Every major GPT-5.x release before this one was a post-training improvement layered on top of the same underlying model. GPT-5.5 is different: OpenAI rebuilt the base from scratch, which is why the capability jumps feel qualitative, not incremental.
GPT-5.5 completes the same tasks as GPT-5.4 using significantly fewer tokens. That means lower cost, lower latency, and longer productive agent runs before context limits bite.
Powers OpenAI's Codex tool. NVIDIA deployed it internally to over 10,000 employees and reported debugging cycles dropping from days to hours, with multi-week experiments finishing overnight.
Better at understanding what you actually want, not just what you literally said. It can handle a messy, multi-part brief, build its own plan, and navigate ambiguity across real software environments.
Financial modeling, legal drafting, investment-banking tasks, data analysis, document creation — GDPval covers 44 occupations across 9 industries, and GPT-5.5 scores near the top of the public leaderboard.
OpenAI's chief research officer says GPT-5.5 shows meaningful gains in scientific and technical workflows. Early use cases include drug discovery pipelines and mathematical research under expert oversight.
GPT-5.5 introduces stricter classifiers for cybersecurity risk, third-party red-team testing for both cyber and bio risks, and tighter controls around sensitive requests, built on safeguards first deployed with GPT-5.2.
Numbers without context are marketing. Here's how GPT-5.5 and GPT-5.5 Pro sit against the current competitive field, with notes on where rivals still hold an edge.
GPT-5.5 Pro isn't the right tool for every situation. Here's an honest read on where it earns its premium, and where alternatives make more sense.
Is GPT-5.5 the same as GPT-5.4 with better fine-tuning?
No. GPT-5.5 is a fully retrained base model, which sets it apart from the GPT-5.1 through 5.4 releases that were primarily post-training improvements layered on the same underlying weights. The architecture-level retraining is why capability gains feel qualitative rather than marginal.
What's the difference between GPT-5.5 and GPT-5.5 Pro?
GPT-5.5 is the standard model available to Plus and above. GPT-5.5 Pro is the extended-reasoning variant, with adjustable reasoning effort settings (medium, high, xhigh), available to Pro, Business, and Enterprise tiers. Pro is the version OpenAI positions for demanding research and complex professional tasks.
Will GPT-5.5 replace GPT-5.4 in existing API integrations?
Not automatically. The API uses model strings and snapshot aliases. You'll need to explicitly update to gpt-5.5 or gpt-5.5-pro once your integration is ready for the capability and safety profile changes that come with the new model.
Measured on the AI/ML API gateway across live traffic. Figures are medians unless stated. Last updated 2026-10-12.
GPT-5.5 Pro is documented as suited to harder, higher-accuracy work, with especially strong performance in business, legal, education, and data science.
It is also described as strong for writing and debugging code, researching online, analyzing data, creating documents and spreadsheets, and operating software across tools until a task is finished.
OpenAI also positions it for complex, real-world work and advanced production workflows, including coding use cases, tool-heavy agents, grounded assistants, long-context retrieval, and product-spec-to-plan workflows.
A further documented fit is demanding decision-support work, such as legal review and financial modeling, where first-pass accuracy matters more than cost or latency.
import requests r = requests.post( "https://api.aimlapi.com/v1/chat/completions", headers={"Authorization": "Bearer " + AIMLAPI_KEY}, json={ "model": "openai/gpt-5.5-pro", "messages": [ { "role": "user", "content": "Hello!" } ] }, ) print(r.json())
const r = await fetch("https://api.aimlapi.com/v1/chat/completions", { method: "POST", headers: { Authorization: `Bearer ${process.env.AIMLAPI_KEY}`, "Content-Type": "application/json", }, body: JSON.stringify({ "model": "openai/gpt-5.5-pro", "messages": [ { "role": "user", "content": "Hello!" } ] }), }); console.log(await r.json());
curl -X POST https://api.aimlapi.com/v1/chat/completions \ -H "Authorization: Bearer $AIMLAPI_KEY" \ -H "Content-Type: application/json" \ -d '{"model":"openai/gpt-5.5-pro","messages":[{"role":"user","content":"Hello!"}]}'
OpenAI-compatible — swap the base URL and it works with your existing SDK.
| Type | Price |
|---|---|
| Input | |
| Output | |
| Model | Input | Output | Context | Best for |
|---|---|---|---|---|
GPT-5.5 Pro This page | Reasoning + agents | |||
| Reasoning + agents | ||||
| Balanced coding + agents | ||||
| Long-context, multimodal & agentic workflows | ||||
| Reasoning + agents |
GPT-5.5 Pro has a 1,050,000 tokens context window and can return up to 128,000 tokens.
GPT-5.5 Pro takes image, text as input and returns text.
Use openai/gpt-5.5-pro as the model id. Requests go to https://api.aimlapi.com/v1/chat/completions.
GPT-5.5 Pro is priced at input $41.262 / 1M tokens, output $247.572 / 1M tokens.
Yes, GPT-5.5 Pro can stream responses as they are generated.
Yes, GPT-5.5 Pro accepts image input alongside text.
GPT-5.5 Pro was built by OpenAI.
Yes, it supports function calling, tool use, and parallel tool calls.
