The conversation around “Agentic” engineering often falls into a trap of false binaries: Cloud vs. Local, Server-Side vs. Client-Side, AI-FDE vs. Antigravity.
This is the wrong way to look at it.
For elite engineering teams, the goal isn’t to choose a side. It’s to build a Unified Stack where each agent operates in its native domain, connected by the single source of truth: The Foundry Ontology.
The Ontology: The Silver Bullet
What makes this hybrid architecture possible (and powerful) is the standard definition of data and logic provided by the Ontology.
- AI-FDE (The Platform Specialist) reads the Ontology to understand dependencies, pipelines, and security boundaries.
- Antigravity (The Project Generalist) reads the Ontology to scaffold applications, generate SDKs, and validate user interfaces.
Because they speak the same language (Object Types, Actions, Functions), you can seamlessly pass work between them.
The Roles: Specialist + Generalist
The most effective workflow we’ve seen looks like a relay race:
- Antigravity (Local): You start on your laptop. Antigravity acts as your Personal Project Folder 2.0. It scaffolds a React app, mocks up the UI, and helps you iterate on the frontend logic with zero latency. It “sees” what the user sees via the browser.
- AI-FDE (Platform): When it’s time to change the backend, you hand off to AI-FDE. It operates inside the container, running the heavy migrations, checking downstream impacts, and ensuring strict compliance.
- Unified: The result is a system that is both secure by default (thanks to AI-FDE) and delightful to use (thanks to Antigravity’s UI tuning).
Why You Need Both
- If you only use AI-FDE: You get perfect backend compliance, but miss the automated UI feedback loop. The visual nuances of the application need to be feed by the end user via screenshots.
- If you only use Antigravity: You get a great local dev experience, but you risk drifting from platform governance or hitting walls with complex pipeline migrations or limitations (e.g. you can't create an Ontology Action with the current version of Palantir MCP)
Go Deeper
The “Unified Stack” is powerful, but it implies mastering two distinct environments. There are subtle technical differences in Functions, Operation Modes, and Capabilities that determine which tool you should reach for in any given moment.
We’ve compiled a detailed technical breakdown (including a side-by-side comparison matrix) and guide you through our set up in our latest Playbook.
Check our Playbook: Agentic Engineering on Foundry