Spline on Thursday released Version 2 of its 3D design platform, a full rebuild that allows external coding agents to modify live, editable scenes directly inside the editor. The standout feature, called Spline MCP Server, connects the editor to Claude Code, Cursor, Codex, Google Antigravity, and VS Code, enabling those tools to work within an active Spline project while preserving full editability. The update also introduces Spline's own AI agent, capable of constructing and modifying scenes from text prompts.
The MCP server ships as part of Spline's redesigned desktop application for macOS and Windows—it doesn't function in browsers, and there's no separate server package to download. When the desktop app launches, it scans for compatible clients and adds the server to their configuration files automatically. Developers then reboot the AI client and issue normal prompts. For instance, if someone asks Claude Code to generate a floating island, Claude converts that into structured MCP tool calls that Spline routes to an open 3D editor tab, executing them against the live document. If no appropriate file is open, the application creates one. The model can inspect what's already present in the scene before making changes, allowing it to navigate between visual design and code on the canvas, tap Spline's AI tools for new models or images, and continue working on interface or game logic. All modifications remain within the Spline project, so designers receive the live scene rather than a flattened image or static mesh and can keep editing immediately after the agent finishes.
According to the report, Spline's internal AI agent uses the same method, with each alteration treated as a standard editor operation that shows up in the undo history and synchronizes to everyone else working in the file. The setup gains utility when an agent needs to switch between the application and its interface, since Spline V2 places the 3D editor and Hana behind the same MCP connection and manages the handoff automatically—routing scene work to the 3D editor and interface changes to Hana. In Hana, the agent can convert an existing component into an editable frame and then carry visual changes back into the application code, using stable references on exported elements to locate the correct spot in the source. That round trip has constraints because Hana supports only a subset of HTML and CSS built around flexbox, so complex markup and framework-specific components may require reconciliation with existing code rather than direct replacement. For 3D work, a developer can construct or alter a scene through Claude Code, refine it visually in Spline, and export it for the web in formats from Vanilla JavaScript and Three.js to React, Next.js, and React Three Fiber—those exports default to WebGPU and fall back to WebGL when needed.
The connection remains on the developer's machine, with the server bound to 127.0.0.1 and shielded by an origin allowlist that rejects arbitrary web pages, and developers can select which clients gain access through Spline's MCP settings. Spline states that prompts and scene data exchanged with its MCP server stay between the desktop app and the connected client, though if the agent uses one of Spline's AI generation features, that work still runs in the cloud just as it would if initiated manually from the editor. Multiple agent sessions can connect to the same editor, but Spline's documentation doesn't clarify how teams can attribute or review individual MCP changes before publishing a shared file. The MCP server operates while the scene is still under construction, giving the agent direct access to the editable document so it can understand its structure and make changes before export—MCP acts as a control interface for the editor, while Spline continues to manage the visual project and render changes as they occur. The integration extends beyond visual design alone: when a professional environment demands both conceptual iteration and technical precision at the same rhythm, removing the handoff friction between creative tools and development workflows becomes the constraint that determines velocity.