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Model

GPT-5.5

GPT-5.5 is an OpenAI model released on 23 April 2026 as GPT-5.5 Thinking and Pro, with an API version the next day. It succeeded GPT-5.4 and had a cybersecurity variant in limited preview.

Status AvailableModality Text, ImageContext (K tokens) 1050 Era Generative AI for everyone

License
Proprietary
Access
API, App
Release date
Developer
OpenAI

What it is

GPT-5.5 is a model from OpenAI. It was released on 23 April 2026 as GPT-5.5 Thinking and GPT-5.5 Pro in ChatGPT, and it was not available to free users.[1][2] Axios reported that its codename was “Spud”.[2]

Origins

GPT-5.5 succeeded GPT-5.4, and it was in turn succeeded by GPT-5.6 in July 2026.[1]

Access

API access followed on 24 April 2026. OpenAI had initially withheld API access, citing the need for “different safeguards”.[1]

The model was made available in Codex as well.[1]

Benchmarks

OpenAI reported 82.7% on Terminal-Bench 2.0, 51.7% on FrontierMath Tiers 1–3 and 35.4% on FrontierMath Tier 4.[1]

The UK AI Security Institute reported on 30 April 2026 that GPT-5.5 passed 71.4% of expert-level cyber tasks on average. It said the model “may be the strongest model we have tested” on that measure.[4]

Benchmarks are standardised tests that let different models be compared on the same tasks. Terminal-Bench 2.0 measures how well a model completes tasks in a command-line environment. FrontierMath is a set of hard mathematics problems, and its tiers describe increasing difficulty. The scores above are the results OpenAI reported on those tests, and they describe performance on those tests rather than a complete measure of ability.[1]

Main features

The API documentation gives GPT-5.5 a context window of 1,050,000 tokens and a limit of up to 128,000 output tokens. Its knowledge cutoff is 1 December 2025. It accepts text and image input, and reasoning effort can be set from “none” to “xhigh”.[3]

The API price was $5 per million input tokens and $30 per million output tokens. GPT-5.5 Pro cost $30 and $180 on the same basis.[3][5]

Later changes

GPT-5.5 Instant became ChatGPT’s default model for all users on 5 May 2026, replacing GPT-5.3 Instant.[1]

GPT-5.5-Cyber was announced on 7 May 2026 as a limited preview for vetted cybersecurity teams under the Trusted Access for Cyber program.[1]

OpenAI traced the model’s tendency to mention goblins and gremlins to the rewards used to train its “Nerdy” personality. It removed that personality and the reward signal.[1]

GPT-5.5 was retired from ChatGPT and Codex on 14 October 2026, while remaining available in the API. The gpt-5.5-cyber-preview model was deprecated on 5 November 2026.[6][7]

CapabilitiesLarge language modelsReasoningCode

Governance & standardsSafety & governance

Version history

22
  1. 2018
    • Jun 11, 2018 GPT-1

      GPT-1 was OpenAI's first generative pre-trained transformer, published in June 2018. It showed that one language model, pre-trained on unlabelled text and then fine-tuned, could improve results on many language tasks.

  2. 2019
    • Feb 14, 2019 GPT-2

      GPT-2 is a large language model that OpenAI announced in February 2019. Its largest version has 1.5 billion parameters. OpenAI first withheld the full model, then released it in stages through November 2019.

  3. 2020
    • May 28, 2020 GPT-3

      GPT-3 is an autoregressive language model with 175 billion parameters, described in a May 2020 paper. It could perform new tasks from a few examples in the prompt, without any gradient updates, and it was first offered through OpenAI's API.

  4. 2022
    • Mar 15, 2022 GPT-3.5 (text-davinci-002/003)

      GPT-3.5 is the family of OpenAI language models between GPT-3 and GPT-4, released through API models such as text-davinci-002 and text-davinci-003 and underlying the first version of ChatGPT.

  5. 2023
    • Mar 1, 2023 GPT-3.5 Turbo

      GPT-3.5 Turbo was the chat-optimised GPT-3.5 model OpenAI released through its API on 1 March 2023, priced at a tenth of the cost of earlier models and later replaced in ChatGPT by GPT-4o mini.

    • Mar 14, 2023 GPT-4

      GPT-4 is OpenAI's large multimodal model, released on 14 March 2023. It accepts image and text input, scored near the top of human test-takers on a simulated bar exam, and was succeeded by GPT-4 Turbo, GPT-4o and GPT-5.

    • Nov 6, 2023 GPT-4 Turbo

      GPT-4 Turbo is a cheaper, more capable version of OpenAI's GPT-4, announced on 6 November 2023 with a 128,000-token context window and lower API prices.

  6. 2024
    • May 13, 2024 GPT-4o

      GPT-4o is a multimodal model from OpenAI, released in May 2024, that takes text, audio, image and video as input and generates text, audio and image output within one neural network. It was removed from ChatGPT in February 2026.

