PS DEV

Programme

Monday, October 12

08:00
Doors open 08:00 – 09:00 · Kesselhaus
09:00
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Opening Session & Keynote: The End of Programming?

Martin Odersky
Keynote
09:00 – 10:00
Kesselhaus
Coding agents are fundamentally upsetting our routines and expectations about software development. Are we witnessing the end of (human) programming, where software construction will be exclusively the domain of agents? Many claim so, but I would like to think otherwise. I believe it's essential that humans stay in the loop, even if large parts of a software system will be written and reviewed by agents. To achieve this, we will likely need fundamental changes in programming languages and programming workflows, This talk will start the discussion about what kind of possible innovations could help.
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10:00
Keynote Discussions & Coffee 10:00 – 10:30 · Kesselhaus
10:30
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sbt 2.0: takeoff

Eugene Yokota
Talk
10:30 – 11:00
Kesselhaus
sbt 2.0 is a new major series of sbt that propels itself to the modern standards. In this talk, we will focus on the new features such as the native client, Bazel-compatible caching, and new test command. We will also go over the plugin migration effort, the differences between sbt 1 vs 2, and common pitfalls during migration.
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Simpler User Interfaces with Capability-Passing

Noel Welsh
Talk
10:30 – 11:00
Maschinenhaus
Representing user interfaces as effects in the capability-passing style gives a simple framework for creating UIs. In this talk I'll explain how capability-passing works and use it to implement a simple terminal user interface library. We'll then discuss what general principles we can take from this, that can apply to any problem.
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11:00
Speaker Discussions & Snacks 11:00 – 11:20 · Kesselhaus, Maschinenhaus, Palais Atelier
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A Distributed System On Fire: Diagnosing Failures with otel4s

Antonio Jimenez, Maksym Ochenashko
Interactive labs
11:00 – 13:00
Frannz Salon: Lab 1
Learn to diagnose realistic production failures in a distributed Typelevel streaming platform. Through a curated set of incidents, you will debug failures using telemetry and iteratively improve observability through manual instrumentation with otel4s, leaving with a practical mental model for telemetry-driven debugging in Scala.
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Building Real Applications in Scala Native

Noel Welsh
Interactive labs
11:00 – 13:00
Frannz Salon: Lab 2
Scala Native is great! It creates small and fast binaries, and can access all operating systems features. This workshop will introduce working with Scala Native by building a terminal based application. We'll learn how to setup and build Native code, call into with system libraries, and use the archaic but powerful features of the terminal.
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11:20
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A brief history of Scala

Odd Möller, Martin Zachrison
Talk
11:20 – 11:50
Kesselhaus
What can one tiny function teach you about twenty years of Scala? We rewrite isPalindrome version by version and let the code tell the story. Watch it grow from classic Scala 2 into the modern Scala 3; tail recursion, type classes, extension methods, all earning their place. A palindrome reads the same both ways, Scala's history does not.
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AI Multiplies — Let Scala Hold the Line

Krzysztof Romanowski
Talk
11:20 – 11:50
Maschinenhaus
AI is a multiplier, not a fixer — point it at a mess, and it scales the mess up: defects climb, reviews balloon, tests become a farce. Scala's honest compiler and typed libraries are a base that holds as you push harder. We'll assemble the workflow around them with agents, context, deterministic refactors, hermetic builds and more.
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How OOP Earned Our Trust and Let Us Down

Pavel Kozlov
Talk
11:20 – 11:50
Palais Atelier
Object-oriented programming helped shape modern software engineering — but also gave us shared mutable state, fragile hierarchies, and accidental complexity. Using real Scala adoption stories, this talk explores why legacy OOP thinking fails and how functional principles help teams build simpler systems.
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11:50
Speaker Discussions 11:50 – 12:10 · Kesselhaus, Maschinenhaus, Palais Atelier
12:10
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A Maiden Voyage into Open Source, Datatypes, and Scala

L Denney
Lightning Talk
12:10 – 12:15
Kesselhaus
What optimizations can we find by making a simple change to a traditional data structure? In the summer of 2026 I developed a faster immutable linked list; implementing it was my first experience both writing Scala and working with an open source community. This talk explores my approach to data structure optimization and my acquisition of Scala.
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12:20
12:30
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Inline Traits for Specialization

