What are the strengths of this model?

Provides advanced reasoning abilities Extensive 400K context understanding Latest design from OpenAI

What are the weaknesses of this model?

Non-open-source license Limited public release of specifications Closed usage environment

What are the best use cases?

Tasks requiring complex logical thinking Analysis of lengthy documents Problem-solving needing advanced reasoning

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OpenAIProprietary

GPT-5.1 Instant

Name: GPT-5.1 Instant
Price: 1.25 USD
Author: OpenAI

GPT-5.1 Instant is an inference model developed by OpenAI. It features a long 400K context window and provides advanced reasoning capabilities.

Parameters

Undisclosed

Context Window

400K

License

Proprietary

Release Date

2025-11-12

API Pricing

Input Price (per 1M tokens)

$1.25

Output Price (per 1M tokens)

Billing Mode: standard

Strengths

・Provides advanced reasoning abilities
・Extensive 400K context understanding
・Latest design from OpenAI

Weaknesses

・Non-open-source license
・Limited public release of specifications
・Closed usage environment

Use Cases

・Tasks requiring complex logical thinking
・Analysis of lengthy documents
・Problem-solving needing advanced reasoning

Deep Analysis

Release Date

November 12, 2025

Context Window

128K tokens

Max Output

16K tokens

Input Price

$1.25 / 1M tokens

Output Price

$10.00 / 1M tokens

Cache Read

$0.13 / 1M tokens

Latency (P50 TTFT)

0.6s (OpenAI), 1.2s (Azure)

Throughput (P50)

102 TPS

Strengths

・Fastest model in the GPT-5.1 family with 0.6s P50 time-to-first-token
・High throughput at 102 tokens per second for real-time applications
・Supports tool use, vision, file input, reasoning, and web search
・Available on both OpenAI and Azure with zero data retention support
・Good for high-throughput backend APIs with many concurrent requests

Weaknesses

・Limited to 16K max output tokens — not suitable for long-form generation
・Smaller context window (128K) compared to GPT-5.1 Thinking (410K)
・Higher hallucination rate than Thinking variant due to reduced reasoning
・Superseded by GPT-5.2 Chat (Instant) which offers better quality at lower cost
・Same pricing as GPT-5.1 Thinking ($1.25/$10) despite reduced capabilities

Competitor Comparison

Model	Arena	SWE	GPQA	Price
Claude Haiku 4	~1350	~45%	~72%	$0.25/$1.25 per 1M tokens
Gemini 3 Flash	~1370	~50%	~78%	$0.15/$0.60 per 1M tokens
GPT-5.2 Instant	~1400	~60%	~85%	$0.875/$7 per 1M tokens
GPT-5.1 Thinking	~1400	~74%	~88%	$1.25/$10 per 1M tokens

Overview

GPT-5.1 Instant is the fastest model in the GPT-5.1 family, optimized for low-latency responses across general-purpose tasks. Released November 12, 2025, it offers 0.6s time-to-first-token and 102 TPS throughput at $1.25/$10 per 1M tokens. It brings GPT-5.1 generation quality to real-time workloads, though it has been superseded by the cheaper and higher-quality GPT-5.2 Instant.

Benchmarks & Performance

GPT-5.1 Instant achieves 0.6s P50 TTFT on OpenAI (1.2s on Azure) with 102 tokens/second throughput. While specific benchmark scores for the Instant variant are not individually published, it is designed to trade reasoning depth for speed. The model supports tool use, vision, file input, implicit caching, and web search capabilities. It is best suited for latency-sensitive workloads where GPT-5.1 Thinking's extended reasoning is unnecessary.

Detailed Comparison

GPT-5.1 Instant has been superseded by GPT-5.2 Chat (Instant) which offers better quality at $0.875/$7 per 1M tokens (vs $1.25/$10). Compared to Claude Haiku 4 ($0.25/$1.25), it is significantly more expensive but offers better quality. Gemini 3 Flash ($0.15/$0.60) is the cheapest fast model but trails on quality. For users on the GPT-5.1 family, the Thinking variant offers much better accuracy at the same price point.

Community Feedback

GPT-5.1 Instant was popular for real-time chat applications and preprocessing pipelines during its active period. Users appreciated the fast response times and multimodal capabilities. With GPT-5.2 Chat's release at lower cost and better quality, most users have migrated. The model remains in use for existing integrations and Azure deployments where zero data retention is required.

Use Cases

Ideal for: real-time chat interfaces, streaming applications, high-throughput backend APIs, interactive search, preprocessing/classification pipelines, routing requests to specialized models, and quick Q&A. NOT suitable for: long-form content generation (16K output limit), complex reasoning tasks, long-document analysis (128K context), coding-heavy workloads, or any task requiring maximum accuracy. For new projects, GPT-5.2 Instant is recommended.

Latest News

Released November 12, 2025 alongside GPT-5.1 Thinking. The GPT-5.1 System Card Addendum was published by OpenAI. Superseded by GPT-5.2 Chat (Instant) in February 2026. Available on both OpenAI API and Azure with zero data retention support.

Sources

Analysis generated: 2026-05-24