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Free preview — limited time

Frontier-level AI
for coding and research

Union Alpha is a multimodal AI model built for coding, research, and agentic workflows. It delivers frontier-level performance at zero cost during the preview period — available now on OpenRouter and OpenCode.

Try on OpenRouter See benchmarks

OpenAI-compatible API

Text + Image Multimodal input

$0 During preview

quick_start.py

from openai import OpenAI

client = OpenAI(
  base_url="https://openrouter.ai/api/v1",
)

response = client.chat.completions.create(
  model="stealth/union-alpha",
  messages=[
    {"role": "user", "content": "Refactor this repo"}
  ]
)

2.4B+

Tokens processed in 48h

74.2%

SWE-bench Verified

256K

Context window

Languages supported

Union Alpha is available on leading AI platforms

Get started

Start using Union Alpha in 3 steps

No account needed to begin

Choose a platform

OpenRouter, OpenCode, or Cloudflare AI Gateway — pick whichever fits your workflow.

Get an API key

Send your first request

Use model ID stealth/union-alpha with any OpenAI-compatible client. Supports tools and image input.

Capabilities

Frontier-level capabilities

What developers are doing with Union Alpha right now.

Feed it your entire codebase

With a 256K token context window, you can paste a full repository and get coherent multi-file refactoring without losing a single type annotation.

Debug from a screenshot

Paste a broken UI and get back the exact CSS fix. Point it at an architecture diagram for instant analysis.

Automate without glue code

Native tool-calling support plugs into Cursor, Cline, or your custom agent loop without a single adapter.

More than one brain

Behind the scenes, multiple specialized models compete on every request. A consensus layer picks the best answer before you see it.

Proven on real benchmarks

Union Alpha scores 74.2% on SWE-bench Verified and 74.0% on DeepSWE — matching models that charge $50 per million tokens.

Your code stays yours

Prompts and outputs are not used for model training. Zero data retention throughout the free preview period.

Architecture

Not one model — a consensus pipeline

Union Alpha routes your request through specialized models and synthesizes the best answer.

Speculative fan-out

Your request is sent to 3-4 specialized base models simultaneously.

Syntax verification

A fast tree-sitter validator filters hallucinated code before it reaches you.

Consensus synthesis

An aggregator model combines the best parts into a single output.

Pipeline

Parallel Mixture-of-Agents routing with syntax verification and consensus synthesis.

See benchmarks

Multi-file patches

Generates correct type annotations without dropping interface contracts.

Repository refactoring

Tracks file deletions and renames across long multi-turn sessions.

Test generation

Produces clean JSON tool calls with zero schema parse errors across 120 steps.

Coding

Frontier-level code generation with AST awareness across TypeScript, Python, Go, and Rust.

Try on OpenRouter

Screenshot debugging

Identifies visual layout bugs from UI screenshots and generates CSS fixes.

Diagram interpretation

Reads architecture diagrams, flowcharts, and technical drawings.

Document analysis

Extracts structured information from PDFs and formatted documents.

Multimodal

Process images alongside text for UI debugging, diagram analysis, and document understanding.

See capabilities

Benchmarks

How Union Alpha compares

Independent evaluation results against commercial frontier models.

Feature	Most Popular Union Alpha $0 (preview)	GPT-6 Astra $10/$50 per 1M	Claude 3.7 Sonnet $3/$15 per 1M
SWE-bench Verified	74.2%	79.4%	70.3%
DeepSWE	74.0%	79.1%	71.4%
HumanEval+	91.8%	94.2%	92.0%
MMLU-Pro	89.8%	91.2%	82.1%
Context window	256K	1M+	200K
Image input
Tool calling
Input price / 1M	$0.00	$10.00	$3.00
	Try it

Integrations

Works with your coding stack

Plug Union Alpha into the tools you already use.

Cursor

AI-first code editor with multi-file editing.

IDEs

Cline

Open-source coding agent with tool execution.

