Overview
Union Alpha is a multimodal model built for research, coding, and agentic workflows, while delivering frontier-level performance across a broad range of general-purpose tasks. Union Alpha is a stealth model....
Our take
Union Alpha is primarily suited for those developing agent-style workflows, given its support for tool and function calling. Unlike alternatives such as Claude or ChatGPT, which are often accessed directly, this model is free to use via the OpenRouter API, though its availability and rate limits are dependent on that upstream provider. Its 262,144-token context window is substantial, and the inclusion of vision capabilities means it can process image inputs, broadening its utility beyond text-only models. Ideal for developers or researchers requiring a multimodal model for integration into custom applications, particularly those focused on agentic tasks, but less so for general users seeking a standalone chat interface.
How Union Alpha stacks up
Among the 384 chatbots & llms tools in our directory, it ranks #231 of 370 on quality (7.6/10), 5% below the 370-tool average of 8.0, and it's one of the free-to-use options in the category.
Union Alpha in depth
Union Alpha, built by Stealth, sits in the chatbots & llms space and is completely free to use. Our editors rate it 7.6 out of 10 based on capability, ecosystem and value. It handles a context window of 262,144 tokens.
On the feature side, Union Alpha brings 262,144-token context window, vision (image input) and tool / function calling. These are the capabilities that most shape day-to-day use and separate it from thinner alternatives.
Its biggest strength is completely free to use via the openrouter api, while the main trade-off to weigh is that availability and rate limits depend on the upstream provider. Keep both in mind when deciding whether it fits your workflow.
Union Alpha is most often chosen for research and writing. If that matches your goals, it's a strong candidate to shortlist.
Key features
- ✓262,144-token context window
- ✓Vision (image input)
- ✓Tool / function calling
Pricing
Pros
- +Completely free to use via the OpenRouter API
- +Accepts images as input (vision-capable)
- +Supports tool / function calling for agent-style workflows
Cons
- −Availability and rate limits depend on the upstream provider
Who should use Union Alpha
- →Anyone looking for a chatbots & llms tool from Stealth.
- →Teams and individuals focused on research and writing.
- →Users who want to try before they buy — there's a free tier.
- →People who value completely free to use via the openrouter api.
Who should look elsewhere
- →Those for whom availability and rate limits depend on the upstream provider is a dealbreaker.
Best for
10 Best Union Alpha Alternatives in 2026
Union Alpha is a strong chatbots & llms tool, but it is not the only option. Whether you are after a lower price, different features or a better fit for your workflow, here are the 10 best alternatives to Union Alpha, ranked and compared.
Anthropic
Claude is Anthropic's family of AI assistants, known for long-context reasoning, careful writing and strong coding…
OpenAI
ChatGPT is OpenAI's flagship conversational AI, powering hundreds of millions of weekly users across web, mobile and…
Google DeepMind
Gemini is Google's natively multimodal model family, deeply integrated across Search, Workspace, Android and the Pixel…
~deepseek
This model always redirects to the latest model in the DeepSeek Flash family.
~openai
This model always redirects to the latest model in the GPT Astra family.
~openai
This model always redirects to the latest model in the GPT Sol family.
~openai
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~openai
This model always redirects to the latest model in the GPT Luna family.
Sakana AI
Fugu Ultra v2 is the higher-performance model in Sakana AI's Fugu family.
Sakana AI
Fugu Max is the cost-performance model in Sakana AI's Fugu family. Rather than a single monolithic model, Fugu is a…
Union Alpha vs top alternatives
A side-by-side look at how Union Alpha stacks up against its closest rivals.
| Feature | Union AlphaStealth | ClaudeAnthropic | ChatGPTOpenAI | GeminiGoogle DeepMind |
|---|---|---|---|---|
| Quality score | 7.6 / 10 | 9.6 / 10 | 9.5 / 10 | 9.2 / 10 |
| Starting price | Free | $20/mo | $20/mo | $20/mo |
| Free tier | Yes — Free tier available | Yes — Free tier available | Yes — Free tier available | Yes — Free tier available |
| API input price | $0 / 1M tokens | $5 / 1M tokens | $5 / 1M tokens | $0.375 / 1M tokens |
| API output price | $0 / 1M tokens | $25 / 1M tokens | $25 / 1M tokens | $1.875 / 1M tokens |
| Speed | — | Fast | Fast | Fast |
| Context window | 262,144 tokens | 200K tokens | 128K tokens | 1M-2M tokens |
| Categories | Chatbots & LLMs | Chatbots & LLMs, Coding, Writing | Chatbots & LLMs, Coding, Writing | Chatbots & LLMs, Coding, Writing |
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Frequently asked questions
Q. Is Union Alpha free?
Yes — Union Alpha offers a free tier. Paid plans start at Free.
Q. How much does Union Alpha cost?
Union Alpha starts at Free. API usage is around $0 per 1M input tokens and $0 per 1M output tokens.
Q. What is Union Alpha best for?
Union Alpha is best suited to research and writing, within the chatbots & llms category.
Q. What are the best Union Alpha alternatives?
Popular alternatives to Union Alpha include Claude, ChatGPT, Gemini and DeepSeek: DeepSeek Flash Latest. Each trades off price, quality and ecosystem differently.
Q. Is there a free alternative to Union Alpha?
Yes. Claude, ChatGPT, Gemini offer a free tier, making them good starting points if you want to avoid an upfront subscription.
Q. Why switch from Union Alpha?
Common reasons include pricing, specific feature gaps (Availability and rate limits depend on the upstream provider), data-privacy requirements, or simply wanting a tool that fits your stack better.
How we rate AI tools
Our quality score weighs capability on real tasks, breadth of features and integrations, pricing and value, and how actively the tool is maintained. Scores are editorial guidance, not benchmarks — always trial a tool on your own workflow before committing. Pricing and features change frequently, so verify current details on the official site.
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