A pluggable language substrate.
Arth is not just a language – it is a compiler infrastructure with pluggable frontends, multiple backends, and a shared HIR that any language can target. TypeScript and Arth ship out of the box.
One HIR. Many frontends. Many backends.
The HIR is the universal convergence point. Any language that lowers to HIR gets type checking, optimization, and all backends for free.
Write in what you know.
- Java-like syntax, Rust-grade memory safety
- Ownership + borrowing with inferred lifetimes
- Modules for behavior, not classes
- Typed exceptions, no null
- Providers for shared state
- Async/await with controlled scheduling
- Familiar syntax for web developers
- Compiles through the same HIR pipeline
- Gets the same backend targets
- Same type checking and optimization passes
Both ship out of the box. More frontends can be added by implementing the AST → HIR lowering.
Compile to anything.
VM
Compiles to .abc bytecode for the Arth VM runtime. Portable, inspectable, and ideal for sandboxed execution where determinism matters most.
LLVM
Emits LLVM IR for ahead-of-time native compilation. Full optimization pipeline. Targets any architecture LLVM supports.
Cranelift JIT
Just-in-time compilation via Cranelift. Fast startup, native speed at runtime. Ideal for interactive and REPL-style workflows.
Choose the backend that fits your deployment: VM for safety, LLVM for performance, Cranelift for speed of iteration.
Sandboxed or full access. Your choice.
- Runs inside the Arth VM
- No direct system calls
- Memory-safe by construction
- Deterministic execution guarantees
- Ideal for untrusted code and agents
- Native compilation via LLVM or Cranelift
- Direct hardware and OS access
- FFI with extern functions
- Full performance, no VM overhead
- For trusted systems-level code
The same source compiles to either mode. One language, two trust levels.
Designed for correctness.
Java-like syntax. Rust-grade memory safety. No runtime surprises.
When determinism is non-negotiable.
Arth powers Rune's deterministic mode.
When Arth targets Rune, it compiles directly to IR – bypassing browser semantics entirely. No DOM, no arbitrary layout. The result is deterministic, replayable, auditable UI execution.
Arth is optional. Web compatibility mode remains available for existing apps. Arth is chosen when deterministic control outweighs ecosystem breadth.
Where Arth leads.
Arth is open source.
The Arth compiler, language specification, and toolchain are open source. Build on it, extend it, plug in new frontends. The language substrate belongs to the community.