🐛 Describe the bug

Dynamo does not match CPython semantics for invalid raise operands. When user code raises a string, tuple, or non-BaseException class/instance, CPython raises TypeError: exceptions must derive from BaseException. Dynamo instead hits an internal unimplemented() graph break path, preventing user except TypeError handlers from executing within the traced graph.

Failing CPython 3.13 conformance tests:

PYTORCH_TEST_WITH_DYNAMO=1 pytest \
  test/dynamo/cpython/3_13/test_baseexception.py::UsageTests::test_raise_string \
  test/dynamo/cpython/3_13/test_baseexception.py::UsageTests::test_raise_new_style_non_exception \
  test/dynamo/cpython/3_13/test_raise.py::TestRemovedFunctionality::test_strings \
  test/dynamo/cpython/3_13/test_raise.py::TestRemovedFunctionality::test_tuples

Root cause: The fallback path in _raise_exception_variable (symbolic_convert.py) calls unimplemented() for non-BaseException raise operands instead of raising an observed TypeError.

Versions

Collecting environment information... PyTorch version: N/A Is debug build: N/A CUDA used to build PyTorch: N/A ROCM used to build PyTorch: N/A

OS: Fedora Linux 41 (Container Image) (x86_64) GCC version: (GCC) 14.3.1 20251022 (Red Hat 14.3.1-4) Clang version: Could not collect CMake version: version 3.30.8 Libc version: glibc-2.40

Python version: 3.13.9 (main, Oct 14 2025, 00:00:00) [GCC 14.3.1 20250808 (Red Hat 14.3.1-3)] (64-bit runtime) Python platform: Linux-5.14.0-615.el9.x86_64-x86_64-with-glibc2.40 Is CUDA available: N/A CUDA runtime version: 12.8.93 CUDA_MODULE_LOADING set to: N/A GPU models and configuration: GPU 0: NVIDIA H200 GPU 1: NVIDIA H200 GPU 2: NVIDIA H200 GPU 3: NVIDIA H200 GPU 4: NVIDIA H200 GPU 5: NVIDIA H200 GPU 6: NVIDIA H200 GPU 7: NVIDIA H200

Nvidia driver version: 580.82.07 cuDNN version: Probably one of the following: /usr/local/cuda-12.8/targets/x86_64-linux/lib/libcudnn.so.9.6.0 /usr/local/cuda-12.8/targets/x86_64-linux/lib/libcudnn_adv.so.9.6.0 /usr/local/cuda-12.8/targets/x86_64-linux/lib/libcudnn_cnn.so.9.6.0 /usr/local/cuda-12.8/targets/x86_64-linux/lib/libcudnn_engines_precompiled.so.9.6.0 /usr/local/cuda-12.8/targets/x86_64-linux/lib/libcudnn_engines_runtime_compiled.so.9.6.0 /usr/local/cuda-12.8/targets/x86_64-linux/lib/libcudnn_graph.so.9.6.0 /usr/local/cuda-12.8/targets/x86_64-linux/lib/libcudnn_heuristic.so.9.6.0 /usr/local/cuda-12.8/targets/x86_64-linux/lib/libcudnn_ops.so.9.6.0 Is XPU available: N/A HIP runtime version: N/A MIOpen runtime version: N/A Is XNNPACK available: N/A Caching allocator config: N/A

CPU: Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 46 bits physical, 57 bits virtual Byte Order: Little Endian CPU(s): 160 On-line CPU(s) list: 0-159 Vendor ID: GenuineIntel Model name: Intel Xeon Processor (SapphireRapids) CPU family: 6 Model: 143 Thread(s) per core: 2 Core(s) per socket: 40 Socket(s): 2 Stepping: 4 BogoMIPS: 4200.00 Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology cpuid tsc_known_freq pni pclmulqdq vmx ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch cpuid_fault ssbd ibrs ibpb stibp ibrs_enhanced tpr_shadow flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid avx512f avx512dq rdseed adx smap avx512ifma clflushopt clwb avx512cd sha_ni avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves avx_vnni avx512_bf16 wbnoinvd arat vnmi avx512vbmi umip pku ospke waitpkg avx512_vbmi2 gfni vaes vpclmulqdq avx512_vnni avx512_bitalg avx512_vpopcntdq la57 rdpid bus_lock_detect cldemote movdiri movdir64b fsrm md_clear serialize tsxldtrk amx_bf16 avx512_fp16 amx_tile amx_int8 arch_capabilities Virtualization: VT-x Hypervisor vendor: KVM Virtualization type: full L1d cache: 5 MiB (160 instances) L1i cache: 5 MiB (160 instances) L2 cache: 320 MiB (80 instances) L3 cache: 32 MiB (2 instances) NUMA node(s): 2 NUMA node0 CPU(s): 0-79 NUMA node1 CPU(s): 80-159 Vulnerability Gather data sampling: Not affected Vulnerability Indirect target selection: Mitigation; Aligned branch/return thunks Vulnerability Itlb multihit: Not affected Vulnerability L1tf: Not affected Vulnerability Mds: Not affected Vulnerability Meltdown: Not affected Vulnerability Mmio stale data: Unknown: No mitigations Vulnerability Reg file data sampling: Not affected Vulnerability Retbleed: Not affected Vulnerability Spec rstack overflow: Not affected Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl Vulnerability Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Vulnerability Spectre v2: Mitigation; Enhanced / Automatic IBRS; IBPB conditional; PBRSB-eIBRS SW sequence; BHI SW loop, KVM SW loop Vulnerability Srbds: Not affected Vulnerability Tsx async abort: Not affected

cc @chauhang @penguinwu @voznesenskym @EikanWang @jgong5 @Guobing-Chen @XiaobingSuper @zhuhaozhe @blzheng @wenzhe-nrv @jiayisunx @kadeng @amjames @Lucaskabela @jataylo