[Phase 0.3.2] Create operator_use/guardrails/ module

[richard-devbot]

Phase

Phase 0 — Foundations | Track 0.3 — AI Principles Framework | Priority: P0

Summary

Create the guardrails module with base classes for action validation, content filtering, and policy enforcement.

What

Create operator_use/guardrails/ package:

operator_use/guardrails/
├── __init__.py          # Public API exports
├── base.py              # Abstract base classes
├── action_validator.py  # Pre-execution tool call validation
├── content_filter.py    # Post-execution output filtering
├── policy_engine.py     # Risk classification and policy decisions
└── registry.py          # Guardrail registration and lookup

Base classes:

• Guardrail — abstract base with check(context) -> GuardrailResult
• ActionValidator — validates tool calls before execution (block/allow/confirm)
• ContentFilter — filters LLM output before sending to user
• PolicyEngine — evaluates risk level of an action given context
• GuardrailResult — result object with action (allow/block/confirm), reason, severity

Integration points:

• Hook into agent tool execution loop (before tool call)
• Hook into response pipeline (before sending to user)
• Configurable per-agent (some agents may have stricter policies)

Why

This module is the backbone for all Phase 2 guardrails. Having clean base classes and a registry pattern means each guardrail is a plugin — easy to add, test, and configure independently.

Acceptance Criteria

• operator_use/guardrails/ package exists with all base classes
• ActionValidator has abstract validate(tool_name, args, context) method
• ContentFilter has abstract filter(content, context) method
• PolicyEngine has classify_risk(action) returning safe|review|dangerous
• Registry pattern for registering and looking up guardrails
• Unit tests for base classes in tests/security/test_guardrails_base.py

References

• OWASP LLM Top 10
• Design Doc: docs/plans/2026-03-29-security-ai-guardrails-performance-design.md

Blocks

All Phase 1 issues (guardrail rules registered here), All Phase 2 issues