In my years working as a programmer, I’ve often encountered situations where using a full-featured IDE like VSCode wasn’t ideal—whether working on a small codebase, accessing servers via SSH, or simply preferring a lightweight environment.
While VSCode is a powerful tool, I’ve never been particularly enthusiastic about how it’s managed. Despite being open-source at its core, key features—like the SSH extension—are tightly controlled, making it difficult for forks or alternative versions to fully replicate its functionality.
For a long time, there seemed to be little demand for alternatives. But with the rise of AI-assisted development, things are changing. Various projects have begun forking VSCode to integrate AI capabilities natively. This shift has prompted Microsoft to respond, selectively open-sourcing some extensions, such as GitHub Copilot, though much of the ecosystem remains closed.
Still, forking VSCode comes with a series of problems to consider, and, even if there wasn’t any cost, should the future of coding—especially in the AI era—be tied so closely to a single platform, managed by a single company?
In this article, I want to explore an alternative: a project that takes some open source parts of VSCode, supports its open-source extensions, and integrates AI natively—offering a truly open and forward-thinking development experience.
Eclipse Theia IDE – An Open, Adaptable Foundation for Modern Development
Eclipse Theia IDE stands as a modern, open-source, and highly extensible Integrated Development Environment. Its core identity extends beyond that of a mere standalone IDE; it is purposefully designed as a robust platform for building custom tools and specialized IDEs. This fundamental distinction is crucial, as it positions Theia not just as another development environment for individual users, but as a strategic asset for organizations seeking to embed development capabilities within their own products or to craft highly specialized internal tooling. This approach directly facilitates the integration of custom AI providers, as building such a bespoke AI-driven tool necessitates a flexible and adaptable foundational platform.
Theia’s architecture is rooted in web technologies, adhering to a client-server model where the user interface typically runs in a browser or a browser-like environment, while the backend manages intensive tasks such as data storage, computation, and integration with external systems. This design enables versatile deployment across various environments, including web browsers, desktop applications (facilitated by frameworks like Electron), and cloud-based setups. The web-based nature offers significant advantages in terms of scalability, allowing resources to be dynamically adjusted in the cloud to accommodate varying workloads. It also simplifies rollouts and updates, making deployment more straightforward compared to traditional setups, and enhances accessibility, empowering developers to work from any location with internet access. This architectural choice future-proofs development environments, enabling them to seamlessly adapt to evolving deployment models, such as remote development and cloud workspaces, while ensuring broad accessibility unconstrained by specific platforms. Furthermore, it inherently simplifies the integration of distributed AI services, which often operate in a client-server or distributed fashion.
Theia reuses key components from popular tools, notably the Monaco editor from VS Code, ensuring a familiar and performant code editing experience. This modular architecture allows for profound customization and the creation of tailored development experiences that cater precisely to specific domain needs. The core value proposition of Theia lies in its ability to serve as a flexible foundation, empowering organizations to develop specialized tooling without the prohibitive effort of building core functionalities from scratch.
The Strategic Advantage: Open Source and Vendor Neutrality
Eclipse Theia IDE distinguishes itself through its commitment to being a fully open-source platform, entirely free from proprietary components. It operates under the commercially friendly Eclipse Public License and its development and governance model are explicitly vendor-neutral and community-driven, overseen by the reputable Eclipse Foundation. This structure cultivates a diverse range of contributions, promoting continuous innovation and reliability, and critically, ensuring that the project’s direction is not dictated or controlled by a single entity or corporate agenda.
In contrast, while Visual Studio Code (specifically Code OSS, its open-source foundation) also originates from an open-source project, its evolution is primarily driven and controlled by Microsoft. This means that users and organizations adopting VS Code strategically rely on Microsoft for its ongoing direction and feature set. Moreover, VS Code incorporates several proprietary, closed-source components and features, such as Live Share, remote container support, and the integration of GitHub Copilot within the VS Code product (distinct from Code OSS). This trend towards closed-source features within VS Code is noted as potentially continuing. Conversely, Theia’s feature set is entirely community-driven, allowing contributors to directly influence its evolution, and all implementations remain completely open.
The benefits derived from Theia’s vendor neutrality are substantial. Organizations utilizing Theia effectively avoid vendor lock-in, thereby retaining complete control over their chosen toolset and deployment options. This independence is paramount for long-term strategic planning and for mitigating risks associated with potential policy changes or shifts in business models from a single vendor. The fully open-source nature of Theia provides unparalleled transparency into its codebase, enabling thorough auditing and customization. This ensures compliance with internal security and governance policies, a particularly critical aspect when dealing with sensitive data and the integration of AI capabilities. Furthermore, the vendor-neutral governance model actively encourages broader participation and ensures that the platform evolves in response to the diverse needs of its community, rather than being shaped by a singular corporate agenda.
