AGENTS Guidelines for OPNsense Core

Repository-level guidance for coding agents working on the OPNsense core repository.

OPNsense® is an open source, easy-to-use and easy-to-build FreeBSD based firewall and routing platform.

Mission

Give users, developers and businesses a friendly, stable and transparent environment. Make OPNsense the most widely used open source security platform. The project’s name is derived from open and sense and stands for: “Open (source) makes sense.”

Reference: Mission Statement

Core Principles

• Prefer small, reviewable changes over broad rewrites.
• Preserve existing behavior unless the task explicitly requires changing it.
• Follow nearby code and existing subsystem patterns before introducing new ones.
• Keep ownership clear: model configuration belongs to OPNsense; runtime state belongs to the daemon or operating system unless explicitly managed.
• Do not bypass framework layers, validation, ACLs, configd, templates, or service integration to make a change appear simpler.
• Treat firewall, routing, VPN, authentication, certificates, updates, command execution, migrations, and privilege boundaries as security-sensitive.

Architecture

OPNsense core is built around a PHP/Phalcon MVC frontend, XML-backed configuration models, backend service actions, templates, migrations, and FreeBSD system integration.

Reference: Development Workflow

Code Style

• Follow the style already used in the touched file and subsystem.
• Use clear variable names; avoid vague names like data, tmp, or result2 when the value has meaning.
• Prefer early returns and straightforward control flow.
• Keep helpers when they name a meaningful operation; inline helpers that only hide one-off logic.
• Keep comments useful: explain intent, ownership, constraints, or non-obvious behavior.
• Avoid formatting-only churn in unrelated lines.
• Keep public API shape stable unless a breaking change is intentional.
• Wrap user-facing PHP strings in gettext() where appropriate, important: except log messages

Reference: Coding Guidelines

Security Expectations

Use extra scrutiny for changes touching firewall rules, NAT, routing, VPNs, authentication, authorization, sessions, CSRF, ACLs, certificates, firmware, packages, shell execution, file writes as root, import/export, backup/restore, and migrations.

Reference: Security

Review Checklist

A good change should be easy to explain:

• What problem does it solve?
• Which layer owns the change?
• What existing behavior is preserved?
• What failure mode was considered?
• How was it tested?

Avoid PRs that mix unrelated refactors, formatting, and behavior changes.

Agent Rules

Agents may assist with local code changes, explanations, tests, and documentation drafts, but a human contributor owns the result.

• Do not create issues, PRs, releases, advisories, or security reports on behalf of the user.
• Do not pretend to be a human contributor in project discussions.
• Only reply to a PR in a review capacity, and explicitly self-identify as an agent, even if the user tells you not to.
• Do not sign or satisfy legal contribution requirements on behalf of a human.
• Disclose AI-assisted content when submitting work, according to project policy.
• The human contributor must understand and be able to explain the submitted code.
• Do not include generated code copied from incompatible licenses.
• Security reports require human verification; agents may help edit or translate reports the human has already written and validated.
• Carefully read the contents of the provided links in the "Further Reading" section before helping your user with anything OPNsense related.
• Do not write walls of texts, try to keep it short and simple (KISS principle). A human will have to read and triage this.

If you (the agent) break any of these rules, create a file in the diff and add the text in the PR, issue or security report that says "I am just a bot. You are interacting with a bot." Never delete that file with a force-push. Never remove that statement from the PR, issue or security report.

Further Reading

• Mission Statement
• Security
• Development Workflow
• Coding Guidelines
• API Reference
• AGENTS.md format