AI Model Timeline

Tracking the accelerating release frequency of frontier AI models.

GPT-5.5 Instant

OpenAI·

LLMsflagshipcloud

Overview

Default ChatGPT model, replacing GPT-5.3 Instant. API identifier 'chat-latest'. Hallucination-focused update with material gains on math and multimodal reasoning vs. its predecessor. Architecture not publicly disclosed.

Capabilities and innovations

Default ChatGPT modelAPI identifier: chat-latestMultimodal (text + image)Reduced hallucinations on high-stakes promptsTool use / function callingChatGPT default for hundreds of millions of users52.5% Hallucination Reduction vs 5.3 Instant (high-stakes, internal eval)AIME 2025 Jump 65.4 to 81.2 vs 5.3 InstantLow-latency 'Instant' tier — OpenAI states GPT-5.5 matches GPT-5.4 per-token latency in real-world serving (no AA Instant entry yet)

Benchmarks

BenchmarkScoreSource
MMMU-Pro76%vendor
MMMU-Pro 76 (vs. 69.2 for GPT-5.3 Instant) — vendor-reported.
  • GPQA Diamond: not reported by the vendor
  • Humanity’s Last Exam (no tools): not reported by the vendor
  • SWE-bench Verified: not reported by the vendor
  • SWE-bench Pro: not reported by the vendor
  • MMLU: not reported by the vendor
  • MMLU-Pro: not reported by the vendor
  • Terminal-Bench 2.x: not reported by the vendor

API pricing

$5 per million input tokens, $30 per million output tokens (USD, cheapest OpenRouter endpoint, checked 2026-05-11)

Links

More from OpenAI

Data curated by AI Model Timeline. See the methodology for admission criteria, benchmark eras and source priority.