Theia is explicitly positioned as an “open alternative to VS Code” and an “open alternative to Github Copilot, Cursor etc.”. This narrative extends beyond a mere feature comparison; it centers on the critical aspects of trust and control. The recurring emphasis on “full control” over various facets of the development environment and AI integration directly addresses and counters the concerns regarding “lack of transparency” and “limited customizability” often associated with proprietary AI solutions. For enterprises, especially those managing sensitive intellectual property or operating under stringent regulatory compliance frameworks, Theia’s open and vendor-neutral stance offers a significant advantage in terms of data governance, security, and strategic independence. This cultivates a foundation of trust that proprietary, black-box solutions often struggle to provide.
The fact that Theia’s feature set is “community-driven” and that “contributors can influence it easily” , coupled with the assurance that the project is “not controlled by a single stakeholder” , highlights a key differentiator. While VS Code benefits immensely from Microsoft’s substantial contributions, Theia’s strength lies in its collective adaptability. If a feature is open source within Code OSS, Theia can often adopt it with relative ease. However, Theia also develops and integrates its own unique features, such as flexible toolbars, detachable views, and support for multiple extension registries, which are not available in VS Code. This collective influence means Theia is inherently more responsive to the diverse and often niche needs of its adopter community, particularly those engaged in building highly specialized tools. This implies a more democratic and resilient development trajectory, less susceptible to the shifting priorities or business models of a single corporation.
Extensibility and Ecosystem: Seamless VS Code Extension Compatibility
Theia IDE’s strategic design allows it to achieve remarkable compatibility with the vast ecosystem of VS Code extensions. This compatibility is rooted in Theia’s reuse of core components from VS Code, most notably the Monaco editor, which forms the foundation of its code editing experience. Critically, Theia implements the same extension API as VS Code, enabling it to seamlessly host and utilize nearly all existing VS Code extensions. This provides immediate access to a rich array of features, including comprehensive language support (via the Language Server Protocol, LSP), robust debugging capabilities, and a wide variety of development tools. While Theia typically operates with a lag of approximately one month in implementing new API updates released by VS Code, this delay rarely poses a practical impediment, as extensions generally do not adopt new APIs instantaneously.
By default, Theia integrates with the Open VSX registry, which serves as an open-source alternative to the proprietary VS Code Marketplace. A significant differentiator for Theia is its inherent flexibility to connect to multiple extension registries, including self-hosted ones. This capability is particularly valuable for corporate environments that necessitate stringent control over their extension ecosystem to meet specific security or compliance requirements. This feature directly addresses enterprise security and governance needs, allowing organizations to curate, vet, and manage extensions before they are deployed, thereby reducing supply chain risks and ensuring adherence to internal policies.
Beyond its compatibility with VS Code extensions, Theia provides its own powerful, modular extension mechanisms, designed for deeper customization and the creation of highly tailored tools. These mechanisms include:
- Theia Extensions: These are integrated at compile time and offer complete access to Theia’s internal APIs through dependency injection. They are primarily utilized for building custom products and for implementing features that are not feasible or are restricted by the more limited VS Code extension API. The core components of Theia itself are modularly built using Theia extensions.
- Theia Plugins: These function similarly to VS Code extensions but provide additional access to frontend APIs specific to Theia.
- Headless Plugins: These operate in a dedicated backend process, interacting exclusively with Theia’s backend services, without a direct connection to the frontend.
This multi-layered extensibility empowers tool builders to adapt or even remove almost any element within Theia, including default workbench components such as menus and views, a level of modification not achievable through the standard VS Code extension API.
Theia’s architectural design provides a significant value proposition by offering the best of both worlds: immediate access to a vast and mature ecosystem of VS Code extensions for common functionalities, coupled with the architectural flexibility to construct highly specialized, domain-specific tools that transcend the capabilities of a generic IDE. This dual approach significantly reduces development effort by enabling the reuse of existing components while simultaneously facilitating the creation of unique value for niche markets or specific internal enterprise requirements.
The repeated emphasis that Theia is “not a fork of VS Code” is a critical distinction. Forking a project typically implies a divergence that necessitates continuous, high-maintenance synchronization with the original codebase. Theia’s modular architecture, despite reusing certain components, means it can evolve independently while maintaining compatibility. This architectural choice is crucial for ensuring Theia’s long-term viability and adaptability. It signifies that Theia is not merely a derivative but a distinct, robust platform engineered for sustained evolution and deep integration, thereby serving as a more stable and reliable foundation for custom projects with extended lifespans.
