# GPT-5.6 Terra

> GPT-5.6 Terra is the middle of the GPT-5.6 line, and for most production traffic it is the one that should be running. It keeps everything structural about Sol — the 1.05M-token context window, vision input, tool calling, configurable reasoning, persisted reasoning, prompt caching — and asks $0.20 / $1.20 per 1M tokens against Sol's $0.40 / $2.00.

Canonical: https://routemux.com/openai/gpt-5.6-terra
Provider: OpenAI

## Key facts

| Field | Value |
| --- | --- |
| Model ID | openai/gpt-5.6-terra |
| Official model ID | gpt-5.6-terra |
| Context window | 1.1M |
| Max output | 128K |
| Input modalities | text, image |
| Output modalities | text |
| Capabilities | Vision, Reasoning, Tool Calling, Coding, Cache, Paid Cache Write, Strip Responses Summary Input |
| Upstream release | 2026-07-09 |
| Availability | available |

## Pricing

- RouteMux input: $0.2 per 1M tokens
- RouteMux output: $1.2 per 1M tokens
- Official input: $2 per 1M tokens
- Official output: $12 per 1M tokens
- Cache read: $0.02 per 1M tokens
- Cache write: $0.25 per 1M tokens
- Saving vs official: 90%
- Official price source: openai_x0.10, verified 2026-08-24

Billing is prepaid wallet, charged per successful request only.

## API access

Base URL: https://api.routemux.com

Supported protocols:

- openai_chat
- openai_responses
- anthropic_messages

## What is GPT-5.6 Terra

GPT-5.6 Terra is the middle of the GPT-5.6 line, and for most production traffic it is the one that should be running. It keeps everything structural about Sol — the 1.05M-token context window, vision input, tool calling, configurable reasoning, persisted reasoning, prompt caching — and asks $0.20 / $1.20 per 1M tokens against Sol's $0.40 / $2.00.

Through RouteMux that works out to $0.20 per 1M input tokens against OpenAI's $2, and $1.20 against $12 on output. Three protocols are available: OpenAI Chat Completions, OpenAI Responses, and Anthropic Messages.

The practical way to use the family is to default to Terra and escalate. Because all three models share the same context window and the same request shape, escalation is a one-line change, and you find out quickly whether a task actually needed Sol or just needed a better prompt.

## Key capabilities

- **Same structure as Sol** — 1.05M context, vision, tools, reasoning controls and caching are identical — only price and depth differ.
- **Built for steady production load** — Priced so that a high-traffic assistant or coding agent can run on it continuously rather than as a treat.
- **Escalation is one line** — Moving a hard request up to Sol means changing the model string, nothing else.
- **Three protocols** — OpenAI Chat, OpenAI Responses, and Anthropic Messages all route here.

## Other variants in this family

- GPT-5.6 Sol (`openai/gpt-5.6-sol`)
- GPT-5.6 Luna (`openai/gpt-5.6-luna`)
- GPT-5.4 mini (`openai/gpt-5.4-mini`)
- GPT-5.4 (`openai/gpt-5.4`)
- GPT-5.5 (`openai/gpt-5.5`)

## Sources

- [OpenAI — Models](https://platform.openai.com/docs/models)
- [OpenAI — Pricing](https://openai.com/api/pricing/)

_Content reviewed by Jerry Fan on 2026-08-22._