James You
Lightning Talk
12:30 – 12:35
Kesselhaus
Inline traits are a language feature that eliminate allocations and virtual dispatch associated with trait composition in Scala. They do so by inlining their methods into their implementing subclasses. When inline traits are combined with the Specialized type class, they enable trait-based abstractions to be zero-cost.
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12:40
Lunch & Networking 12:40 – 14:10
14:10
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The state of Scala in 2026

Piotr Chabelski, Lukas Rytz
Talk
14:10 – 14:40
Kesselhaus
With Scala 3.9 LTS out, three Scala distributions will exist in parallel: Scala Next (3.10+), the current 3.9 LTS and the old 3.3 LTS. We will explain how to think about it: why you should migrate your libraries to 3.9 LTS, what cool features have we cooked up in Scala Next, and how the standard library can evolve now that it’s no longer frozen.
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Quality Pipelines for Generative AI

Bill Venners
Talk
14:10 – 14:40
Palais Atelier
How do you achieve reliable results from stochastic AI models? This talk presents practical techniques for building quality pipelines around generative AI that improve output quality before human review begins, making more effective use of limited human time and attention.
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14:40
Speaker Discussions 14:40 – 15:00 · Kesselhaus, Maschinenhaus, Palais Atelier
15:00
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Hard to Hire, Hard to Learn, Hard to Break: A CTO’s Scala Case

Gordon Cooke
Talk
15:00 – 15:30
Maschinenhaus
To business leadership, Scala looks like a high-risk bet: the talent is expensive and the learning curve is a wall. So why willingly sign off on a technology that makes recruiting harder? Because optimizing for cheap headcount is a false economy. This fast-paced session bridges the gap between engineering elegance and CFO mathematics. You will learn how to expose the "shadow payroll" of bloated polyglot teams, and leave armed with the exact financial vocabulary needed to prove that a lean, elite Scala team is the most aggressive risk-mitigation strategy a CTO can deploy.
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On Folding

Johanna Odersky
Talk
15:00 – 15:30
Palais Atelier
Where does computation live? In origami, it lives in a paper crease. We build a functional crease pattern generator in Scala to explore what origami teaches us about programs. The insight is material before it is mathematical: pure functional programming emerges naturally from the physics of folding.
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15:30
Speaker Discussions & Snacks 15:30 – 15:50 · Kesselhaus, Maschinenhaus, Palais Atelier
15:50
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The State of Scala on WebAssembly

Rikito Taniguchi
Talk
15:50 – 16:20
Kesselhaus
WebAssembly is increasingly used beyond browsers for serverless, sandboxing, AI workloads, and more. This talk explores the current state of Scala on Wasm with Scala.js and scala-wasm, an experimental project targeting standalone runtimes, WASI, and the Component Model. This session covers current capabilities, limitations, and future directions.
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Is metaprogramming just functional programming?

Kathryn Frid
Talk
15:50 – 16:20
Maschinenhaus
Metaprogramming is the act of treating code as data, to transform it, yielding new programs. Is that not also what functional programming is all about? Similarly, what does compile time mean, when mixed with IO, where programs are constructed and run in separate phases? Let's talk about it together.
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Back to the roots – VirtusLab Scala Stack

Jacek Kunicki
Talk
15:50 – 16:20
Palais Atelier
Scala is evolving to be more welcoming than ever. Explore the VirtusLab Scala Stack, an innovative toolkit that combines Scala 3 and Project Loom to champion direct-style programming by making concurrency more intuitive. With libraries like Ox and Tapir, the entry barrier is lowered, inviting new developers to build robust, scalable apps.​
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16:20
Speaker Discussions 16:20 – 16:40 · Kesselhaus, Maschinenhaus, Palais Atelier
16:40
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Caching in Scala using Cats Ref

Katrina Petrevice
Talk
16:40 – 17:10
Kesselhaus
Modern distributed systems depend on caching for performance, yet implementing caching correctly and safely remains a persistent challenge. This talk explores how Cats Ref from the Typelevel ecosystem enables developers to build thread-safe, testable cache while maintaining functional purity.
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Optimizing Scala bytecode for fun and profit

