diff --git a/SourceCode/Code2026/CoreLibrary/AecDbX3dPart.cpp b/SourceCode/Code2026/CoreLibrary/AecDbX3dPart.cpp
index fdf7375..30ab4ce 100644
--- a/SourceCode/Code2026/CoreLibrary/AecDbX3dPart.cpp
+++ b/SourceCode/Code2026/CoreLibrary/AecDbX3dPart.cpp
@@ -20,6 +20,138 @@ static const Adesk::UInt16 kMagenta        = 6;
 static const Adesk::UInt16 kWhite          = 7;
 static const Adesk::UInt16 kColorByLayer   = 256;
 
+// ===========================================================================
+//  试点探针（AEC_X3D_SIZEPROBE=1 才生效，Release 零开销）
+//
+//  目的：量清楚"把一个 part 的 m_pSolid 存进 DWG"到底要多大、多贵。
+//  - acisOut 出来的 SAT 文本字节数：二进制 SAB 一般比它小，所以这是体积**上界**；
+//  - acisOut 的耗时：二进制写只要格式化更少，所以这是"序列化一次"的耗时**上界**；
+//  - 顺带对比同一次 Rebuild 的耗时，算出"恢复 vs 重建"的比值。
+//  汇总写 %TEMP%\aec_x3d_probe.txt（每 100 个 part 刷新一次）。
+// ===========================================================================
+namespace
+{
+	struct X3dProbeStat
+	{
+		X3dProbeStat() : n(0), bytes(0), maxBytes(0), outUs(0), rebuildUs(0) {}
+		long long n;
+		long long bytes;
+		long long maxBytes;
+		long long outUs;
+		long long rebuildUs;
+	};
+
+	X3dProbeStat& ProbeStat() { static X3dProbeStat s; return s; }
+
+	bool ProbeEnabled()
+	{
+		static int s_nOn = -1;
+		if (s_nOn < 0)
+		{
+			const char* psz = ::getenv("AEC_X3D_SIZEPROBE");
+			s_nOn = (psz != NULL && psz[0] != '\0' && psz[0] != '0') ? 1 : 0;
+		}
+		return s_nOn == 1;
+	}
+
+	long long ProbeQpc()
+	{
+		LARGE_INTEGER li;
+		::QueryPerformanceCounter(&li);
+		return (long long)li.QuadPart;
+	}
+
+	long long ProbeQpcFreq()
+	{
+		static long long s_f = 0;
+		if (s_f == 0)
+		{
+			LARGE_INTEGER li;
+			if (!::QueryPerformanceFrequency(&li) || li.QuadPart == 0) s_f = 1;
+			else s_f = (long long)li.QuadPart;
+		}
+		return s_f;
+	}
+
+	void ProbeDump()
+	{
+		TCHAR szTmp[MAX_PATH + 1];
+		::memset(szTmp, 0, sizeof(szTmp));
+		if (::GetTempPath(MAX_PATH, szTmp) == 0)
+			return;
+		TCHAR szFile[MAX_PATH + 1];
+		::_stprintf_s(szFile, MAX_PATH, _T("%saec_x3d_probe.txt"), szTmp);
+
+		FILE* fp = NULL;
+		if (_tfopen_s(&fp, szFile, _T("w")) != 0 || fp == NULL)
+			return;
+
+		const X3dProbeStat& s = ProbeStat();
+		fprintf(fp, "---- X3dPart geometry size probe ----\n");
+		fprintf(fp, "parts measured      : %lld\n", s.n);
+		fprintf(fp, "total SAT bytes     : %lld  (%.1f MB)\n", s.bytes, (double)s.bytes / 1048576.0);
+		if (s.n > 0)
+		{
+			fprintf(fp, "avg SAT bytes/part  : %lld\n", s.bytes / s.n);
+			fprintf(fp, "max SAT bytes/part  : %lld\n", s.maxBytes);
+			fprintf(fp, "avg acisOut per part: %.3f ms\n", (double)s.outUs / (double)s.n / 1000.0);
+			fprintf(fp, "avg Rebuild per part: %.3f ms\n", (double)s.rebuildUs / (double)s.n / 1000.0);
+			if (s.outUs > 0)
+				fprintf(fp, "rebuild / acisOut   : %.1f x\n", (double)s.rebuildUs / (double)s.outUs);
+		}
+		fclose(fp);
+	}
+
+	// 对一个 solid 量 SAT 字节数 + acisOut 耗时
+	void ProbeOneSolid(AcDb3dSolid* pSolid, long long nRebuildUs)
+	{
+		if (!ProbeEnabled())
+			return;
+
+		X3dProbeStat& s = ProbeStat();
+		++s.n;
+		s.rebuildUs += nRebuildUs;
+
+		if (pSolid != NULL)
+		{
+			TCHAR szTmp[MAX_PATH + 1];
+			::memset(szTmp, 0, sizeof(szTmp));
+			if (::GetTempPath(MAX_PATH, szTmp) != 0)
+			{
+				TCHAR szFile[MAX_PATH + 1];
+				::_stprintf_s(szFile, MAX_PATH, _T("%saec_x3d_probe_%lu.sat"),
+					szTmp, (unsigned long)::GetCurrentProcessId());
+
+				AcDbVoidPtrArray arSolids;
+				arSolids.append(pSolid);
+
+				const long long t0 = ProbeQpc();
+				Acad::ErrorStatus es = AcDbBody::acisOut(szFile, arSolids);
+				const long long t1 = ProbeQpc();
+				s.outUs += (t1 - t0) * 1000000LL / ProbeQpcFreq();
+
+				if (es == Acad::eOk)
+				{
+					WIN32_FILE_ATTRIBUTE_DATA fad;
+					::memset(&fad, 0, sizeof(fad));
+					if (::GetFileAttributesEx(szFile, GetFileExInfoStandard, &fad))
+					{
+						const long long nSize =
+							((long long)fad.nFileSizeHigh << 32) | (long long)fad.nFileSizeLow;
+						s.bytes += nSize;
+						if (nSize > s.maxBytes)
+							s.maxBytes = nSize;
+					}
+					::DeleteFile(szFile);
+				}
+			}
+		}
+
+		if (s.n % 100 == 0)
+			ProbeDump();
+	}
+}
+
 static void FreeBuffer(int n,AcDbVoidPtrArray& arEntPtrs)
 {
 	AcDbEntity* pEnt = NULL;
@@ -960,7 +1092,11 @@ bool AecDbX3dPart::EnsureCreated() const
 	SectionPerf::NoteEnsure("X3dPart", this, true);
 	//试点计时：X3dPart 重建总耗时（用来看"几何存盘"这套机制的天花板在哪）
 	SectionPerf::Scope perfScope("X3dPart::Rebuild");
+	const bool bProbe = ProbeEnabled();
+	const long long nProbeT0 = bProbe ? ProbeQpc() : 0;
 	const bool bOk = const_cast<AecDbX3dPart*>(this)->Rebuild();
+	if (bProbe)
+		ProbeOneSolid(m_pSolid, (ProbeQpc() - nProbeT0) * 1000000LL / ProbeQpcFreq());
 	SectionPerf::NoteEnsure(m_pSolid != NULL ? "X3dPart.rebuild_ok" : "X3dPart.rebuild_null", this, false);
 	if (m_pSolid == NULL)
 	{