Aider and Devin are the two faces of AI coding agents — and the cheapest and the most autonomous ones, respectively. Aider is free and open source (Apache 2.0): a terminal pair programmer where you bring your own API key and pay only for the tokens you burn, or run a local model for near-zero cost. Devin (by Cognition) is the canonical autonomous software engineer: you assign it tickets from Slack or Linear and it works in its own cloud sandbox, opening pull requests while you're away — starting from a free tier, with Pro at $20/month (quota-based, overage at API pricing).
The trade is control versus delegation. Aider keeps you in the driver's seat and your code on your machine: every change happens where you can see it, and you choose the model and the budget. Devin takes the wheel: parallel agents, end-to-end execution, code review as the only checkpoint. Both are loved by terminal-first developers, but for opposite reasons — this page compares them on the dimensions that decide.
| Aider | Devin | |
|---|---|---|
| Category | Terminal AI pair programmer (open source) | Autonomous AI software engineer |
| Price | Free tool; you pay only your LLM API usage (can be near $0) | Free tier; Pro $20/mo; Max $200/mo; Teams $80/mo + $40/seat — quota-based, overage at API pricing |
| Open source | Yes (Apache 2.0) | No (proprietary) |
| Model choice | Any LLM, including local models via Ollama | OpenAI, Claude, and Gemini frontier models plus Cognition's own |
| Where it runs | Locally on your machine | Its own cloud sandbox |
| Work model | Supervised: you prompt, it edits; auto-commits to your branch | Autonomous: plans, codes, tests, opens PRs; you review |
| Parallelism | One session at a time | Many agents in parallel across repos |
| Setup | pip install + your API key | Sign up, connect GitHub/GitLab, assign a task |
| Privacy | Local by default; code leaves only via your chosen model API — never, with a local model | Code is processed in Cognition's cloud; SOC 2 Type II on Enterprise plans |
| Cheapest real-world cost | Near $0 with a cheap API model or a local one | Free tier covers small quotas; serious use starts at $20/mo plus overage |
Open-source AI pair programmer for your terminal.
Free and open source (pay only for your LLM API usage)
Try Aider →The autonomous AI software engineer that works while you sleep.
Free tier (limited); Pro from $20/mo, Max $200/mo, Teams from $80/mo
Try Devin →Pick Aider if cost and control dominate: it is the cheapest way to get a capable agent, runs locally, and lets you pick any model — including local ones for full privacy. Pick Devin if your bottleneck is throughput: nothing in Aider's world replicates handing off ten well-scoped tickets and reviewing ten PRs in the morning. The pragmatic setup many developers describe is both: Aider for the focused session where you want a specific model or no cloud at all, Devin for the batch of background tickets. One warning that survives Devin's pricing overhaul: the metered part of the bill is where budgets surprise people, so set usage limits and confirm the current quotas on the official pricing page.
The tool is free and open source (Apache 2.0). Your only cost is model API usage from whichever provider you connect — near zero with a cheap model, exactly zero with a local model.
Pro is $20/month with daily and weekly usage quotas; heavy use adds overage billed at API pricing. Devin added budget caps after developers reported surprise bills, so set a limit and confirm the current quotas on the official pricing page.
Not really. Aider is a supervised pair programmer — you stay in the loop for every change. Devin is built to work alone on delegated tasks. If you want hands-off execution while you're away, that is Devin's job.