Solal Pirelli
Talk
16:40 – 17:10
Maschinenhaus
Can high-level code have the same perf as low-level hand-tuned code? That’s what Scala’s optimizer is for! Your call to map on a list turns into the same bytecode as if you had written a while loop. In this talk, I’ll introduce bytecode and optimization basics, present the Scala optimizer, and discuss fundamental and temporary limitations.
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Teaching Software Architecture using Scala

Michael Sperber
Talk
16:40 – 17:10
Palais Atelier
At Active Group, we have taught more than 30 three-day trainings on Functional Software Architecture since 2019, mostly to audiences with little or no prior exposure to functional programming. For the examples, we use Scala or Haskell. I report on the constraints, successes, and learnings of this course.
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17:10
Speaker Discussions 17:10 – 17:30 · Kesselhaus, Maschinenhaus, Palais Atelier
18:00
18:15
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Community Party

#ScalaDays
18:15 – 22:15
Kesselhaus
ScalaDays is a good place to meet great people, and while there is ample time to chat and discuss during the conference, we also want to provide an opportunity for everyone to meet up outside of the regular conference program with our Community Party on Monday! Our Community Party is a casual meet-up in a relaxed atmosphere and provides a perfect opportunity to meet old and new friends, business contacts or get to know other participants of ScalaDays. We will offer food as well as alcoholic and non-alcoholic drinks.
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Tuesday, October 13

08:00
Doors open 08:00 – 09:00 · Kesselhaus
09:00
09:15
10:00
Keynote Discussion & Snack 10:00 – 10:30 · Kesselhaus
10:30
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A Typelevel Prospectus

Arman Bilge
Talk
10:30 – 11:00
Kesselhaus
Learn more about Typelevel, the open source organization that stewards development of projects such as Cats Effect, http4s, and Circe, and offers one of the most comprehensive cross-platform stacks for the Scala ecosystem. In this talk, you will discover the people and processes driving this work and how you can participate.
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11:00
Speaker Discussions & Snack 11:00 – 11:20 · Kesselhaus, Maschinenhaus, Palais Atelier
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Build a webapp with Cats Effect and FS2

Arman Bilge
Interactive labs
11:00 – 13:00
Frannz Salon: Lab 2
Learn about Cats Effect and FS2 while building a collaborative webapp with Calico! In this lab you will build an interactive widget for a webapp. Along the way we will learn about the IO, Resource, Stream, and Signal monads, and how the Typelevel stack can be used to make frontend applications.
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Reactive UI with Laminar

Jamie Thompson
Interactive labs
11:00 – 13:00
Frannz Salon: Lab 3
Laminar is a Scala.js-first approach to reactive UI for the web, combining declarative presentation with logic for how to make updates based on events or other state changes. Beyond basics, lets also explore interop with JS libraries, and even concerns such as code organisation, and effective error handling practises.
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11:20
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Where Scala meets AI

Adam Warski
Talk
11:20 – 11:50
Kesselhaus
The AI revolution raises questions about the utility of various technologies, especially programming languages. And when it comes to developer experience, Scala might have just the right answers. We'll take a tour of how to use Scala efficiently for and with AI.
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First-class Logical Refinement Types for Scala

Matt Bovel
Talk
11:20 – 11:50
Maschinenhaus
What if assertions such as x > 0 were part of the type system? We present a prototype implementation of logical refinement types for Scala: types like {x: Int | x > 0}. In our system, refinement types are first-class: they can be nested, used as type arguments, and related by subtyping. We demonstrate the system through concrete examples.
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Blazing-Fast Lambda Calculus via Metaprogramming

Alex Nemish
Talk
11:20 – 11:50
Palais Atelier
Interpreting lambda calculus is simple but slow. Using multi-stage metaprogramming, we built a JIT that compiles each program to native JVM code at load time, running 2–10x faster than existing interpreters – including heavily optimized Rust and Haskell implementations. The surprising part: staging resulted in remarkably little code.
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11:50
Speaker Discussions 11:50 – 12:10 · Kesselhaus, Maschinenhaus, Palais Atelier
12:10
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Stop testing, start proving

