In torch.onnx.export(..., dynamo=True), when fallback=True, the current behavior involves attempting four different strategies within the FX-based exporter (exported program-based exporter) before falling back to the TorchScript-based exporter. These strategies include TorchExportNonStrictStrategy, TorchExportStrategy, TorchExportDraftExportStrategy, and JitTraceConvertStrategy:

The original intent was to maximize export coverage by trying all known strategies. However, the additional strategies (TorchExportStrategy, TorchExportDraftExportStrategy, and JitTraceConvertStrategy) do not significantly improve coverage beyond what TorchExportNonStrictStrategy already handles. Furthermore, the complex try-catch error messages make it harder for users to understand the root cause of failures.

To simplify the process and reduce confusion, especially in light of upcoming changes #151693, torch.onnx.export(..., dynamo=True) should directly use torch.export.export(..., strict=False) (TorchExportNonStrictStrategy), as the primary strategy. If this fails, it should immediately fall back to torch.onnx.export(..., dynamo=False).

cc @chauhang @penguinwu @avikchaudhuri @gmagogsfm @zhxchen17 @tugsbayasgalan @angelayi @suo @ydwu4