    • Jul 18, 2024 GPT-4o mini

      A small, low-cost language model OpenAI released on 18 July 2024, priced far below GPT-4o and reported at 82% on MMLU; it replaced GPT-3.5 Turbo in ChatGPT on launch day.

    • Sep 12, 2024 OpenAI o1

      OpenAI o1 is the first reasoning model series from OpenAI, introduced in September 2024. It thinks through a long internal chain of thought before answering, and it was the base for later reasoning models such as o3.

  7. 2025
    • Feb 27, 2025 GPT-4.5

      GPT-4.5 is a large language model OpenAI released on 27 February 2025 under the code name "Orion". It was its largest chat model at the time, priced far above GPT-4o, and was retired from general availability within months.

    • Apr 14, 2025 GPT-4.1 (with mini and nano)

      OpenAI's April 2025 family of three API models — GPT-4.1, GPT-4.1 mini and GPT-4.1 nano — offering a context window of over a million tokens, low prices per token and stronger coding scores. It was succeeded by GPT-5.

    • Apr 16, 2025 OpenAI o3

      OpenAI's second-generation reasoning model, announced in December 2024 and released in April 2025, which posted large gains over o1 on science, software-engineering and competitive-programming benchmarks before being succeeded by GPT-5.

    • Aug 7, 2025 GPT-5

      GPT-5 is OpenAI's fifth GPT foundation model, released on 7 August 2025. It pairs a fast model with a deeper reasoning model and a router that chooses between them for each request.

    • Nov 12, 2025 GPT-5.1

      GPT-5.1 is an update to GPT-5 released by OpenAI on 12 November 2025. It added a warmer default personality with selectable styles, and its API version has been scheduled for shutdown in 2027.

    • Dec 11, 2025 GPT-5.2

      GPT-5.2 is a model family OpenAI released on 11 December 2025, with Instant, Thinking and Pro versions and a coding variant. It was aimed at professional work such as spreadsheets and presentations.

  8. 2026
    • Mar 5, 2026 GPT-5.4

      GPT-5.4 is a model OpenAI released on 5 March 2026 in Thinking and Pro versions. It added built-in computer use and improved deep research, and it was the model that succeeded GPT-5.2.

    • Apr 23, 2026 GPT-5.5 · This page

      GPT-5.5 is an OpenAI model released on 23 April 2026 as GPT-5.5 Thinking and Pro, with an API version the next day. It succeeded GPT-5.4 and had a cybersecurity variant in limited preview.

    • Jul 8, 2026 GPT-Live-1

      GPT-Live-1 is OpenAI's full-duplex voice model family, launched 8 July 2026, which lets ChatGPT listen and speak at the same time and replaced the earlier chained speech pipeline in ChatGPT Voice.

    • Jul 9, 2026 GPT-5.6 (Sol, Terra and Luna)

      OpenAI's three-model family released on 9 July 2026 — Luna, Terra and Sol, ordered from least to most capable — with Sol pitched as the company's strongest coding and agent model.

    • Sep 3, 2026 GPT-6 (Astra, Sol, Luna, Instant)

      GPT-6 is OpenAI's sixth-generation model family, launched from 3 September 2026 with GPT-6 Astra, followed by Sol, Luna and Instant. Astra was the first OpenAI model to reach its internal critical cybersecurity threshold.

    • Sep 29, 2026 GPT-6.1 (Sol and Terra)

      OpenAI's late-2026 model family: Sol, released at DevDay on 29 September 2026, and the faster, cheaper Terra on 26 October 2026. A planned Astra version was withheld over safety concerns.

20261

  1. ReleaseOpenAI releases GPT-5.5

    OpenAI released GPT-5.5 Thinking and GPT-5.5 Pro to paid ChatGPT users on 23 April 2026, then extended the models to Codex and the API, reporting strong benchmark results and later making a faster GPT-5.5 Instant the default.

Developed by1

OpenAI

Succeeded by1

GPT-5.6 (Sol, Terra and Luna)

Successor of1

GPT-5.4

Powers2

Codex (OpenAI coding agent)ChatGPT

Uses1

Chain of thought and reasoning models

Notes and sources

  1. GPT-5.5https://en.wikipedia.org/wiki/GPT-5.5
  2. OpenAI releases "Spud" GPT-5.5 modelhttps://www.axios.com/2026/04/23/openai-releases-spud-gpt-model
  3. GPT-5.5 Model | OpenAI APIhttps://developers.openai.com/api/docs/models/gpt-5.5
  4. Our evaluation of OpenAI's GPT-5.5 cyber capabilitieshttps://www.aisi.gov.uk/blog/our-evaluation-of-openais-gpt-5-5-cyber-capabilities
  5. OpenAI model release dateshttps://opper.ai/model-releases/openai
  6. OpenAI GPT Model Release Timelinehttps://hidekazu-konishi.com/entry/openai_gpt_model_release_timeline.html
  7. Deprecationshttps://developers.openai.com/api/docs/deprecations

Cite this page: GPT-5.5. TellWorld, https://www.tellworld.net/models/gpt-5-5. Updated 2026-11-08