Thursday, November 13, 2025

GPT-5 → GPT-5.1: What’s New, What’s Better & What the Benchmarks Say

GPT-5 to GPT-5.1: Updates and Benchmarks
Note: GPT‑5.1 is an incremental upgrade to GPT‑5 focusing on user experience, conversation tone, and variant choice (Instant vs Thinking).

Introduction

OpenAI launched GPT‑5 in August 2025 with major improvements in reasoning, code generation, and multimodal capabilities. Learn more.

On November 12, 2025, GPT‑5.1 was released to refine conversational style, add personality presets, and improve UX. Read announcement.

Feature Enhancements

GPT‑5 Key Features

  • Unified routing system choosing between fast vs thinking modes.
  • Large context window (~400,000 tokens) and max output tokens ~128k.
  • New API parameters: reasoning effort, verbosity control, tool calls.
  • Improved reasoning, coding, and multimodal task support.
  • Benchmarks: biomedical NLP five-shot macro-average ~0.557 vs GPT‑4 ~0.506. Source

GPT‑5.1 Key Enhancements

  • Two named variants: Instant (fast, casual) and Thinking (deep reasoning).
  • Expanded personality/tone presets: Friendly, Candid, Nerdy, Cynical, etc.
  • Improved instruction-following, conversation naturalness, and UX.
  • Legacy GPT‑5 available for transition (~3 months).
  • Better bias handling and response stability. Source

Benchmark Highlights

Biomedical NLP (five-shot): GPT‑5 macro-average ~0.557 vs GPT‑4 ~0.506. GPT‑5.1 numbers not yet published.
Ophthalmology MCQ dataset: GPT‑5 accuracy ~0.965. GPT‑5.1 domain-specific results pending.
Coding / agentic tasks: GPT‑5-Codex 74.5% success. GPT‑5.1 expected incremental improvement.
Cost / efficiency: GPT‑5 multiple reasoning-effort levels; GPT‑5.1 variant segmentation (Instant vs Thinking) likely similar.

Summary Table: GPT‑5 vs GPT‑5.1

Feature GPT‑5 GPT‑5.1
Release Date August 7, 2025 November 12, 2025
Architecture Unified routing, large context, tool-use, multimodal Same lineage, with Instant & Thinking variants + UX/personality enhancements
Variant Names gpt-5-main, gpt-5-thinking, mini/nano GPT‑5.1 Instant, GPT‑5.1 Thinking
Conversation Style Natural, improved instruction-following “Warmer” conversations, personality options, better casual use
Benchmarks / Performance Strong gains in reasoning, coding, health Quantitative data emerging; focus on UX improvements
User-Facing Changes Router chooses variant automatically Explicit variant choice + personality presets; legacy GPT‑5 remains

Final Thoughts

GPT‑5.1 is a meaningful refinement, not a full overhaul. Biggest value: UX, personality control, and variant choice.
  • For casual users: Instant variant improves speed and conversation style.
  • For developers: test workflows; consider variant selection for speed vs depth.
  • For enterprise: improved UX, alignment, and tone may reduce human-in-loop effort.
  • Monitor cost and token usage for efficiency with variant choice.

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