git clone --depth 1 --branch v1.0.0 https://github.com/pytorch/executorch.git
cd executorch
git submodule update --init --recursive --rebase; git submodule sync --recursive
uv venv --python=3.12; source .venv/bin/activate # or any other virtualenv tool
python -m ensurepip
source ./install_requirements.sh --use-pt-pinned-commit
source ./install_executorch.sh --use-pt-pinned-commit
# at the time of writing, the issue also reproduces with torch nightly without pinned commit
cd examples/llm_manual
curl https://raw.githubusercontent.com/karpathy/nanoGPT/master/model.py -O
# curl https://huggingface.co/openai-community/gpt2/resolve/main/vocab.json -O
# had some weird redirect, had to resolved the link in a browser to get the actual vocab
curl "https://huggingface.co/api/resolve-cache/models/openai-community/gpt2/607a30d783dfa663caf39e06633721c8d4cfcd7e/vocab.json?%2Fopenai-community%2Fgpt2%2Fresolve%2Fmain%2Fvocab.json=&etag=%221f1d9aaca301414e7f6c9396df506798ff4eb9a6%22" -O
python export_nanogpt.py
# CMakeLists.txt expect executorch to be at third-party/executorch
mkdir third-party
git clone --depth 1 --branch v1.0.0 https://github.com/pytorch/executorch.git third-party/executorch
pushd third-party/executorch
git submodule update --init --recursive --rebase; git submodule sync --recursive
popd
# Fix CMakeLists.txt to enable NamedDataMap extension
sed -i '' '/option(EXECUTORCH_BUILD_EXTENSION_FLAT_TENSOR "" ON)/a\
option(EXECUTORCH_BUILD_EXTENSION_NAMED_DATA_MAP "" ON)\
' CMakeLists.txt
# edit manually if sed doesn't work on your platform
mkdir build; cd build; cmake ..; cmake --build . -j16; cd ..
./build/nanogpt_runner
# enter "hello" as a prompt

E 00:00:07.545846 executorch:op_index.cpp:94] Index -1 out of range for tensor with size 1 at dimension 1
E 00:00:07.546512 executorch:op_index.cpp:98] Check failed (is_valid_index): Some index values are not within bounds of input tensor at indexed dim
E 00:00:07.546513 executorch:op_index.cpp:131] Check failed (check_fast_path_args(ctx, in, indices, dim, out)):
E 00:00:07.546518 executorch:method.cpp:1355] KernelCall failed at instruction 0:608 in operator aten::index.Tensor_out: 0x12
E 00:00:07.546520 executorch:method.cpp:1361] arg 0 with type id 1
E 00:00:07.546521 executorch:method.cpp:1361] arg 1 with type id 11
E 00:00:07.546522 executorch:method.cpp:1361] arg 2 with type id 1
E 00:00:07.546523 executorch:method.cpp:1361] arg 3 with type id 1
F 00:00:07.546530 executorch:result.h:170] In function CheckOk(), assert failed: hasValue_
hellozsh: abort ./build/nanogpt_runner

Collecting environment information...
PyTorch version: 2.9.0
Is debug build: False
CUDA used to build PyTorch: None
ROCM used to build PyTorch: N/A
OS: macOS 14.8.1 (arm64)
GCC version: Could not collect
Clang version: 20.1.5
CMake version: version 3.31.6
Libc version: N/A
Python version: 3.12.11 (main, Oct 7 2025, 15:53:48) [Clang 20.1.4 ] (64-bit runtime)
Python platform: macOS-14.8.1-arm64-arm-64bit
Is CUDA available: False
CUDA runtime version: No CUDA
CUDA_MODULE_LOADING set to: N/A
GPU models and configuration: No CUDA
Nvidia driver version: No CUDA
cuDNN version: No CUDA
Is XPU available: False
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True
CPU:
Apple M3 Pro
Versions of relevant libraries:
[pip3] executorch==1.0.0a0+8c84780
[pip3] numpy==2.3.4
[pip3] pytorch_tokenizers==0.1.0
[pip3] torch==2.9.0
[pip3] torchao==0.14.0+git02941240f
[pip3] torchaudio==2.9.0
[pip3] torchdata==0.11.0+cpu
[pip3] torchsr==1.0.4
[pip3] torchtune==0.7.0+cpu
[pip3] torchvision==0.24.0
[conda] Could not collect