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+# Copilot Coding Agent Instructions for Enzyme-JAX
+
+## Repository Overview
+
+Enzyme-JAX provides custom bindings for the Enzyme automatic differentiation (AD) tool integrated with JAX. It enables automatic importing and differentiation (JVP and VJP) of external C++ code into JAX. The project is language-agnostic via Enzyme, supporting Julia, Swift, Fortran, Rust, and Python.
+
+**Project Type:** Python/C++ library with MLIR-based compiler passes  
+**Build System:** Bazel 7.7.0  
+**Languages:** Python 3.10-3.12, C++17  
+**Key Dependencies:** JAX, XLA, LLVM/MLIR, Enzyme, StableHLO, Triton
+
+## Repository Structure
+
+```
+/                       # Root: BUILD, WORKSPACE, workspace.bzl, package.bzl
+├── src/enzyme_ad/jax/  # Main source code
+│   ├── primitives.py   # Core Python API (cpp_call, enzyme_jax_ir, etc.)
+│   ├── __init__.py     # Package exports
+│   ├── Passes/         # MLIR optimization passes
+│   ├── Implementations/# AD derivative implementations
+│   ├── Dialect/        # Custom MLIR dialects (EnzymeXLA, Distributed, Tessera)
+│   └── TransformOps/   # MLIR transform operations
+├── test/               # Tests (Python and lit tests)
+│   ├── lit_tests/      # MLIR FileCheck-based lit tests (.mlir, .pyt files)
+│   ├── test.py         # Main Python tests
+│   └── BUILD           # Test build configuration
+├── builddeps/          # Python requirements
+├── third_party/        # External dependency configurations (JAX, XLA, Enzyme, etc.)
+└── patches/            # Patches for JAX and XLA
+```
+
+## Build Instructions
+
+### Prerequisites
+- Bazel 7.7.0 (specified in `.bazelversion`)
+- clang++ (C++17 support required)
+- Python 3.10, 3.11, or 3.12
+- python-virtualenv, python3-dev
+
+### Build Commands
+
+**Build the wheel:**
+```sh
+bazel build :wheel
+# Output: bazel-bin/enzyme_ad-VERSION-SYSTEM.whl
+```
+
+**Build enzymexlamlir-opt:**
+```sh
+bazel build //:enzymexlamlir-opt
+```
+
+**Update Python requirements (run before building if requirements change):**
+```sh
+bazel run //builddeps:requirements.update
+```
+
+**Generate compile_commands.json for LSP support:**
+```sh
+bazel run :refresh_compile_commands
+```
+
+### Environment Variables
+
+Set `HERMETIC_PYTHON_VERSION` to specify Python version:
+```sh
+HERMETIC_PYTHON_VERSION=3.11 bazel build :wheel
+```
+
+For macOS builds, add: `--define using_clang=true`  
+For Linux ARM64, add: `--linkopt=-fuse-ld=lld`
+
+### Build Notes
+- Builds can take 2-3+ hours on first run (downloads and compiles LLVM, XLA, etc.)
+- Use `bazel-bin/` output directory for built artifacts
+- Build artifacts are cached; subsequent builds are faster
+
+## Testing
+
+**Run all tests:**
+```sh
+bazel test //test/...
+```
+
+**Run lit tests only:**
+```sh
+bazel test //test/lit_tests/...
+```
+
+**Run specific test:**
+```sh
+bazel test //test:test  # Main Python tests
+bazel test //test:testffi
+bazel test //test:llama
+```
+
+**Test flags for verbose output:**
+```sh
+bazel test --test_output=errors --experimental_ui_max_stdouterr_bytes=-1 --test_verbose_timeout_warnings //test/...