Revolutionizing Development with Custom AI Providers
The Eclipse Theia ecosystem is at the forefront of integrating artificial intelligence into development environments through its innovative Theia AI framework. Theia AI is an open-source framework specifically engineered to seamlessly integrate Large Language Models (LLMs) into custom tools and IDEs. Built upon this framework, this development environment, serves as a tangible demonstration of Theia AI’s capabilities, enhancing developer productivity with intelligent, transparent, and controllable AI assistance. This initiative directly addresses the escalating demand for open, adaptable, and transparent AI development tools, offering a compelling alternative to the opacity and inflexibility often associated with proprietary AI solutions.
Theia AI provides unparalleled control and flexibility in AI integration, empowering developers and organizations across several critical dimensions:
Freedom to Choose and Integrate Any LLM: Theia AI offers complete freedom in LLM selection, allowing developers to connect to any AI model, whether it is cloud-hosted (e.g., OpenAI, Anthropic, Azure), self-hosted, or fully local (e.g., Ollama, Llama-File, Hugging Face). This flexibility ensures that users are not constrained by specific vendors, subscription models, or pricing structures. It allows for a strategic balance between reasoning capabilities, response time, and cost requirements, tailored to specific domain needs and user preferences. Furthermore, this open approach facilitates the immediate integration of new models as the AI landscape continues its rapid evolution, ensuring that tools built on Theia remain cutting-edge.
Customizable AI Interactions, Prompts, and Agent Behaviors: Developers retain full control over orchestrating the prompt engineering flow, enabling them to tailor prompts precisely to their unique workflows and define custom agentic behaviors. Theia AI supports the design of specialized AI agents equipped with domain-specific knowledge, capable of interacting natively with tool components and automating workflows through custom tool actions. Users can directly edit messages within the chat UI, which creates new conversation branches for iterative refinement, and configure workspace-specific custom agents, ensuring AI assistance is highly relevant to the active project. This comprehensive control over AI interactions positions Theia AI as a solution for complex enterprise AI strategies, where fine-grained management of data, model choice, user experience, and compliance is paramount, moving beyond a “black box” AI solution. It enables organizations to build AI capabilities that are deeply embedded and aligned with their unique domain requirements.
The Model Context Protocol (MCP) for Integrating AI with External Tools and Contextual Data: The Model Context Protocol (MCP) serves as a standardized bridge, conceptually akin to the Language Server Protocol (LSP) for programming languages. MCP enables AI applications to tap into diverse data sources and external tools (such as Git, GitHub, databases, testing frameworks, and internet search) without requiring custom API integrations for each. This protocol is instrumental in creating tailored AI agents that can access and utilize contextual data directly from the development environment, significantly enhancing automation and interoperability within the workflow. MCP is a critical enabler for scalable and maintainable AI-powered development environments, fostering a modular approach to AI integration where AI agents can seamlessly interact with various tools and data sources without constant re-engineering, thereby accelerating the adoption of sophisticated AI workflows in complex environments.
SCANOSS Integration for Open-Source License Compliance in AI-Generated Code: The AI-powered Theia IDE includes a built-in SCANOSS integration that automatically scans AI-generated code for open-source licensing compliance. This feature is vital for helping developers identify potential open-source components within generated code and ensuring adherence to licensing requirements, effectively mitigating legal and operational risks associated with incorporating AI-generated code into projects.
The practical applications and benefits of AI-powered workflows within Theia are extensive. Theia AI powers intelligent coding agents, providing features like AI-powered code completion, terminal assistants for context-aware command suggestions, and architect chat agents for project-specific queries. Theia Coder, an integrated AI coding agent, facilitates what is termed “Dibe Coding,” which involves delegating tasks, clearly describing intentions, and reviewing AI-generated changes for efficient code generation and modification. This signals that AI within Theia is not merely adding features but enabling a fundamental paradigm shift in how software development is performed, moving towards a deeper, more integrated human-AI collaboration.
Tool builders can design AI agents specifically customized for their domain’s knowledge and workflows, leveraging components for function calling, context retrieval, and integrating external behaviors or knowledge graphs. These agents can perform tasks such as file searches and execute predefined tasks (e.g., building projects, running tests), enabling more autonomous behavior and verification of code changes. Interactive AI chats allow agents to engage users in dynamic, multi-step interactions, requesting clarifications and guiding them through complex workflows, making even intricate AI-driven processes more intuitive.
Theia AI also addresses critical privacy, security, and enterprise compliance concerns. It prioritizes user control and transparency, allowing developers to fine-tune AI behavior and maintain full visibility into AI processes and data exchange. The framework supports local or self-hosted models, which is crucial for environments where sensitive data cannot be transmitted to third-party cloud services. Organizations can precisely control where AI data processing occurs, facilitating on-premises solutions and adherence to strict compliance standards. The ability to pin applications to specific model versions further ensures predictable performance and behavior, which is essential for projects requiring regulatory compliance or consistent outputs.
