TL;DR
Aider is an open-source CLI holding your own API keys, talking straight to the AI provider. Cursor is a closed-source IDE that routes every request through its own servers, with Privacy Mode as an opt-in. The real split isn't features, it's whether you can verify the privacy claim or have to take it on trust. Both still send your code to a cloud model unless you run Aider against a local one.
The difference between these two isn't the editor. It's how many companies touch your code on the way to the model.
Aider runs in your terminal alongside whatever editor you already use, and you connect it to the AI provider yourself. Cursor is a VS Code fork with a managed service sitting between you and the model. That one architectural choice drives almost every security difference below.
Platform Overview
What Is Aider?
Aider is an open-source AI pair programmer that runs in your terminal. It connects straight to AI providers (OpenAI, Anthropic, and others) with your own API keys, reads your codebase, follows your git history, and edits files in place. Because the source is public, "what does it send?" is a question you can answer by reading, not by asking.
What Is Cursor?
Cursor is a closed-source editor forked from VS Code, with AI wired through the whole thing: completion, chat, multi-file edits. Behind it sits Cursor's own backend, which handles API routing, accounts, and codebase indexing. Privacy Mode stops your code being stored on those servers. It doesn't stop it passing through them.
Security Feature Comparison
| Security Feature | Aider | Cursor |
|---|---|---|
| Open Source | Yes (Apache 2.0) | No |
| API Key Control | Your keys, direct connection | Cursor-managed or BYOK |
| Middle Layer | None | Cursor servers |
| Privacy Mode | Inherent (no intermediary) | Optional setting |
| Codebase Indexing | Local only | Can be cloud-synced |
| Auditability | Full source available | Limited to policies |
| Local Models | Supported (Ollama, etc.) | Not supported |
| Enterprise Features | DIY | Business tier |
Data Flow Transparency
Aider's Direct Connection
Aider connects from your machine to the provider and stops there. Point it at OpenAI and your code goes to OpenAI's API, with nothing in between collecting telemetry or routing requests. You don't have to believe that: read the source, or watch the network traffic. Two parties, one hop.
Aider transparency benefits:
- Open source code you can audit
- Direct API connections with no intermediary
- Your API keys stay on your machine
- No account or telemetry required
Cursor's Service Layer
Cursor routes requests through its backend even when the API key is yours. That's what makes usage tracking, team management and codebase indexing possible, and it's a reasonable trade for most teams. Privacy Mode is a commitment not to store your code. Storage and transit are different things, and only one of them is covered. What you're relying on here is a policy, not something you can check.
Cursor service layer considerations:
- Requests route through Cursor servers
- Privacy Mode prevents storage but not transit
- Features like indexing may sync data
- Can't independently verify behavior
Local Model Support
Aider with Local Models
Aider works with local models through Ollama, LM Studio and similar inference servers, which means AI coding help where nothing leaves the machine. Local models are still weaker than the frontier ones, and you'll feel it. But if the codebase is sensitive enough that the question keeps coming up, "nothing left the building" ends the argument in a way no privacy policy can.
Cursor's Cloud Requirement
Cursor has no local model story. Every request goes to a cloud provider through Cursor's services. If on-premise is a hard requirement rather than a preference, that settles it: Cursor is out, and no setting changes that.
Choose Aider When: You need to be able to prove what happens to your code, not just describe it. Open source plus a direct API connection means the privacy claim is checkable. Best if you're working on sensitive code, if someone will eventually audit your tooling, or if you want local models.
Choose Cursor When: The experience matters more to you than verifiability, and Cursor's commitments are ones you're willing to take at their word. Autocomplete and codebase chat are genuinely better here. Best for teams who'd rather ship than audit, which is most teams.
API Key Management
Aider's Approach
Aider reads keys from environment variables or a config file on your machine, and they leave only to authenticate the API call itself. Rotation, access control and billing are your relationship with the provider. Nobody else is holding the credential. That also means nobody else is going to notice when it's been sitting unrotated for a year.
Cursor's Approach
Cursor gives you a choice: their managed API access, included in the subscription, or bring your own key. Worth reading the second option carefully. Even with BYOK, it's Cursor's service that holds the key and calls the provider on your behalf, so "my own key" doesn't mean "my own connection." You've saved yourself the setup and handed over a credential.
Git Integration Security
Aider's Git Awareness
Aider leans hard on git, committing its own changes with written messages and reading history to understand the codebase. The git operations themselves are local; nothing goes out beyond the code sent for generation. You can audit all of it.
Cursor's Git Features
Cursor inherits VS Code's git integration, so the operations are local there too. The difference is context: Cursor's AI features may pull git history in as context for a suggestion, and that context goes through Cursor's services. Privacy Mode keeps it from being stored. It still gets processed.
Best Practices
- Use Aider with local models for maximum privacy on sensitive code
- Enable Cursor Privacy Mode for any commercial work
- Configure .aiderignore or .cursorignore to exclude sensitive files
- Audit Aider's source code for high-security environments
- Use separate API keys for coding tools vs production systems
- Review AI-generated code regardless of tool choice
Can I use Aider without sending code to the cloud?
Yes, Aider supports local models through Ollama and similar tools. With a local model, your code never leaves your machine. This provides maximum privacy at the cost of reduced AI capability compared to cloud models.
Does Cursor store my code even with Privacy Mode?
Privacy Mode stops your code being stored on Cursor's servers. It still transits their infrastructure on the way to the AI provider. That's a commitment you're trusting, not an architecture you can inspect the way you can with Aider's direct connection.
Which tool is better for enterprise compliance?
Aider makes the documentation easier, because you control the whole data flow and can describe it accurately without asking anyone. Cursor Business has the enterprise features, but the compliance story rests on their claims rather than yours. Which one your auditor prefers depends on whether they want evidence or attestations.
Can I verify what Aider sends to AI providers?
Yes, Aider is open source and you can read exactly what code it sends to APIs. You can also run it with verbose logging or inspect network traffic. This auditability is a significant security advantage over closed-source alternatives.
Further Reading
Made your choice? Here's how to secure your selected stack.
Validate AI-Generated Code
CheckYourVibe scans code from Aider, Cursor, and other AI tools for security vulnerabilities.