GPT-5.1

GPT-5.1 is OpenAI's GPT-5 series flagship for coding and agentic tasks, with stronger reasoning, better instruction adherence, and a more natural style than GPT-5.

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input · usd / 1m tok

$1.25

output · usd / 1m tok

$10.00

context window

400ktokens

modalities · in → out

pricing

base api ratesusd per 1m tokens

input: $1.25
output: $10.00
cache read: $0.125

providers

Different companies host GPT-5.1. 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-5.1

creatorOpenAI
model typeText generation
context window400,000 tokens
maximum outputnot published
input
takes text and image in, gives text out
outputtext
tool callingnot verified
releasednov 12, 2025
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-5.1",
    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-5.1",
    input="▌",
)
print(resp.output_text)

edit the prompt, then run

benchmarks

intelligence index

24.7#65 of 108 models on the gateway

coding index49.4#44 of 64
omniscience5.4#26 of 84
gpqa87.3%#34 of 80
humanity’s last exam28.5%#45 of 87

AIME 202594.0%
GPQA87.3%
LiveCodeBench86.8%
Tau281.9%
AA-LCR80.0%
MMMU-Pro75.5%
IFBench72.9%
Terminal-Bench Hard45.5%
Humanity’s Last Exam28.5%
Tau Banking15.9%
CritPt4.9%

Intelligence Index24.74
Omniscience Index5.40
GDPval Elo825.88
coding index (API)49.4
intelligence index (API)24.7

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 2026-10-14.

compare GPT-5.1 with other models

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

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impossibl models --all →

frequently asked questions

What is GPT-5.1?

GPT-5.1 is OpenAI's GPT-5 series flagship for coding and agentic tasks, with stronger reasoning, better instruction adherence, and a more natural style than GPT-5. Its distinguishing feature is adaptive, configurable reasoning effort, including a none setting for fast non-reasoning responses.

How much does GPT-5.1 cost?

GPT-5.1 costs $1.25 per million input tokens and $10.00 per million output tokens through the Impossibl API. Cache reads cost $0.125 per million tokens. All rates are in USD.

view the pricing table ↑

What is the context length of GPT-5.1?

GPT-5.1 has a 400,000-token context window through the Impossibl API.

What inputs and outputs does GPT-5.1 support?

GPT-5.1 accepts text and image as input. GPT-5.1 returns text.

How do I use GPT-5.1 through an API?

GPT-5.1 is available through the Impossibl API. Use openai/gpt-5.1 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-5.1 released?

OpenAI released GPT-5.1 on November 12, 2025.

Creator release announcement ↗

this page describes GPT-5.1 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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