Reasonix
Reasonix is an open-source, MIT-licensed coding agent that runs locally and is designed to be left running for hours. It offers one engine with four ways in, a terminal CLI, a desktop app, a browser interface, and an editor integration over ACP. Plan mode holds writes until approved, permissions gate each tool call, and per-turn checkpoints let users rewind a six-hour run without touching git history. Users bring their own DeepSeek API key.
What is Reasonix?
Reasonix is an open-source coding agent built around a simple premise: letting an agent run for hours is only useful if you can see what it did and undo the parts you do not want. The engine runs locally as a single CGO-free Go binary that cross-compiles for macOS, Windows, and Linux on both amd64 and arm64, with nothing else to install underneath it. Users bring their own DeepSeek API key, and the engine sends code only to the configured model, which makes the tool attractive for privacy-sensitive work. Reasonix offers four ways to interact with the same local engine: a terminal CLI, a desktop app, a browser interface, and an editor connection over the ACP protocol, with official extensions for Visual Studio Code and VSCodium-compatible editors. Safety and control are the product's core differentiators: plan mode holds every write until the user reads and approves the plan, a permissions system gates each tool call, a workspace sandbox contains the agent's actions, and per-turn checkpoints are written outside git so a long run can rewind to any point without polluting commit history. The site positions it as built to be left running, and it pairs with the DeepSeek platform's models, currently tracking a v1.22.0 release with deepseek-v4-flash shown in examples. Reasonix is MIT-licensed, developed in public on GitHub under the esengine organization, and includes a skills marketplace, documentation, changelog, and community section, plus an optional sign-in for synced features. The engine sends code only to the configured model, which makes the tool attractive for privacy-sensitive work. Reasonix offers four ways to interact with the same local engine: a terminal CLI, a desktop app, a browser interface, and an editor connection over the ACP protocol, with official extensions for Visual Studio Code and VSCodium-compatible editors. Safety and control are the product's core differentiators: plan mode holds every write until the user reads and approves the plan, a permissions system gates each tool call, a workspace sandbox contains the agent's actions, and per-turn checkpoints are written outside git so a long run can rewind to any point without polluting commit history. The site positions it as built to be left running, and it pairs with the DeepSeek platform's models, currently tracking a v1.22.0 release with deepseek-v4-flash shown in examples. Reasonix is MIT-licensed, developed in public on GitHub under the esengine organization, and includes a skills marketplace, documentation, changelog, and community section, plus an optional sign-in for synced features.
Reasonix Core Features
Four surfaces, one engine
Use the same local engine from the terminal, desktop app, browser, or editor over ACP.
Plan mode
/plan holds every write until you read the plan and approve it.
Per-turn checkpoints
Checkpoints are written outside git, so a six-hour run rewinds to any point without touching commit history.
Workspace sandbox and permissions
Gate each tool call and contain the agent inside the workspace.
Bring your own DeepSeek key
Code goes to the model you configure and nowhere else.
Single Go binary
CGO-free, cross-compiled for macOS, Windows, and Linux on amd64 and arm64.
Editor integrations
Official extensions for Visual Studio Code and VSCodium-compatible editors.
MIT licensed and developed in public
Open source on GitHub with a skills marketplace and community.
Who is Reasonix for?
Reasonix is aimed at developers who want a long-running autonomous coding agent that stays readable and reversible. Solo developers who leave agents working on a codebase for hours will value the per-turn checkpoints that make any six-hour run rewritable, while teams that need oversight benefit from plan mode, which holds all writes until a human approves them. Developers working across multiple machines will like the four surfaces, terminal, desktop app, browser, and editor over ACP, and the VSCode and VSCodium extensions make it easy to bring Reasonix into an existing editor workflow. Users who are privacy-conscious about their code will appreciate that the engine runs locally and code only goes to the model they configure, which makes it attractive for work with sensitive or proprietary codebases. The skills marketplace and community sections suggest it also appeals to developers who like to share and reuse agent skills, and the MIT license invites contributors and tinkerers who want to modify the tool itself. The browser surface also makes it convenient for developers who want to supervise long runs from a tablet or another machine, and the skills marketplace appeals to developers who like to share reusable agent skills with the community. The MIT license invites contributors who want to modify the tool itself, and teams that standardize on DeepSeek models can adopt Reasonix as their agent runtime. Because it works locally, it also fits developers who are skeptical of cloud-based coding agents that send code to third-party servers.
Reasonix Use Cases
Leave Reasonix running overnight on a large refactor, then rewind any turn you do not like.
Review a proposed plan before the agent writes a single line of code with plan mode.
Run the agent from your editor through ACP without switching to a separate tool.
Use the browser surface to supervise a long autonomous run from another machine.
Add retry-with-backoff logic to an HTTP client and let the agent run the tests itself.
Work on proprietary code with confidence that it only goes to your configured model.
Reasonix Pros and Cons
Pros
- Free and open source under MIT with a single-binary install.
- Checkpoint system makes long autonomous runs safe to undo.
- Code stays local and only goes to the model you configure.
- Four interfaces including editor integration over ACP.
- No account required for local use.
Cons
- Requires your own DeepSeek API key and its associated costs.
- Aimed at developers comfortable with CLI and agent workflows.
- The VSCode extension requires Reasonix installed and configured locally.
FAQ About Reasonix
Reasonix Pricing
Free: open-source MIT-licensed engine; users bring their own DeepSeek API key and pay only for model usage.
Check official pricingFree
Open-source Reasonix engine with terminal, desktop, browser, and editor surfaces. Bring your own DeepSeek API key.
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