AI Radar

GPT-5.5

Available · Language, Multimodal, Reasoning

GPT-5.5 is an OpenAI reasoning model for text and image input, released on 23 April 2026 in ChatGPT as GPT-5.5 Thinking and in Codex, with the API a day later. OpenAI describes it as a model for complex work across tools that needs less guidance and checks its own work. GPT-5.5 Pro runs the same model with parallel test-time compute. [1] [2]1. Introduction [3]Model details Primary source

Timeline of GPT-5.5 →

Claims and evidence

  • Released Rollout in ChatGPT and Codex; the API followed on 2026-04-24. Primary source[1]opening and Availability and pricing
  • Released in the API Primary source[1]update note of April 24, 2026 [4]Apr 24 (2026)
  • Status AvailableListed in the API model catalog and not on the deprecations page. Primary source[3] [5]
  • Successor of GPT-5.4The announcement presents GPT-5.5 as a step up from GPT-5.4 and compares the two throughout. Primary source[1]
  • Change · Efficiency OpenAI says it matches GPT-5.4's per-token latency in real-world serving while using fewer tokens for the same Codex tasks.Compared with GPT-5.4 Primary source[1]
  • Change · Training data Knowledge cutoff moves to 1 December 2025, from 31 August 2025 for GPT-5.4.Compared with GPT-5.4 Primary source[3] [6]
  • Change · Reasoning Default API reasoning effort is medium, where GPT-5.4 defaulted to none.Compared with GPT-5.4 Primary source[4]Apr 24 (2026) [3] [6]
  • Change · Safety Released after targeted red-teaming for cybersecurity and biology; the API launch came a day later because OpenAI said API deployment needed different safeguards.Compared with GPT-5.4 Primary source[1] [2]
  • Input text, image Primary source[3]Model details
  • Output text Primary source[3]Model details
  • Feature Reasoning modeReasoning effort none, low, medium (default), high and xhigh. Primary source[3]
  • Feature Computer useBuilt-in computer use in the API. Primary source[4]Apr 24 (2026)
  • Feature Function calling Primary source[4]Apr 24 (2026)
  • Feature Long context Primary source[4]Apr 24 (2026) [3]Model details
  • Context window 1,050,000 tokensThe announcement and changelog round this to 1M tokens for the API; in Codex GPT-5.5 has a 400K context window. Primary source[3]Model details
  • Parameters Not disclosedNot disclosed by OpenAI. No claim madeNo source
  • Access consumer app, API Primary source[1]Availability and pricing [4]Apr 24 (2026)

Lineage

Predecessors

Successors

Based on

Not derived from another model.

Variants and derived

None recorded.

Siblings

None recorded.

All ancestors

All descendants

Variants

GPT-5.5 Pro

  • Released ChatGPT (Pro, Business and Enterprise); the API followed on 2026-04-24. Primary source[1]opening and Availability and pricing
  • Variant Inline variant in this record.The system card describes GPT-5.5 Pro as the same underlying model as GPT-5.5 with a setting that uses parallel test-time compute. In the API it is offered for Responses API requests as gpt-5.5-pro. Primary source[1] [2]1. Introduction [4]Apr 24 (2026)

Also known as: gpt-5.5-pro, gpt-5.5-pro-2026-04-23

Differs in:

  • Context window: 1,050,000 tokens Evidence not assessed [7]Model details

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