Add AGENTS.md guidance for coding agents

.github/AGENTS.md

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+# AGENTS.md - CI Workflows (.github/)
+
+## Rules for Changes
+These keep zizmor (`zizmor.yml`, fails on medium or higher findings) and the OpenSSF Scorecard clean.
+- Pin every third-party action to a full commit SHA with a `# <release tag>` comment.
+- Every workflow declares top-level `permissions` (`read-all`, `contents: read` or `{}`). Grant more per job, with a comment saying why.
+- Every `actions/checkout` sets `persist-credentials: false`.
+- Never inline untrusted contexts (`github.event.*`, `github.head_ref`, `inputs.*`) in `run:`; pass them through `env:`. Prefer `env:` for every value in new code.
+- Every job sets `timeout-minutes`; for a job that calls a reusable workflow, set it inside the called workflow.
+- `actionlint` runs in pre-commit.
+- `workflows/array-api-skips.txt` lists array-api-tests node IDs skipped by the conformance job; precede each with a comment naming the upstream issue.
+- `bump-sycl-deps.yml` rewrites the `DRIVER_PATH`, `OCLCPUEXP_FN` and `TBB_*` pins in `os-llvm-sycl-build.yml` with `sed`; keep their format.
+- Dependabot (`dependabot.yml`) bumps actions, `environments/` pins and pre-commit hooks weekly with a 7-day cooldown.

