gpt-5-4
GPT-5.4 is an OpenAI frontier model that unifies the Codex and GPT lines into a single system, with a context window of over 1M tokens (922K input, 128K output).
Pricing: Input 500 credits / 1M tokens (≈ $2.50), Output 3000 credits / 1M tokens (≈ $15.00).
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GPT-5.4 API on ModelFold
GPT-5.4 is an OpenAI frontier model that unifies the Codex and GPT lines into a single system, with a context window of over 1M tokens (922K input, 128K output). Try GPT-5.4 in the ModelFold Playground, then call it from your own code through an OpenAI-compatible chat completions API.
What Is the GPT-5.4 API
GPT-5.4 at a glance
GPT-5.4 is a chat model from OpenAI. It accepts text, images and files (such as PDF) as input and returns text, with a context window of up to 1M tokens.
Use it without hosting anything
On ModelFold you call GPT-5.4 with a single API key — no model weights to download and no inference servers to run. The same key also works for the other chat, image, video and audio models on ModelFold.
Core Capabilities of GPT-5.4
Up to 1M tokens of context
Keep long conversations, large documents and sizeable code in a single request, so the model can reason over the full material instead of fragments.
Understands images and files (such as PDF)
Besides text, GPT-5.4 accepts images and files (such as PDF) as input, so a single request can combine instructions with visual or other media.
Function calling
GPT-5.4 supports tool (function) calling: describe your functions in the request and the model returns structured calls your code can run — the basis for agents and integrations.
Adjustable reasoning effort
Choose a reasoning effort level (low, medium or high) per request to balance depth of thinking against speed and token usage.
Structured outputs
Ask for JSON that follows a schema (response_format), which makes extraction, classification and system integrations more reliable.
How to Use GPT-5.4 on ModelFold
- 1
Step 1: Try it in the Playground
Open the Playground at the top of this page, type a prompt and see how GPT-5.4 responds before writing any code.
- 2
Step 2: Create an API key
Sign in to ModelFold and create an API key in the console. Keep it secret and send it as a Bearer token.
- 3
Step 3: Send a request
Call POST https://modelfold.ai/v1/chat/completions with "model": "gpt-5-4" and your messages. Existing OpenAI-compatible SDKs work by changing the base URL and key.
- ✓
Step 4: Ship and monitor
Integrate the response into your product and check token usage and spend for every call in the console logs.
What You Can Build with GPT-5.4
AI coding assistants
Generate, explain, debug and refactor code, review pull requests and work through multi-file changes in developer tools and IDE plugins.
Autonomous agents
Build agents that plan multi-step tasks, call your tools and APIs, and keep working toward a goal across long sessions.
Long-document workflows
Feed in long reports, contracts, manuals or codebases and ask for summaries, comparisons and answers grounded in the material.
Analysis and complex reasoning
Work through research questions, data interpretation, planning and other problems that need careful step-by-step reasoning.
Frequently Asked Questions
What is GPT-5.4?⌄
GPT-5.4 is an OpenAI frontier model that unifies the Codex and GPT lines into a single system, with a context window of over 1M tokens (922K input, 128K output).
Which inputs does GPT-5.4 support?⌄
GPT-5.4 accepts text, images and files (such as PDF) and returns text. Through ModelFold you can send text and images (OpenAI-style image_url content); in the Playground you can also attach documents, which are converted to text.
How long is the context window of GPT-5.4?⌄
Up to 1M tokens, shared between your input and the model’s output.
Does GPT-5.4 support function calling?⌄
Yes. GPT-5.4 supports tools / function calling through the standard tools parameter of the chat completions API.
How is GPT-5.4 billed on ModelFold?⌄
Pay as you go by tokens: input and output tokens are charged at the per-million-token prices shown on this page. There is no monthly fee, and failed requests are not charged.
How do I call GPT-5.4 through the API?⌄
Send a POST request to https://modelfold.ai/v1/chat/completions with "model": "gpt-5-4", using your ModelFold API key as the Bearer token.
| Input | 500 credits 1M tokens≈ $2.50 |
| Output | 3000 credits 1M tokens≈ $15.00 |
Billed per token: input and output are priced separately, and thinking tokens count as output. The Playground charges exactly the same way.
Read API docs →AI Agents · Claude Code / Cursor / Trae →curl https://modelfold.ai/v1/chat/completions \
-H "Authorization: Bearer $MODELFOLD_API_KEY" \
-H "Content-Type: application/json" \
-d '{"model":"gpt-5-4","messages":[{"role":"user","content":"Hello"}]}'