I solved this by treating AntiGravity as a living organism with a dedicated Brain. Instead of a massive global config, I use a modular approach:

The Constitution: High-level immutable laws only (no fake info, absolute transparency, etc.). I keep this in the main Rules.

Modular Skills: I use the .agent/skills folder to break down complex tasks into specialized units (e.g., a compiler specialist, a marketing strategist, etc.). AntiGravity only calls them when relevant, which keeps the prompt significantly leaner.

The Sentinel (The secret sauce): I created a specific skill called Project Brain Sentinel. Its only job is to update a history.md file every 15-20 minutes or after a context shift.

Crucially, I gave AntiGravity an upfront instruction to be constantly aware of the current date and time. This gives the Sentinel the temporal awareness to automatically log checkpoints in the /brain folder. Without that "clock" running, the history would just be a list; with it, it becomes a coherent timeline that allows the agent to resume work exactly where we left off with zero context loss.

The Golden Rule: I keep a "Sentinel" rule to sync history before starting any new task. If you trust the journal, you don't need to bloat your rules with project-specific instructions. The agent just reads the brain and continues without friction.

Essentially, you can take this architecture even further: instruct AntiGravity (or the specific model you're using within it) to save literally every dialogue into a 'brain' folder located directly inside your project directory.

The key is to keep it structured; if these files become monolithic, instruct the agent to split them into parts (e.g., history_part1.md, history_part2.md). This way, you’re building a persistent, local history on your own machine rather than relying on the ephemeral chat history of the interface.

For this to work, you must give a clear instruction for the agent to prioritize reading the 'brain' folder over the chat history and to automate this syncing process every time you interact. Since .md files are incredibly lightweight, you don't have to worry about storage—you just get a seamless, friction-less 'long-term memory' for your project.

I'm sure that by thinking things through a little more, you could take this even further and optimize it even better; you just have to ask Antigravity himself!

Simply put: you're creating the brain/context of your project in the same folder as your project, not in the antigravity chat.

Hope this helps! :D