AGENTS.md

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+# AGENTS.md - dpnp
+
+dpnp is a NumPy-compatible array library for SYCL devices. Its main namespace, `dpnp.fft` and `dpnp.linalg` also conform to the Python Array API standard (2025.12, `doc/reference/array_api.rst`). The Python layer (`dpnp/`) is built on `dpnp.tensor` (Array API, `dpnp/tensor/`) and pybind11 SYCL extensions (`dpnp/backend/extensions/`); `dpctl` provides devices, queues and USM memory.
+
+## Rules for Changes
+
+These come from recurring maintainer review comments. Directory-specific rules are in the nearest `AGENTS.md`.
+
+- Match NumPy, or SciPy for `dpnp.scipy`: shape, dtype, memory layout, edge cases (empty, 0-d, NaN/inf) and error and warning text. Following CuPy instead is an exception. Any deliberate difference is documented in the docstring and covered by a test with a comment.
+- Don't break Array API conformance. Where NumPy and the spec differ, raise it in the PR rather than silently picking one (precedent: `ndarray.T` on non-2-D arrays was deprecated to match the spec).
+- Code and tests must work on devices without fp64 support (e.g. Iris Xe). Don't hardcode float64/complex128; use `dpnp.default_float_type()` or the dtype helpers in `dpnp/tests/helper.py`.
+- Compute follows data: allocate results and temporaries on the inputs' SYCL queue with their coerced USM type, and raise when inputs computed together are on different queues (`get_usm_allocations` raises `ValueError`, `dpnp.tensor` raises `ExecutionPlacementError`). Never move inputs silently.
+- Avoid hidden host transfers and queue syncs: `int()`/`bool()` on device arrays, `.wait()`, `asnumpy`, redundant full-size copies.
+- Accept both `dpnp.ndarray` and `usm_ndarray`; validate and unwrap with `dpnp.check_supported_arrays_type` and `dpnp.get_usm_ndarray`, not ad-hoc `isinstance` or method calls.
+- Every user-visible change, including build, recipe and C-API changes, gets a one-line `CHANGELOG.md` entry (format below).
+- A new public function needs an export in `dpnp/__init__.py` (or in its subpackage's `__init__.py`), a numpydoc docstring, an entry in `doc/reference/*.rst`, tests (including `test_sycl_queue.py` and `test_usm_type.py`) and a changelog entry. Don't export names that NumPy/SciPy don't.
+- Deprecate before removing: keep the old API for at least one release with a `DeprecationWarning`, and add a `Deprecated` changelog entry and a test for the warning. Removing something NumPy itself has removed can land directly with a `Removed` entry.
+- A removal, rename or version bump also updates every other place that names or relies on the old thing: grep the whole repository, workflows and recipes included. A site kept on purpose gets a `TODO`, unless a directory `AGENTS.md` says to keep it. Past `CHANGELOG.md` entries stay.
+- Every new branch and error path has a test; a bug fix comes with a test that fails without it. Use `# pragma: no cover` only for branches the Linux coverage job can't reach (CUDA, HIP, Windows-only) or that can't happen by construction.
+- A workaround, skip or xfail gets a comment with the full issue URL so it can be reverted later. In `dpnp/tests/third_party/`, a skip for an unsupported feature needs only its reason string.
+- Keep comments short and accurate: one line of why. Don't narrate the change, restate the code, or mention "this PR".
+- One PR, one change. Search for an existing helper before adding one.
+- New files carry the BSD-3 license header from a neighbouring file with the current year; never change the year in existing files. Test files directly in `dpnp/tests/` and under `dpnp/tests/third_party/` have no header.
+- Don't edit generated files: `dpnp/_version.py`, `dpnp/include/dpnp/tensor/_usmarray*.h`, `dpnp/resources/cmake/`, `doc/reference/generated/`, `doc/reference/*.inc`.
+
+## Verification Before You Push
+
+```bash
+pre-commit run --all-files         # the required `Check` job; pylint must be on PATH
+python scripts/build_locally.py    # in-place build + editable install
+python -m pytest -ra dpnp/tests/test_<area>.py
+```
+
+The build needs the packages in `environments/build_with_oneapi.yml`, `environments/oneapi_pkgs.yml` and `environments/dpctl_pkg.yml`. The `no-commit-to-branch` hook fails on `master` and `maintenance/*`, so work on a branch. Full-suite commands and test env vars are in `dpnp/tests/AGENTS.md`; build options in `dpnp/backend/AGENTS.md`.
+
+### Changelog format
+
+Append to the end of the matching `### Added` / `Changed` / `Deprecated` / `Removed` / `Fixed` / `Security` list in the top `## [X.Y.Z] - YYYY-MM-DD` section. Past tense, code in backticks, no trailing period:
+
+```
+* Added support for the `"nuc"` (nuclear) norm in `dpnp.linalg.cond` [#3084](https://github.com/IntelPython/dpnp/pull/3084)
+```
+
+### Where the checks live
+
+| Check | Workflow | Required on master |
+| --- | --- | --- |
+| pre-commit (`Check`) | `.github/workflows/pre-commit.yml` | yes |
+| conda build and tests, Linux and Windows, py3.13-3.15 and 3.14t (`Test (...)`) | `conda-package.yml` | yes |
+| Internal Jenkins (`jenkins-test-dpnp-3.13-linux-dev`, `...-3.14-...`) | external | yes |
+| Array API conformance of `dpnp`, not yet `dpnp.tensor` (array-api-tests; never fails, results posted as a PR comment) | `conda-package.yml` | no |
+| pybind11 examples | `conda-package.yml` | no |
+| conda-forge build and tests | `conda-package-cf.yml`, matrix in `conda-build-test.yml` | no |
+| oneMath build, open-source LLVM SYCL build | `check-onemath.yaml`, `os-llvm-sycl-build.yml` | no |
+| Sphinx docs (`make spelling`, `make html`) | `build-sphinx.yml` | no |
+| Coverage (Coveralls), zizmor | `generate_coverage.yaml`, `zizmor.yml` | no |
+
+GitHub-hosted runners have no GPU, so tests there run on a CPU device: a green run says nothing about GPUs or devices without fp64.
+
+## Reviewing
+
+Report source-confirmed problems with NumPy compatibility, Array API conformance, compute-follows-data, devices without fp64, SYCL event ordering and lifetimes, error handling and test coverage. Don't report what pre-commit enforces (formatting, import order, spelling), and don't report that `@pytest.mark.slow` tests are skipped in CI: that is by design.
+
+## Directory Guides
+
+Read the `AGENTS.md` nearest the files you change. When editing these files, every command, path and name must match the repository; delete what can't be verified rather than soften it.
+
+- [dpnp/AGENTS.md](dpnp/AGENTS.md): Python layer, adding a function, docstrings
+- [dpnp/tests/AGENTS.md](dpnp/tests/AGENTS.md): test helpers, fp64, CuPy tests, running the suite
+- [dpnp/backend/AGENTS.md](dpnp/backend/AGENTS.md): pybind11 SYCL extensions, C++ rules, build options
+- [dpnp/tensor/AGENTS.md](dpnp/tensor/AGENTS.md): `dpnp.tensor` and libtensor
+- [doc/AGENTS.md](doc/AGENTS.md): Sphinx docs
+- [benchmarks/AGENTS.md](benchmarks/AGENTS.md): ASV benchmarks
+- [.github/AGENTS.md](.github/AGENTS.md): workflow hardening rules
+
+## Further Reading
+
+- `doc/quick_start_guide.rst`: build from source, CUDA/HIP targets
+- `.github/pull_request_template.md`: the PR checklist

