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