Technical Specifications of GPT-5.5 Pro
| Specification | GPT-5.5 Pro |
|---|---|
| Model family | GPT-5.5 Pro (high-compute reasoning variant) |
| Primary modality | Text + image input, text output |
| Context window | 1,050,000 tokens |
| Max output | 128,000 tokens |
| Knowledge cutoff | Dec. 1, 2025 |
| Reasoning profile | High-compute reasoning optimized |
| API access | Responses API |
| Tool support | Function calling, web search, file search, code interpreter, hosted shell, MCP |
| Streaming | Not supported |
| Snapshot | gpt-5.5-pro-2026-04-23 |
What is GPT-5.5 Pro?
GPT-5.5 Pro is OpenAIโs high-compute variant within the GPT-5.5 family optimized for difficult reasoning, agentic workflows, deep research, and precision-heavy professional tasks. It is positioned less as a general โfast defaultโ model and more as a model for difficult problems where latency is secondary to quality.
Main Features of GPT-5.5 Pro
- 1M+ context window: Supports 1,050,000 tokens for extremely large repositories, contracts, logs, or research corpora.
- High-accuracy reasoning: Tuned for tougher questions where correctness matters more than latency.
- Tool orchestration: Can use web search, files, code interpreter, and hosted shell in Responses API workflows.
- Vision input support: Accepts images for charts, diagrams, screenshots, and scanned content.
- Enterprise-scale automation: Suitable for agent workflows that combine planning, retrieval, execution, and verification.
- Large outputs: Up to 128,000 output tokens for reports, code generation, and long-form synthesis.
Benchmark Performance (Reported)
Selected published benchmark figures include:
- GDPval: 82.3%
- BrowseComp: 90.1%
- FrontierMath Tier 1โ3: 52.4%
- FrontierMath Tier 4: 39.6%
- Investment Banking Modeling Tasks (internal): 88.6%
These reported results position it particularly strongly for difficult knowledge work and tool-augmented reasoning.
GPT-5.5 Pro vs GPT-5.5 vs GPT-5.4 Pro
| Model | Best for | Context | Reasoning | Notable point |
|---|---|---|---|---|
| GPT-5.5 Pro | Highest-precision professional work | 1,050,000 | Highest | Slower, more compute, stronger on hard tasks |
| GPT-5.5 | General frontier coding and professional work | 1,050,000 | Highest | Faster and cheaper than Pro |
| GPT-5.4 Pro | Previous Pro-tier option | 1,050,000 | Highest | Similar price/context, older snapshot and slightly different benchmark mix |
In OpenAIโs published benchmark table, GPT-5.5 Pro edges GPT-5.4 Pro on several measures such as GDPval, BrowseComp, GeneBench, and FrontierMath, while GPT-5.4 Pro slightly leads on Humanityโs Last Exam with tools. That makes GPT-5.5 Pro a newer โbest effortโ option rather than a strict across-the-board replacement.
How to access and use GPT-5.5 Pro API
Step 1: Sign Up for API Key
Log in toย cometapi.com. If you are not our user yet, please register first. Sign into yourย CometAPI console. Get the access credential API key of the interface. Click โAdd Tokenโ at the API token in the personal center, get the token key: sk-xxxxx and submit.
Step 2: Send Requests toย GPT-5.5 Proย API
Select the โgpt-5.5-proโ endpoint to send the API request and set the request body. The request method and request body are obtained from our website API doc. Our website also provides Apifox test for your convenience. Replace <YOUR_API_KEY> with your actual CometAPI key from your account.ย Where to call it:ย ย ย responseย format.
Insert your question or request into the content fieldโthis is what the model will respond to . Process the API response to get the generated answer.
Step 3: Retrieve and Verify Results
Process the API response to get the generated answer. After processing, the API responds with the task status and output data.