# Season 1 — December 2025 (Winter Holiday Edition)

Canonical Web URL: https://adventofagents.com/2025/12/

- **Day 01: [Launch Initiative](https://adventofagents.com/2025/12/01?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day01)** ([.md](https://adventofagents.com/2025/12/01.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day01)) — 25 days. Zero to Production-Ready AI Agents on Google Cloud.
- **Day 02: [Hello World with YAML](https://adventofagents.com/2025/12/02?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day02)** ([.md](https://adventofagents.com/2025/12/02.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day02)) — Build your first AI agent with Gemini 3 in under 5 minutes without writing a single line of code.
- **Day 03: [Gemini 3 + ADK](https://adventofagents.com/2025/12/03?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day03)** ([.md](https://adventofagents.com/2025/12/03.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day03)) — Build a powerful AI Agent using Gemini 3 and ADK with native support for Google Search grounding, computer use, and real-time streaming.
- **Day 04: [Source-Based Deployment](https://adventofagents.com/2025/12/04?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day04)** ([.md](https://adventofagents.com/2025/12/04.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day04)) — Deploy your agents directly from source code with Agent Engine - no more serialization headaches.
- **Day 05: [Production Observability](https://adventofagents.com/2025/12/05?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day05)** ([.md](https://adventofagents.com/2025/12/05.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day05)) — Agent Starter Pack includes production-grade observability with zero config. Cloud Trace, Log Analytics, and BigQuery integration out of the box.
- **Day 06: [🧑‍💻 ADK ready in Antigravity, Gemini CLI, Cursor, Firebase Studio and more](https://adventofagents.com/2025/12/06?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day06)** ([.md](https://adventofagents.com/2025/12/06.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day06)) — Building agents shouldn't require an hour of environment configuration. If you use the Agent Starter Pack you already have IDE magnet context baked in for the Agent Development Kit (ADK).
- **Day 07: [LLMs Can Execute Code: Autonomous Problem Solving](https://adventofagents.com/2025/12/07?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day07)** ([.md](https://adventofagents.com/2025/12/07.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day07)) — Explore how LLMs can not only write but also execute, debug, and refine code autonomously, transforming them into powerful problem solvers.
- **Day 08: [Effective Context Management with ADK Layers](https://adventofagents.com/2025/12/08?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day08)** ([.md](https://adventofagents.com/2025/12/08.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day08)) — ADK Context design thesis: context as a compiled view
- **Day 09: [⏪ Undo buttons for your Agents](https://adventofagents.com/2025/12/09?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day09)** ([.md](https://adventofagents.com/2025/12/09.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day09)) — Building an "Edit Message" or "Regenerate" feature shouldn't require complex database migrations. In the ADK, time travel is built-in.
- **Day 10: [Big Context ≠ Better Memory](https://adventofagents.com/2025/12/10?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day10)** ([.md](https://adventofagents.com/2025/12/10.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day10)) — Long-running agent sessions face two enemies: latency and "lost in the middle" syndrome. The ADK solves this with Context Caching and Context Compaction.
- **Day 11: [Google Managed MCP](https://adventofagents.com/2025/12/11?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day11)** ([.md](https://adventofagents.com/2025/12/11.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day11)) — Connect Agents to Google Services with Managed MCP.
- **Day 12: [Multimodal Agents with Gemini Live API](https://adventofagents.com/2025/12/12?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day12)** ([.md](https://adventofagents.com/2025/12/12.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day12)) — Explore ADK Bi-Directional Streaming: A visual guide to real-time multimodal AI agent development with WebSockets and Gemini Live.
- **Day 13: [Interactions API](https://adventofagents.com/2025/12/13?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day13)** ([.md](https://adventofagents.com/2025/12/13.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day13)) — Interactions API marks a fundamental shift from stateless text generation to stateful, autonomous workflows.
- **Day 14: [Connecting Agents with A2A](https://adventofagents.com/2025/12/14?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day14)** ([.md](https://adventofagents.com/2025/12/14.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day14)) — Connect agents across teams, frameworks, and languages with the Agent2Agent (A2A) Protocol. ADK makes implementing A2A simple.
- **Day 15: [Introducing A2UI](https://adventofagents.com/2025/12/15?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day15)** ([.md](https://adventofagents.com/2025/12/15.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day15)) — Discover A2UI (Agent-to-User Interface), an open project that enables agents to stream dynamic, generative UIs as JSONL payloads, decoupling UI definition from rendering and breaking the ceiling of traditional chat interfaces.
- **Day 16: [LangGraph + A2A](https://adventofagents.com/2025/12/16?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day16)** ([.md](https://adventofagents.com/2025/12/16.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day16)) — Build LangGraph agents with full A2A capabilities using Agent Starter Pack. Your agent becomes instantly discoverable by other agents.
- **Day 17: [Gemini 3 Flash is here!](https://adventofagents.com/2025/12/17?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day17)** ([.md](https://adventofagents.com/2025/12/17.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day17)) — Google's fastest model just got smarter with configurable thinking levels and granular controls.
- **Day 18: [Cloud API Registry + ADK](https://adventofagents.com/2025/12/18?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day18)** ([.md](https://adventofagents.com/2025/12/18.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day18)) — The biggest friction in enterprise agent development isn't the model—it's the tools. Vertex AI Agent Builder now integrates with Cloud API Registry, providing a centralized tool repository.
- **Day 19: [Register to Gemini Enterprise](https://adventofagents.com/2025/12/19?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day19)** ([.md](https://adventofagents.com/2025/12/19.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day19)) — Register your agent to Gemini Enterprise! 🌐 and make it discoverable to everyone in your organization, right alongside Google's built-in agents.
- **Day 20: [A2A Extensions: The Flexible Sidecar for Custom Data](https://adventofagents.com/2025/12/20?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day20)** ([.md](https://adventofagents.com/2025/12/20.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day20)) — The Agent-to-Agent (A2A) protocol relies on a strict format, but real-world complexity often requires unique data. A2A Extensions provide a "Sidecar" pattern for custom data without breaking backward compatibility.
- **Day 21: [Kaggle Capstone Winners Highlight](https://adventofagents.com/2025/12/21?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day21)** ([.md](https://adventofagents.com/2025/12/21.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day21)) — 🏆 The Hall of Fame: Meet the Winners
- **Day 22: [Security & Guardrails](https://adventofagents.com/2025/12/22?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day22)** ([.md](https://adventofagents.com/2025/12/22.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day22)) — Prompt Engineering is not a Security Strategy. Asking an LLM nicely to "please ignore PII" is not governance; it's wishful thinking.
- **Day 23: [Durable, Resilient Agents with Google ADK + Restate](https://adventofagents.com/2025/12/23?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day23)** ([.md](https://adventofagents.com/2025/12/23.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day23)) — Most agents are fragile. Durable Execution with Google ADK and Restate ensures your agent never loses context, survives crashes, and can pause execution for days.
- **Day 24: [A2A-ify Anything](https://adventofagents.com/2025/12/24?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day24)** ([.md](https://adventofagents.com/2025/12/24.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day24)) — Take any ADK or LangGraph sample and launch it with A2A on top. Layer A2A capabilities onto existing agents with a single flag.
- **Day 25: [🎉 Grand Finale: Mission Accomplished!](https://adventofagents.com/2025/12/25?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day25)** ([.md](https://adventofagents.com/2025/12/25.md?utm_source=adventofagents&utm_medium=markdown&utm_campaign=adventofagents_s1_2025&utm_content=day25)) — Congratulations! You've successfully completed the 25-day Advent of Agents journey.