Long agent tasks are fragile. A dropped connection, a closed laptop, or a client crash can end a session and discard hours of delegated work, along with the traces that could have improved the agent. Mirror is an open source, extensible platform for building agentic products that treats a session as a durable, portable unit of work rather than something tied to a single client or connection. This demo shows a coding agent session that survives a full client disconnect, moves between cloud and local execution mid-task, and is controlled from a terminal, web UI, GitHub, and Slack. Every session is logged at high fidelity, and the user owns those traces for debugging, auditing and fine-tuning agent behavior on their own infrastructure. This demo is aimed at researchers who want greater ownership and visibility over agent traces for evaluation and post-training.