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GPT-5.6 is available through AnyFast via the OpenAI Responses API (/v1/responses). According to OpenAI’s official model guidance, the gpt-5.6 alias routes to gpt-5.6-sol, the frontier GPT-5.6 model for complex professional work, reasoning, coding, and production workflows. AnyFast exposes the GPT-5.6 family as gpt-5.6, gpt-5.6-sol, gpt-5.6-terra, and gpt-5.6-luna.
Model IDPositioning
gpt-5.6Alias that routes to gpt-5.6-sol
gpt-5.6-solFrontier model for complex professional work
gpt-5.6-terraBalanced intelligence and cost
gpt-5.6-lunaCost-sensitive, high-volume workloads

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Key capabilities

  • Responses API — Uses the newer /v1/responses endpoint with input instead of messages
  • Frontier capability — Routes to GPT-5.6 Sol, OpenAI’s GPT-5.6 flagship tier for complex professional work
  • Long context — Supports a 1.05M token context window and up to 128K output tokens
  • Advanced reasoning — Supports reasoning effort levels: none, low, medium (default), high, xhigh, and max
  • Pro mode — Set reasoning.mode to pro for quality-first requests that can tolerate higher latency and token use
  • Persisted reasoning — Use reasoning.context to control whether prior reasoning is reused across turns
  • Verbosity control — Set response verbosity to low, medium, or high
  • Streaming — Supports real-time token streaming via SSE
  • Tool use — Supports function calling, web search, file search, code interpreter, computer use, and other Responses API tools
  • Programmatic Tool Calling — Supports bounded tool-heavy workflows where the model can write JavaScript to coordinate eligible tools

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Quick example

curl https://www.anyfast.ai/v1/responses \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5.6",
    "input": [
      { "role": "user", "content": "Explain quantum entanglement in simple terms." }
    ],
    "reasoning": {
      "effort": "high",
      "summary": "auto",
      "context": "auto"
    },
    "text": {
      "format": { "type": "text" },
      "verbosity": "medium"
    },
    "store": true
  }'

from openai import OpenAI

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

response = client.responses.create(
    model="gpt-5.6",
    input=[
        {"role": "user", "content": "Explain quantum entanglement in simple terms."}
    ],
    reasoning={"effort": "high", "summary": "auto", "context": "auto"},
    text={"format": {"type": "text"}, "verbosity": "medium"},
    store=True
)

print(response.output[0].content[0].text)

from openai import OpenAI

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

stream = client.responses.create(
    model="gpt-5.6",
    input=[
        {"role": "user", "content": "Write a short poem about the sea."}
    ],
    stream=True
)

for event in stream:
    if hasattr(event, 'delta'):
        print(event.delta, end="")

​
Parameters

ParameterTypeRequiredDescription
modelstringYesMust be gpt-5.6
inputarrayYesList of { role, content } objects
streambooleanNoEnable SSE streaming. Default: false
temperaturefloatNo0–2. Controls randomness. Default: 1
max_output_tokensintegerNoMaximum output tokens to generate. Minimum: 16
stopstring / arrayNoSequences that stop generation
reasoningobjectNo{ effort, summary, mode, context } — effort: none / low / medium / high / xhigh / max; mode can be pro; context can be auto, all_turns, or current_turn
textobjectNo{ format, verbosity } — controls output format and verbosity
toolsarrayNoList of tools the model may call
prompt_cache_optionsobjectNoConfigure explicit prompt caching behavior when supported
safety_identifierstringNoStable privacy-preserving end-user identifier for safety systems
storebooleanNoStore response for later retrieval. Default: true

API Reference

View the interactive API playground for GPT-5.6.