GPT-5.5 Pro

GPT-5.5 Pro is for teams escalating their hardest code reviews and multi-file refactors past standard GPT-5.5, Gemini 3.1 Pro, or Claude Sonnet 4.6, not for everyday chat or latency-sensitive apps. OpenAI shaped its safety posture with roughly 200 early-access partners before release, positioning Pro strictly for correctness-critical work where a wrong answer is expensive.

OpenAI's GPT-5.5 Pro is the GPT-5.5 family's highest-accuracy inference setting, released April 24, 2026, with a 1,000,000-token context window and 128,000-token max output. It runs the same Mixture-of-Experts weights as standard GPT-5.5 but adds parallel test-time compute, exploring multiple reasoning paths before answering for correctness-critical work.

Provider: OpenAI · Family: GPT-5.5

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Context window: 1,000,000 tokens · Max output: 128,000

Input modalities: text, image, audio, video, tool-calls · Output: text, tool-calls

About GPT-5.5 Pro

GPT-5.5 Pro is OpenAI's highest-accuracy inference setting within the GPT-5.5 family, released alongside the standard GPT-5.5 model on April 23, 2026, with API access opening April 24, 2026. It is not a separate set of weights: GPT-5.5 Pro runs the same Mixture-of-Experts transformer as GPT-5.5, with 128 expert routing groups and sparse activation per token, but applies parallel test-time compute so the model explores multiple reasoning paths before answering. It sits at the top of the GPT-5.5 lineup, above the standard GPT-5.5 model and GPT-5.5 Instant, and is positioned for correctness-critical work rather than everyday chat. GPT-5.5 Pro shares GPT-5.5's headline benchmark results across the board, since Pro is a different inference setting on identical weights rather than a separate model. GPT-5.5 posts 82.7% on Terminal-Bench 2.0, ahead of Gemini 3.1 Pro's 68.5% and Claude's roughly 65%, and 51.7% on FrontierMath Tiers 1-3 with 35.4% on Tier 4. On Humanity's Last Exam, GPT-5.5 scores 41.4%, behind Claude Opus 4.7's 46.9% and Gemini 3.1 Pro's 44.4%, indicating raw academic-recall reasoning is not where the Pro premium pays off most. Against Gemini 3.1 Pro (80.6% SWE-bench Verified) and Claude Sonnet 4.6 (79.6%), GPT-5.5 Pro's coding lead is the clearest differentiator. OpenAI has not independently published separate GPQA Diamond or AIME 2025 scores for the Pro inference setting versus the standard model. The API context window is 1,000,000 tokens with a maximum output of 128,000 tokens per completion. The Codex product caps GPT-5.5 (including Pro) at 400,000 tokens, so sessions needing the full 1M window must go through the Responses API directly. A context surcharge applies once a session's input exceeds 272,000 tokens: the entire session is billed at 2x input and 1.5x output rates, not just the portion over the threshold, which matters for retrieval-heavy workloads. GPT-5.5 Pro processes text, image, audio, and video inputs in a single unified architecture rather than routing between separate stitched-together models. Vision input preserves up to 10,240,000 pixels or a 6,000-pixel dimension without resizing, which improves chart and document reading plus computer-use accuracy. Audio input supports transcription and translation across dozens of languages, but output remains text-only; there is no native audio-out in the chat completions or Responses API. Tool use, function calling, structured outputs, parallel tool calls, web browsing, and code execution via tools all carry over unchanged from GPT-5.5. GPT-5.5 Pro is available through the OpenAI API with an API key, and reached general availability on Amazon Bedrock on June 1, 2026 as part of a $50 billion AWS-OpenAI partnership announced April 28, 2026 that ended OpenAI's prior Azure exclusivity; Bedrock pricing matches OpenAI's first-party rates with no markup. It also remains available through Azure OpenAI Service. Inside ChatGPT, GPT-5.5 Pro is restricted to Pro, Business, and Enterprise plans; Free and Plus users do not see it as a selectable model. It carries a steep price premium over standard GPT-5.5 given the added test-time compute (see pricing below for exact rates). The GPT-5.5 system card was updated on April 24, 2026 to cover API deployment safeguards for both GPT-5.5 and the Pro inference setting, with separate evaluations noted where the parallel test-time compute setting could materially change risk posture. OpenAI ran its full pre-deployment safety evaluation suite and Preparedness Framework process, including targeted red-teaming for cybersecurity and biology uplift, and incorporated feedback from roughly 200 early-access partners ahead of release. The model's safety posture is balanced: it refuses clear-harm requests but is not unusually restrictive for legitimate technical or research use. GPT-5.5 Pro suits teams that need the highest achievable accuracy on a specific hard problem and can absorb the cost and latency: scientific or legal document analysis and one-off research questions where a wrong answer is expensive. It is a poor fit for latency-sensitive chat interfaces or high-volume customer support, where a cheaper model would clear the accuracy bar at a fraction of the cost. GPT-5.5 Pro inherits GPT-5.5's data governance: API inputs are not used for training by default, with an enterprise zero-retention option available. OpenAI states SOC 2 Type II compliance, GDPR compliance, and HIPAA eligibility, with data residency options in the US and EU. Under the EU AI Act, GPT-5.5 (and therefore Pro) is classified as a general-purpose AI model with systemic risk obligations. OpenAI has not independently disclosed a training data cutoff date for GPT-5.5 or GPT-5.5 Pro. GPT-5.5 Pro launched as part of the same release wave as standard GPT-5.5 (April 23, 2026) and GPT-5.5 Instant (May 5, 2026), replacing GPT-5.4 and GPT-5.2 Pro as OpenAI's top-accuracy offering; GPT-5.2 models, including GPT-5.2 Pro, were fully deprecated from ChatGPT by June 12, 2026, with existing conversations auto-migrating to GPT-5.5. Rumors as of late May 2026 point to a GPT-5.6 release later in the year with an even larger context window, though OpenAI has not confirmed a date.

