Software Engineering (SE) is shifting from AI-assisted development (SE 2.0) to Agentic Software Engineering (SE 3.0), where autonomous AI agents act as collaborators. This technical briefing establishes the foundations of a disciplined SE 3.0 practice. We synthesize: (1) a large-scale characterization of agent activity in the wild based on the AIDev dataset, (2) an empirical study of 567 Claude Code pull requests across 157 open-source software projects, and (3) the Structured Agentic Software Engineering (SASE) framework that reframes actors, processes, artifacts, and tools. Attendees will leave with evidence-backed mental models, evaluation patterns for agent-authored PRs, and a practical vocabulary (e.g., agent command environment and agent execution environment) for designing trustworthy human-agent workflows.