GPT-5.6 Terra

GPT-5.6 Terra is the balanced tier of OpenAI's GPT-5.6 series, designed for workloads that weigh intelligence against cost in everyday coding, reasoning, and agentic tasks.

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input · usd / 1m tok

$2.00

output · usd / 1m tok

$12.00

context window

1.05mtokens

modalities · in → out

pricing

base api ratesusd per 1m tokens

input: $2.00over 272k · $4.00
output: $12.00over 272k · $18.00
cache read: $0.20over 272k · $0.40
cache write · default ttl: $2.50over 272k · $5.00

brackets are by input tokens per request: a request over a threshold is billed at that bracket's rates for all of its tokens. cache creation can have a separate charge.

providers

Different companies host GPT-5.6 Terra. Impossibl routes your request intelligently and handles failover automatically when a provider is down.

Azure OpenAI
OpenAI

specifications

takes text and image in, gives text outopenai/gpt-5.6-terra

creatorOpenAI
model typeText generation
context window1,050,000 tokens
maximum outputnot published
input
takes text and image in, gives text out
outputtext
tool callingnot verified
releasedjul 9, 2026
endpoint/v1/chat/completions

unknown means the public catalog does not establish that fact. a model's documented capabilities can differ from what a particular api supports. see the model documentation for integration details.

try it · your prompt, this model, live

# responses API
import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["IMPOSSIBL_API_KEY"],
    base_url="https://api.impossibl.com/v1",
)

resp = client.responses.create(
    model="openai/gpt-5.6-terra",
    input="▌",
)
print(resp.output_text)

edit the prompt, then run

# responses API
import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["IMPOSSIBL_API_KEY"],
    base_url="https://api.impossibl.com/v1",
)

resp = client.responses.create(
    model="openai/gpt-5.6-terra",
    input="▌",
)
print(resp.output_text)

edit the prompt, then run

benchmarks

intelligence index

42.3#10 of 90 models on the gateway

coding index76.7#6 of 60
agentic index43.7#15 of 49
omniscience0.1#39 of 86
gpqa92.5%#20 of 88
humanity’s last exam42.9%#15 of 89
terminal-bench v2.188.0%#5 of 57

GPQA92.5%
Terminal-Bench v2.188.0%
Tau286.3%
Harvey LAB85.2%
AA-LCR83.0%
MMMU-Pro80.7%
IFBench71.2%
AutomationBench Partial59.6%
Terminal-Bench Hard57.6%
SciCode55.0%
ITBench51.0%
Humanity’s Last Exam42.9%
Tau Banking40.2%
APEX-Agents38.9%
Terminal-Bench v4.035.4%
Multilingual LCR31.7%
CritPt30.0%
GDP.pdf All-pass24.0%

Intelligence Index42.25
Omniscience Index0.05
GDPval Elo1476.96
coding index (API)76.7
agentic index (API)43.7
intelligence index (API)42.3

view source ↗all source data and breakdowns (json) ↗

each configuration is listed separately; these evaluations describe the tested model configuration, and performance and costs can differ on impossibl. unmeasured scores are omitted and api values keep their source units. last checked 2026-09-10.

compare GPT-5.6 Terra with other models

frontier labs and open weights, best-ranked firstusd / 1m tok · in / out

anthropic/claude-fable-5-1$10.00 / $50.00compare →
meta/muse-spark-1.3$1.25 / $4.25compare →
zai/glm-5.3$1.40 / $4.40compare →
xai/grok-4.6$2.00 / $6.00compare →

impossibl models --all →

frequently asked questions

What is GPT-5.6 Terra?

GPT-5.6 Terra is the balanced tier of OpenAI's GPT-5.6 series, designed for workloads that weigh intelligence against cost in everyday coding, reasoning, and agentic tasks. It sits between the flagship Sol and the budget Luna, roughly matching the mini tier of earlier GPT-5 families, with configurable reasoning effort.

How much does GPT-5.6 Terra cost?

GPT-5.6 Terra costs $2.00 per million input tokens and $12.00 per million output tokens through the Impossibl API. Cache reads cost $0.20 per million tokens; cache writes cost $2.50 per million tokens. These base rates apply through 272,000 total input tokens per request. Above 272,000 input tokens, the long-context rates in the pricing table apply to the whole request. All rates are in USD.

view the pricing table ↑

What is the context length of GPT-5.6 Terra?

GPT-5.6 Terra has a 1,050,000-token context window through the Impossibl API.

What inputs and outputs does GPT-5.6 Terra support?

GPT-5.6 Terra accepts text and image as input. GPT-5.6 Terra returns text.

How do I use GPT-5.6 Terra through an API?

GPT-5.6 Terra is available through the Impossibl API. Use openai/gpt-5.6-terra as the model identifier with /v1/chat/completions. The quickstart explains how to create an API key and send your first request.

follow the api quickstart →

When was GPT-5.6 Terra released?

OpenAI released GPT-5.6 Terra on July 9, 2026.

Creator release announcement ↗

this page describes GPT-5.6 Terra as listed by the impossibl public api. prices and availability come from that catalog, refreshed here every five minutes. this is an impossibl offering, not a comparison of independent hosting-provider quotes. model descriptions and release dates, where available, use the creator sources linked under the answers above.

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