diff --git a/App/lib/core/Gen/ImportsGenMixin.vp b/App/lib/core/Gen/ImportsGenMixin.vp
index 9a08989..64a7260 100644
--- a/App/lib/core/Gen/ImportsGenMixin.vp
+++ b/App/lib/core/Gen/ImportsGenMixin.vp
@@ -556,6 +556,9 @@ novirtual class ImportsGenMixin:
         if string.strcmp(mod_name, "ctraits") == 0: return 1
         if string.strcmp(mod_name, "viperbuild") == 0: return 1
         if string.strcmp(mod_name, "ffilib") == 0: return 1
+        # runtime CDLL 的 thunk 会调用 _ffilib（真实运行时库），把它登记为已导入模块，
+        # 让按需可达性扫描收录它并分配 SHA1（否则 thunk 生成时报 module not found）。
+        if string.strcmp(mod_name, "_ffilib") == 0: return 1
         mod_sha1: str = StubMergerStore.LookupSha1ByModName(mod_name)
         if mod_sha1 is None:
             # App sibling exemption: a {mod_name}.vp/.py exists next to the current file
diff --git a/App/lib/core/builtin/ViperBuild.vp b/App/lib/core/builtin/ViperBuild.vp
index 1953980..fd9186c 100644
--- a/App/lib/core/builtin/ViperBuild.vp
+++ b/App/lib/core/builtin/ViperBuild.vp
@@ -10,6 +10,7 @@ import lib.Projectrans.Utils as Utils
 import lib.Projectrans.Config as Config
 import lib.core.VLogger as VLogger
 import lib.core.IncludesScanner as IncludesScanner
+import stdio
 
 # kernel32!GetEnvironmentVariableA (DWORD(LPCSTR, LPSTR, DWORD)) - declared here, same as includes/traceback.vp;
 # win32base.vp omits it but kernel32 is linked anyway; only for selfmachine host detection.
@@ -465,6 +466,9 @@ def _HandleImport(stmt: ast.Import*) -> int:
                 # 宏库：不参与 BFS，只记别名（CDLL 语句由 _HandleCDLL 抽取）
                 if al.asname is not None: _ffi_alias = _DupScratch(al.asname)
                 else: _ffi_alias = _DupScratch("ffilib")
+                # runtime CDLL 的 thunk 要调 _ffilib（真实运行时库）：显式加入闭包，
+                # 否则按需可达性扫描不会收录它，_resolve_module_sha1("_ffilib") 会返回 None。
+                _AddPending("_ffilib")
             else: _AddPending(al.name)
     return 0