---
description: Union Alpha is a multimodal model designed for research, coding, and agentic workflows. It delivers frontier-level performance across diverse general-purpose tasks.
title: Union Alpha
image: https://developers.cloudflare.com/og-docs.png
---
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# Union Alpha
Text Generation • stealth
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`stealth/union-alpha`
- Third-party
Union Alpha is a multimodal model designed for research, coding, and agentic workflows. It delivers frontier-level performance across diverse general-purpose tasks.
## Usage
```ts
const response = await env.AI.run(
'stealth/union-alpha',
{
messages: [{ content: 'What is the capital of France? Answer in one word.', role: 'user' }],
max_tokens: 16,
},
)
console.log(response)
```
```bash
curl https://api.cloudflare.com/client/v4/accounts/$CLOUDFLARE_ACCOUNT_ID/ai/v1/chat/completions \
--header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
--header "Content-Type: application/json" \
--data '{
"model": "stealth/union-alpha",
"messages": [
{
"content": "What is the capital of France? Answer in one word.",
"role": "user"
}
],
"max_tokens": 16
}'
```
```
Paris
```
```json
{
"id": "chatcmpl-mu3b7o02sf9tov9z",
"object": "chat.completion",
"model": "union-alpha",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "Paris"
},
"finish_reason": "stop"
}
],
"usage": {
"prompt_tokens": 29,
"completion_tokens": 5,
"total_tokens": 34,
"prompt_tokens_details": {
"cached_tokens": 28
},
"cost": 0
},
"gatewayMetadata": {
"keySource": "Unified"
}
}
```
## Examples
**System Guidance** — Set a helpful system role before asking a question.
```ts
const response = await env.AI.run(
'stealth/union-alpha',
{
messages: [
{ content: 'You explain technical topics in plain language.', role: 'system' },
{ content: 'What is an API? Explain it in two sentences.', role: 'user' },
],
max_tokens: 64,
},
)
console.log(response)
```
```bash
curl https://api.cloudflare.com/client/v4/accounts/$CLOUDFLARE_ACCOUNT_ID/ai/v1/chat/completions \
--header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
--header "Content-Type: application/json" \
--data '{
"model": "stealth/union-alpha",
"messages": [
{
"content": "You explain technical topics in plain language.",
"role": "system"
},
{
"content": "What is an API? Explain it in two sentences.",
"role": "user"
}
],
"max_tokens": 64
}'
```
```
An API (Application Programming Interface) is a set of rules that lets different software programs communicate with each other. For example, a weather app can use an API to request the latest forecast from a weather service.
```
```json
{
"id": "chatcmpl-mu3b7pxpj3kdi2v5",
"object": "chat.completion",
"model": "union-alpha",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "An API (Application Programming Interface) is a set of rules that lets different software programs communicate with each other. For example, a weather app can use an API to request the latest forecast from a weather service."
},
"finish_reason": "stop"
}
],
"usage": {
"prompt_tokens": 19,
"completion_tokens": 46,
"total_tokens": 65,
"prompt_tokens_details": {
"cached_tokens": 0
},
"cost": 0
},
"gatewayMetadata": {
"keySource": "Unified"
}
}
```
**Coding Example** — Ask for a short coding example.
```ts
const response = await env.AI.run(
'stealth/union-alpha',
{
messages: [
{
content: 'Write a JavaScript function that reverses a string. Include one example call.',
role: 'user',
},
],
max_tokens: 128,
},
)
console.log(response)
```
```bash
curl https://api.cloudflare.com/client/v4/accounts/$CLOUDFLARE_ACCOUNT_ID/ai/v1/chat/completions \
--header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
--header "Content-Type: application/json" \
--data '{
"model": "stealth/union-alpha",
"messages": [
{
"content": "Write a JavaScript function that reverses a string. Include one example call.",
"role": "user"
}
],
"max_tokens": 128
}'
```
````
```javascript
function reverseString(str) {
return [...str].reverse().join("");
}
// Example call:
console.log(reverseString("hello")); // "olleh"
```
````
```json
{
"id": "chatcmpl-mu3b7t0objtvuaa4",
"object": "chat.completion",
"model": "union-alpha",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "```javascript\nfunction reverseString(str) {\n return [...str].reverse().join(\"\");\n}\n\n// Example call:\nconsole.log(reverseString(\"hello\")); // \"olleh\"\n```"
},
"finish_reason": "stop"
}
],
"usage": {
"prompt_tokens": 14,
"completion_tokens": 39,
"total_tokens": 53,
"prompt_tokens_details": {
"cached_tokens": 0
},
"cost": 0
},
"gatewayMetadata": {
"keySource": "Unified"
