Nebula is a local-first security assessment workbench designed for penetration testing and red teaming operations. It functions as a desktop application built with a Tauri shell (Rust) wrapping a React/TypeScript frontend and a Python FastAPI backend sidecar. The system manages security engagements, scope policies, evidence collection, and AI-assisted analysis, emphasizing operator control, auditability, and data privacy through local-first execution and content-addressed artifact storage. The architecture follows a sidecar pattern where the Python Core service handles database operations (SQLite with Alembic), containerized command execution (Kali Linux via Docker/Podman), and AI provider integration. The frontend manages the UI state and terminal sessions via WebSocket. Key data flows involve user actions triggering API calls that validate against scope policies before executing commands in isolated containers, with all outputs stored as immutable artifacts for evidence integrity. The codebase demonstrates strong engineering practices with extensive test coverage (Pytest, Vitest, Playwright), a robust diagnostic system with secret redaction, and a policy engine for deterministic scope enforcement. It supports multiple AI providers and includes features for knowledge indexing, mission orchestration, and report generation. The project is actively maintained with recent commits and zero security alerts, though it is currently in alpha release.