+```
+
+**Important:** Do NOT run Python tests from the repository root. If testing manually after installing the wheel:
+```sh
+cd test && python test.py
+```
+
+## Code Formatting
+
+### Python (Black)
+- Style: Black formatter
+- Check: `black --check .`
+- Fix: `black .`
+- CI workflow: `.github/workflows/python_format.yml`
+
+### C++/Header Files (clang-format)
+- Style: LLVM (see `.clang-format`)
+- Source directory: `src/` (excludes `src/external/`)
+- clang-format version: 16
+- CI workflow: `.github/workflows/format.yml`
+
+### Bazel Files (buildifier)
+- Check: `buildifier -mode check -r .`
+- Fix: `buildifier -r .`
+- CI workflow: `.github/workflows/format-check-bazel.yml`
+
+## CI/CD Workflows
+
+Located in `.github/workflows/`:
+
+| Workflow | Trigger | Purpose |
+|----------|---------|---------|
+| `build.yml` | Push/PR to main | Full build and test on multiple platforms |
+| `format.yml` | Push/PR (C++ files) | clang-format check |
+| `python_format.yml` | Push/PR (Python files) | Black format check |
+| `format-check-bazel.yml` | Push/PR (Bazel files) | Buildifier format check |
+
+## Key Source Files
+
+- **`src/enzyme_ad/jax/primitives.py`** - Main Python API: `cpp_call`, `ffi_call`, `hlo_call`, `enzyme_jax_ir`, `optimize_module`
+- **`src/enzyme_ad/jax/__init__.py`** - Public API exports
+- **`BUILD`** (root) - Main Bazel build file, defines `:wheel`, `:enzymexlamlir-opt`, `:enzyme_ad`
+- **`WORKSPACE`** - Dependency loading and workspace setup
+- **`workspace.bzl`** - Version pins for JAX, Enzyme, LLVM targets, XLA patches
+
+## Adding/Modifying Code
+
+### Python Changes
+1. Edit files in `src/enzyme_ad/jax/`
+2. Run `black .` to format
+3. Test with `bazel test //test:test`
+
+### C++ Changes
+1. Edit files in `src/enzyme_ad/jax/` (.cpp, .h, .cc files)
+2. Format with clang-format (LLVM style, version 16)
+3. Build with `bazel build //:enzymexlamlir-opt` or `bazel build :wheel`
+
+### Bazel File Changes
+1. Edit BUILD, WORKSPACE, or .bzl files
+2. Format with `buildifier -r .`
+3. Verify with `bazel build :wheel`
+
+### Adding MLIR Passes
+- Passes are in `src/enzyme_ad/jax/Passes/`
+- TableGen definitions in `.td` files
+- Register in `src/enzyme_ad/jax/RegistryUtils.cpp`
+
+**When adding a new pass to `EnzymeHLOOpt.cpp`:**
+1. Add the pattern class to `src/enzyme_ad/jax/Passes/EnzymeHLOOpt.cpp`
+2. Add the corresponding entry to `src/enzyme_ad/jax/TransformOps/TransformOps.td`
+3. Add the pass name to the list in `src/enzyme_ad/jax/primitives.py`
+
+## Dependencies
+
+External dependencies are configured in `third_party/`:
+- `enzyme/workspace.bzl` - Enzyme AD
+- `jax/workspace.bzl` - Google JAX
+- `xla/workspace.bzl` - OpenXLA
+- `ml_toolchain/workspace.bzl` - ML toolchain
+
+Version pins are in `workspace.bzl`:
+- `JAX_COMMIT`, `ENZYME_COMMIT`, `ML_TOOLCHAIN_COMMIT`, `HEDRON_COMPILE_COMMANDS_COMMIT`
+
+## Troubleshooting
+
+- **Build timeout:** Initial builds can exceed 180 minutes. Increase timeout or use cached builds.
+- **Python import errors:** Install wheel before running Python: `pip install bazel-bin/enzyme_ad-*.whl`
+- **Format failures:** Run formatters locally before committing.
+- **Test failures in lit_tests:** These are MLIR FileCheck tests; check `.mlir` and `.pyt` files.
+
+## Trust These Instructions
+
+These instructions are verified and accurate. Only perform additional searches if:
+1. The instructions appear incomplete for your specific task
+2. You encounter errors not documented here
+3. File locations have changed from what's documented