The gpt-5.1 chat latest API exposes the exact GPT-5.1 snapshot that powered ChatGPT, delivered through GPTProto's unified endpoint. Unlike the full gpt-5.1 reasoning model, the chat-latest alias is tuned for fast, conversational replies — a 128K context window, text-and-image input, streaming, and native function calling — which makes it a drop-in pick for chatbots, support flows, and lightweight RAG. One key reaches gpt 5.1 chat and every other model on the platform.
GPT-5.1 Chat latest vs GPT 5.1 vs GPT 5.5
| gpt-5.1 chat latest | gpt 5.1 | gpt 5.5 | |
|---|---|---|---|
| Best for | Chat, support bots, light RAG | Agentic + coding, reasoning | Frontier reasoning, long-doc |
| Context window | 128K | 400K | 1M |
| Max output | 16K | 128K | 128K |
| Reasoning control | Chat-tuned (fixed) | reasoning_effort none–high |
reasoning_effort none–xhigh |
| Input | Text + image | Text + image | Text + image |
| Video / audio | ✗ / ✗ | ✗ / ✗ | ✗ / ✗ |
| Knowledge cutoff | Sep 30 2024 | Sep 30 2024 | Dec 1 2025 |
| Price (OpenAI list) | $1.25 / $10 | $1.25 / $10 | $5 / $30 |
| Price on GPTProto | $1 / $8 | $0.875 / $7 | $4 / $24 |
| Status | Deprecated snapshot | Current | Current flagship |
gpt 5.1 chat latest vs gpt 5.1
The difference is snapshot vs base model. The full gpt-5.1 model ships a 400K context window and configurable reasoning_effort (none, low, medium, high) for agentic and coding work. The gpt-5.1 chat latest alias mirrors the ChatGPT chat experience: lower latency, a 128K window, and conversational tuning rather than long step-by-step reasoning. Choose the chat alias for dialogue; choose gpt 5.1 for tool-heavy autonomous tasks.
gpt-5.1 chat latest vs gpt 5.5
gpt 5.5 is OpenAI's current flagship — a 1M-token context window and stronger reasoning at a higher price. gpt 5.1 chat is cheaper and faster for everyday chat, but for long-document analysis or frontier accuracy, gpt 5.5 is the upgrade — available under the same GPTProto key, so migrating is a one-line model swap.
Is ChatGPT 5.1 being retired? Is it better than GPT-5.0?
Yes — OpenAI retired the GPT-5.1 family from ChatGPT on March 11, 2026, migrating conversations to newer 5.x models, and the gpt-5.1-chat-latest API snapshot is now marked deprecated. It stays reachable through GPTProto for teams that pinned to it. Versus GPT-5.0, gpt 5.1 chat brought a warmer tone and more reliable instruction-following; against the 5.5 line it now trails on context length and reasoning. Starting fresh? Build on gpt 5.5 and keep gpt 5.1 chat for parity testing or legacy compatibility.
At GPTProto, gpt-5.1 chat latest API pricing runs $1 / $8 per 1M input/output tokens — under OpenAI's $1.25 / $10 list — with one key spanning every model on the platform.