The concept of “AI-Powered Theia IDE” and the goal to “transform domain-specific environments and specialized IDEs into fully AI-native tools” indicates that Theia is not merely integrating AI as an add-on. Instead, it is enabling the creation of tools where AI is a fundamental, deeply embedded component of the development process. This positions Theia as a leader in the shift towards truly intelligent development environments, where AI is seamlessly integrated into core workflows, offering significant competitive advantages for organizations adopting this advanced approach.
The following table outlines the dimensions of control offered by Theia AI:
| Dimension | Description |
| Control Over User Experience | Design custom AI experiences, including flexible chat interfaces, inline suggestions, or entirely custom UI elements. Embed AI capabilities into any part of the tool, such as custom editors, configuration panels, or standard IDE components like terminals and code editors. |
| Control Over AI Agents, Tool Context, and Functions | Create domain-specific AI agents with specialized knowledge. Automate workflows via custom tool actions. Manage context with a powerful prompt system. Enable direct AI interaction with the tool through robust function-calling support. |
| Control Over Language Models and Business Model | Connect to any LLM of choice (cloud-based, self-hosted, or fully local). Balance reasoning capabilities, response time, and cost requirements. Design custom pricing models, from subscriptions to pay-as-you-go or fully offline solutions. |
| Control Over Integrations and Data | Seamlessly integrate AI into the tool ecosystem with full control over APIs, databases, and services. Support for the Model Context Protocol (MCP). Determine precisely what data is shared with AI services to accommodate privacy requirements and ensure compliance. Includes SCANOSS integration for open-source license compliance. |
Integrating regolo.ai in theia IDE
Theia IDE itself represents a different way of developing for those who use VSCode as code editor. Still, it being fairly new, means its AI capabilities are still in alpha state, but that doesn’t mean they do not look extremely interesting.
If you do desire to test them, and to integrate regolo.ai with Theia’s ability to chat with LLMs and write AI agents, you can do this by going into Theia’s preferences and activate the “Enable AI” preference.
Then, you’ll click on the “open settings (JSON)” button in the upper right of the preferences page and add the following line of JSON into the main bracket:
"ai-features.openAiCustom.customOpenAiModels": [
{
"model": "Llama-3.3-70B-Instruct",
"url": "https://api.regolo.ai",
"apiKey": "<your_api_key>",
"developerMessageSettings": "system"
}
]Code language: JSON / JSON with Comments (json)You can change the “model” parameter to use a different LLM supported by regolo, or you can change “developerMessageSettings” based on your needs. For any other personalization, you can refer to the docs.
Then you can open the “AI Chat View” and select your model into the “Open Agent settings”
Once you’ve selected everything, you can work with regolo just as you would’ve with any provider available by default.
Conclusion
Eclipse Theia IDE occupies a distinct and strategic position in the landscape of modern development tools. It is established as an open-source, vendor-neutral platform designed not just for use as a generic IDE, but fundamentally for building highly customized IDEs and specialized tools. This differentiates it from extensible editors like VS Code, which, while powerful, operate under a single corporate stewardship and incorporate proprietary components. Theia’s dual extensibility—its ability to leverage the vast VS Code extension ecosystem while simultaneously offering deeper, native customization capabilities—provides a unique advantage, allowing organizations to benefit from existing functionalities while tailoring solutions to their precise, often niche, requirements.
The introduction of Theia AI further amplifies this unique value proposition, heralding a transformative potential for development workflows. It provides unparalleled control over LLM integration, enabling organizations to choose any AI model—cloud-based, self-hosted, or local—and to meticulously design AI agent behaviors and prompt engineering flows. The adoption of the Model Context Protocol (MCP) is a significant advancement, standardizing the integration of AI with external tools and contextual data, thereby streamlining complex AI-powered workflows. Furthermore, the built-in SCANOSS integration addresses critical open-source license compliance concerns associated with AI-generated code, enhancing trust and mitigating risk.
Theia represents a strategic choice for organizations seeking to circumvent vendor lock-in, ensure data privacy, and construct highly tailored development environments that align precisely with their specific domain requirements and stringent compliance needs. It champions the values of openness, transparency, and community-driven innovation, presenting a compelling counterpoint to the growing prevalence of proprietary AI solutions in the development space. The ability of Theia AI to allow the community to rapidly contribute integrations for new models and providers provides a significant agility advantage in the fast-moving AI landscape, ensuring its continued relevance and innovation.
Ultimately, Theia empowers developers and tool builders to define their AI strategy, create truly AI-native workflows, and adapt to the rapidly evolving AI landscape on their own terms. We hope you will like using regolo with its modular, protocol-based architecture, which positions it as a future-proof foundation for the next generation of intelligent, collaborative development tools, where AI is not just an add-on feature but an integral, deeply embedded component of the development process.
If you had any problems integrating Regolo in Theia, if you want generic support for Regolo, or if you want to become part of our community, you can join our discord server or send us an email through our website.