'):
             continue
         try:
diff --git a/docs/superpowers/plans/2026-10-22-trade-pro-theme-port.md b/docs/superpowers/plans/2026-10-22-trade-pro-theme-port.md
index 8c8d3be..817b5cc 100644
--- a/docs/superpowers/plans/2026-10-22-trade-pro-theme-port.md
+++ b/docs/superpowers/plans/2026-10-22-trade-pro-theme-port.md
@@ -12,6 +12,7 @@
 - 工作目录：`C:\Users\30997\Downloads\SiteForge_Factory_V5_Web_Docker\SiteForge_Enterprise_V8_10`（下称 `$ROOT`，bash 里用正斜杠）
 - Docker 实例已运行：`http://127.0.0.1:8787`（容器 siteforge-v8-10-siteforge-1/-worker-1），admin 密码在 `.env`
 - 测试命令：`python -m pytest -q`（当前 210 项全绿，任何改动后必须保持）；JS 检查 `node --check app/static/<file>.js`
+- **宿主机快速循环**（V8_12 起）：`PYTHONUTF8=1 .venv/Scripts/python -m pytest -q`，基线 **227 passed + 2 known-fail**（test_p0_backup.py::test_sqlite_backup_and_restore_with_media、test_p0_p4_completion_v89.py::test_restore_replaces_directory_atomically_and_preserves_previous——均为 Windows sqlite 文件锁环境问题，改动前即失败）；任何新失败都是回归。权威全量验证用容器：`MSYS_NO_PATHCONV=1 docker run --rm -v "$(pwd -W):/project" -w /project python:3.12-slim sh -c "python -m pip install -q -r requirements-dev.lock && python -m pytest -q"`（容器基线 226 passed + 1 node 环境失败）
 - cms 设计源：`D:/project/cms/runtimes/astro-site-runtime/src`（tokens.css 250 行、base.css 445 行、components/*.astro、pages/[locale]/*.astro）；像素基准 `dist/hesupipe/en/`
 - 改动 Python 后需 `docker compose up -d --build` 重建容器再验证 HTTP 层（构建约 1 分钟，有缓存）
 - 契约清单已固化于 spec §2（F1-F13），本计划直接引用
diff --git a/tests/test_theme_pro_v3.py b/tests/test_theme_pro_v3.py
index ee711ed..dde6d31 100644
--- a/tests/test_theme_pro_v3.py
+++ b/tests/test_theme_pro_v3.py
@@ -6,8 +6,7 @@ import zipfile
 from pathlib import Path
 from bs4 import BeautifulSoup
 from test_factory_v2 import factory, site, zip_theme
-
-THEMES=('automotive','industrial','corporate','minimal')
+from app.core import THEMES
 
 def test_four_complete_theme_families_have_distinct_markup(factory):
     main=[]
diff --git a/tests/test_theme_registry.py b/tests/test_theme_registry.py
index 6070702..cc079ac 100644
--- a/tests/test_theme_registry.py
+++ b/tests/test_theme_registry.py
@@ -14,5 +14,26 @@ def test_discover_returns_builtin_themes_with_manifests():
         assert manifest.get('id') == tid
 
 def test_three_whitelists_agree():
+    # Tripwire: the three names must stay the same object. Fails only if someone
+    # reintroduces a hardcoded copy of the list anywhere.
     assert set(core.THEMES) == set(theme_pro.THEMES) == set(theme_store.BUILTIN)
     assert isinstance(core.THEMES, tuple)
+
+def test_discover_skips_broken_theme_dirs(tmp_path, monkeypatch):
+    themes = tmp_path / 'themes'
+    good = themes / 'good-one'; good.mkdir(parents=True)
+    (good / 'manifest.json').write_text(json.dumps({'id': 'good-one'}), encoding='utf-8')
+    broken = themes / 'broken'; broken.mkdir()
+    (broken / 'manifest.json').write_text('{not json', encoding='utf-8')
+    mismatch = themes / 'mismatch'; mismatch.mkdir()
+    (mismatch / 'manifest.json').write_text(json.dumps({'id': 'other-name'}), encoding='utf-8')
+    no_manifest = themes / 'no-manifest'; no_manifest.mkdir()
+    underscore = themes / '_shared'; underscore.mkdir()
+    monkeypatch.setattr(core, 'ROOT', tmp_path)
+    assert core.discover_themes() == ('good-one',)
+
+def test_discover_fails_fast_when_themes_dir_missing(tmp_path, monkeypatch):
+    monkeypatch.setattr(core, 'ROOT', tmp_path)
+    import pytest
+    with pytest.raises(RuntimeError, match='themes directory missing'):
+        core.discover_themes()