---

name: repo-development description: "Work safely in a PennyLane source checkout: focused tests, linting, module boundaries, changelog, new operators/devices/plugins, and AI/GitHub policy." metadata: disco-role: operating disable-model-invocation: true license: Apache 2.0

PennyLane source-checkout development

Use this sub-skill when the user asks to edit, test, review, document, or maintain a PennyLane checkout. It is not needed for simple installed-package usage.

Read first

• ../../references/development-conventions.md: distilled repo policy for environments, AI/GitHub safety, tests, linting, formatting, changelog, new files, and import conventions.
• references/workflows.md: common source-change workflows for operators, devices/plugins, tests, docs, and changelog updates.
• references/troubleshooting.md: pytest markers, lint/tach failures, architecture boundaries, optional frameworks, and policy blockers.
• scripts/dev_command_plan.py: prints relevant commands for changed source/test files without running them.

Non-negotiable policy

• Do not act autonomously on GitHub. The user must review and approve exact issue/PR/comment content before any GitHub action.
• Do not commit unless explicitly asked.
• Mark AI-generated content destined for issue/PR/comment contexts.
• Do not solve good-first-issue tasks with an AI agent.
• Do not silence pylint or add pragma: no cover without human approval.

Environment and test flow

1. Check for .venv with shell ls -ld .venv ../.venv before claiming no venv.
2. Use existing environment executables when present; otherwise use the user-approved environment.
3. Run focused tests relevant to changed files before linting.
4. Run pylint directly with the correct rcfile, then black, then isort, then repo-wide tach check when imports/modules changed.

Common commands

python -m pytest tests/path/test_file.py
pylint -rn -sn --persistent=n --rcfile=.pylintrc pennylane/path/file.py
pylint -rn -sn --persistent=n --rcfile=tests/.pylintrc tests/path/test_file.py
black --config ./pyproject.toml pennylane/path/file.py tests/path/test_file.py
isort --settings-path ./pyproject.toml pennylane/path/file.py tests/path/test_file.py
tach check

Route by change type

• New or changed operation/template: read operators/transforms, add or update tests in the matching tests/ops/ or tests/templates/ area, and validate with assert_valid(op) for new operators.
• Device/plugin work: read circuits/devices; use pl-device-test for plugin/device validation and device-specific focused tests.
• Gradient/interface behavior: read gradients/interfaces and use interface markers in tests.
• Application modules: read applications/qchem/resource and install optional dependencies only when the selected tests need them.
• Docs/examples: use import pennylane as qp; run Sybil/docstring tests by pointing pytest at the source/doc file when applicable.

Verification cues

A safe development answer should name the changed files, focused tests, lint/format/tach commands, optional dependencies or skipped backends, changelog decision, and unresolved policy approvals. Never claim a repo task is complete if relevant tests are failing.