Cursor vs Cline vs Claude Code: Which Has the Best API Support?

How I Tested

I didn't just install each tool and poke around for 10 minutes. I used each one as my primary coding tool for a full week, working on real projects. The specific criteria I evaluated:

• Custom API setup difficulty: How many steps to connect a third-party provider?
• Protocol support: OpenAI-compatible? Anthropic? Both?
• Model switching: Can you easily switch between models mid-session?
• Error handling: What happens when the API returns an error?
• Streaming support: Does it stream responses in real-time?
• Cost visibility: Can you see how much you're spending?

#1: Cline — The API Flexibility King

Cline is a VS Code extension, which means it inherits VS Code's entire ecosystem. But what makes it special for API users is its configuration panel — it supports virtually every API provider out of the box.

Setup Process

Open the Cline sidebar in VS Code, go to Settings, select "OpenAI Compatible" as the provider type, and paste your Base URL and API key. That's it. Three fields, one click.

API Provider: OpenAI Compatible
Base URL: https://api.provider.com/v1
API Key: sk-your-key-here
Model: gpt-5

What I loved: Cline doesn't care which provider you use. As long as it speaks OpenAI's API format, it works. I tested with 4 different providers and all connected instantly.

What Cline Does Better

• Multi-provider support: Switch between providers without restarting
• Cost tracking: Shows token usage and estimated cost per conversation
• Model flexibility: Use GPT-5, Claude, Gemini — whatever your provider offers
• Open source: You can audit exactly what data is being sent

#2: Cursor — Polished but Restrictive

Cursor has the best UX of any AI coding tool I've used. The tab completion, the inline edits, the chat — everything feels native. But when it comes to custom API providers, it's surprisingly limited.

Setup Process

Go to Settings → Models → Override OpenAI Base URL. You can set a custom Base URL and API key, but only for OpenAI-compatible models. Want to use Claude through a third-party provider? You're out of luck.

Settings → Models:
  Override OpenAI Base URL: https://api.provider.com/v1
  Override OpenAI API Key: sk-your-key-here

Where Cursor Falls Short

• OpenAI only: Custom API support is limited to OpenAI-compatible endpoints
• No cost tracking: You can't see how much you're spending through custom providers
• Subscription required: Even with a custom API key, you still need a Cursor subscription

#3: Claude Code — Powerful but Locked In

Claude Code is Anthropic's official CLI tool. It's incredibly powerful for agentic coding — it can read your entire codebase, run commands, and make multi-file changes. But it only speaks one protocol: Anthropic's Messages API.

Setup Process

You need to set environment variables pointing to an Anthropic-compatible endpoint:

export ANTHROPIC_BASE_URL="https://api.provider.com/llm-api"
export ANTHROPIC_API_KEY="sk-your-key-here"

The catch: your provider must support the Anthropic Messages API format exactly. Most third-party providers only support OpenAI's format, which severely limits your options.

The Good and the Bad

Pros	Cons
Best agentic coding experience	Only works with Anthropic protocol
Full codebase awareness	Few third-party providers support it
Can run shell commands	No GUI — terminal only
Excellent for complex refactoring	No cost tracking built in

Head-to-Head Comparison

Feature	Cline	Cursor	Claude Code
Custom API Setup	3 fields	2 fields	2 env vars
OpenAI Protocol	Yes	Yes	No
Anthropic Protocol	Yes	No	Yes
Model Switching	Instant	Settings menu	Env var change
Cost Tracking	Built-in	No	No
Streaming	Yes	Yes	Yes
Free to Use	Yes (OSS)	$20/mo + API	API only
Provider Options	Unlimited	OpenAI only	Anthropic only

My Recommendation

After a month of daily use, here's what I'd tell a friend:

• If you want maximum flexibility: Use Cline. It works with everything, it's free, and the cost tracking alone saves you from billing surprises.
• If you want the best UX: Use Cursor for the editing experience, but know that you're limited to OpenAI-compatible providers.
• If you need agentic coding: Use Claude Code for complex multi-file refactoring, but budget for the higher API costs.
• Best combo: Cline for daily coding + Claude Code for big refactoring tasks. This gives you flexibility AND power.

What I'd Do Differently

I wish I'd tested Windsurf and Trae as well — both are gaining traction and I've heard good things about their API support. That's a follow-up article.