diff --git a/app/builder.py b/app/builder.py
index 8a7ccfe..c33af61 100644
--- a/app/builder.py
+++ b/app/builder.py
@@ -36,6 +36,11 @@ def output_path(dist,route):
     if not target.is_relative_to(dist.resolve()):raise ValueError('非法生成目标目录')
     return out
 
+def copy_blocks_css(theme_dir,dist_assets):
+    """Theme-provided blocks.css wins; platform default is the fallback."""
+    src=theme_dir/'blocks.css' if (theme_dir/'blocks.css').is_file() else ROOT/'app'/'static'/'blocks.css'
+    shutil.copy2(src,dist_assets/'blocks.css')
+
 def link(path):
     return (path or '/').lstrip('/') or './'
 
@@ -188,7 +193,7 @@ def build(site_id,mirror=False):
     theme_pin=theme_store.pinned(site_id)
     theme_dir=theme_store.resolve(site['theme'],theme_pin['version'] if theme_pin and theme_pin['theme_id']==site['theme'] else None)
     shutil.copy2(theme_dir/'theme.css',dist/'assets'/'theme.css')
-    shutil.copy2(ROOT/'app'/'static'/'blocks.css',dist/'assets'/'blocks.css')
+    copy_blocks_css(theme_dir,dist/'assets')
     shutil.copy2(ROOT/'app'/'static'/'pro-base.css',dist/'assets'/'pro-base.css')
     shutil.copy2(ROOT/'app'/'static'/'commercial.css',dist/'assets'/'commercial.css')
     visuals=theme_dir/'visual'
diff --git a/tests/test_theme_registry.py b/tests/test_theme_registry.py
index 7a73c17..6941b98 100644
--- a/tests/test_theme_registry.py
+++ b/tests/test_theme_registry.py
@@ -91,3 +91,16 @@ def test_env_for_degraded_branch_not_cached_and_single_path(tmp_path, monkeypatc
         assert 'industrial' not in theme_pro._ENVS
     finally:
         core.THEMES = core.discover_themes()
+
+def test_theme_blocks_css_overrides_platform(tmp_path):
+    from app import builder
+    dist = tmp_path / 'assets'; dist.mkdir()
+    theme_dir = tmp_path / 'theme'; theme_dir.mkdir()
+    (theme_dir / 'blocks.css').write_text('/* theme version */', encoding='utf-8')
+    builder.copy_blocks_css(theme_dir, dist)
+    assert (dist / 'blocks.css').read_text(encoding='utf-8') == '/* theme version */'
+    # 无主题版时回落平台版
+    dist2 = tmp_path / 'assets2'; dist2.mkdir()
+    builder.copy_blocks_css(tmp_path / 'nonexistent', dist2)
+    assert (dist2 / 'blocks.css').is_file()
+    assert (dist2 / 'blocks.css').read_text(encoding='utf-8') != '/* theme version */'