Yasumu
The modern, open-source API laboratory for designing, testing, and debugging workflows.
Download • Documentation • Contributing
[!IMPORTANT]
Yasumu is currently in active Beta.
We are rapidly prototyping and iterating. While the core is functional, you may encounter unfinished features or bugs. We highly value your feedback and contributions as we polish the experience toward a stable v1.0 release!
Overview
Yasumu is built for developer productivity, speed, and freedom. It uses Tauri as the desktop shell with a Next.js frontend, while the core backend runs on an embedded custom JavaScript runtime powered by Deno.
It feels like the tools you already know, but with the flexibility to handle complex, experimental workflows directly in your file system.
Why Yasumu?
Most API clients store your collections in proprietary formats or require cloud accounts just to use basic features. Yasumu takes a different approach: everything lives in your project folder as plain .ysl files that you can commit, diff, and review like any other code.
The app runs on Tauri with an embedded custom JavaScript runtime powered by Deno. This handles everything from request execution to scripting—write your pre-request logic in TypeScript without setting up external tooling.
No account required. No cloud sync. No paid tiers. Just a tool that works offline and stays out of your way.
Interface
Protocol Support
Yasumu is evolving to become a protocol-agnostic powerhouse.
| Protocol | Status | Notes |
|---|
| REST API | ✓ | HTTP/HTTPS plus streamed SSE responses |
| Catch-all SMTP | ✓ | Integrated local email server for testing |
| GraphQL | ✓ | Queries, mutations, and subscriptions |
| WebSocket | — | In development |
| Server-Sent Events | ✓ | Streaming, reconnects, scripts, and tests |
| Socket.IO | — | In development |
Concepts & Workflow
Yasumu acts as an IDE for your API interactions. Unlike tools that hide data in proprietary databases or cloud silos, Yasumu lives in your repo.
Project-Based Workspaces
When you initialize Yasumu in a project, it creates a yasumu directory. Your definitions, tests, and workflows are stored here using the Yasumu Schema Language (.ysl)—a custom format designed for readability and clean git diffs.
Collaboration via Git
- Commit & Push: Treat your API collections as code.
- Review:
.ysl files are text-based, making Pull Request reviews easy.
- Sync: Teammates simply pull the branch to get the latest API workflows.
- Secure: Sensitive secrets are managed via local environment variables, and each workspace's editable cookie jar stays only in Yasumu's local database. Neither is committed to YSL.
Runtime Architecture
Tauri provides the desktop shell and OS-level operations. The backend—request execution, scripting, and core logic—runs on an embedded custom JavaScript runtime built on deno_runtime.
Tech Stack
- Frontend: Next.js (React)
- Desktop Shell: Tauri
- Backend Runtime: Embedded custom JS runtime powered by Deno
- Platforms: Windows, Linux, macOS
Installation
Get the latest installer for your operating system:
Download Yasumu
Tanxium CLI
Install the latest prebuilt Tanxium CLI on macOS or Linux:
curl -fsSL https://raw.githubusercontent.com/neplextech/yasumu/main/scripts/install-tanxium.sh | sh
Install it on Windows from PowerShell:
irm https://raw.githubusercontent.com/neplextech/yasumu/main/scripts/install-tanxium.ps1 | iex
Set TANXIUM_INSTALL_DIR to override the default installation directory. If
you have Rust installed, you can alternatively build and install the CLI from
crates.io:
cargo install tanxium-cli
Philosophy
- Open Source by Default: Transparency builds trust.
- Zero Vendor Lock-in: Your data belongs to you, on your disk.
- Developer Experience First: Fast, beautiful, and keyboard-friendly.
- Sustainability: Built for long-term maintainability over hype.
License
Yasumu is developed by Neplex and is licensed under the AGPL-3.0. See LICENSE for details.
