Imported from PennyLaneAI/pennylane (AGENTS.md). Install upstream with npx skills add PennyLaneAI/pennylane. Copyright stays with the author.

Environment

1. Check .venv via ls -ld .venv ../.venv; no file-search/glob tools — may skip ignored dirs.
2. If found, run through its executables (e.g. .venv/bin/python, .venv/bin/pre-commit) or activate.
3. Report no venv only after shell check fails.

AI Policy

• Never act autonomously on GitHub. Do NOT open, edit, comment on, or reply to any issue or PR unless user reviewed and explicitly approved exact content.
• Mark all AI-generated content. Any text you produce going into issue, PR, or comment must wrap in code or quote block. Never present output as human-written.
• Never emit only raw AI text as reply. Any AI content must carry human commentary explaining relevance.
• No code user hasn't read. Keep changes minimal, strip AI artifacts and needless complexity. PR not ready or not user reviewed, draft mode.
• No commit unless user explicitly asks.
• Disclose work authored with AI assistant, in individual commits and PR description.
• No solving good-first-issue with AI Agent.
• No silencing pylint warning or marking line pragma: no cover without human approval.

Testing

Tests use pytest, live under tests/. Run only tests relevant to change, not whole suite.

New functionality and bug fixes need tests.

Docstring/code-example tests collected by Sybil (see conftest.py); run by pointing pytest at source file, e.g. pytest pennylane/path/to/file.py.

Validate new operator with pennylane.ops.functions.assert_valid(op).

Linting and formatting

Run configured tools directly on changed files. Pylint first, then formatting (black, isort) once at end.

• Lint: pylint -rn -sn --persistent=n --rcfile=.pylintrc <path> ... for files under pennylane/ (use --rcfile=tests/.pylintrc for tests/ or pennylane/labs/tests/)
• Format: black --config ./pyproject.toml <path> ...
• Sort imports (only pennylane/ and tests/ files): isort --settings-path ./pyproject.toml <path> ...
• Module boundaries (repo-wide, no per-file mode): tach check

Config in pyproject.toml (black, isort, line length 100) and .pylintrc files (.pylintrc source, tests/.pylintrc tests, pennylane/labs/.pylintrc labs).

Changelog

Add bullet to doc/releases/changelog-dev.md under proper section, ending with PR link on next line [(#XXXX)](...).

Module architecture

tach.toml enforces layered architecture (ui/tertiary/auxiliary/core), forbids circular dependencies. No cross-layer or circular imports; pennylane.labs and pennylane.ftqc restricted. Run tach check to verify.

New files

New .py files must start with Apache 2.0 copyright header ("Copyright Xanadu Quantum Technologies Inc." + standard license block) — copy from existing module.

Conventions

In tests, examples, docstrings, import PennyLane as qp (import pennylane as qp), not legacy qml alias. Avoid importing pennylane in source code unless circular dependency.

Use pennylane.math library, not NumPy.

Keep validation and sanity checks minimal and opt-in.