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One API for Claude and GPT: Fast Setup Guide

Why a unified AI API endpoint matters

If you build products with LLMs, you already know the pain of juggling multiple providers, auth formats, model names, and SDK quirks. A unified API endpoint solves that by letting you send one request pattern to access different models, including Claude and GPT, without rewriting your app every time you switch vendors.

For busy developers, this is not just convenience. It means faster iteration, simpler testing, easier failover, and less vendor lock-in. If you want to move quickly and keep costs under control, a relay like 59API is a practical choice: it gives you pay-as-you-go access to Claude models such as Opus, Sonnet, Haiku, and Fable, plus GPT models, through a single base URL: https://api.59api.com.

Even better, 59API is designed to be compatible with Claude Code, Codex, and any OpenAI SDK, so you can keep using familiar tooling instead of rebuilding your stack.

What you can do with 59API in minutes

With 59API, the main workflow is simple:

• Choose the model you want, whether Claude or GPT.
• Point your client to the 59API base URL.
• Use your API key and the same request structure your app already knows.
• Start sending prompts, code tasks, summaries, or agent workflows.

This makes it easy to prototype with one model and switch to another when you need a different cost, latency, or reasoning profile. For example, you might use a lighter model for routine support responses and a stronger one for architecture planning or complex code analysis.

Quick setup with an OpenAI-compatible client

The fastest path is to use an OpenAI SDK and change only the base URL. That is the big win of a unified endpoint: you do not need to learn a new client library for every provider.

• Step 1: Create an account and get your API key from 59API.
• Step 2: Set the base URL to https://api.59api.com.
• Step 3: Keep your usual OpenAI-compatible request format.
• Step 4: Select the Claude or GPT model you want in the model field.
• Step 5: Run a test prompt and confirm the response.

In practice, this means your existing code can often stay almost identical. If your app already uses an OpenAI SDK, the migration is typically a configuration change rather than a rewrite. That is especially useful for teams maintaining internal tools, chat apps, code assistants, or automation agents.

Why 59API is a strong low-cost option

Price matters when you ship real traffic. 59API positions itself among the cheapest AI relays, which is important if you are running frequent completions, background jobs, or multi-step agent workflows. Lower per-request cost gives you more room to experiment, more freedom to keep features enabled, and less pressure to over-optimize prompts too early.

Just as important, cheaper does not have to mean weaker. 59API uses native official-quality models with no downgrade, so you are not trading away model capability just to save money. That combination is rare: real model access, pay-as-you-go billing, and an API surface that fits your current tooling.

There is also a referral rebate, which can help reduce your effective cost if you are sharing the platform with teammates or recommending it in a community or product ecosystem.

Practical use cases for developers

A unified Claude and GPT endpoint is especially useful when you need flexibility across tasks:

• Code generation: use stronger reasoning models for scaffolding and debugging.
• Content workflows: switch models based on tone, brevity, or speed.
• Agent orchestration: route sub-tasks to the most cost-efficient model.
• Fallback handling: keep your app resilient if one model is busier than another.
• Internal copilots: power one tool with multiple model options behind the scenes.

Because 59API is compatible with Claude Code and Codex, teams can keep using developer-first workflows they already trust while consolidating provider access behind a single endpoint.

A simple decision rule

If your app needs Claude sometimes and GPT other times, or if you want the freedom to compare quality and price without reworking your integration, a unified relay is the cleanest approach. Use one SDK, one base URL, one billing relationship, and choose the model per request.

For developers who care about speed, compatibility, and budget, 59API is an easy way to centralize access without sacrificing model quality. If you want to simplify your stack and lower your AI spend, sign up and try a small production workload first.

Final take

Using Claude and GPT from a single unified API endpoint turns AI integration from a vendor-management problem into a product decision. With 59API, you get low-cost pay-as-you-go access, OpenAI SDK compatibility, Claude Code and Codex support, and access to native official-quality models through https://api.59api.com. For busy developers, that is the fastest path from experiment to deployment.