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Infrastructure Engineer

Chert
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Chert (YC P26) is the infrastructure to build and scale AI agents on the channels people already use. We started by making iMessage programmable at scale, and now we let anyone put a realtime AI video agent on a live FaceTime call with one API. 

We're backed by Y Combinator (P26), Z Fellows, Beta Fund, and angels from OpenAI, Anthropic, NVIDIA, Meta, Scale AI, Grafana, and LinkedIn. 

What you'll do: 

Build the core infrastructure that powers realtime agents across FaceTime and iMessage. Concretely: 

  • Design and build the macOS-level systems that enable stable and reliable programmatic control of FaceTime and iMessage
  • Design and build APIs and SDKs for WebRTC that developers love to use
  • Build systems for managing concurrent sessions, streams, and agent processes at scale 
  • Diagnose and solve hard problems, such as race conditions, latency spikes, dropped sessions, and failures that only show up in production

You: 

A strong systems engineer who wants to own hard infrastructure at the OS and network layer. You might be a fit if you: 

  • Are strong with Swift and macOS/iOS internals
  • Have built realtime, distributed, or low-latency systems
  • Have worked with WebRTC and realtime video
  • Debug relentlessly and care deeply about reliability and observability
  • Are strong with AI coding tools (Codex, Claude Code, Cursor, etc.)
  • Like ambiguous problems at the edge of what's currently possible

Compensation: 

$40–$70/hour, plus performance-based bonuses.