GPT-5.1 Codex Mini

OpenAI’s GPT-5.1 Codex Mini — compact code-optimized GPT-5.1.

GPT-5.1 Codex Mini is available through AnyFast via an OpenAI-compatible interface.

Key capabilities

• OpenAI-compatible — Works as a drop-in replacement with the OpenAI SDK
• Streaming — Supports real-time token streaming via SSE
• Tool use — Supports function calling and tool use
• Flexible output — Supports JSON mode and structured output

Quick example

cURL

curl https://www.anyfast.ai/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5.1-codex-mini",
    "messages": [
      { "role": "user", "content": "Explain quantum entanglement in simple terms." }
    ]
  }'

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_API_KEY",
    base_url="https://www.anyfast.ai/v1"
)

response = client.chat.completions.create(
    model="gpt-5.1-codex-mini",
    messages=[
        {"role": "user", "content": "Explain quantum entanglement in simple terms."}
    ]
)

print(response.choices[0].message.content)

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_API_KEY",
    base_url="https://www.anyfast.ai/v1"
)

stream = client.chat.completions.create(
    model="gpt-5.1-codex-mini",
    messages=[
        {"role": "user", "content": "Write a short poem about the sea."}
    ],
    stream=True
)

for chunk in stream:
    print(chunk.choices[0].delta.content or "", end="")

Parameters

Parameter	Type	Required	Description
model	string	Yes	Must be gpt-5.1-codex-mini
messages	array	Yes	List of { role, content } objects
max_tokens	integer	No	Maximum tokens to generate
temperature	float	No	0\u20132. Controls randomness. Default: 1
stream	boolean	No	Enable SSE streaming. Default: false
top_p	float	No	Nucleus sampling threshold. Default: 1
stop	string / array	No	Sequences that stop generation
tools	array	No	List of tools the model may call
response_format	object	No	Specify output format (e.g. JSON mode)

API Reference

View the interactive API playground for GPT-5.1 Codex Mini.