Fix

CLAUDE.md

@@ -1,12 +1,18 @@
-# btcprice
+# CLAUDE.md
 
-Bitcoin price tracker UI — Python FastAPI web application. Serves the HTML/Tailwind UI. Connects to btcdata for live price data via WebSocket.
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Overview
+
+Bitcoin price tracker UI — Python FastAPI web application. Serves an HTML/Tailwind page with live price updates streamed from btcdata (separate service) via WebSocket using HTMX.
 
 ## Build & Development Commands
 
-- `make run` — Start dev server on port 4000
-- `make tailwind` — Watch Tailwind CSS for changes
-- `make test` — Run tests
+- `make run` — Start dev server on port 4000 (connects to btcdata at BTCDATA_URL from `.env`)
+- `make run-local` — Start dev server using BTCDATA_LOCAL_URL from `.env`
+- `make tailwind` — Watch Tailwind CSS for changes (run in separate terminal)
+- `make test` — Run tests with pytest (`tests/` directory)
+- `npm run css:build` — One-off Tailwind CSS build
 
 ## Docker
 
@@ -17,20 +23,26 @@ Docker runs alongside local dev on different ports:
 | btcprice | localhost:4000 | localhost:4041 |
 | btcdata  | localhost:4100 | localhost:4101 |
 
-btcprice's docker-compose includes btcdata via `include: ../btcdata/docker-compose.yml`.
+Uses external `btc-network` Docker network. btcdata must be running separately (or via its own docker-compose).
 
 ## Architecture
 
-- **Framework:** FastAPI
-- **Server:** Uvicorn
-- **Templates:** Inline HTML strings + HTMX (WebSocket extension)
-- **Styling:** Tailwind CSS v4
+- **Framework:** FastAPI + Uvicorn
+- **Templates:** Inline HTML strings in Python + HTMX (WebSocket extension)
+- **Styling:** Tailwind CSS v4 — scans `app/**/*.py` for class names (configured in `resources/css/input.css` via `@source`)
 - **Data backend:** btcdata (separate service at BTCDATA_URL, default http://localhost:4100)
 - **No database** — all data comes from btcdata
 
-## Source Layout
+### Data Flow
 
-```
-app/
-└── main.py    # FastAPI app: routes, WebSocket proxy, HTML rendering
-```
+btcprice acts as a WebSocket proxy between the browser and btcdata:
+1. Browser connects via HTMX WebSocket to `/ws/price` or `/ws/strike`
+2. btcprice proxies to btcdata's `/api/price/ws` or `/api/strike/ws`
+3. JSON from btcdata is transformed into HTML fragments (in `price_json_to_html` / `strike_json_to_html`)
+4. HTMX swaps the HTML into the DOM by matching element IDs (`price-display`, `strike-display`)
+
+### Key Conventions
+
+- Numbers use Danish locale formatting (dots for thousands, commas for decimals) via `da_fmt()`
+- Price changes are color-coded: green (up), red (down), gray (unchanged)
+- All HTML is built as string concatenation in Python — no template engine