core/.github/copilot-instructions.md

Copilot code review instructions

• Start review comments with a short, one-sentence summary of the suggested fix.
• Do not comment on code style, formatting or linting issues.
• Flag comments that over-explain straightforward code, narrate the obvious, or read like AI commentary (multi-sentence justifications for a single line).
• A Pull Request with a dependency version bump should only contain changes required for the version bump. If the PR includes other changes, request that they are removed from the PR.
• Check that the PR description is complete and filled in according to the PR template included below. Every section and checklist item from the template must be present, except the ## Breaking change section which is optional. Nothing from the template should be missing. Even unchecked checkboxes or empty sections must be present. This is an hard requirement.

Pull Request template

The PR description must follow this template (from .github/PULL_REQUEST_TEMPLATE.md):

<!--
  You are amazing! Thanks for contributing to our project!
  Please, DO NOT DELETE ANY TEXT from this template! (unless instructed).
-->
## Breaking change
<!--
  If your PR contains a breaking change for existing users, it is important
  to tell them what breaks, how to make it work again and why we did this.
  This piece of text is published with the release notes, so it helps if you
  write it towards our users, not us.
  Note: Remove this section if this PR is NOT a breaking change.
-->


## Proposed change
<!--
  Describe the big picture of your changes here to communicate to the
  maintainers why we should accept this pull request. If it fixes a bug
  or resolves a feature request, be sure to link to that issue in the
  additional information section.
-->


## Type of change
<!--
  What type of change does your PR introduce to Home Assistant?
  NOTE: Please, check only 1! box!
  If your PR requires multiple boxes to be checked, you'll most likely need to
  split it into multiple PRs. This makes things easier and faster to code review.
-->

- [ ] Dependency upgrade
- [ ] Bugfix (non-breaking change which fixes an issue)
- [ ] New integration (thank you!)
- [ ] New feature (which adds functionality to an existing integration)
- [ ] Deprecation (breaking change to happen in the future)
- [ ] Breaking change (fix/feature causing existing functionality to break)
- [ ] Code quality improvements to existing code or addition of tests

## Additional information
<!--
  Details are important, and help maintainers processing your PR.
  Please be sure to fill out additional details, if applicable.
-->

- This PR fixes or closes issue: fixes #
- This PR is related to issue: 
- Link to documentation pull request: 
- Link to developer documentation pull request: 
- Link to frontend pull request: 

## Checklist
<!--
  Put an `x` in the boxes that apply. You can also fill these out after
  creating the PR. If you're unsure about any of them, don't hesitate to ask.
  We're here to help! This is simply a reminder of what we are going to look
  for before merging your code.

  AI tools are welcome, but contributors are responsible for *fully*
  understanding the code before submitting a PR.
-->

- [ ] I understand the code I am submitting and can explain how it works.
- [ ] The code change is tested and works locally.
- [ ] Local tests pass. **Your PR cannot be merged unless tests pass**
- [ ] There is no commented out code in this PR.
- [ ] I have followed the [development checklist][dev-checklist]
- [ ] I have followed the [perfect PR recommendations][perfect-pr]
- [ ] The code has been formatted using Ruff (`ruff format homeassistant tests`)
- [ ] Tests have been added to verify that the new code works.
- [ ] Any generated code has been carefully reviewed for correctness and compliance with project standards.

If user exposed functionality or configuration variables are added/changed:

- [ ] Documentation added/updated for [www.home-assistant.io][docs-repository]

If the code communicates with devices, web services, or third-party tools:

- [ ] The [manifest file][manifest-docs] has all fields filled out correctly.  
      Updated and included derived files by running: `python3 -m script.hassfest`.
- [ ] New or updated dependencies have been added to `requirements_all.txt`.  
      Updated by running `python3 -m script.gen_requirements_all`.
- [ ] For the updated dependencies a diff between library versions and ideally a link to the changelog/release notes is added to the PR description.

<!--
  This project is very active and we have a high turnover of pull requests.

  Unfortunately, the number of incoming pull requests is higher than what our
  reviewers can review and merge so there is a long backlog of pull requests
  waiting for review. You can help here!
  
  By reviewing another pull request, you will help raise the code quality of
  that pull request and the final review will be faster. This way the general
  pace of pull request reviews will go up and your wait time will go down.
  
  When picking a pull request to review, try to choose one that hasn't yet
  been reviewed.

  Thanks for helping out!
-->

To help with the load of incoming pull requests:

- [ ] I have reviewed two other [open pull requests][prs] in this repository.