Valentin Bergeron
Lightning Talk
12:10 – 12:15
Kesselhaus
Tests and types are our correctness gates. But who verifies the gates themselves? With agentic codegen flooding our pipelines with code we didn't write, that question has never been more dangerous to ignore. In this talk, we explore how theorem provers complement existing practices, adding mathematical certainty where it matters most.
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12:15
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Scala OSS vs. the LLM Era

Patryk Zieliński
Lightning Talk
12:15 – 12:20
Kesselhaus
LLMs are changing how people contribute to open source – but are they really helping? In this talk, we’ll look at compiler maintenance in the age of AI-generated PRs, issues and comments, and ask what maintainers gain, lose, and how the rules of contribution are changing.
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12:20
12:25
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DimWit – Tensor programming with wit

Benjamin Meyer, Marcel Lüthi
Lightning Talk
12:25 – 12:30
Kesselhaus
We present DimWit, a system for writing readable numerical and machine learning code. DimWit's core feature is a trait-based implementation of the named tensor notation, which improves readability and type-safety compared to standard tensors. We illustrate how to write machine learning models using DimWit, and discuss our experience training GPT-2.
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12:35
Lunch & Networking 12:35 – 14:10
14:10
14:55
Community Discussions 14:55 – 15:15 · Kesselhaus, Maschinenhaus, Palais Atelier
15:15
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Making the AI agents safe with Scala

Łukasz Biały, Jakub Warchoł
Talk
15:15 – 15:45
Kesselhaus
Everyone and their dog are building permanent AI agents, but nobody is solving the real problem – how to prevent the agent from doing something it should never, ever do while preserving its general problem-solving capability. In this talk, we will introduce the CapybaraClaw – the agent built with safety in mind that gives you the peace of mind.
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Scoverage: Test Coverage for the Scala Codebases

Anatolii Kmetiuk
Talk
15:15 – 15:45
Palais Atelier
You will learn about how to measure test coverage of your Scala codebase with Scoverage, the Scala 3 coverage tool. After learning the basics, we will dive deeper into how it is implemented, and talk about the hardening work done by the Scala Center to make the feature robust and reliable in interaction with the rest of the language features.
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15:45
Speaker Discussions & Snacks 15:45 – 16:05 · Kesselhaus, Maschinenhaus, Palais Atelier
16:05
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Cyfra: Scala on GPU

Szymon Rodziewicz, Marcin Złakowski
Talk
16:05 – 16:35
Maschinenhaus
Learn how to accelerate Scala code by orders of magnitude with Cyfra. There are many libraries that give you access to low-level GPU APIs, but a high-level, functional one is a different story. That’s why we created the Cyfra GPGPU framework. In this talk, we’ll demonstrate how to use it to build high-performance GPU applications with Scala.
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16:35
Speaker Discussions 16:35 – 16:55 · Kesselhaus, Maschinenhaus, Palais Atelier
16:55
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Type-Driven AI: High quality Scala code with LLM

Giovanni Ruggiero
Talk
16:55 – 17:25
Kesselhaus
Speed without quality is debt. This talk shows how Scala's type system, combined with a multi-layer validation pipeline (compiler, linting, property tests, mutation testing, and formal verification) helped by a concepts inventory and types generation acts as a guardrail for LLM-generated code, keeping correctness non-negotiable.
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Metals Reimagined – LSP in the age of LLMs

Tomasz Godzik
Talk
16:55 – 17:25
Maschinenhaus
We are currently working on Metals 2, which is a new indexing and compilation approach, designed to make indexing as fast as possible and ensure the editor remains functional even if parts of the project fail to compile. Thanks to this even while working on large monorepos it should be possible to quickly set up your editor.
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Bridging between Scala & Python with GraalVM

Hamza Remmal
Talk
16:55 – 17:25
Palais Atelier
We will present our ongoing work to bridge between Scala 3 (& Kotlin) and Python 3 using GraalVM. We will explain how the interoperability was designed; how type hints map to Scala 3's type system, how other Python 3 concepts translate to Scala, and our the progress to publish python wheels to close.
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17:25
Speaker Discussions 17:25 – 17:45 · Kesselhaus, Maschinenhaus, Palais Atelier
17:45