Union Alpha is an anonymous multimodal model with a 262K-token context window and up to 131K output tokens. It accepts text and images and answers directly, without a reasoning step.
Model ID
union-alpha
Context
262K tokens
Input
Text, image
Output
Text
Capabilities
Capabilities & endpoints
Chat generation through three API formats. Each was called successfully on tokenra.io on 2026-10-23; pick one to switch the code examples.
POSThttps://tokenra.io/v1/chat/completionsTested
OpenAI SDK with base_url="https://tokenra.io/v1". Auth: Authorization: Bearer. Recommended.
POSThttps://tokenra.io/v1/responsesTested
OpenAI Responses API, same SDK and key. Text answer in output_text.
POSThttps://tokenra.io/v1/messagesTested
Anthropic SDK or Claude Code with base URL https://tokenra.io. Auth: x-api-key (or Bearer) plus anthropic-version.
Request
Request parameters
Fields for POST /v1/chat/completions. Everything listed was accepted by the model in testing.
Parameter
Type
Required
Description
model
string
Yes
The model ID to call, for example union-alpha.
messages
array
Yes
Conversation messages in order (system, user, assistant, tool). For multi-turn chat, send the earlier turns back in this array. content can be a string or an array of text and image_url parts.
stream
boolean
No
Return the answer as server-sent events. Default false.
stream_options
object
No
With {"include_usage": true}, the last chunk carries usage and an empty choices array.
max_tokens
integer
No
Upper limit for generated tokens.
max_completion_tokens
integer
No
Upper limit for all generated tokens, reasoning included. If it is too low the answer can be empty (finish_reason: "length").
temperature
number
No
Sampling temperature.
top_p
number
No
Nucleus sampling threshold. Usually tune either this or temperature.
presence_penalty
number
No
Penalises tokens that already appeared, nudging the model toward new topics.
frequency_penalty
number
No
Penalises frequent tokens to reduce repetition.
response_format
object
No
{"type": "json_object"} asks for a JSON object.
tools
array
No
Function tools the model may call (type: "function").
tool_choice
string / object
No
auto, none, required, or a specific function.
parallel_tool_calls
boolean
No
Allow several tool calls in one response.
user
string
No
Your own end-user identifier for auditing or abuse handling. It is not part of the conversation.
Not supported by this model
response_format with json_schema is not enforced: plain text came back. Use json_object and describe the fields in the prompt.
Other formats
Format
Required fields
Answer location
OpenAI Responses
model, input
output_text
Anthropic Messages
model, max_tokens, messages
content[] blocks of type text
Response
Response format
Example response
{
"id": "chatcmpl-1792766122484",
"object": "chat.completion",
"created": 1792766122,
"model": "union-alpha",
"choices": [
{
"index": 0,
"message": {
"role": "assistant",
"content": "An API gateway is the single entry point that receives client requests and routes them to the right backend service. It also handles shared concerns such as authentication, rate limiting and logging."
},
"finish_reason": "stop"
}
],
"usage": {
"prompt_tokens": 26,
"completion_tokens": 58,
"total_tokens": 84,
"prompt_tokens_details": {
"cached_tokens": 0
}
}
}
Field
Type
Description
id
string
Completion ID. Include it when you contact support.
object
string
chat.completion, or chat.completion.chunk when streaming.
created
integer
Unix timestamp in seconds.
model
string
The model that produced the answer.
choices[].message.content
string
The answer text.
choices[].message.tool_calls
array
Tool calls requested by the model, when tools were sent.
choices[].finish_reason
string
stop, length or tool_calls.
usage
object
prompt_tokens, completion_tokens, total_tokens, plus prompt_tokens_details.cached_tokens and completion_tokens_details.reasoning_tokens.
With stream: true the answer arrives as data: lines of chat.completion.chunk objects and ends with data: [DONE].
Errors
Errors & limits
Common errors
HTTP
error.code
Meaning
What to do
401
—
Missing, wrong or deleted API key. The message is Invalid token.
Check the Authorization: Bearer header and the key in the console.
400
—
The body is not valid JSON.
Fix the JSON and send Content-Type: application/json.
500
invalid_request
A required field is missing, for example messages.
Add the field named in the message. Retrying will not help.
403
insufficient_user_quota
Your balance or plan quota is used up.
Top up in the console, then retry.
503
model_not_found
Unknown model ID, or no channel serves it for your group.
Check the ID in the model list or with GET /v1/models.
429
—
Too many requests.
Back off exponentially and retry.
5xx
—
The upstream provider failed or timed out.
Retry a few times; keep the request id if it persists.
Limits and notes
Image input was tested with an image_url part that points to a public HTTPS image.
The model answers directly; responses contain no reasoning_content.
