At the tool level, free vibe coding is real: Cline, Aider, OpenCode and Continue are open source, and you can install and run them without paying anything. But the tool is only a shell. The model that writes the code is a separate line in your budget, and it is free only in weak or local variants. What follows: what each of the four does, where they truly cost nothing, and how to get Claude if you decide not to save on the model.
What "free vibe coding" actually means
Two different questions get mixed together here. How much does the tool cost, the one you use to talk to a model? And how much does the model itself cost? The answers are almost never the same.
Cline, Aider, OpenCode and Continue answer the first question identically: open source, open license, no subscription for the tool itself. The second answer depends on the model you connect. With a weak open model or a free web chat, vibe coding costs zero rubles. With a top model such as Claude, you pay for every API call, and the money goes to the model provider, not to the tool.
Cline: an agent inside VS Code
Cline is an open-source VS Code extension. It works as an agent in the editor: it reads project files, proposes edits and, with your permission, runs commands in the terminal. It installs from the VS Code extension marketplace in a minute.
It connects as an OpenAI-compatible provider. If you point Cline at codexkey, the settings look like this:
| Setting | Value |
|---|---|
| Base URL | https://api.codexkey.online/v1 |
| API Key | your codexkey key |
| Model ID | claude-sonnet-5 |
Cline itself is free with no limits. The only money that leaves is for the model you attached to it.
Aider: pair programming in the terminal
Aider is an open-source terminal tool built around git. It commits changes for you as the session goes, so rolling back is easy when a generation heads the wrong way. According to the official Aider documentation (aider.chat), an arbitrary OpenAI-compatible endpoint is configured through environment variables:
export OPENAI_API_BASE="https://api.codexkey.online/v1"
export OPENAI_API_KEY="sk_cdx_your_key"
You name the model at launch, with a provider prefix:
aider --model openai/claude-sonnet-5
Aider needs no IDE and runs in a plain terminal. It suits people who prefer a git-centered workflow without a visual interface.
OpenCode: an open agent for the terminal
OpenCode is an open-source terminal agent meant as a vendor-neutral alternative to Claude Code. Same idea, an agent in the shell, but tied to no single model. The configuration lives in opencode.jsonc:
// ~/.config/opencode/opencode.jsonc
{
"$schema": "https://opencode.ai/config.json",
"provider": {
"anthropic": {
"options": {
"baseURL": "https://api.codexkey.online/v1",
"apiKey": "sk_cdx_your_key"
}
}
}
}
After that, the opencode command in your terminal works with the connected model right away. Instructions for Windows, macOS and Linux, including where the config file sits on each system, are in the OpenCode guide.
Continue: an extension with a flexible model choice
Continue is another open-source VS Code extension, and it keeps its settings in the JSON file ~/.continue/config.json. You can list several models at once: a cheap one for routine work and a stronger one for hard tasks.
{
"models": [
{
"title": "Claude Sonnet 4.6 (codexkey)",
"provider": "openai",
"model": "claude-sonnet-5",
"apiBase": "https://api.codexkey.online/v1",
"apiKey": "sk_cdx_your_key"
}
]
}
Switching the model for a given task is a pick from a dropdown in the interface. No config editing on the fly.
What is free in these tools and what is not
| Tool | Type | Free | What you pay for |
|---|---|---|---|
| Cline | VS Code extension | The tool itself, no limits | Tokens of the connected model |
| Aider | Terminal | The tool itself, no limits | Tokens of the connected model |
| OpenCode | Terminal | The tool itself, no limits | Tokens of the connected model |
| Continue | VS Code extension | The tool itself, no limits | Tokens of the connected model |
The picture is simple: the software is open and asks for no money. You pay only for the model named in the config.
Fully free: local models
If the goal is not to save but to spend nothing at all, one workable route remains. Run an open model locally on your own hardware and point any of the four tools at it over the same OpenAI-compatible protocol. The entry bar is higher: you need a graphics card with enough memory, a configured local inference server, and a readiness to accept weaker code than top cloud models write. For prototypes and learning, this setup works. On a real project with real deadlines, the quality gap usually justifies the move to a paid model fast.
Cheap access to Claude for these tools through codexkey
Say the comparison showed that the free model gets things wrong too often and you need Claude specifically. Then the cheapest route is a codexkey API key, not a subscription or a direct account with Anthropic. The balance tops up from $1, billing follows actual token use, and there is no mandatory monthly payment.
A key of the form sk_cdx_... is created in your account, under "API keys", and works in all four tools from this article. Only the base URL and the key change in the settings; the rest of the tool's config stays as it was.
# Example for Aider; Cline, OpenCode and Continue work the same way
export OPENAI_API_BASE="https://api.codexkey.online/v1"
export OPENAI_API_KEY="sk_cdx_your_key"
Top-up methods: YooKassa (Russian cards, SBP, the Russian Faster Payments System), Platega (SBP by QR code, foreign cards), plus CryptoCloud, CryptoBot and 2328 for crypto payments. The current model list and the price per million tokens are on the models page. If you decide to add Claude Code too, its basic setup is covered in the installation guide.
FAQ
Are Cline, Aider, OpenCode and Continue really free?
Yes. In each case the tool itself is open source, with no subscription and no usage limits. What you pay for is not the tool but the model you connect to it.
Can I vibe code with no money at all?
You can: connect an open model running locally, or use a free web chat instead of an API. The fully free route needs either a powerful computer or a willingness to live with weaker code.
How is Aider different from Cline and Continue?
Aider runs in the terminal and is built around git, committing changes as the session goes. Cline and Continue are VS Code extensions with a visual interface inside the editor. Pick whichever you are more used to: terminal or IDE.
Does OpenCode work with Claude?
Yes. OpenCode is not tied to a model and connects to any provider that fits its configuration, including Claude through codexkey. Setup goes through the opencode.jsonc file and takes a few minutes.
What is the cheapest way to connect Claude to these tools?
Top up your codexkey balance from $1, create an API key and enter it, together with the base URL, in the settings of the tool you chose. Billing follows actual token use, with no mandatory monthly amount.
Are there risks with free open-source tools?
The main risk is the same as with paid ones: the model key you paste into a config file must not end up in a public git repository. Make sure files with keys are listed in .gitignore, whichever of the four tools you pick.