Menlo Ventures AI investor Deedy Das posted the following tweet on X, claiming OpenAI will launch GPT-5 next week. According to information from an anonymous source that provided “reasonable proof,” GPT-5 will support context windows of up to 1 million tokens (input) and up to 100,000 tokens (output). GPT-5 will also support the Model Context Protocol (MCP) standard, which lets AI models connect to external data sources and “parallel tool calls.” Das also said GPT-5 will support dynamic (short and long) reasoning, Code Interpreter, and other tools.
🚨 BREAKING: OpenAI is dropping GPT-5 next week!
—1M token input window, 100k output tokens
—MCP support, parallel tool calls
—Dynamic short + long reasoning
—Uses Code Interpreter and other toolsCodenames are:
o3-alpha > nectarine (GPT-5) > lobster (mini) > starfish (nano)— Deedy (@deedydas) July 29, 2025
The leaker also mentioned the codenames OpenAI is supposedly using for GPT-5 models: “o3-alpha > nectarine (GPT-5) > lobster (mini) > starfish (nano).” Put differently, Nectarine, Lobster, and Starfish are the three GPT-5 models that will supposedly be available to users.
so far, 5-6 mysterious models on LMArena are rumored to be from openAI:
• zenith
• summit
• lobster
• nectarine
• starfish
• o3-alphazenith, lobster, and o3-Alpha claim to be top-tier coding models
surely at least one of them has to be the full GPT-5
— Haider. (@slow_developer) July 26, 2025
These codenames also appeared in a report from The Neuron earlier this week, which speculated that GPT-5 is being tested. “At least six anonymous models—Zenith, Summit, Lobster, Nectarine, Starfish, and o3-alpha—that are supposedly outperforming nearly every other known model,” have been spotted on LMArena. This report indicates Zenith might be the top-tier version of GPT-5, not Nectarine.
Head of design at cursor shares image teasing GPT 5 alpha pic.twitter.com/gvrKlrsHOq
— Chris (@chatgpt21) July 29, 2025
Separately, X user chatgpt21 posted screenshots supposedly coming from the head of design at Cursor, who has been testing GPT-5 Alpha. The images in the following tweet show an interaction with an AI model in a Mac app, probably Cursor. The model name is blurred but in a way that’s still legible. It reads gpt-5-alpha, likely a test AI model that some people have been able to use for a while. Finally, some testers have noticed a GPT-5-powered Smart Mode that Microsoft is preparing for Copilot.
BREAKING 🚨: Microsoft is preparing Copilot for GPT-5 release with a new Smart Mode!
“Smart Mode uses GPT-5 to think quickly or deeply”
Was GPT-5 release delayed b/c of that? 👀 pic.twitter.com/xSXeHKBh24
— TestingCatalog News 🗞 (@testingcatalog) July 24, 2025