OpenAIFastUltra

GPT-5.4

OpenAI's newest flagship model with 1M context window and 128K output tokens. Delivers top-tier reasoning across all domains with adjustable reasoning effort levels from none to xhigh.

5 credits

per request

1M token context window

128K max output tokens

Adjustable reasoning (none/low/medium/high/xhigh)

Function calling, web search, file search, computer use

Native vision support

Use with AI Assistant

Copy usage instructions for Claude, ChatGPT, or other AI

llms.txt

Model Specifications

Context Window

tokens

Max Output

128K

tokens

Training Cutoff

2025-08

Compatible SDK

OpenAI

Capabilities

Vision

Function Calling

Streaming

JSON Mode

System Prompt

Token Pricing (per 1M tokens)

Token Type	Credits	USD Equivalent
Input Tokens	2,500	$2.50
Output Tokens	15,000	$15.00

* 1 credit ≈ $0.001 (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-5.4",
  "messages": [
    {
      "role": "system",
      "content": "You are an expert analyst with deep domain knowledge."
    },
    {
      "role": "user",
      "content": "Compare the architectural trade-offs between microservices and monolithic architectures for a fintech startup processing 10M transactions per day."
    }
  ],
  "reasoning_effort": "high",
  "max_completion_tokens": 4000
}'

Parameters

Parameter	Type	Required	Default	Description
`messages`	array	Yes	-	Array of message objects with role and content
`model`	string	Yes	gpt-5.4	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: none, low, medium, high, or xhigh nonelowmediumhighxhigh
`temperature`	float	No	1.0	Sampling temperature (0-2)
`stream`	boolean	No	false	Enable Server-Sent Events streaming
`top_p`	float	No	1.0	Nucleus sampling threshold (0-1)

Examples

Advanced Reasoning

Complex multi-step analysis with GPT-5.4

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-5.4",
  "messages": [
    {
      "role": "system",
      "content": "You are an expert analyst with deep domain knowledge."
    },
    {
      "role": "user",
      "content": "Compare the architectural trade-offs between microservices and monolithic architectures for a fintech startup processing 10M transactions per day."
    }
  ],
  "reasoning_effort": "high",
  "max_completion_tokens": 4000
}'

Code Generation

Generate production-quality code with GPT-5.4

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-5.4",
  "messages": [
    {
      "role": "system",
      "content": "You are a senior software engineer. Write clean, well-tested, production-ready code."
    },
    {
      "role": "user",
      "content": "Implement a rate limiter using the token bucket algorithm in Go with Redis backend."
    }
  ],
  "temperature": 0.3,
  "max_completion_tokens": 4000
}'