OpenAIFastHigh

GPT-5.6 Terra

The balanced tier of OpenAI's GPT-5.6 family (GA July 2026). Terra offers near-flagship quality at half the price of Sol, with a 1M token context window, 128K max output tokens, and cached inputs at a 90% discount.

4,645/27,870credits

input / output · per 1M tokens

Balanced tier of the GPT-5.6 family

1M token context window

128K max output tokens

Knowledge cutoff: February 2026

Cached input pricing (90% discount)

Adjustable reasoning effort

Function calling and native vision support

Run it right now

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

Use with AI Assistant

Copy usage instructions for Claude, ChatGPT, or other AI

llms.txtllms.txt ↗

Model Specifications

Context Window

tokens

Max Output

128K

tokens

Training Cutoff

2026-02

Compatible SDK

OpenAI

Capabilities

Vision

Function Calling

Streaming

JSON Mode

System Prompt

Token Pricing (per 1M tokens)

Token Type	Credits	USD Equivalent
Input Tokens	4,645	$3.10
Output Tokens	27,870	$18.58
Cached Tokens	464	$0.31

* 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-5.6-terra",
  "messages": [
    {
      "role": "system",
      "content": "You are a helpful customer support assistant."
    },
    {
      "role": "user",
      "content": "My webhook deliveries started failing with 403 yesterday. What should I check?"
    }
  ],
  "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-5.6-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, or xhigh nonelowmediumhighxhigh
`temperature`	float	No	1.0	Sampling temperature (0-2)
`stream`	boolean	No	false	Enable Server-Sent Events streaming

Examples

Production Assistant

Balanced quality and cost for high-volume assistant traffic

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-5.6-terra",
  "messages": [
    {
      "role": "system",
      "content": "You are a helpful customer support assistant."
    },
    {
      "role": "user",
      "content": "My webhook deliveries started failing with 403 yesterday. What should I check?"
    }
  ],
  "max_completion_tokens": 2000
}'

Code Review

Review a diff with near-flagship reasoning at half the cost

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-5.6-terra",
  "messages": [
    {
      "role": "system",
      "content": "You are a strict code reviewer. Report bugs first."
    },
    {
      "role": "user",
      "content": "<unified diff>"
    }
  ],
  "reasoning_effort": "high",
  "max_completion_tokens": 4000
}'