GPT-5.6 Spotted in Codex Logs: Polymarket Bets 89% on a June Launch

Just forty days after GPT-5.5 went live, a single routing entry in OpenAI's Codex backend gave away the next model. Polymarket now sits at 89% probability for a public GPT-5.6 release before June 30. OpenAI hasn't said a word, but the breadcrumbs are hard to ignore.

GPT-5.6 leak: what the Codex logs actually showed

On May 14, 2026, a researcher known as Haider spotted a single anomalous line in the routing logs of Codex, OpenAI's coding agent: a mapping entry pointing to a model called gpt-5.6. It vanished minutes later. Sound familiar? GPT-5.5 surfaced in Codex logs roughly 10 to 14 days before its April 23 launch, and GPT-5.4 appeared the same way before its March release.

Since that first sighting, multiple internal codenames have leaked. Developers traced the progression from « iris-alpha » through « ember-alpha » and « beacon-alpha » to « kepler » and « kindle », with kindle-alpha confirmed as the release candidate by early June.

A 1.5 million token context window for GPT-5.6?

Developers using ChatGPT Pro OAuth reportedly invoked the model with up to 1.5M tokens of context, a roughly 43% increase over GPT-5.5's capabilities. If that holds, OpenAI would close the context-length gap with Google's largest Gemini configurations. The other headline improvement targets front-end UI generation, a long-standing weak spot where AI-generated code has been notoriously sloppy.

Polymarket odds and OpenAI's breakneck release cadence

Polymarket's « GPT-5.6 released by June 30 » contract sits at 80 to 89% probability, comparable to where the GPT-5.5 market stood in early April before that model shipped on schedule. OpenAI's chief scientist Jakub Pachocki reportedly described GPT-5.6 as a « meaningful improvement » in efficiency, reasoning, and safety.

The timeline is staggering: GPT-5.4 on March 5, GPT-5.5 on April 23, and now GPT-5.6 likely in June. That's roughly a six-week cadence between flagship models.

June is shaping up as a three-way showdown

OpenAI isn't the only lab sprinting. Anthropic is preparing its Mythos model preview for June 2026, and Google may drop Gemini 3.5 Pro in the same window. As we saw when Gemini and Claude both went down on June 10, reliability matters as much as raw capability.

No official date, no verified benchmarks, no pricing. But when Codex logs leak, history says the launch is never far behind. The next two weeks could be very interesting.