How LegionEdge Built a Real-Time AI Prototyping Platform with Together Code Sandbox

When Sean Filimon and his co-founder set out to build LegionEdge, they weren’t new to engineering. They met running Minecraft servers, migrated into Roblox, and eventually built deep backend systems for high-scale web infrastructure. So when they saw how limited today’s AI prototyping tools were—slow, shallow, and disconnected from real software life cycles—they didn’t just build another playground.

They built the future of app development: a full lifecycle platform where anyone can go from design → prototype → code → deploy—all powered by AI and ready for production.

But they didn’t do it alone. To move fast without burning resources building GPU infra and microVM orchestration, they partnered with Together AI.

The Problem: AI Prototyping Tools Aren’t Built for Builders

Most no-code or AI-assisted tools are optimized for speed, not scale. They work fine for demos, but fall apart when users want to ship real software.

“We were seeing tools like Bolt.new and Cursor make interesting progress,” Sean said, “but when you try to build something full-stack or production-ready, you hit a wall.”

LegionEdge had a bold vision:

• Cloud development environments with sub-2s cold starts
• Live previews and persistent file snapshots
• Prompt-driven project generation that turns ideas into real code
• Real-time team collaboration across the editor and dashboard
• Instant deployment via first-party integrations (e.g. Vercel)

The problem? Building all of that from scratch would have taken months of engineering time—and valuable focus away from the product itself.

The Solution: Together Code Sandbox

Instead of reinventing infrastructure, Sean’s team turned to Together’s platform, using:

• Together Code Sandbox to power the entire CDE experience
• Together’s infrastructure to manage inference and runtime execution
• Persistent file storage and snapshots, managed via Together and Convex
• DeepSeek models (coming soon) to power server-side code completions

“We originally planned to build our own VM and preview system,” Sean explained. “But Together made that unnecessary and saved us at least 3 months of work.”

LegionEdge uses Together Code Sandbox SDK across multiple surfaces—not just in the editor, but also in the dashboard and project preview system. That integration means users can prototype and persist work in real-time, with the responsiveness of local development and the reliability of the cloud.

“It’s honestly so simple, a 5-year-old could use it,” Sean said. “The Together Code Sandbox SDK is that clean. It gave us developer-friendly primitives out of the box—and let us focus on building the product.”

Powered by Code Sandbox: Real-Time Cloud Dev, Without the Pain

At the heart of LegionEdge’s UX is Together Code Sandbox, which provides:

• Real-time collaborative editing in Firecracker microVMs
• Cold starts in ~2s (vs. 16s on other platforms)
• Previews, template cloning, and environment mirroring
• File storage and snapshotting

LegionEdge delivers a fully interactive cloud development experience where users can write code, preview changes in real time, and collaborate across shared environments. Powered by Together Code Sandbox, each session runs in lightweight Firecracker microVMs with cold starts under 2 seconds—ensuring the platform feels as responsive as local development.

Developers can start from a growing set of templates—like single-page React apps or multi-file TypeScript projects—and clone or modify them within seconds. Each project is automatically persisted using TCSB’s snapshotting system, which stores file state and allows users to revisit, update, or resume work without losing context.

These capabilities aren’t just nice to have—they’re foundational to LegionEdge’s value prop: live editing, zero local setup, and team-ready collaboration, all from a browser.

A Reliable Partner with Developer-Friendly Tools

Together played a key role in helping LegionEdge meet their launch timeline, offering both a solid infrastructure foundation and responsive support.

• The Together SDK made it easy to integrate cloud development environments without heavy lifting.
• Slack-based support enabled fast troubleshooting and helped the team stay unblocked during development.
• The partnership allowed LegionEdge to stay focused on product innovation instead of building and maintaining complex infra.

“Together’s support has been amazing,” Sean shared. “It made us feel confident moving forward and helped us deliver faster.”

The Results

By partnering with Together AI, LegionEdge accelerated their launch by more than three months. Instead of spending engineering cycles building custom infrastructure for VM orchestration, persistent storage, and preview rendering, they were able to focus entirely on product development.

The result is a lightning-fast developer experience. Cold start times have been reduced to around two seconds—far outperforming other common platforms, which can take up to 16 seconds—enabling real-time iteration and responsiveness that feels local.

Thanks to this foundation, LegionEdge now supports full lifecycle prototyping in the cloud. Users can go from dashboard to editor to live preview within a single environment, without any local setup or installation required.

Looking ahead, LegionEdge is preparing to launch GPU-powered code completions using Together’s DeepSeek models and inference infrastructure—enabling fast, context-aware suggestions that enhance developer productivity across the entire workflow.

Now in Early Access

LegionEdge is now live in Early Access for technical founders and AI builders.

“If you’re thinking about building your own infrastructure—don’t.” Sean said. “You’ll get farther, faster, by partnering with Together AI.”

About Together Code Sandbox

Together Code Sandbox lets you spin up secure, fast microVMs in the cloud—no setup needed. With instant cold starts, snapshots, and built-in previews, it’s the easiest way to run and iterate on code at scale.

Explore Together Code Sandbox