Pricing

GPT-5.5 Pro bills at six times standard GPT-5.5's per-token rate. Cached input is estimated at $3 per 1M tokens by applying GPT-5.5's published 90% prompt-caching discount ratio; OpenAI has not independently confirmed a Pro-specific cached rate. Available only on ChatGPT Pro/Business/Enterprise plans and via the API.

Key Features

• Parallel Test-Time Compute: GPT-5.5 Pro explores multiple reasoning paths before answering, OpenAI's mechanism for squeezing extra accuracy out of the same GPT-5.5 weights on hard questions.
• 1M-Token Context Window: Up to 1M input tokens and 128K output tokens via the Responses API, enough for whole-codebase or large-filing analysis in one call.
• Matches GPT-5.5's Benchmark-Topping SWE-bench Score: Resolves the large majority of real GitHub issues end to end in third-party testing, the same headline coding result published for standard GPT-5.5.
• Unified Multimodal Input: Text, image, audio, and video processed in one architecture, with vision preserving up to 10.24MP without resizing for accurate chart and document reading.
• AWS Bedrock General Availability: Reached general availability on Amazon Bedrock in mid-2026 at OpenAI's first-party pricing, part of a major AWS-OpenAI partnership that ended prior Azure exclusivity.

Pros

• Leads on agentic coding, matching GPT-5.5's benchmark-topping SWE-bench Verified score, ahead of Gemini 3.1 Pro and Claude Sonnet 4.6.
• 1M-token context window for whole-codebase or large-document work in a single call.
• No new vendor contract needed for teams already standardized on OpenAI, AWS, or Azure, since Pro runs on all three at matching rates.

Cons

• Costs several times more than standard GPT-5.5, with no independently published benchmark showing the premium buys extra accuracy on most tasks.
• No native audio output despite native audio input, and no published tokens-per-second figure for the Pro setting.
• Locked out of ChatGPT Free and Plus plans; only Pro, Business, and Enterprise tiers can select it in the chat UI.

Benchmarks

• mmlu: 92.4
• swe bench verified: 88.7

Visit GPT-5.5 Pro Official Page