diff --git a/VKernel/Kernel/execrunner/elf.vp b/VKernel/Kernel/execrunner/elf.vp
index c5438f3..fedc766 100644
--- a/VKernel/Kernel/execrunner/elf.vp
+++ b/VKernel/Kernel/execrunner/elf.vp
@@ -130,6 +130,11 @@ def load_elf(path: t.CConst | str, do_map: t.CInt = 1) -> t.CVoid | t.CPtr:
     ehdr_buf: t.CArray[t.CUInt8T, 64]
     string.memset(c.Addr(ehdr_buf), 0, 64)
     read_len: t.CUInt32T = fat32.read(fp, c.Addr(ehdr_buf), 64)
+    # [DIAG] read_len 实际值（fat32.read 内部打印 br=64 但 load_elf 收到 <64
+    # 触发 "failed to read ehdr" —— 跨模块返回值间歇性丢失）
+    _dbrl: t.CArray[t.CChar, 64]
+    viperlib.snprintf(c.Addr(_dbrl), 64, "[elf] read_len=%lu\n", read_len)
+    serial.puts(c.Addr(_dbrl))
     if read_len < 64:
         serial.puts("[elf] failed to read ehdr\n")
         fat32.close(fp)
diff --git a/VKernel/Kernel/main.vp b/VKernel/Kernel/main.vp
index 01f3988..ead55cc 100644
--- a/VKernel/Kernel/main.vp
+++ b/VKernel/Kernel/main.vp
@@ -243,6 +243,10 @@ class ViperKernel:
                     viperlib.snprintf(c.Addr(slog), 64, "[main] Hello spawned as pid=%d\n", hello_pid)
                     serial.puts(slog)
                 term_pid: t.CInt = elf.spawn_elf("/APPS/terminal.elf")
+                # [DIAG] spawn_elf 返回 pid=1 但 main 收到 0 —— 跨模块返回值间歇性丢失
+                _dbtp: t.CArray[t.CChar, 64]
+                viperlib.snprintf(c.Addr(_dbtp), 64, "[main] term_pid=%d\n", term_pid)
+                serial.puts(c.Addr(_dbtp))
                 if term_pid < 0:
                     serial.puts("[main] Terminal spawn failed\n")
                 else: