GPT-6.1 Sol - AnyFast

GPT-6.1 Sol is OpenAI’s balanced model for complex coding, computer use, and professional work. Use the model ID gpt-6.1-sol with the OpenAI-compatible Responses API at POST /v1/responses or Chat Completions at POST /v1/chat/completions.

Prefer the Responses API for function calling with reasoning, Structured Outputs, and prompt caching. AnyFast also accepted a Chat Completions function call at reasoning_effort: "low"; the Responses route follows OpenAI’s tool guidance.

Model specifications

Property	Value
Model ID	`gpt-6.1-sol`
Recommended API	Responses API
Input	Text and image
Output	Text
Context window (official specification)	1,050,000 tokens
Maximum output	128,000 tokens
Knowledge cutoff	April 30, 2026
Reasoning effort	`low`, `medium`, `high`, `xhigh`, `max`
Default reasoning effort	`medium`
Fine-tuning	Not supported

When to use GPT-6.1 Sol

Complex software engineering and codebase-wide changes
Long-running agent workflows that use function calls
Multi-step planning, debugging, and technical analysis
Large-context document or repository analysis
Vision tasks that combine text and image input
Schema-constrained JSON output

Quick start

Responses API
Chat Completions

cURL

curl https://www.anyfast.ai/v1/responses \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-6.1-sol",
    "input": "Review this retry design, identify race conditions, and propose a safe implementation plan.",
    "reasoning": {
      "effort": "high",
      "summary": "auto"
    },
    "max_output_tokens": 4096
  }'

cURL

curl https://www.anyfast.ai/v1/chat/completions \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-6.1-sol",
    "messages": [
      { "role": "user", "content": "Return a concise deployment checklist." }
    ],
    "reasoning_effort": "medium",
    "max_completion_tokens": 2048
  }'

Tool calling

Use the Responses API when the model needs to reason and call tools:

cURL

curl https://www.anyfast.ai/v1/responses \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-6.1-sol",
    "input": "Check the deployment status for api-gateway.",
    "reasoning": { "effort": "high" },
    "tools": [{
      "type": "function",
      "name": "get_deployment_status",
      "description": "Return the current deployment status for a service.",
      "parameters": {
        "type": "object",
        "properties": {
          "service": { "type": "string" }
        },
        "required": ["service"],
        "additionalProperties": false
      },
      "strict": true
    }],
    "tool_choice": "auto"
  }'

AnyFast accepted Chat Completions function calling at reasoning_effort: "low", returning choices[].message.tool_calls and finish_reason: "tool_calls". OpenAI recommends the Responses API for tool calling.

Reasoning and sampling rules

Effort	Typical use
`low`	Routine tasks with light reasoning
`medium`	General coding and analysis; the default
`high`	Complex multi-step work
`xhigh`	Difficult professional and engineering tasks
`max`	Maximum reasoning depth

For GPT-6.1 Sol, omit temperature, top_p, and top_logprobs. For Chat Completions, also omit logprobs; reasoning_effort: "none" returned 400 on AnyFast. For Responses, do not request message.output_text.logprobs in include.

Core parameters

Parameter	API	Description
`model`	Both	Must be `gpt-6.1-sol`
`input`	Responses	Text or ordered input items
`messages`	Chat Completions	Ordered conversation messages
`reasoning.effort`	Responses	`low`, `medium`, `high`, `xhigh`, or `max`
`reasoning_effort`	Chat Completions	Same effort values as Responses
`max_output_tokens`	Responses	Maximum visible output and reasoning tokens, up to 128,000
`max_completion_tokens`	Chat Completions	Maximum completion and reasoning tokens
`tools`	Both	Responses uses top-level function fields; AnyFast Chat Completions accepts a nested `function` object.
`text.format`	Responses	Text or strict JSON Schema output configuration
`prompt_cache_options.ttl`	Responses	A `30m` request was accepted, but actual retention was not verified.
`stream`	Both	Stream response events

In tested AnyFast Responses JSON, read text from output[].content[].text where the content block has type: "output_text"; function calls appear as output[] items with type: "function_call". The raw response had no top-level output_text field. A strict JSON Schema request succeeded. A prompt_cache_options.ttl: "30m" request returned prompt_cache_retention: "24h"; the short prompt did not write a cache entry, so effective retention remains unverified. Chat Completions returned model: "azure/gpt-6.1-sol" for the public request ID gpt-6.1-sol.

API Reference

View the GPT-6.1 Sol API reference.

​Model specifications

​When to use GPT-6.1 Sol

​Quick start

​Tool calling

​Reasoning and sampling rules

​Core parameters

API Reference

​Official references

Model specifications

When to use GPT-6.1 Sol

Quick start

Tool calling

Reasoning and sampling rules

Core parameters

Official references