Valen is a lightweight coding-agent harness in a single Go binary, inspired by OpenCode. It has no server and no runtime dependencies.
The aim is the same agent loop at a small fraction of the resource footprint: about 50 MB of RAM in use, and less than 10% CPU per agent running.
It has a terminal chat UI and a one-shot headless mode, talks to OpenCode Go/Zen and OpenRouter models, and runs the tool loop locally.
Valen is built macOS first, with Linux as a secondary target.
| Interface | Bubble Tea terminal UI and headless -p mode. |
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| Tools | shell, read, write, edit, glob, grep, web_search, web_fetch, plus todos and questions. |
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| Attachments | @ fuzzy picker for files and folders, drag-and-drop paths and ctrl+v screenshots. |
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| Models | Live model, reasoning-effort and OpenRouter routing switching (/model, /effort, /route). |
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| Subagents | Foreground tasks with isolated history, up to 5 in parallel. | — |
| Sessions | JSONL session logs, resume, and summary-style auto-compaction. | — |
| MCP | Stdio MCP servers. | — |
| Plan Mode | Read-only investigation before making changes. | — |
| Sandboxed | macOS sandbox-exec first, Linux bubblewrap. Blocks writes outside the workdir and hides secrets. |
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git clone https://github.com/keyle/valen && cd valen
make install
Requires Go. macOS is the primary target; Linux works too, with bubblewrap. Set an API key and run valen.