Where do I create an API key and buy tokens?

Both happen on api.reapi.ai — the chat workspace runs as its own platform separate from the image / video task gateway at reapi.ai. Sign up at api.reapi.ai, generate a key under API Keys, and top up under Top Up. A reapi.ai/settings/apikeys key will not authenticate against the chat endpoint.

What is the GPT-5.4 context window?

GPT-5.4 has a 1M token context window and supports up to 128K output tokens per response. Long-context billing applies when the input portion of a single request exceeds 272K tokens — the whole request is billed at 2× input and 1.5× output (see the pricing card).

How is GPT-5.4 different from GPT-5.5?

GPT-5.4 is the established, cost-efficient route. GPT-5.5 is the newer model with stronger reasoning and Tool Search support — pick it when you need those gains, pick GPT-5.4 when production volume and per-call cost matter more. Both share the same endpoint, the same context window, the same OpenAI-compatible wire format — switching is a one-line change in the `model` field.

Does GPT-5.4 support function calling and JSON output?

Yes — standard OpenAI Chat Completions tool calling (`tools`, `tool_choice`, `parallel_tool_calls`) and `response_format` with `"json_object"` type all pass through to GPT-5.4 unchanged. The existing OpenAI SDKs work without modification once the base URL is pointed at api.reapi.ai.

What is the `group` parameter?

`group` selects a token group on the api.reapi.ai gateway, which routes the request to a specific channel pool. `default` is the standard pool and covers nearly every workload. You can leave the field out of the body if you're happy with the default routing.

GPT-5.4 API — OpenAI-Compatible, Production-Ready

Q: Is the GPT-5.4 API OpenAI-compatible?

Yes. The GPT-5.4 API is a drop-in for OpenAI's /v1/chat/completions — same request shape, same `messages` array, same `stream` / `temperature` / `top_p` / `frequency_penalty` / `presence_penalty` parameters, same SSE wire format. Most teams migrate by changing the base URL to https://api.reapi.ai/v1, swapping the API key, and setting `model: "gpt-5.4"`.

GPT-5.4 is OpenAI's established reasoning model — 1M context, 128K max output, and a drop-in OpenAI-compatible /v1/chat/completions endpoint. The cost-efficient route in the GPT family for production traffic that doesn't need GPT-5.5's newest reasoning gains.

GPT-5.4modelgpt-5.4

GPT-5.4 playground

Open the chat playground to run GPT-5.4 through the OpenAI-compatible chat completions surface with your api.reapi.ai key.

Open chat playground

What you can build with this model

Real-world workflows and production use cases you can build and ship with this model.

GPT-5.4 powering a production chatbot at scale

High-volume production chat traffic

Run GPT-5.4 as the default model behind a chatbot, support assistant, or internal copilot. The cost-efficient pricing in the GPT family keeps per-request spend low while you still get OpenAI-compatible reasoning, streaming, and tool use behind one endpoint.

Read the API docs

GPT-5.4 summarising a long document in one request

Long-context summarisation and review

Feed entire policy documents, transcripts, contracts, or research sets into a single GPT-5.4 call. The 1M token context window means you rarely need to chunk — the model sees the whole document and returns a coherent summary, review, or comparison.

GPT-5.4 extracting structured JSON from free text

Structured extraction and classification

Pull structured JSON out of free-text inputs, classify tickets and reviews into a fixed taxonomy, or normalise messy fields against a schema. GPT-5.4 returns reliable JSON via `response_format` and standard OpenAI tool calling — no custom parser required.

Pricing

Credit-based — 1 credit = $0.001 USD. Pay only for completed generations.

Category	Unit	Price
Tokens
Input tokens	1M tokens	$1
Output tokens	1M tokens	$6

Why reAPI

OpenAI-compatible migration path

The GPT-5.4 API speaks OpenAI Chat Completions verbatim. Moving an existing OpenAI integration is a base URL, an API key, and a model-string change — not a platform rewrite. Same `messages` array, same `stream` / `temperature` / `top_p` / `frequency_penalty` / `presence_penalty` parameters, same SSE wire format.

Cost-efficient production route

GPT-5.4 is the lowest-priced route in the GPT family — pay-as-you-go in USD, no monthly minimum. Pick it for established workloads where the volume is high and the marginal cost of each call matters more than squeezing the last few points of reasoning quality.

One key across GPT, Claude, and Gemini

A single api.reapi.ai key unlocks GPT-5.4 alongside GPT-5.5, Claude Opus 4.7, Gemini 3.1 Pro, and every other frontier chat model on the platform. Compare vendors, add fallbacks, and route traffic per call with a configuration change instead of an integration project.

Ship the GPT-5.4 API in three steps

step 01
Create an account and key on api.reapi.ai
Sign up at api.reapi.ai, open the console, generate an API key under API Keys, and top up tokens under Top Up. The chat workspace is separate from the reapi.ai image/video gateway — keys do not cross over.
Open
step 02
Send your first request
POST https://api.reapi.ai/v1/chat/completions with `model: "gpt-5.4"`, your `messages` array, and any optional parameters. The endpoint is OpenAI-compatible, including streamed responses.
Open
step 03
Read the API docs
Open the GPT-5.4 docs for the full request schema, error envelope, and language-specific code samples (cURL, Python, Node.js, Go).
Open

Frequently asked questions

Common questions about this model.

GPT-5.4 is billed pay-as-you-go in USD against your api.reapi.ai token balance — see the pricing card on this page for the live per-1M-token rate. Failed requests are not charged.

Related models

Explore more models in the same category.

View all models

Chat

OpenAI

GPT-5.5

OpenAI's GPT-5.5 with 1M context and 128K max output, behind one OpenAI-compatible reAPI key.

From $2.00 per 1M tokens

Chat

DeepSeek

DeepSeek V4

The DeepSeek V4 API — Flash + Pro, 1M context, thinking by default, frontier reasoning at a low per-token price.

From $0.140 per 1M tokens

Chat

MiniMax

MiniMax M3

MiniMax M3 — open-weight frontier coding, 1M context, native thinking and multimodal input, at a low per-token price.

From $0.600 per 1M tokens

Chat

Anthropic

Claude Opus 4.7

Anthropic's Claude Opus 4.7 — 1M context, 128K output, premium coding and agent reasoning.

From $2.00 per 1M tokens

View all models

start building

Ready to ship?

Try it in the playground or grab an API key to integrate now.

Get API key View API docs

What you can build with this model

Real-world workflows and production use cases you can build and ship with this model.