Coding Agents

Roo Code

Autonomous coding workflows with multi-step planning.

Coding Agents

OpenCode

Terminal-native coding agent for CLI workflows.

Coding Agents

OpenRouter

Multi-provider API gateway with unified interface.

Gateways

Cloudflare AI

Edge-deployed AI gateway with global reach.

Gateways

Access

How to start using Union Alpha

Free during preview. No credit card required.

Monthly Yearly Save 20%

What developers are saying

What developers are saying about Union Alpha.

"Union Alpha is a blended AI model that engages multiple language models in parallel for each request, synthesizes one answer. The coding results speak for themselves."

r/singularity

"First impressions: I could daily drive it. Free, no data training, supports images, built for agentic coding."

@blueemi99

X / Twitter

"Near GPT-6 Astra and Opus 5 performance for ~18x less. The tool-calling reliability across 120 consecutive steps is remarkable."

Cline community

Discord

"Tested both with the same prompt at highest reasoning. Union Alpha took 30 minutes and produced something I would actually ship."

@notjazii

X / Twitter

Blog

Latest updates

Analysis, benchmarks, and community findings about Union Alpha.

Analysis

Sep 16, 2026 8 min read

Introducing Union Alpha: capabilities and how to get started

A stealth model with 256K context and frontier coding scores. Community investigation traces its architecture and possible operator.

Union Alpha

Benchmarks

Sep 17, 2026 6 min read

Union Alpha scores 74.2% on SWE-bench Verified

Independent benchmarks show Union Alpha competing with models 50× more expensive. Here is the data behind the claim.

Union Alpha

Architecture

Sep 17, 2026 10 min read

MoA architecture: why consensus routing beats single-model inference

Community reverse engineering reveals a parallel Mixture-of-Agents pipeline with syntax verification. What this means for your workflow.

Union Alpha

FAQ

Frequently asked questions

Everything you need to know about Union Alpha.

What is Union Alpha?

Union Alpha is a multimodal AI model with a 256K token context window, image input, and tool calling support. It is available on OpenRouter, OpenCode, and Cloudflare AI Gateway.

Is it really free?

Yes, during the limited preview period it costs $0 on OpenRouter, OpenCode, and Cloudflare AI Gateway. No post-preview pricing has been announced yet.

Does it train on my data?

Prompts and outputs are not used for model training. Zero Data Retention is stated in the model listing on OpenRouter.

Who built Union Alpha?

Union Alpha is listed under the provider name "Stealth". The development team has chosen to remain anonymous during the preview period.

How does it compare to GPT-6 or Claude?

Independent benchmarks show SWE-bench Verified at 74.2% (vs GPT-6 Astra 79.4%, Claude 3.7 Sonnet 70.3%) and DeepSWE at 74.0%. It is competitive at a fraction of the cost.

What coding tools does it work with?

Any OpenAI-compatible client works: Cursor, Cline, Roo Code, OpenCode, and direct API calls. It supports tools, tool_choice, and response_format.

Frontier-level AI for coding and research

Start using Union Alpha in 3 steps

Choose a platform

Get an API key

Send your first request

Frontier-level capabilities

Feed it your entire codebase

Debug from a screenshot

Automate without glue code

More than one brain

Proven on real benchmarks

Your code stays yours

Not one model — a consensus pipeline

Speculative fan-out

Syntax verification

Consensus synthesis

Pipeline

How Union Alpha compares

Works with your coding stack

Cursor

Cline

Roo Code

OpenCode

OpenRouter

Cloudflare AI

How to start using Union Alpha

OpenRouter

OpenCode

Cloudflare AI Gateway

What developers are saying

Latest updates

Introducing Union Alpha: capabilities and how to get started

Union Alpha scores 74.2% on SWE-bench Verified

MoA architecture: why consensus routing beats single-model inference

Frequently asked questions

Stay updated on Union Alpha

Frontier-level AI
for coding and research