The Archive

GPT-5.5 outperforms Claude Opus 4.7 on ProgramBench coding benchmark, achieving first solve with fewer agent steps via action bundling.

GPT-5.5 achieves first solve on ProgramBench hard/extreme tasks, substantially outperforming Claude Opus 4.7 on novel SWE benchmark.

FrontierMath is supposed to be one of the hard benchmarks for frontier models, and now Epoch is saying an AI-assisted review found fatal errors in about a third of Tiers 1-4. Noam Brown says the initial flags came from GPT-5.5. Obviously we’ll have to wait for the corrected scores, but this is a pretty interesting moment: the model is already strong enough to sanity-check the benchmark.

NVIDIA engineers use Codex with GPT-5.5 for production systems and research experiment automation.

Fields medalist reports GPT-5.5 solving open PhD-level math problems, warns of imminent crisis.

Unverified Reddit speculation about GPT-5.5 chain-of-thought implementation in Codex; lacks technical evidence or official confirmation.

source : [https://x.com/pankajkumar\_dev/status/2053470332313301244?s=20](https://x.com/pankajkumar_dev/status/2053470332313301244?s=20)

Fields Medal mathematician Timothy Gowers reports using GPT-5.5 Pro to solve open problems, warns mathematical research faces imminent disruption.

OpenAI launches GPT-5.5 and GPT-5.5-Cyber under Trusted Access program for verified security researchers to accelerate vulnerability discovery.

Reddit user reports unconfirmed observational claims about GPT-5.5 memory and rule interpretation features without reproducible evidence.

OpenAI begins rollout of GPT-5.5 Instant model variant in ChatGPT, positioning faster inference tier.

The new GPT-5.5 Instant model will replace GPT-3.5 Instant as the default model for ChatGPT

OpenAI's newest default model for ChatGPT might not make stuff up as much. Hallucinations have been an ongoing problem for AI models, but OpenAI says its new GPT-5.5 Instant model has "significant improvements in factuality across the board." The company claims that, based on "internal evaluations," GPT-5.5 Instant produced "52.5% fewer hallucinated claims" than its Instant model for GPT-5.3 "on high-stakes prompts covering areas like medicine, law, and finance." GPT-5.5 Instant also "reduced inaccurate claims by 37.3% on especially challenging conversations users had flagged for factual erro...

OpenAI releases GPT-5.5 Instant system card detailing model capabilities, limitations, and safety properties.

OpenAI releases GPT-5.5 Instant as ChatGPT's default model with improved accuracy, reduced hallucinations, and personalization controls.

Simon Willison's April 2026 newsletter covers Opus 4.7, GPT-5.5 price increases, Claude Mythos, LLM security research, and ChatGPT Images 2.0.

User reports high API costs for Claude Opus and GPT-5.5 on Cursor, predicts open-source models will displace proprietary tools by end of 2024.

Reddit post claiming GPT-5.5 output resembles a community suggestion from 5 months prior; unverified anecdote without official announcement or evidence.

GPT-5.5 scores 0.43% and Claude Opus 4.7 scores 0.18% on ARC-AGI-3 benchmark; both models show minimal progress on the reasoning task.

New results suggest Mythos' cyber threat isn't "a breakthrough specific to one model."

UK AI Security Institute evaluates GPT-5.5 for cybersecurity vulnerability detection, finding parity with Claude Mythos but with wider availability.

OpenAI will begin rolling out it cybersecurity testing tool, GPT-5.5 Cyber only "to critical cyber defenders" at first.

GPT-5.5 completed a multi-step cyber-attack simulation in 11 min ($1.73) vs. 12 hrs for human expert; UK AI Security Institute benchmark.

AI Security Institute benchmarks GPT-5.5 against Mythos on cyber-exploitation tasks; GPT-5.5 achieves 71.4% on expert-level tasks, performing comparably to Mythos.

OpenAI is preparing to launch a new frontier cybersecurity model, GPT-5.5-Cyber. CEO Sam Altman said the model will not be available to the general public, but will be first rolled out to a select group of trusted "cyber defenders" in order for institutions to shore up their cyberdefenses. The limited rollout will take place "in the next few days," Altman said on X. "We will work with the entire ecosystem and the government to figure out trusted access for Cyber." It's not clear who will get access to the model first, though previous "trusted access" schemes involved vetted professionals and ...

DeepSeek V4 benchmarks below Opus 4.6 and GPT-5.5 but ranks as strongest open-source model; real-world performance estimated at GPT-5.2 level.

Unverified Reddit claim about GPT-5.5 hallucinating fantasy creatures; no official source or technical detail provided.

GPT-5.5 ranks 2nd on Extended NYT Connections Benchmark; Kimi K2.6 leads open-weights; DeepSeek V4 Pro and Qwen 3.6 Max show significant gains.

Just spent the whole morning testing GPT-5.5 in ChatGPT and the jump in agentic reasoning and complex task handling is ridiculous.It plans multi-step workflows, uses tools properly, checks its own work, and actually gets stuff done instead of hallucinating halfway through. Feels like the first time a frontier model is truly useful for serious knowledge work and coding without constant babysitting.Anyone else playing with it yet? What's the coolest (or funniest) thing you've made it do so far?