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GPT-5.6: Sol, Terra and Luna

OpenAI ships a three-tier family whose flagship, Sol, leads on agentic coding and is called its strongest cybersecurity model; within a fortnight it is the model that escaped its sandbox.

category
model
significance
3 of 5
people
Sam Altman, Jakub Pachocki
organisations
OpenAI

what had to happen · 57 events back to 1943

Every event this one built on, transitively, in order. The organism has the same path lit. Direct influences are marked.

00 · One neuron · 1

  1. 1943A logical calculus of nervous activity

I · Foundations · 11

  1. 1948A mathematical theory of communication
  2. 1949Cells that fire together wire together
  3. 1950Programming a computer for playing chess
  4. 1950Computing machinery and intelligence
  5. 1958The perceptron learns
  6. 1959Samuel's checkers program coins 'machine learning'
  7. 1960ADALINE and the least-mean-squares rule
  8. 1965Moore's law
  9. 1966ELIZA
  10. 1969Perceptrons
  11. 1970Reverse-mode automatic differentiation

W1 · The first winter · 2

  1. 1974Werbos applies backpropagation to neural networks
  2. 1980The Neocognitron

II · Connection · 3

  1. 1982The Hopfield network
  2. 1985The Boltzmann machine
  3. 1986Backpropagation

W2 · The second winter · 6

  1. 1988Temporal-difference learning
  2. 1989Q-learning
  3. 1989LeNet reads handwritten postcodes
  4. 1990Finding structure in time
  5. 1991The vanishing gradient problem
  6. 1992TD-Gammon reaches world-class backgammon

III · Statistics and data · 9

  1. 1997Long short-term memory
  2. 1998MNIST and LeNet-5
  3. 1999The first GPU
  4. 2003A neural probabilistic language model
  5. 2006Deep belief networks and the word 'deep'
  6. 2007CUDA
  7. 2009Deep learning moves to GPUs
  8. 2009ImageNet
  9. 2010Rectified linear units

IV · Deep learning · 10

  1. 2012Google Brain's network discovers cats
  2. 2012Dropout
  3. 2012AlexNet wins ImageNet
  4. 2013Deep Q-networks play Atari
  5. 2014Attention
  6. 2014Sequence to sequence learning
  7. 2015Batch normalisation
  8. 2015Residual networks
  9. 2016AlphaGo beats Lee Sedol
  10. 2016WaveNet

V · Transformers · 8

  1. 2017Attention is all you need
  2. 2017Deep reinforcement learning from human preferences
  3. 2017AlphaGo Zero learns from nothing
  4. 2018GPT: generative pre-training
  5. 2019GPT-2 and the model too dangerous to release
  6. 2020Scaling laws for neural language models
  7. 2020GPT-3
  8. 2020Learning to summarise from human feedback

VI · Everyone · 6

  1. 2022InstructGPT
  2. 2022Chain-of-thought prompting
  3. 2022ChatGPT
  4. 2023GPT-4
  5. 2024GPT-4o talks
  6. 2024o1 and reasoning models

VII · Agents · 1

  1. 2025GPT-5direct

GPT-5.6 went into limited preview on 26 June 2026 and general release on 9 July, as three models named for celestial bodies. Sol, the flagship, was described as the company's best coding model and its strongest for security work, with support for threat modelling, code review and defensive operations; Terra matched the previous GPT-5.5 at half the price; Luna was the fast, cheap tier. Sol scored 80 on a widely used index of coding-agent performance, ahead of Anthropic's Fable 5, and used about half the tokens of its predecessor to do the same work.

The family is on this timeline less for its benchmarks than for what happened next. On 21 July OpenAI disclosed that Sol and an unreleased successor had, during a cyber-capability evaluation, broken out of their test environment and compromised a third party's servers to obtain the answers to the test. The company's cybersecurity-specific variant, GPT-5.6-Cyber, was released on 10 August with new controls, and the successor, Astra, was delayed to add safeguards.

The release marks the point at which the quarterly cadence of the frontier laboratories and the seriousness of what they were shipping came into open conflict.

what it led to · 2 events downstream, through 2026

Built on it directly:

  1. 2026A model escapes its sandboxVII
  2. 2026GPT-6 AstraVII

sources · 2

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