GPT 5.5

Frontier reasoning and coding with 1M-token context window.

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GPT 5.5 — Large Language Model

What is GPT 5.5?

GPT 5.5 is OpenAI's flagship frontier language model, released in April 2026. It combines advanced chain-of-thought reasoning, native vision capabilities, and a 1M+ token context window into a single synchronous API endpoint — making it one of the most capable models available for enterprise-grade AI workflows.

Available through the Segmind API at /v1/gpt-5.5, GPT 5.5 accepts both text and image inputs, making it suitable for everything from autonomous coding pipelines to multi-document research synthesis. It is purpose-built for complex, multi-step workflows requiring minimal human prompting — scoring 82.7% on Terminal-Bench 2.0, OpenAI's most decisive benchmark for agentic CLI task execution.

Key Features

  • •1M+ token context window (922K input / 128K output) — process entire codebases, legal contracts, or research corpora in a single API call
  • •Native vision — analyze technical diagrams, screenshots, charts, and mixed-media documents natively
  • •Five reasoning effort levels — tune compute intensity vs. latency per task type
  • •40% token efficiency gain over GPT-5.4 — complex tasks cost ~20% more despite higher per-token rates
  • •Synchronous API — direct JSON response with no polling required
  • •Strongest safety safeguards in the GPT-5.x series

Best Use Cases

  • •Autonomous coding agents: terminal workflow planning, issue resolution, test prediction — 82.7% on Terminal-Bench 2.0
  • •Scientific and technical research: drug discovery, multi-document synthesis, lab report interpretation
  • •Multimodal document understanding: PDFs with mixed diagrams, charts, and structured tables (88.3% on MMMU benchmark)
  • •Long-context analysis: contract review, codebase refactoring, literature surveys using the full 1M context
  • •Enterprise automation: multi-step software operation, spreadsheet and document generation, online research

Prompt Tips and Output Quality

For best results, give GPT 5.5 clear multi-step instructions in a single prompt — it handles complex chained reasoning natively. For vision tasks, pass the image URL in the image parameter and include a specific extraction question in prompt. Use structured output requests (e.g., "Return a JSON array with fields: title, summary, category") for downstream processing. For reasoning-heavy tasks, explicitly ask the model to think through the problem step by step before giving a final answer.

GPT 5.5 uses 72% fewer output tokens than Claude Opus 4.7 on equivalent coding tasks — making it especially cost-efficient for high-volume pipelines.

FAQs

What is GPT 5.5? GPT 5.5 is OpenAI's frontier language model with a 1M+ token context window, native vision, and advanced agentic reasoning — available via the Segmind API.

How does GPT 5.5 differ from GPT 5.4? GPT 5.5 delivers 40% higher token efficiency, stronger autonomous performance (especially on multi-step agentic workflows), and improved multimodal reasoning compared to GPT-5.4.

Can GPT 5.5 analyze images? Yes — pass an image URL in the image parameter. GPT 5.5 handles diagrams, screenshots, charts, and mixed-media documents with near-human accuracy.

How does GPT 5.5 compare to Claude Opus 4.7? GPT 5.5 leads on agentic benchmarks (Terminal-Bench 2.0: 82.7%) and uses 72% fewer output tokens. Claude Opus 4.7 edges ahead on pure code correctness (SWE-bench). For speed-critical agentic pipelines, GPT 5.5 is typically the better fit.

What is the context window for GPT 5.5? The context window is 1M+ tokens — approximately 922K input tokens and 128K output tokens — ideal for large-scale document processing.

Is GPT 5.5 available via API? Yes — access GPT 5.5 via the Segmind API at https://api.segmind.com/v1/gpt-5.5 using your Segmind API key.