# GPT-6.1 Terra - Core.Today AI API

> OpenAI's GPT-6.1 Terra — a fast, efficient model of the GPT-6.1 generation for visual reasoning, precise computer use and clear, natural writing, at $1/$5 per million tokens with cached inputs at a 95% discount ($0.05/M). 1.05M token context window (up to 922K input), 128K max output tokens, text and image input. Supports Fast mode. Prompts above 272K input tokens are billed at 2x input / 1.5x output for the whole request.

- **Provider**: OpenAI
- **Model ID**: gpt-6.1-terra
- **Category**: LLM
- **Credits**: 1 per request
- **Speed**: Fast
- **Quality**: High

## Model Specifications
- **Context Window**: 1.1M tokens
- **Max Output**: 128K tokens
- **Training Cutoff**: 2026-06
- **Supported Formats**: text, json, markdown
- **Compatible SDK**: OpenAI

### Capabilities
- Vision (image input)
- Function Calling
- Streaming
- JSON Mode
- System Prompt

### Token Pricing (per 1M tokens)
- **Input Tokens**: 1,858 credits ($1.24)
- **Output Tokens**: 9,290 credits ($6.19)
- **Cached Tokens**: 92.9 credits ($0.06)

## Features
- Terra tier of the GPT-6.1 generation — fast and efficient
- 1.05M token context window (up to 922K input tokens)
- 128K max output tokens
- Knowledge cutoff: June 1, 2026
- Cached input pricing (95% discount)
- Adjustable reasoning effort (none to max, default medium)
- Text and image input, structured outputs, streaming
- Tool calling through the Responses API
- Fast mode (service_tier)

## Use Cases
- Visual reasoning over screenshots, charts and documents
- Computer-use and tool-using agents (Responses API)
- Clear, natural writing and editing
- Cost-efficient long-context processing up to 922K input tokens
- Repeated context with cached inputs (RAG, codebases)

## API Endpoint

Base URL: https://api.core.today
Endpoint: POST /llm/openai/v1/chat/completions

## Authentication
Header: Authorization: Bearer YOUR_API_KEY

Note: LLM endpoints use OpenAI-compatible format with Authorization Bearer token.

## Input Parameters

### Required
- **messages**: array - Array of message objects with role and content
- **model**: string (default: gpt-6.1-terra) - Model identifier

### Optional
- **max_completion_tokens**: integer (default: 4096) - Maximum tokens in response (up to 128000). Note: use max_completion_tokens, not max_tokens
- **reasoning_effort**: string (default: medium) - Reasoning effort level: none, low, medium, high, xhigh, or max
  Options: none, low, medium, high, xhigh, max
- **service_tier**: string (default: auto) - Processing tier. 'fast' bills token charges at 2x; settled on the tier the response reports. Ultrafast is not available on this model
  Options: auto, default, fast
- **stream**: boolean (default: false) - Enable Server-Sent Events streaming

## Examples

### Visual Reasoning
Read a chart image and explain the trend with GPT-6.1 Terra
```json
{
  "model": "gpt-6.1-terra",
  "messages": [
    {
      "role": "user",
      "content": [
        {
          "type": "text",
          "text": "What trend does this chart show? Answer in three sentences."
        },
        {
          "type": "image_url",
          "image_url": {
            "url": "https://example.com/chart.png"
          }
        }
      ]
    }
  ],
  "max_completion_tokens": 2000
}
```

### Fast Writing Without Reasoning
Use reasoning_effort none for low-latency writing
```json
{
  "model": "gpt-6.1-terra",
  "messages": [
    {
      "role": "system",
      "content": "You are a concise, friendly copy editor."
    },
    {
      "role": "user",
      "content": "Rewrite this release note so a non-engineer can follow it: ..."
    }
  ],
  "reasoning_effort": "none",
  "max_completion_tokens": 1000
}
```

## Response Format
```json
{
  "id": "chatcmpl-abc123",
  "object": "chat.completion",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "Response text here"
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 100,
    "completion_tokens": 50,
    "total_tokens": 150
  }
}
```

## Tips
- Half the price of GPT-6.1 Sol ($1/$5 vs $2/$10 per M) with the same 1.05M context and 128K output — start here and move up to Sol only when the task needs it
- For tool calling use the Responses API (POST /llm/openai/v1/responses) — Chat Completions is supported on this model without tool calling
- reasoning_effort accepts none, low, medium (default), high, xhigh and max — use none for the lowest latency and cost
- Keep prompts under 272K input tokens where possible — above that the whole request bills at 2x input and cache / 1.5x output
- Cache writes bill at 1.25x the input rate ($1.25/M) — implicit caching writes by default, so most of a large first prompt is billed as a cache write, then reads are 95% off
- Fast mode (service_tier: fast or priority) bills token charges at 2x and is settled on the tier the response reports, so a request downgraded to standard is billed at the standard rate

## Documentation
https://developers.openai.com/api/docs/models/gpt-6.1-terra