A proof-of-concept writing app with AI feedback. You write in a distraction-free editor, and as you pause, Redline surfaces inline editorial notes anchored to specific spans of your text with suggested rewrites you can accept with a click — like an editor's redlines, in real time.

• Automatic feedback — after you stop typing, the app sends your text to Claude and gets back notes anchored to spans. Notes appear as colored inline highlights (orange = suggestion, red = issue).
• Click to review — click a highlight to open a pinned panel showing the note plus suggested rewrites in different styles.
• Accept a rewrite — accepting replaces the highlighted span in place.
• Stays in sync — a note disappears if you edit its text (the feedback no longer applies), and accepting a rewrite doesn't trigger a new round of feedback.

• src/app/api/feedback/route.ts — calls the Claude API (Anthropic SDK) with the document text and returns structured notes. The model returns a verbatim quote for each note; the server resolves it to a character range (models copy text reliably but count offsets poorly).
• src/components/feedback-extension.ts — a ProseMirror plugin that renders the notes as inline decorations and drops a note when its underlying text changes.
• src/components/use-feedback.ts — owns the generation lifecycle: debounced auto-runs, request cancellation, and applying the results.
• src/components/feedback-panel.tsx / editor.tsx — the review UI.

Prerequisites: Node.js 18.18+ and an Anthropic API key.

1. Install dependencies:

   npm install

2. Add your API key to a .env.local file in the project root:

   ANTHROPIC_API_KEY=sk-ant-...

3. Start the dev server:

   npm run dev

4. Open http://localhost:3000 and start writing. After you pause, feedback highlights will appear; click one to review and accept a rewrite.