Klar

Ambiguity is more dangerous than verbosity.

Klar exists to fight the upgrade treadmill: systems that require periodic “big rewrites” because the stack evolves through accumulated implicit behavior, defaults, and patch-on-patch fixes.

Klar is an experimental language focused on explicitness, rigor, and deterministic compilation. It treats diagnostics as a stable API — not a side effect — because long-lived systems need predictable meaning, not guessed intent.

This is for you if:

You’ve inherited a codebase where updates feel like paying off yesterday’s workaround.
You want fewer “major migrations” because the semantics stay stable.
You care about actionable diagnostics and no silent fallbacks as a contract.

Get Started Diagnostics Language Spec →

Strict by defaultNo implicit behaviorPolyglot orchestration

Klar Snapshot

What you get — at a glance.

EXPERIMENTAL

Why: Reduce rewrite cycles by making semantics explicit

Core: Explicitness • Determinism • Diagnostics

Guarantee: No silent fallbacks

Diagnostics: Stable codes + actionable fixes

Target: JVM / Java integration (today)

Read the intro →See diagnostics →

Quickstart

Minimal steps. No marketing. Just a working path.

Install

Install tooling and verify the CLI. Keep it explicit.

# example
git clone https://github.com/KlarLang/loom
cd loom
./install.sh   # install.bat on Windows
loom install

Installation guide →

Example

@Use("java")
public integer calculateSum(integer a, integer b) {
    return a + b;
}

Hello World →

Principles

Klar is strict by default because defaults shape behavior.

Explicitness

If something matters, it must be written down.

Rigor & intent →

Determinism

No silent fallbacks. No guessed intent.

Semantics →

Diagnostics

Errors must explain what failed, why, and how to fix.

Diagnostics API →

Ready to explore Klar?

Start with the minimal path. Then go deep on rigor and diagnostics.

Start Now Read Intro