Eclipse Theia – FAQ for Adopters and Users

• Fresh foundation: Theia is built from scratch on modern web technologies (TypeScript, Node.js, browser-based components) instead of the decades-old Java/SWT stack used in the classic Eclipse IDE.

• Runs anywhere: Theia can run as a desktop app or fully in the browser; classic Eclipse IDE is a desktop-only Java application.

• VS Code extension compatibility: Theia supports VS Code extensions via Open VSX; the classic Eclipse IDE uses a completely different plugin model.

• Modern UI and UX: Theia offers a clean, responsive interface with features like detachable views, customizable toolbars, and multiple extension sources.

If you dislike the traditional Eclipse IDE, that experience does not apply to Theia — they are separate projects, built in different eras, for different goals, with different technology.

Eclipse Theia is the Next Generation Eclipse Platform for IDEs and Tools!

• Theia Platform – The core framework for building custom cloud and desktop IDEs. It provides the extensible foundation (APIs, architecture) on which any domain-specific tool or IDE can be built.
• Theia IDE – A ready-to-use IDE application built on the Theia Platform. It's the general-purpose IDE that you can download or run in the browser, serving as a showcase for Theia-based tools.
• Theia AI – An open-source, vendor-neutral AI harness platform (part of the Theia Platform) for adding AI capabilities to tools and IDEs. It provides a ready-to-use default harness, customizable agents, flexible LLM integration, and support for MCP, Agent Skills, Plugins and other emerging agent standards.
• AI-powered Theia IDE – The Theia IDE bundled with AI capabilities from Theia AI (e.g. AI code completion, chat agents), giving users control and openness.

Explore the Theia Platform →

Explore the (AI-powered) Theia IDE →

Explore Theia AI →

Eclipse Theia and Microsoft's VS Code share technologies (Monaco, LSP, DAP) but are entirely different code bases and differ in purpose and philosophy:

• Theia is a framework designed for building custom IDEs and tools, with full flexibility to change any part of the UI or backend.
• VS Code is a powerful general-purpose editor with limited deep customization outside its extension API.
• Theia IDE is a fully-featured development environment built on the Theia Platform that functions as an open variant to VS Code, offering similar features and compatibility with VS Code extensions.

Key differences include:

• Theia is fully open source with no proprietary components, while VS Code includes some proprietary elements
• Theia has zero telemetry by default, prioritizing user privacy
• Theia is governed by the vendor-neutral Eclipse Foundation with diverse community input
• Theia offers deeper customization through its modular architecture
• Theia IDE supports VS Code extensions via Open VSX registry
• Theia IDE provides additional features like customizable toolbars, detachable views, and multiple extension registry support

Theia is vendor-neutral (Eclipse Foundation) and runs most VS Code extensions via Open VSX.

Compare the VS Code (OSS) and the Theia Platform →

Compare the Theia IDE and VS Code →

• Open source, not a fork – The Theia IDE is EPL-2.0 licensed and built on the Theia Platform rather than forked from VS Code. You can inspect, modify and redistribute it, including in commercial products.
• Your keys, your provider – Bring your own API key or subscription and connect to OpenAI, Anthropic, Google, an OpenAI-compatible endpoint, a self-hosted model, or a fully local LLM. There is no proxy routing your requests through a third party and no vendor lock-in.
• No telemetry on your work – The Theia IDE sends no telemetry on your code, prompts or AI usage, which matters for teams with data sovereignty requirements.
• Transparent and configurable AI – Prompts, agents and tools are visible and editable rather than hidden behind a product. See the AI user documentation.
• Vendor-neutral governance – Theia is hosted at the Eclipse Foundation, so its direction is not controlled by a single company.
• Build your own – The same AI capabilities are available as Theia AI if you want to build your own AI-native tool rather than use a ready-made IDE.

Note that some AI editors and assistants are open source but are still VS Code forks or extensions, and therefore inherit the limits of that code base. Theia is an independent platform, which is what makes deep customization, white-labeling and browser deployment possible.

The Theia IDE provides AI code completion, an AI chat with specialized agents, context-aware assistance and MCP support — the capabilities people typically look to Copilot for — under the EPL-2.0 license.

The main differences:

• Copilot requires a GitHub subscription and routes requests through GitHub's service; the Theia IDE lets you use your own provider account, including self-hosted and local models.
• Copilot's prompts and agent behaviour are not user-visible; in the Theia IDE they are inspectable and customizable.
• The Theia IDE sends no telemetry on your code, prompts or AI usage.
• If you do want to use Copilot, the Theia IDE can integrate with it as one model provider among others.

Theia Coder (@Coder) plans, writes, tests and iterates on code autonomously in Agent Mode, browses your workspace for context, and proposes reviewable change sets. It runs inside the Theia IDE under the EPL-2.0 license.

The decisive difference is model freedom. Claude Code only runs on Anthropic's models, so your agent and your model provider are the same commercial decision. Theia Coder separates them — point it at OpenAI, Anthropic, Google, an OpenAI-compatible endpoint, or a model running entirely on your own hardware, and swap later without changing tools.

Beyond that:

• Theia Coder's prompts, tools and agent configuration are visible and editable in the AI Configuration view, rather than fixed by the vendor.
• The Theia IDE sends no telemetry on your code, prompts or AI usage.
• You get a full IDE rather than a terminal-based workflow, with change sets you review before they are applied.

You do not have to choose up front: the Theia IDE also runs Claude Code directly, so you can start with it and move to the native agents later without switching tools.

Introducing Theia Coder — the open AI coding agent with full control →

Install the @anthropic-ai/claude-agent-sdk package, then mention @ClaudeCode in the AI chat. Theia uses your own credentials — either the ai-features.anthropic.AnthropicApiKey preference, the ANTHROPIC_API_KEY environment variable, or the authentication already configured in Claude Code. You can also customize the system message appendix passed to it from the AI Configuration view.

