As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/m/gpt-5-5-pro/

# GPT-5.5 Pro

OpenAI, GPT-5 family. Status: legacy. Type: reasoning model. Released: 2026-04-24. Training cutoff: 2025-12.

## How to call it

| Provider | Model id | Endpoint | Docs |
|---|---|---|---|
| OpenAI API | `gpt-5.5-pro` | https://api.openai.com/v1/responses | https://developers.openai.com/api/docs/models/gpt-5.5-pro |
| OpenRouter | `openai/gpt-5.5-pro` |  | https://openrouter.ai/openai/gpt-5.5-pro |
| Web app |  |  | https://chatgpt.com |

## Pricing

- Input: $30 per 1M tokens
- Output: $180 per 1M tokens
- Unit as published: per 1M tokens (USD), no cached-input discount
- Source: https://developers.openai.com/api/docs/pricing
- Last checked: 2026-09-29

## Specs

- Input: text, image
- Output: text
- Context window: 1,050,000 tokens
- Max output: 128,000 tokens
- Open weights: no
- Licence: proprietary

## What it has not seen

- Published training cutoff: 2025-12 (December 2025).
- AI events after it on Post-Cutoff: 1,962 (449 major, 85 historic), as of 2026-11-13.
- Already missing at launch: 93.
- Briefings of the news since December 2025: https://postcutoff.com/briefings/cutoff-2025-12-s.md (short), https://postcutoff.com/briefings/cutoff-2025-12-m.md (medium), https://postcutoff.com/briefings/cutoff-2025-12.md (full).
- Its card, with five things it has never heard of: https://postcutoff.com/you/gpt-5-5-pro/

## What stands out

- Extended compute: Uses more compute per request; some requests take several minutes. Effort medium/high/xhigh. Source: https://developers.openai.com/api/docs/models/gpt-5.5-pro
- Responses/Batch only: Not available on Chat Completions. Source: https://developers.openai.com/api/docs/models/gpt-5.5-pro

## Notes

Last separately-billed "-pro" API id; for GPT-5.6/GPT-6 OpenRouter exposes pro as reasoning.mode pro. Snapshot gpt-5.5-pro-2026-04-23. Azure id not verified.

Hardest problems where latency does not matter.

```bash
curl https://api.openai.com/v1/responses \
 -H "Authorization: Bearer $OPENAI_API_KEY" -H "Content-Type: application/json" \
 -d '{"model":"gpt-5.5-pro","input":"Hello"}'
```

Sources:
- https://developers.openai.com/api/docs/models/gpt-5.5-pro
- https://developers.openai.com/api/docs/pricing
- Models overview: https://developers.openai.com/api/docs/models

Model page: https://postcutoff.com/m/gpt-5-5-pro/