AI Grammar Checker — viral distribution engine #4015

Originally written by @ccantynz-alt on GitHub.
Imported from https://github.com/ccantynz-alt/48co.v1/pull/22

Summary

• AI Grammar Checker built into Chrome extension — checks grammar in real-time on ANY website
• Shows clean tooltip with corrections when errors found
• Click to fix individual errors or "Fix all" button
• Uses Claude Haiku (fast, cheap — ~$0.001 per check)
• Daily free tier (10 corrections/day) to drive upgrades
• Zero visible UI until an error is actually found

How it works

1. User types in any text field on any website
2. 1.5 seconds after they stop typing, grammar.js sends text to Claude Haiku
3. Claude returns structured corrections (original, corrected, reason)
4. Clean white tooltip appears above the field showing corrections
5. User clicks a correction → it's applied inline with undo support
6. "Fix all" button applies everything at once

This is the viral engine

Users install free extension → see grammar corrections everywhere → tell colleagues → upgrade to Pro. Same model as Grammarly.

https://claude.ai/code/session_01PBeNmPHrD2W6A2YKZRC7V3