}
}
```
**Follow-up Conversation** — Continue a short conversation with prior assistant context.
```ts
const response = await env.AI.run(
'stealth/union-alpha',
{
messages: [
{ content: 'I am planning a weekend trip to a coastal city.', role: 'user' },
{
content: 'Consider walkable neighborhoods, local food, and a nearby beach.',
role: 'assistant',
},
{ content: 'What should I prioritize when choosing where to stay?', role: 'user' },
],
max_tokens: 96,
},
)
console.log(response)
```
```bash
curl https://api.cloudflare.com/client/v4/accounts/$CLOUDFLARE_ACCOUNT_ID/ai/v1/chat/completions \
--header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
--header "Content-Type: application/json" \
--data '{
"model": "stealth/union-alpha",
"messages": [
{
"content": "I am planning a weekend trip to a coastal city.",
"role": "user"
},
{
"content": "Consider walkable neighborhoods, local food, and a nearby beach.",
"role": "assistant"
},
{
"content": "What should I prioritize when choosing where to stay?",
"role": "user"
}
],
"max_tokens": 96
}'
```
```
Prioritize **location over amenities** for a short weekend—you’ll get more out of your trip if you spend less time in transit.
- **Your main activity:** Stay near the beach for a relaxing getaway, or near the center for restaurants, sightseeing, and nightlife.
- **Walkability and transport:** Look for cafés and dinner options within walking distance, plus easy access to the airport or train station. If you’re driving, check parking costs.
- **Total
```
```json
{
"id": "chatcmpl-mu3b7wo2jrkvi2t8",
"object": "chat.completion",
"model": "union-alpha",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "Prioritize **location over amenities** for a short weekend—you’ll get more out of your trip if you spend less time in transit.\n\n- **Your main activity:** Stay near the beach for a relaxing getaway, or near the center for restaurants, sightseeing, and nightlife.\n- **Walkability and transport:** Look for cafés and dinner options within walking distance, plus easy access to the airport or train station. If you’re driving, check parking costs.\n- **Total"
},
"finish_reason": "length"
}
],
"usage": {
"prompt_tokens": 43,
"completion_tokens": 96,
"total_tokens": 139,
"prompt_tokens_details": {
"cached_tokens": 0
},
"cost": 0
},
"gatewayMetadata": {
"keySource": "Unified"
}
}
```
**Creative Writing** — Generate a compact piece of creative writing.
```ts
const response = await env.AI.run(
'stealth/union-alpha',
{
messages: [
{ content: 'Write a four-line poem about finding light after a difficult day.', role: 'user' },
],
max_tokens: 96,
},
)
console.log(response)
```
```bash
curl https://api.cloudflare.com/client/v4/accounts/$CLOUDFLARE_ACCOUNT_ID/ai/v1/chat/completions \
--header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
--header "Content-Type: application/json" \
--data '{
"model": "stealth/union-alpha",
"messages": [
{
"content": "Write a four-line poem about finding light after a difficult day.",
"role": "user"
}
],
"max_tokens": 96
}'
```
```
The weary day sank softly out of sight,
And left me searching shadows for a spark.
Then one small star unfolded into light—
Enough to lead me gently through the dark.
```
```json
{
"id": "chatcmpl-mu3b80ptkze4dltt",
"object": "chat.completion",
"model": "union-alpha",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "The weary day sank softly out of sight,\nAnd left me searching shadows for a spark.\nThen one small star unfolded into light—\nEnough to lead me gently through the dark."
},
"finish_reason": "stop"
}
],
"usage": {
"prompt_tokens": 12,
"completion_tokens": 39,
"total_tokens": 51,
"prompt_tokens_details": {
"cached_tokens": 0
},
"cost": 0
},
"gatewayMetadata": {
"keySource": "Unified"
}
}
```
## Parameters
▶messages\[]
`array`required
temperature
`number`minimum: 0maximum: 2
max\_tokens
`number`exclusiveMinimum: 0
max\_completion\_tokens
`number`exclusiveMinimum: 0
top\_p
`number`minimum: 0maximum: 1
frequency\_penalty
`number`minimum: -2maximum: 2
presence\_penalty
`number`minimum: -2maximum: 2
stream
`boolean`
▶stream\_options{}
`object`
▶tools\[]
`array`
tool\_choice
response\_format
▶modalities\[]
`array`
▶audio{}
`object`
reasoning\_effort
`string`Optional reasoning control; availability and accepted values are model-dependent.
id
`string`
object
`string`
created
`number`
model
`string`
▶choices\[]
`array`
▶usage{}
`object`
## API Schemas (Raw)
Input [Open](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/ai/models/stealth/union-alpha/schema-input.json) [Download](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/ai/models/stealth/union-alpha/schema-input.json)
Output [Open](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/ai/models/stealth/union-alpha/schema-output.json) [Download](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/ai/models/stealth/union-alpha/schema-output.json)
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## On this page
[Docs](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/)
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