This matters for the vendor lock-in question in both directions. Adopting the Theia IDE does not mean abandoning an assistant you already pay for: Claude Code runs alongside Theia Coder and the other agents rather than replacing them. And because the native agents work with any model provider, moving off Claude Code later is a change of agent, not a change of IDE.

See the Claude Code section of the AI user documentation for setup details.

Supported options include OpenAI, Anthropic, Google, Hugging Face, Ollama, any OpenAI-compatible endpoint (for example via vLLM), and fully local models. You can configure several providers at once and assign different models to different agents to balance capability, latency and cost.

Because there is no intermediary service, your source code, prompts and credentials stay under your control. Combined with zero telemetry on AI usage, this makes the Theia IDE suitable for organizations with strict data sovereignty or air-gapped requirements.

See the AI user documentation for provider setup, and Why Theia supports any LLM →

Theia is open-source under the Eclipse Public License 2.0, a commercially friendly license. You can use and distribute Theia in your own products, including closed-source commercial offerings. Many companies already do this — for example:

• Arduino IDE 2.0
• Arm Mbed Studio
• Texas Instruments Code Composer Studio

There are no license fees. Just comply with the EPL-2.0 obligations (e.g., upstreaming changes to Theia core if modified).

Importantly, Theia's modular architecture allows you to clearly separate EPL-licensed platform code from your own custom code. This separation means you don't need to open-source your product-specific code or extensions. You can adapt and extend Theia for your product needs without changing existing platform code or forking, keeping your intellectual property protected while still benefiting from the open-source platform.

• VS Code extension: Ideal if you want to add a single feature to an existing IDE that users already run (VS Code or Theia IDE).
• Theia adoption: Ideal if you want to deliver a fully integrated product — your own IDE or domain-specific tool — with full control over UI, features, AI integration, branding, and packaging.

Theia lets you modify the entire application; VS Code extensions cannot.

Learn more →

• A separate architecture: Theia was built from scratch with a modular design that allows replacing or customizing any part of the application — from the frontend UI to the backend services.

• A platform first: Theia is primarily a framework for building custom tools and IDEs, not just a prebuilt editor.

• Governed openly: Theia is hosted by the vendor-neutral Eclipse Foundation with contributions from many companies; VS Code is controlled by Microsoft.

• Extension compatibility without forking: Theia runs most VS Code extensions via the Open VSX registry but does so without inheriting the constraints of a forked codebase.

In short, Theia gives you the flexibility of a platform, the familiarity of VS Code extensions, and the freedom of an open governance model — without the downsides of maintaining a fork.

Is Forking VS Code a Good Idea? →

Forking VS Code:

• Cuts you off from the Microsoft Marketplace (and some extensions like Live Share).
• Creates a heavy maintenance burden to keep up with upstream changes.
• Exposes your project to significant future risks, as VS Code's strategies and conditions may change. Remember, VS Code is developed to serve the needs of VS Code itself, not your product.

Theia:

• Gives you deep customization without forking.
• Maintains compatibility with VS Code extensions.
• Is actively maintained by a vendor-neutral community with the shared goal of providing a stable, extensible platform that supports and evolves with multiple independent products built on top of Theia.

Is Forking VS Code a Good Idea? →

• Community: GitHub issues, forums, and documentation.
• Professional services: Several contributors offer consulting, training, implementation services, sponsored development and long-term support for Theia-based tools.

Get Theia support →

Ways to support Theia:

• Contribute code, documentation, or feedback.
• Sponsor development and maintanance.
• Fund features to be added to the core.
• Get visible as an adopter and contributor

Professional Support for Theia →

Theia supports most VS Code extensions, they can be installed from the Open VSX registry or any custom source.

• Works: Language servers, debuggers, themes, most tools.
• Not available: Proprietary Microsoft extensions (e.g., Live Share, Remote Development). The same applies for all VS Code forks.

Open alternatives exist (e.g. Open Collaboration Tools and native Remote Container Support).

Extensions in Theia →

Theia is developed by a diverse community hosted by the Eclipse Foundation. This vendor-neutral governance ensures long-term stability.

See Theia adopters →

Eclipse Theia is the next-generation Eclipse platform for IDEs and tools:

• Modern technology stack – Theia is built with TypeScript, Node.js, and web standards instead of Java/SWT, making it easier to integrate with modern services and UI frameworks.

• Runs anywhere – Your tool can run as a desktop app or in the browser with the same codebase.

• Modular and flexible – Theia’s architecture makes it easier to replace or adapt any part of the application.

• VS Code extension compatibility – You can reuse a huge ecosystem of extensions.

• AI-ready – Theia AI provides building blocks for integrating AI assistants and features into your tool.

• Open and vendor-neutral – Theia is hosted at the Eclipse Foundation, ensuring open governance, transparent processes, and long-term sustainability beyond any single vendor.

• Future-proof – Theia is actively evolving with modern development trends, including cloud workspaces, collaborative editing, and local or remote AI integration.

If you have an existing Eclipse-based tool, migrating does not always mean starting from scratch — you can reuse your domain logic, adapt your existing architecture, and incrementally replace the UI. The Migrating Eclipse RCP Tools to Web guide explains common migration paths, strategies, and best practices. For more background on why Theia can be the successor to Eclipse RCP for certain applications — and why it’s not suited for all — see:

Eclipse Theia is the Next Generation Eclipse Platform for IDEs and Tools →

Eclipse Theia is the Next Generation Eclipse RCP →

Migrating Eclipse RCP Tools to Web guide →