Freelance - Senior iOS Engineer (all genders)

ABOUT BABBEL LABS

Babbel Labs is building the future of language learning. We're an AI-first, independent company within the Babbel group, based in Berlin. Our teams bring AI, R&D and product together to ship experiences that set a new standard for how people learn.

YOUR LEARNING JOURNEY IN THIS ROLE

Babbel is looking for a Senior iOS Engineer to help change the future of language learning within our Learning Experience teams.

This is an Individual Contributor role with team-level scope. You will work closely with product and engineering managers, designers, subject matter experts, and cross-platform engineers to build Babbel's core learning experiences — from the learning path and exercise player to real-time speaking and conversation practice.

You own the experience end to end: it ships as a distributable Swift package consumed by Babbel's main iOS app, and you follow it there — integration points, A/B experiments, rollout. And you'll do this the Labs way: AI coding agents are a first-class part of how we design, build, test, and review.

HOW YOU'LL MAKE AN IMPACT

• Take part in all product development phases: discovery, prototyping, proposing solutions, implementing, reviewing, testing, and deploying learning experiences.

• Own the engineering side of our feature workflow: shape the PRD together with product, then pick it up — write the technical spec, agree Interface Contracts with backend and partner teams, slice the backlog, and build.

• Build quick prototypes to de-risk product ideas — the learnings feed the product, even when the code doesn't.

• Design and evolve the public API of our Swift package with deliberate versioning and breaking-change discipline — and land it in the main app: integration points, A/B experiments, rollout.

• Collaborate closely with product managers, designers, and other cross-functional teams to define and implement features that enhance how learners progress through their learning path, exercises, and speaking practice.

• Maintain and proactively improve the technology stack, build system, and the AI-agent conventions (skills, project rules, documentation) the whole team relies on.

• Share what you learn: technical documentation for core features, and knowledge actively passed on to colleagues.

   

YOUR SKILLS AND QUALIFICATIONS

• 5+ years of experience building scalable iOS applications using Swift.

• An AI-first mindset — a strong must for us. You have actively embraced AI coding tools in your own work — not just autocomplete, but directing agents through real feature work and critically reviewing what they produce — and you treat prompts, skills, and project conventions as engineering artifacts maintained like code. Deep experience with our specific agent stack isn't required — demonstrated adoption and genuine enthusiasm are.

• Strong, up to date Swift — including Swift 6 strict concurrency (actors, Sendable, isolation) and structured concurrency.

• Deep SwiftUI experience and a solid grounding in the Apple ecosystem and Human Interface Guidelines; you think in state-driven UI and know where the framework's sharp edges are.

• Strong opinions on state management and testable architecture — experience unidirectional-data-flow architecture, and willingness to go deep on ours.

• Testing as a first-class habit: deterministic, exhaustive unit tests with controlled dependencies, snapshot tests where the UI is the contract — not coverage theater — and the CI/CD discipline to keep them green.

• Experience designing module boundaries, frameworks, or SDKs that other teams consume — ideally as distributable Swift packages — and the API-stability discipline that comes with it.

• Experience designing or consuming evolving JSON APIs and collaborating with contract-first backend teams.

• An eye for good architectural decisions based on feature requirements, and knowledge of how to balance technical debt against delivery speed.

• Comfort with ambiguity and fast iteration: directions evolve as we learn, and prototypes are a tool, not a deliverable.

• Clear, concise communication, an open mindset for feedback, and enjoyment in working closely with design and product in a lean environment.

• Fluency in written and spoken English.

   

NICE TO HAVE

• Hands-on experience with The Composable Architecture and the Point-Free ecosystem (swift-dependencies, swift-sharing).

• Hands-on experience with agentic coding setups (e.g. Claude Code): agent skills, MCP servers, CLAUDE.md http://CLAUDE.md-style project conventions.

• Experience with Tuist or other project-as-code tooling at scale (modular workspaces, binary caching).

• Experience with Swift Testing (the modern successor to XCTest).

• Experience with real-time client features — live audio capture, streaming over WebSocket/WebRTC, low-latency interactions.

• Comfort navigating a legacy RxSwift/MVVM-C codebase — you'll help integrate our package into Babbel's main iOS app while it migrates to the new stack.

• Experience working in language learning, education technology, or consumer subscription products.

WAYS OF WORKING

Our stack: Swift 6.2 with strict concurrency, SwiftUI, The Composable Architecture with the Point-Free ecosystem (swift-dependencies, swift-sharing), Swift Testing with exhaustive state assertions, and project-as-code with Tuist (modular workspace, binary caching). We ship our features as a distributable Swift package built with multiple consumers in mind — today, Babbel's main iOS app. We work trunk-based with Conventional Commits driving automated versioning, plan in Linear (discovery → PRD → spec → issues), and build AI-first: coding agents, a curated skill library, and conventions good enough that even non-engineers on the team run and prototype in the app.

Success in this role is measured by the quality and impact of the learning experiences you ship, the health of the codebase and its public API, and the knowledge you share with your team and with iOS engineers across Babbel.

DIVERSITY AT BABBEL

As part of our ongoing journey towards building a diverse, equitable, and inclusive company, we welcome everyone to apply, especially individuals who are underrepresented in tech. We are a learning company, inside and out, and we encourage you to apply even if you do not fit all the technical requirements — all candidates are assessed based on skills, qualifications, and our business needs. Please state your pronouns in your application, and let us know if you'd like to be addressed by a name other than the one appearing on your official documents. If you have a disability or special need, feel welcome to inform us so we can provide proper assistance in the application process.