LinkedIn Quietly Migrated From ProseMirror to Quill — and Broke Every Browser Automation Tool That Touched the Composer

I shipped a fix to my MCP server last week for LinkedIn's ProseMirror composer. It worked. Two days later, every LinkedIn post automation broke. This is the post-mortem of what changed, how I figured it out, and why "automate the platform" stories almost always end this way. The crash The symptom was specific. My MCP server's safari_fill tool — which dutifully filled ProseMirror by walking React Fiber and calling editor.commands.setContent(html) — was now crashing the helper daemon and dismissin