Founding Engineer, AI Agents

About Mobster

Agents learned to use the browser first, and the same shift is coming to the phone, where your apps, messages and accounts live. We build Mobster so agents can do anything on your real iPhone, and ask you before anything goes out.

Andy Guo founded Mobster, and Radish Retail, LLC builds, sells and supports it. Mobster for Mac is the app people pay for, and its engine is open source under MIT.

What you’ll do

• Own the loop that reads the screen, decides, acts and checks what happened.
• Build the evals: our task suite on real iPhones, iOSWorld on simulators, and the A/B runs every change goes through.
• Turn a run that passed into a replay that runs again with no model call.
• Route each step to the cheapest model that gets it right.
• Keep the agent safe: it asks before it sends, buys, posts or deletes, and refuses when it isn’t sure.
• Publish what you measure, including where we lose.

What we look for

• You have shipped an agent or a language-model product that people use every day.
• Strong Python, and the habit of measuring before and after every change.
• Evals you built that changed what a team shipped.
• You know where models fail: grounding, long tasks, prompt injection.

Nice to have

• Computer-use agents, mobile agents or UI automation.
• Vision models and accessibility trees.
• Published research or a benchmark.
• Claude, OpenAI and open-weight models run side by side.

Location

Work from anywhere in the United States. We ask for four hours a weekday that overlap with Pacific time.

Pay

$170,000 to $225,000 base salary a year, and meaningful early equity. The range holds anywhere in the US. Where an offer sits in it depends on your experience.

How to apply

Email support@radish.software with “Application: Founding Engineer, AI Agents” as the subject. Send something you built, like an app, a repo, a post or a talk, and a few lines on why this role. A person on the team reads every application.