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DocumentationCatalyst1100252 - Scalus

Scalus - multiplatform Scala implementation of Cardano Plutus

Project Description

Scalus  is a Scala implementation of Cardano Plutus, PlutusTx, including UPLC evaluation machine and built‑ins for V1 and V2.

It allows developers to write Cardano smart contracts using Scala 3  programming language.

Scalus leverages Scala compiler plugin system and macros to convert Scala code to Cardano Untyped Plutus Core (UPLC), similarly to how Plutus converts Haskell to UPLC.

It also provides a full‑featured UPLC parser, pretty‑printer, and an evaluation engine that can run on multiple platforms: JVM (Java, Kotlin, etc.), JavaScript (Node.js, browsers), and even Native ( C/C++/Rust, etc.) via LLVM backend.

Close‑out Video

Project KPIs • How We Addressed Them

Project KPIOutcome
Scala to UPLC compilerHuge amount of unit tests, Scalus Standard library code and real smart contracts like Hydrozoa, Binocular, Cosmex and AdaStream
Full Plutus V1/V2 CEK Coverage100 % of V1 & V2 built‑ins + cost models implemented; V3 core delivered ahead of schedule
Cross‑Platform Reach
Make tooling available beyond Haskell ecosystem		One codebase ships as JVM JAR, JavaScript ESM/NPM package, and Native C‑ABI library (Key Achievements #2)
Script Budget AccuracyVerified against 100k mainnet scripts with exact budget match
Packaging & Documentation12+ tagged releases to Maven Central & NPM, Scalus Starter Project, full API docs, site with documentation and tutorials
Community Uptake100 ★ on GitHub, >50 Discord members, 18 contributors; integrations with leading JS SDKs (Key Achievements #4 & #5)
Ecosystem Collaboration
Demonstrate real‑world adoption		Library already powers Binocular oracle & Hydrozoa mini‑Hydra; Lucid Evolution & Mesh.JS integrations underway (Key Achievements #4)

Key Achievements

  1. Scala to UPLC Compiler – Developed Scala 3 compiler backend to translate Scala code to UPLC, enabling writing Plutus contracts in Scala.
    UPLC CAPE benchmarks  show Scalus‑generated UPLC is on par with and even better than Plinth/Aiken/Plutarch.
  2. Complete CEK & Built‑ins – Implemented Plutus V1 & V2 virtual machines, built‑ins, cost models, UPLC parser & pretty‑printer entirely in Scala 3.
  3. Triple‑Target Build – Single codebase compiles to JVM (JAR), JavaScript (NPM/ESM via Scala.js) and Native shared library (Scala Native + LLVM).
  4. Deterministic Budget Validation – Replayed ≈100,000 mainnet scripts; Scalus results matched the reference node byte‑for‑byte for both outcome and budget.
  5. Ecosystem Integration – Scalus already underpins the Binocular optimistic Bitcoin oracle and the Hydrozoa improved Hydra‑like state channels protocol prototype; active work to embed the JS library into Lucid Evolution and Mesh.JS SDKs.
  6. On‑boarding & Community – Published Scalus Starter Project, full API site, Discord support, CI‑driven release flow to Maven Central & NPM; project has ~100 GitHub stars and several external contributors.
  7. V3 Support – Delivered core UPLC V3 support ahead of schedule, including CEK updates and built‑ins.

These milestones collectively make Scalus the only end‑to‑end, full-stack, multiplatform Cardano DApp development platform.

Key Learnings

  • A rigorously limited, platform‑agnostic subset of Scala 3 can faithfully mirror Plutus semantics while maintaining readable, idiomatic code.
  • Cross‑compiling to three targets from one codebase is achievable with careful boundary abstractions and continuous integration testing.
  • Early usage of Scalus for full-fledged DApps (Binocular, Cosmex, AdaStream, Hydrozoa) surfaced edge‑cases sooner and materially improved library robustness.

Next Steps

  • Plutus V4 support, including new built‑ins and cost models.
  • Improved developer experience and documentation, including more tutorials and examples.
  • Explore funding for formal verification of the CEK implementation using Stainless .

Final Thoughts

Catalyst funding transformed an experimental prototype into production‑ready infrastructure adopted by multiple projects in less than 15 months. We will continue to drive Scalus forward as the de‑facto full‑stack platform for Cardano DApps.

Resources

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Catalyst1100198 - Scalus Multiplatform support