OpenAIFastHigh

GPT-6.1 Terra

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.

1,858/9,290credits

input / output · per 1M tokens

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)

Run it right now

Test this model instantly in the Console Playground — no code required

Use with AI Assistant

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llms.txtllms.txt ↗

Model Specifications

Context Window

1.1M

tokens

Max Output

128K

tokens

Training Cutoff

2026-06

Compatible SDK

OpenAI

Capabilities

Vision

Function Calling

Streaming

JSON Mode

System Prompt

Token Pricing (per 1M tokens)

Token Type	Credits	USD Equivalent
Input Tokens	1,858	$1.24
Output Tokens	9,290	$6.19
Cached Tokens	92.9	$0.06

* 1,500 credits ≈ $1 (actual charges may vary based on usage)

Quick Start

curl -X POST "https://api.core.today/llm/openai/v1/chat/completions" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer cdt_your_api_key" \
  -d '{
  "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
}'

Parameters

Parameter	Type	Required	Default	Description
`messages`	array	Yes	-	Array of message objects with role and content
`model`	string	Yes	gpt-6.1-terra	Model identifier
`max_completion_tokens`	integer	No	4096	Maximum tokens in response (up to 128000). Note: use max_completion_tokens, not max_tokens
`reasoning_effort`	string	No	medium	Reasoning effort level: none, low, medium, high, xhigh, or max nonelowmediumhighxhighmax
`service_tier`	string	No	auto	Processing tier. 'fast' bills token charges at 2x; settled on the tier the response reports. Ultrafast is not available on this model autodefaultfast
`stream`	boolean	No	false	Enable Server-Sent Events streaming

Examples

Visual Reasoning

Read a chart image and explain the trend with GPT-6.1 Terra

curl -X POST "https://api.core.today/llm/openai/v1/chat/completions" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer cdt_your_api_key" \
  -d '{
  "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

curl -X POST "https://api.core.today/llm/openai/v1/chat/completions" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer cdt_your_api_key" \
  -d '{
  "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
}'

Tips & Best Practices

1Half 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

2For tool calling use the Responses API (POST /llm/openai/v1/responses) — Chat Completions is supported on this model without tool calling

3reasoning_effort accepts none, low, medium (default), high, xhigh and max — use none for the lowest latency and cost

4Keep prompts under 272K input tokens where possible — above that the whole request bills at 2x input and cache / 1.5x output

5Cache 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

6Fast 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