benchmarks/AGENTS.md

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+# AGENTS.md - Benchmarks (benchmarks/)
+
+ASV suite that times dpnp only; `README.md` has the full setup.
+
+## Rules for Changes
+- NumPy is not timed: `executor` stays the single value `'dpnp'`. Don't edit the leftover `numpy` branches in `setup`: ASV versions a benchmark by the source of `setup` and `time_*`, so any edit makes its results incomparable with the recorded history.
+- Keep `params` static and their values plain strings, numbers or tuples; skip unsupported devices in `setup` with `SkipNotImplemented`.
+- Timed bodies block on the result (`self.sync(...)` or `dpnp.synchronize_array_data`); otherwise they time only the submission.
+- Parameter axes shared by two or more modules live in `benchmarks/benchmarks/_utils.py`.
+- A new non-ASV dependency goes in both `requirements.txt` (what CI installs) and the `benchmark` extra in `pyproject.toml`; ASV itself is only in the extra.
+
+## Verification
+From `benchmarks/`, against an environment that already has dpnp:
+```bash
+asv machine --yes
+asv check --python=same
+asv run --python=same --launch-method spawn --quick --bench bench_elementwise
+```
+Always pass `--launch-method spawn`: the SYCL runtime is not fork-safe. Don't `pip install ".[benchmark]"`; it rebuilds dpnp.

doc/AGENTS.md

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+# AGENTS.md - Documentation (doc/)
+
+## Layout
+- `conf.py`: Sphinx config (numpydoc, autosummary, furo). It registers the dpnp `Limitations` docstring section, documents the `DPNP*Func` wrapper objects as functions, and regenerates `reference/comparison_table.rst.inc` from `comparison_generator.py` on every build
+- `reference/<category>.rst`: `.. autosummary::` lists under `.. currentmodule::` (`dpnp` or the subpackage); stubs are generated into `reference/generated/`
+- `known_words.txt`: spelling allow-list
+- `quick_start_guide.rst`: install and build-from-source instructions
+
+## Rules for Changes
+- A new public function goes in the autosummary block of the matching `reference/<category>.rst`; ufuncs also go in `reference/ufunc.rst`, `ndarray` members in `reference/ndarray.rst`. These pages already list many NumPy names that dpnp lacks, so check before adding a duplicate.
+- A new namespace needs its own `reference/<name>.rst` and a toctree entry: in `reference/routines.rst` for NumPy namespaces (model: `reference/fft.rst`), in `reference/scipy.rst` for SciPy ones (model: `reference/scipy_linalg.rst`).
+- A page kept out of every toctree on purpose, such as a placeholder, is marked `:orphan:`, or Sphinx warns about it.
+- Move a deprecated function from its reference page to `reference/_deprecated.rst` (an orphan page that keeps its stub) and remove cross-links to it.
+- A new wrapper base class (not a subclass of the existing `DPNP*Func` classes) must be added to `conf.py` and `_can_document_member`, or autodoc skips its instances.
+- Update `quick_start_guide.rst` (and `README.md`) when build options or supported Python versions change, and `reference/array_api.rst` when the Array API version or the conforming namespaces change.
+- Add new legitimate words to `known_words.txt`.
+- Warnings don't fail the build (no `-W`), so check the log and the rendered page yourself.
+
+## Verification
+```bash
+cd doc
+make spelling
+make html
+```
+This needs an importable dpnp build and the packages in `environments/building_docs.yml` (including CuPy, for the comparison table). CI (`build-sphinx.yml`) publishes builds of PRs from IntelPython/dpnp branches at `https://intelpython.github.io/dpnp/pull/<N>/index.html`; fork PRs get an artifact instead.

