sim-on

Agentic mobile testing CLI + your iOS simulator in the browser. Explore an app with an LLM once, save the session as a deterministic Maestro-compatible flow, replay it forever for free.

npx @szdziedzic/sim-on    # → http://localhost:3300

Requires macOS (Apple Silicon) with Xcode command line tools.

What you get

• Simulator in the browser — 60fps WebRTC stream, click/swipe/type forwarding, works headless (no Simulator.app window needed).
• Unified event log — every action (agent, flow, your clicks in the browser, CLI) lands in one ordered stream with source attribution.
• Deterministic flows — record any session (sim-on record start/stop) and it compiles into Maestro-dialect YAML with multi-facet anchors per step; replays are free and self-heal when selectors go stale.
• Maestro interop — sim-on export flow.yaml emits plain Maestro YAML runnable by the upstream maestro test CLI.
• Agentic testing — sim-on explore "verify login works" --save drives the app with Claude (needs ANTHROPIC_API_KEY) and saves the passing run as a flow.
• MCP server — sim-on mcp exposes the same tools to Claude Code, Cursor, or any MCP client: claude mcp add simon -- npx @szdziedzic/sim-on mcp

Commands

sim-on                       # start daemon + browser UI (default)
sim-on devices | boot
sim-on record start <name> / stop
sim-on run <flow.yaml> [--heal]
sim-on explore "<goal>" [--app <bundleId>] [--save <file>]
sim-on export <flow.yaml>    # plain Maestro YAML
sim-on snapshot | tap | screenshot | events --follow
sim-on mcp

Remote mode: run sim-on serve --remote --json on the machine that hosts the simulators and point any command at it with SIMON_REMOTE_URL + SIMON_REMOTE_TOKEN — one port carries the API, the event stream, and the browser UI, so it tunnels cleanly.

Built by Expo. Streaming/input layer shares its lineage (and wire protocol) with serve-sim.