Principal Design Engineer, Mobile (iOS)

We're hiring a Principal Design Engineer to elevate the craft and explore what's possible within Slack's iOS experience. Slack is an app that is used by millions of people every day as a core part of getting their work done.

This role sits at the intersection of design and engineering: you'll rapidly prototype directly in code to bring real life to nascent, half-formed concepts that need both technical and craft judgment to assess their viability and their ability to make what we ship better.

We’d love to find someone who not only is excited about this opportunity, but the unique modalities and possibilities of mobile experiences and how they can overlap and meaningfully differentiate from their desktop counterparts.

We want someone who is an evangelist at heart and will thrive with the charter to elevate the design team’s awareness and abilities by bringing modern, agentic prototyping practices into how designers work in production iOS codebases.

We appreciate designers who think deeply, speak clearly, love collaboration and feedback, and have an excellent collection of animated gifs. At Slack, we have a positive, diverse, and encouraging culture. We look for people who are curious, inventive, and work to be a little better every single day!

What you’ll do

• Exploring nascent, ambiguous interaction and device capability concepts by prototyping directly in code, bringing both technical depth and design craft to ideas before they're fully considered. Turning "what ifs" into something people can feel and react to with tangible experiences in their hand.
• Building a deep, current understanding of iOS platform capabilities (WidgetKit, App Intents, Live Activities, Shortcuts, etc.), rooting solutions in platform-native standards and interaction patterns by default. Knowing when and how to break from them to build something genuinely bespoke.
• Acting as a skill multiplier for the broader design org. Conducting training and documenting agentic prototyping workflows so designers themselves can prototype directly in mobile codebases, not just hand off static specs.
• Creating reusable patterns for interactions and prototyping tooling that raise the craft ceiling for every team working in the iOS app, not just your own projects.
• Partnering with designers and engineers across the org to inject technical and craft expertise wherever it's needed most. Coming to provide direct solutions for various team's current work, or providing creative / technical guidance around native solutions or custom approaches
• Using data and shipped-feature learnings to sharpen judgment about which craft investments matter, and feeding that back into prototyping tools and documentation.

What we're looking for

• 8+ years at the intersection of product design and iOS engineering, with deep hands-on fluency in Swift/SwiftUI and Objective-C
• A track record of building real, working prototypes in code to explore ambiguous concepts. Ideally showing how their execution had a direct correlation to impact and customer love
• Deep, current knowledge of iOS platform standards and capabilities (Apple HIG, native frameworks), paired with the judgment to know when a bespoke, non-standard solution is worth building.
• Experience creating tools, documentation, or training that help other designers and engineers level up their own craft, embodying a multiplier mindset over a "my feature" mindset.
• Strong collaboration instincts. Demonstrating both proactive communications, working out in the open, and comfortable being pulled into ambiguous, cross-team problems rather than owning a dedicated backlog.
• Familiarity with (or excitement about) agentic/AI-assisted coding tools, and interest in teaching design teams to use them to prototype directly in production codebases.
• Excellent communication skills and the ability to evangelize new practices and get adoption across a design org, not just ship personal work.