GPT-5.1

Claims and evidence

• Released 12 November 2025Start of the gradual ChatGPT rollout to paid users; the API followed on 2025-11-13. ● Primary source[1]rollout paragraph [5]November 12, 2025: GPT-5.1 in ChatGPT
• Deprecated 1 October 2026 ● Primary source[4]2026-10-01: GPT-5.3-Codex, GPT-5.1, GPT-5.4-Nano
• Released in the API 13 November 2025 ● Primary source[2] [6]Nov 13 (2025)
• GPT-5.1 Pro released in ChatGPT 19 November 2025 ● Primary source[5]November 19, 2025: GPT-5.1 Pro
• Removed from ChatGPT 11 March 2026 ● Primary source[5]March 11, 2026: Retiring GPT-5.1 models [7]Retiring GPT-5.1 models (March 11, 2026)
• gpt-5.1-chat-latest shut down in the API 23 July 2026 ● Primary source[4]2026-04-22: Legacy GPT model snapshots (July 2026 shutdown)

• Status DeprecatedAPI model gpt-5.1 deprecated on 2026-10-01 with shutdown scheduled for 2027-04-01. GPT-5.1 Instant, Thinking and Pro were already removed from ChatGPT on 2026-03-11; the chat alias gpt-5.1-chat-latest was shut down on 2026-07-23. ● Primary source[4]2026-10-01: GPT-5.3-Codex, GPT-5.1, GPT-5.4-Nano
• Replaced by GPT-6 SolRecommended replacement for gpt-5.1 in the API. In ChatGPT, GPT-5.1 conversations moved to GPT-5.3 Instant, GPT-5.4 Thinking or GPT-5.4 Pro on 2026-03-11. ● Primary source[4]2026-10-01: GPT-5.3-Codex, GPT-5.1, GPT-5.4-Nano

• Successor of GPT-5OpenAI presents GPT-5.1 as an upgrade of the GPT-5 series that replaces GPT-5 Instant and GPT-5 Thinking in ChatGPT. ● Primary source[1]first paragraph [5]November 12, 2025: GPT-5.1 in ChatGPT [6]Nov 13 (2025) [8]Introduction

• Change · Reasoning OpenAI says thinking time adapts more closely to task difficulty, and GPT-5.1 Instant is the first Instant model that can decide to think before answering.Compared with GPT-5 ● Primary source[1]
• Change · Reasoning In the API the default reasoning effort is a new setting called none, where GPT-5 defaulted to medium.Compared with GPT-5 ● Primary source[6]Nov 13 (2025) [2]New no reasoning mode
• Change · Tool use OpenAI introduced apply_patch and shell tools in the API alongside GPT-5.1, plus extended prompt caching with retention of up to 24 hours.Compared with GPT-5 ● Primary source[2]
• Change · Other OpenAI describes a warmer, more conversational default tone in ChatGPT and better adherence to instructions and custom instructions.Compared with GPT-5 ● Primary source[1]

• Input text, image ● Primary source[3]Model details
• Output text ● Primary source[3]Model details
• Feature Reasoning modeReasoning effort none (default), low, medium or high in the API. ● Primary source[2]Adaptive reasoning; New no reasoning mode [3]
• Feature Function calling ● Primary source[3]Supported features
• Context window 400,000 tokensAPI model gpt-5.1 (GPT-5.1 Thinking). ● Primary source[3]Model details
• Parameters Not disclosedNot disclosed by OpenAI. No claim madeNo source
• Access consumer app, API ● Primary source[1]rollout paragraphs [2]Pricing and availability

Lineage

Variants

Related AI Radar coverage

AI Radar coverage starts in June 2026; no coverage linked yet.

All model releases from OpenAI on AI Radar →