dpnp/AGENTS.md

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+# AGENTS.md - Python layer (dpnp/)
+
+## Layout
+- `dpnp_iface_<category>.py`: public functions, grouped like NumPy's routines reference
+- `dpnp_array.py`: `dpnp.ndarray`, a wrapper over `dpnp.tensor.usm_ndarray`; `get_array()` unwraps, `_create_from_usm_ndarray()` wraps
+- `dpnp_algo/dpnp_elementwise_common.py`: ufunc wrapper classes (`DPNPUnaryFunc`, `DPNPBinaryFunc`, two-output and specialised variants)
+- `dpnp_utils/`: shared helpers (`get_usm_allocations`, `map_dtype_to_device`, reduction wrappers)
+- `linalg/`, `fft/`, `random/`, `scipy/`, `lib/`: subpackages, each exporting through its own `__init__.py`
+- Legacy, don't extend: the Cython `dpnp_algo` path and `dpnp_backend_c` (still used by `dpnp.partition` and `dpnp.random`), and the NumPy fallback `call_origin`. New kernels go into pybind11 extensions or `dpnp.tensor`.
+
+## Adding a Public Function
+1. Implement it in the matching `dpnp_iface_*.py` or subpackage module. Iface modules have no `__all__`.
+2. Export it in `dpnp/__init__.py` in two places, both under its NumPy routine category: the `from .dpnp_iface_xxx import (...)` block and the `__all__ += [...]` block. Functions in `linalg`, `fft`, `random`, `scipy.*` and `lib` are exported from that subpackage's `__init__.py` instead (import block and `__all__`). A new subpackage also goes in `packages=` in `setup.py`.
+3. Add it to `doc/reference/` (see `doc/AGENTS.md`), tests (see `dpnp/tests/AGENTS.md`) and `CHANGELOG.md`.
+
+## Patterns
+- Ufuncs are module-level wrapper instances, e.g. `cbrt = DPNPUnaryFunc("cbrt", ti._cbrt_result_type, ti._cbrt, _CBRT_DOCSTRING, mkl_fn_to_call=..., mkl_impl_fn=...)`. The first argument is the public name, with no leading underscore. Kernels come from `dpnp.tensor._tensor_elementwise_impl` or `dpnp.backend.extensions.ufunc._ufunc_impl`; the oneMKL VM path runs first when `mkl_fn_to_call` is given and supported.
+- Other functions: `dpnp.check_supported_arrays_type(...)`, unwrap with `dpnp.get_usm_ndarray`, call `dpnp.tensor` (`import dpnp.tensor as dpt`) or an extension, and wrap with `dpnp_array._create_from_usm_ndarray`. Pass `out` straight to the `dpnp.tensor` or extension call when it accepts one; otherwise `dpnp.get_result_array(res, out)` copies the result into it.
+- Get the result queue and USM type with `get_usm_allocations([...])` (raises `ValueError` on mixed queues) or `dpt.get_execution_queue(...)` (returns `None`; raise `ExecutionPlacementError`). Creation functions take `device`, `usm_type` and `sycl_queue` (normalised by `dpnp.get_normalized_queue_device`); `*_like` functions inherit them from the input.
+- Extension calls are ordered with `_manager = dpctl.utils.SequentialOrderManager[exec_q]`: pass `depends=_manager.submitted_events`, then `_manager.add_event_pair(ht_ev, ev)`. Don't add blocking waits.
+- Use `dpnp.default_float_type(...)` or `map_dtype_to_device(...)` for the default float type.
+- Deprecated ufuncs use `DPNPDeprecatedUnaryFunc(..., deprecated_msg=...)`.
+- Unsupported NumPy keywords raise `NotImplementedError` (`dpnp.check_limitations`) and are listed under `Limitations` in the docstring.
+- The Array API spec version is set in three places that change together: `__array_api_version__` in `dpnp/tensor/_array_api.py`, `ARRAY_API_TESTS_VERSION` in `.github/workflows/conda-package.yml` and `doc/reference/array_api.rst` (plus the version test in `dpnp/tests/test_ndarray.py`). Inspection utilities come from `__array_namespace_info__` in `dpnp_array_api_info.py`.
+- `dpnp.tensor` replaces `dpctl.tensor`, which no longer exists here; `SyclQueue`, `SyclDevice`, `dpctl.memory` and `SequentialOrderManager` still come from `dpctl`.
+
+## Docstrings
+numpydoc, rendered by `doc/conf.py`. `doc/docstring_template.py` shows the layout; model a new docstring on an existing function.
+- Sections in the order `doc/conf.py` renders them: summary, ``For full documentation refer to :obj:`numpy.<name>`.``, Parameters, Returns, Raises, Warns, Warnings, Limitations, See Also, Notes, References, Examples.
+- Array parameters are typed `{dpnp.ndarray, usm_ndarray}`, optional ones `{None, dpnp.ndarray, usm_ndarray}, optional`; the return is `out : dpnp.ndarray`.
+- Every keyword with a default ends with a blank line and ``Default: ``<value>``.``
+- Literals in double backticks (``` ``None`` ```), argument names in single backticks; link with `:obj:`.
+- Copy the `device` / `usm_type` / `sycl_queue` parameter text from an existing creation function such as `dpnp.empty`.
+- Examples start with `>>> import dpnp as np`. A docstring that contains `\` is raw (`r"""`).
+- An `ndarray` method that wraps a function has a one-line summary, a blank line, then ``Refer to :obj:`dpnp.<name>` for full documentation.``