When you’re picking a coding assistant, the LLM API keys you can bring to the table decide your model choices and your bill. Cursor vs Cline API key support splits along clear lines: Cursor is a commercial VS Code fork with a subscription and limited bring-your-own-key (BYO) options, while Cline is an open-source VS Code extension that talks to any OpenAI-compatible endpoint. Below is the concrete breakdown.
Tool basics
Cursor is a standalone Electron app forked from VS Code. It ships a $20/month Pro plan that proxies requests to multiple model providers through Cursor’s own infrastructure. You can also paste an OpenAI or Anthropic key into its settings to bypass Cursor’s metering for those specific models.
Cline (formerly Claude Dev) is a VS Code extension. It has no backend. You supply the key, it calls the provider directly from your machine. Out of the box it supports Anthropic, OpenAI, and any OpenAI-compatible base URL—including OpenRouter, Together, Groq, or a self-hosted vLLM.
Supported keys at a glance
| Dimension | Cursor | Cline |
|---|---|---|
| Bring-your-own Anthropic key | Yes (settings UI) | Yes (settings UI) |
| Bring-your-own OpenAI key | Yes (settings UI) | Yes (settings UI) |
| Arbitrary OpenAI-compatible endpoint | No (closed to first-party) | Yes (base URL field) |
| Subscription covers models | Yes (GPT-4, Claude, etc.) | No (extension free) |
| Direct provider billing | Only for BYO keys | Always |
| Key storage | Local encrypted + Cursor account | Local VS Code settings |
| Multi-key rotation | No | No (single active provider) |
Capabilities
Cursor’s BYO mode restricts you to the models those two vendors expose. If you hook in sk-... from OpenAI, you get gpt-4o, gpt-4-turbo, etc. With an Anthropic key you get Claude 3.5 Sonnet and friends. Cursor’s subscription additionally unlocks model routing across providers, but that uses Cursor’s key, not yours.
Cline imposes no such ceiling. Point it at an OpenAI-compatible gateway and you can drive mistral-large, llama-3.1-405b, or a fine-tune. The extension sends standard chat completion requests:
# What Cline does under the hood when you set an OpenAI-compatible base URL
from openai import OpenAI
client = OpenAI(
base_url="https://your-gateway.example/v1",
api_key="sk-...",
)
client.chat.completions.create(
model="anthropic/claude-3.5-sonnet",
messages=[{"role": "user", "content": "Refactor this function"}]
)Both tools handle file reads, edits, and terminal commands. Cursor bundles a diff viewer inside its custom editor; Cline shows explicit approve/reject prompts for each filesystem action. For agentic loops, Cline’s transparency is better—you see the exact request payloads in the logs. Cursor abstracts the transport, which is convenient but hides the wire format.
Function calling is supported in both, but Cline lets you inspect the tool schema it emits. Cursor’s inline chat uses a proprietary prompt wrapper that you cannot modify. If you need to forward provider cache-control hints (e.g., x-cache-control: ephemeral for Anthropic prompt caching), Cline’s open request pipeline makes that a one-line patch; Cursor does not expose the headers.
Price and cost model
Cursor’s Pro plan is a flat monthly fee with a fair-use quota. If you exceed it, requests fail or fall back to your BYO key if configured. Using your own OpenAI or Anthropic key means you pay the provider’s published per-token price; Cursor adds no markup in BYO mode.
Cline is free. You pay only what your provider charges. There is no intermediary taking a cut. If you route through a gateway such as n4n.ai, you still get per-token metering and automatic fallback when a provider is degraded, but the extension itself stays out of the billing path.
Example: a 10k-token completion on Claude 3.5 Sonnet costs the same whether called from Cline or Cursor’s BYO mode, because both hit Anthropic’s API directly. Cursor’s subscription hides that granularity behind a flat fee. With Cline, your credit balance with the provider (or gateway) is the only limit.
Latency and throughput
Cline opens a TLS connection from your machine to the provider’s endpoint. Latency is dominated by the model itself and your network path. No extra proxy hop.
Cursor’s subscription traffic goes through Cursor’s servers, adding a round-trip. With BYO keys, the client still authenticates with Cursor before forwarding—observed behavior shows a lightweight relay. The difference is usually 20–50 ms, negligible for codegen but relevant for high-frequency agent loops where hundreds of small calls stack up.
Throughput is bounded by provider rate limits. Cline respects the Retry-After header and backs off. Cursor’s subscription may queue requests during peak load; BYO mode inherits your provider’s RPM. If you run Cline against a local model, throughput is limited by your GPU, not a cloud quota.
Ergonomics
Cursor feels like an IDE. Autocomplete, inline chat, and a command palette are native. Configuring a key is a two-field form. The downside: you’re locked into their build; if they drop support for a model, you wait for an update.
Cline lives in the VS Code sidebar. You paste a key, pick a provider, and start. Because it’s open-source, you can patch the request builder to add headers or swap the URL without waiting on a release. Cursor doesn’t expose that level of control.
// Example VS Code settings.json snippet for Cline (illustrative field names)
{
"cline.apiProvider": "openai-compatible",
"cline.baseUrl": "https://api.n4n.ai/v1",
"cline.apiKey": "sk-...",
"cline.model": "anthropic/claude-3.5-sonnet"
}The above is the shape of the config; the exact key names follow Cline’s settings schema. Cursor stores its keys in a similar JSON but only accepts openai or anthropic as provider enums—no baseUrl escape hatch.
Ecosystem and limits
Cursor has a closed plugin system and a commercial roadmap. Limits are: Pro quota (approximately 500 fast requests/month as of writing, subject to change), BYO key rate limits from OpenAI/Anthropic. You cannot use a third-party OpenAI-compatible key; the UI rejects unknown base URLs.
Cline’s ecosystem is GitHub Issues and PRs. Limits are purely those of your key: Anthropic’s 20 req/min, OpenAI’s tier caps, or your self-hosted GPU memory. Because it accepts any OpenAI-compatible URL, you can stand up a local llama.cpp and never hit a cloud quota. You can also script key rotation by writing to the settings file from a cron job—something Cursor’s UI does not allow.
Security posture differs too. Cursor syncs keys to its account cloud for cross-device use; Cline keeps them in local VS Code storage. For air-gapped environments, Cline pointed at a local endpoint is the only viable option.
Which to choose
Choose Cursor if: you want an all-in-one IDE, don’t want to manage provider accounts, and primarily use GPT-4-class or Claude models. The BYO key support is a nice escape hatch when the subscription quota runs dry, but you are still confined to two vendors.
Choose Cline if: you need model diversity, cost transparency, or on-prem inference. Its support for arbitrary OpenAI-compatible endpoints means you can swap providers without changing tools. Point it at a single gateway key and you get 240+ models behind one OpenAI-compatible endpoint. You also keep full control of request headers and local logging.
Choose neither exclusively: many teams run Cursor for quick edits and Cline for deep agentic refactors. Both read the same ~/.vscode settings if you standardize on VS Code, so the migration cost is low.
If you only want one key to rule them all, a gateway that honors client routing directives and forwards cache-control hints lets Cline consume it directly; Cursor’s BYO remains limited to first-party keys, so you’d still need a native Anthropic or OpenAI key there. That’s the practical split—wire up what matches your procurement and latency needs.