GPT-5.1 Thinking

GPT-5.1 Thinking

Quick answer: GPT-5.1 Thinking is the extended chain-of-thought reasoning variant of GPT-5.1. By spending additional compute on internal reasoning tokens before generating a response, it achieves higher scores on hard math (AIME/GPQA) and complex coding problems. It is priced at a premium over standard GPT-5.1 to reflect the additional inference compute.

What GPT-5.1 Thinking Is

GPT-5.1 Thinking continues OpenAI's "o-series" tradition of extended reasoning models, now unified within the GPT-5.1 family. Rather than a separate model family (as o1, o3 were), Thinking is a mode of GPT-5.1 that allocates a larger thinking budget before responding — analogous to Claude's extended thinking mode.

For Benchgen workloads, Thinking mode excels at tasks requiring careful planning: multi-step debugging, architecture design, formal proof-like reasoning over code, and research synthesis. For standard coding agent loops, the standard GPT-5.1 or GPT-5.1 Codex are usually more cost-efficient.

Specifications

Related Models & Benchmarks

• Compare: GPT-5.1 · GPT-5.1 Codex · Claude Opus 4.6
• Benchmarks: SWE-bench Verified

Last updated 2026-06-19.

Pricing

Available via OpenAI API. Refer to OpenAI pricing for GPT-5.1 Thinking.

GPT-5.1 Thinking vs Alternatives

GPT-5.1 Thinking vs Instant: same BrowseComp + GPQA-Diamond but 3.5x higher HLE (23.68% vs 6.80%) — extended thinking pays off on frontier reasoning.

Frequently Asked Questions

Scores from Benchgen evaluations. Last updated 2026-07-24.