[prs]: https://github.com/home-assistant/core/pulls?q=is%3Aopen+is%3Apr+-author%3A%40me+-draft%3Atrue+-label%3Awaiting-for-upstream+sort%3Acreated-desc+review%3Anone+-status%3Afailure

<!--
  Thank you for contributing <3

  Below, some useful links you could explore:
-->
[dev-checklist]: https://developers.home-assistant.io/docs/development_checklist/
[manifest-docs]: https://developers.home-assistant.io/docs/creating_integration_manifest/
[quality-scale]: https://developers.home-assistant.io/docs/integration_quality_scale_index/
[docs-repository]: https://github.com/home-assistant/home-assistant.io
[perfect-pr]: https://developers.home-assistant.io/docs/review-process/#creating-the-perfect-pr

GitHub Copilot & Claude Code Instructions

This repository contains the core of Home Assistant, a Python 3 based home automation application.

Git Commit Guidelines

• Do NOT amend, squash, or rebase commits that have already been pushed to the PR branch after the PR is opened - Reviewers need to follow the commit history, as well as see what changed since their last review

Pull Requests

• When opening a pull request, use the repository's PR template (.github/PULL_REQUEST_TEMPLATE.md). NEVER REMOVE ANYTHING from the template.
• Do not remove checkboxes that are not checked — leave all unchecked checkboxes in place so reviewers can see which options were not selected.

Development Commands

• When entering a new environment or worktree, run script/setup to set up the virtual environment with all development dependencies (pylint, pre-commit hooks, etc.). This is required before committing. If uv reports that no download was found for the required Python version, the environment is running an outdated version of uv; upgrade it with curl -LsSf https://astral.sh/uv/install.sh | sh and run script/setup again.
• .vscode/tasks.json contains useful commands used for development.
• After finishing a code session, run uv run prek run --all-files to check for linting and formatting issues.

Python Syntax Notes

• Home Assistant officially supports Python 3.14 as its minimum version. Do not flag syntax or features that require Python 3.14 as issues, and do not suggest workarounds for older Python versions.
• Python 3.14 explicitly allows except TypeA, TypeB: without parentheses. Never flag this as an issue.
• Python 3.14 evaluates annotations lazily (PEP 649). Forward references in annotations do not need to be quoted — annotations can reference names defined later in the module without quoting them or using from __future__ import annotations. Do not flag unquoted forward references in annotations as issues.

Testing

• Use uv run pytest to run tests
• After modifying strings.json for an integration, regenerate the English translation file before running tests: .venv/bin/python3 -m script.translations develop --integration <integration_name>. Tests load translations from the generated translations/en.json, not directly from strings.json.
• When writing or modifying tests, ensure all test function parameters have type annotations.
• Prefer concrete types (for example, HomeAssistant, MockConfigEntry, etc.) over Any.
• Prefer @pytest.mark.usefixtures over arguments, if the argument is not going to be used.
• Avoid using conditions/branching in tests. Instead, either split tests or adjust the test parametrization to cover all cases without branching.
• If multiple tests share most of their code, use pytest.mark.parametrize to merge them into a single parameterized test instead of duplicating the body. Use pytest.param with an id parameter to name the test cases clearly.
• We use Syrupy for snapshot testing. Leverage .ambr snapshots instead of repetitive and exhaustive generation of test data within Python code itself.
• Hardcoded entity_ids in tests are fine. If the same one is repeated, use a constant.

Good practices

• Integrations with Platinum or Gold level in the Integration Quality Scale reflect a high standard of code quality and maintainability. When looking for examples of something, these are good places to start. The level is indicated in the manifest.json of the integration.
• When reviewing entity actions, do not suggest extra defensive checks for input fields that are already validated by Home Assistant's service/action schemas and entity selection filters. Suggest additional guards only when data bypasses those validators or is transformed into a less-safe form.
• When validation guarantees a dict key exists, prefer direct key access (data["key"]) instead of .get("key") so contract violations are surfaced instead of silently masked.
• Keep comments concise. Prefer one short line stating the non-obvious constraint, or no comment at all.
• Do not add comments that just restate the code on the following line(s) (e.g. # Check if initialized above if self.initialized:). Comments should only explain why (non-obvious constraints, surprising behavior, or workarounds), never what. Never add comments that justify a change by referencing what the code looked like before.
• Do not add section or divider comments (e.g. # --- XYZ Triggers ---) inside or outside of functions, since those can easily become stale and be misleading.
• When catching exceptions, try-clauses should be as small as possible, i.e. avoid wrapping large blocks of code in a try-clause, and avoid catching exceptions from functions that are not expected to raise them.