The GPT-5.4 mini API is our everyday default — GPT-5.4-class reasoning, cheap enough to run on most traffic. The 5% RouterBase discount is pure margin.
The GPT-5.4 mini API is OpenAI's cost-efficient GPT-5.4 tier — a 400K-token context window, adjustable reasoning effort, vision (text + image input), function calling, and structured JSON outputs, for high-volume reasoning, coding, and agentic tasks at a fraction of the cost. The GPT-5.4 mini API is OpenAI-compatible: point any existing SDK at RouterBase and set the model to gpt-5-4-mini. Input at $0.7125 / 1M tokens, output at $4.275 / 1M tokens, cache reads at $0.07125 / 1M tokens — all through one REST endpoint.
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GPT-5.4 mini
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GPT-5.4 mini API: Chat
Use the GPT-5.4 mini API to run OpenAI's cost-efficient GPT-5.4 tier — a 400K-token context, adjustable reasoning, vision, and function calling.
The GPT-5.4 mini API is OpenAI's cost-efficient GPT-5.4 tier — a 400K-token context window, adjustable reasoning effort, vision (text + image input), function calling, and structured JSON outputs, built for high-volume reasoning, coding, and agentic tasks at a fraction of the flagship cost. Routed through RouterBase, the GPT-5.4 mini API is fully OpenAI-compatible: point any existing SDK at RouterBase's base URL, set the model to gpt-5-4-mini, and your first GPT-5.4 mini API call goes through immediately.
Pricing for the GPT-5.4 mini API is $0.7125 / 1M input tokens, $4.275 / 1M output tokens, and $0.07125 / 1M cached-input reads — 5% below the standard rate. One RouterBase key — no OpenAI account required.
Six reasons teams ship on the GPT-5.4 mini API
From cost-efficient reasoning to 5%-off pricing — what makes the GPT-5.4 mini API stand out.
Cost-efficient GPT-5.4
The GPT-5.4 mini API delivers GPT-5.4-class step-by-step reasoning at a fraction of the flagship price — adjust the reasoning effort per request to trade depth against speed and cost.
Built for coding & agents
The GPT-5.4 mini API handles multi-file refactors, long tool-use chains, and agentic workflows — a dependable, low-cost backbone for production coding agents.
400K-token context
Accepts up to 400,000 tokens per request — long documents, multi-file codebases, or full conversation history fit in a single GPT-5.4 mini API call without chunking.
Vision & function calling
The GPT-5.4 mini API accepts text and image input and returns structured tool calls plus strictly valid JSON — ideal for extraction, analysis, and agent pipelines.
OpenAI-compatible endpoint
The GPT-5.4 mini API speaks the OpenAI chat-completions wire format. Point any OpenAI SDK at RouterBase — no separate credentials or call-site changes needed.
One key for 200+ models
The same RouterBase key that calls the GPT-5.4 mini API also routes to GPT-5.4, Claude Opus 4.8, Gemini 3 Pro, and 200+ other models — no per-provider credential management.
Quickstart
Get started with the GPT-5.4 mini API in 3 steps
From sign-up to your first response in under 5 minutes.
Create a RouterBase API key
Sign up and generate an API key — one key reaches the GPT-5.4 mini API and every other model in the catalog.
Send your first message
Point any OpenAI-compatible SDK at routerbase.com/v1 and set the model to gpt-5-4-mini. The GPT-5.4 mini API response follows the standard chat-completions schema — streaming and tool use supported.
Inspect usage
Every GPT-5.4 mini API response includes a detailed token breakdown — input, output, and cache-read tokens — so cost and cache-hit rate are visible on every call.
Pay only for what you use
RouterBase passes through partner-tier pricing. Compared against the model's official published API rate.
What teams build with the GPT-5.4 mini API
Real production loads running on the GPT-5.4 mini API and the RouterBase model catalog.
We run our agent backbone on the GPT-5.4 mini API and it sustains long tool-use chains without drifting — at a fraction of the flagship cost.
Structured JSON outputs from the GPT-5.4 mini API killed our flaky regex parsing. Strictly valid JSON every time, zero retries.
Adjustable reasoning on the GPT-5.4 mini API lets us dial depth against cost per task. RouterBase makes it 5% cheaper and routes around outages automatically.
400K of context at mini prices means I can drop a whole repo in. The GPT-5.4 mini API reasons across files without losing the thread.
RouterBase puts the GPT-5.4 mini API and 200+ other models behind one key. Our team stopped filing requests for new provider accounts.
We A/B the GPT-5.4 mini API against full GPT-5.4 per request — same SDK, one model field. Most traffic stays on mini and the bill dropped sharply.
We routed our high-volume endpoints to the GPT-5.4 mini API over a weekend. The only PR comment was 'wait, that's all?'.
At $0.7125 / 1M input minus 5%, the GPT-5.4 mini API gave us GPT-5.4-class reasoning at a price that scales. The ROI math was instant.
Frequently Asked Questions
Common questions about the GPT-5.4 mini API.
It is RouterBase's pass-through to OpenAI's GPT-5.4 mini — the cost-efficient GPT-5.4 tier with a 400K-token context, adjustable reasoning effort, vision, function calling, and structured outputs, served via an OpenAI-compatible REST interface.