OpenAIFastUltra

GPT-6.1 Sol

OpenAI's GPT-6.1 Sol — the Sol tier of the GPT-6.1 generation at $2/$10 per million tokens, with cached inputs at a 95% discount ($0.10/M, half of GPT-6 Sol's cached rate). 1.05M token context window (up to 922K input), 128K max output tokens, text and image input. Supports Fast mode and Ultrafast mode. Prompts above 272K input tokens are billed at 2x input / 1.5x output for the whole request.

3,716/18,580credits

input / output · per 1M tokens

Sol tier of the GPT-6.1 generation

1.05M token context window (up to 922K input tokens)

128K max output tokens

Knowledge cutoff: April 30, 2026

Cached input pricing (95% discount)

Adjustable reasoning effort (low to max, default medium)

Text and image input, structured outputs, streaming

Tool calling through the Responses API

Fast mode and Ultrafast mode (service_tier)

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Model Specifications

Context Window

1.1M

tokens

Max Output

128K

tokens

Training Cutoff

2026-04

Compatible SDK

OpenAI

Capabilities

Vision

Function Calling

Streaming

JSON Mode

System Prompt

Token Pricing (per 1M tokens)

Token Type	Credits	USD Equivalent
Input Tokens	3,716	$2.48
Output Tokens	18,580	$12.39
Cached Tokens	185.8	$0.12

* 1,500 credits ≈ $1 (actual charges may vary based on usage)

Quick Start

curl -X POST "https://api.core.today/llm/openai/v1/chat/completions" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer cdt_your_api_key" \
  -d '{
  "model": "gpt-6.1-sol",
  "messages": [
    {
      "role": "system",
      "content": "You are a senior software engineer. Think step by step."
    },
    {
      "role": "user",
      "content": "Design a migration plan from a monolithic Express API to modular services, then generate the first service's code with tests."
    }
  ],
  "reasoning_effort": "high",
  "max_completion_tokens": 8000
}'

Parameters

Parameter	Type	Required	Default	Description
`messages`	array	Yes	-	Array of message objects with role and content
`model`	string	Yes	gpt-6.1-sol	Model identifier
`max_completion_tokens`	integer	No	4096	Maximum tokens in response (up to 128000). Note: use max_completion_tokens, not max_tokens
`reasoning_effort`	string	No	medium	Reasoning effort level: low, medium, high, xhigh, or max. 'none' and 'minimal' are not supported on this model lowmediumhighxhighmax
`service_tier`	string	No	auto	Processing tier. 'fast' bills token charges at 2x, 'ultrafast' (Responses API) at 6x; settled on the tier the response reports autodefaultfastultrafast
`stream`	boolean	No	false	Enable Server-Sent Events streaming

Examples

Multi-step Reasoning

Multi-step code reasoning with GPT-6.1 Sol

curl -X POST "https://api.core.today/llm/openai/v1/chat/completions" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer cdt_your_api_key" \
  -d '{
  "model": "gpt-6.1-sol",
  "messages": [
    {
      "role": "system",
      "content": "You are a senior software engineer. Think step by step."
    },
    {
      "role": "user",
      "content": "Design a migration plan from a monolithic Express API to modular services, then generate the first service's code with tests."
    }
  ],
  "reasoning_effort": "high",
  "max_completion_tokens": 8000
}'

Cached Repeated Context

Reuse a large system prompt with 95% cached input discount

curl -X POST "https://api.core.today/llm/openai/v1/chat/completions" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer cdt_your_api_key" \
  -d '{
  "model": "gpt-6.1-sol",
  "messages": [
    {
      "role": "system",
      "content": "<large repeated system prompt or codebase context>"
    },
    {
      "role": "user",
      "content": "Summarize the open TODOs and rank them by risk."
    }
  ],
  "max_completion_tokens": 4000
}'

Tips & Best Practices

1Same $2/$10 per M as GPT-6 Sol, but cached inputs are $0.10/M (95% off) instead of $0.20/M — cache-heavy workloads (RAG, long system prompts) cost less here

2For tool calling use the Responses API (POST /llm/openai/v1/responses) — Chat Completions is supported on this model without tool calling

3reasoning_effort accepts low, medium (default), high, xhigh and max — 'none' and 'minimal' are rejected

4Keep prompts under 272K input tokens where possible — above that the whole request bills at 2x input and cache / 1.5x output

5Cache writes bill at 1.25x the input rate ($2.50/M) — implicit caching writes by default, so most of a large first prompt is billed as a cache write, then reads are 95% off

6Fast mode (service_tier: fast or priority) bills token charges at 2x and Ultrafast mode (service_tier: ultrafast, Responses API) at 6x — both are settled on the tier the response reports, so a request downgraded to standard is billed at the standard rate

7128K output enables single-shot long-form generation