# Static File Caching — Ops Portal

**Pitfall (Jul 10, 2026):** The ops portal serves static HTML/JS/CSS through FastAPI's `FileResponse`. Without explicit `Cache-Control` headers, browsers aggressively cache these files. After editing `app.js`, `servers.html`, or `ops.css`, users see stale versions — even after hard refresh. The login page, server health, and API calls all appear broken because the browser is serving cached JavaScript.

**Symptoms:**
- User reports "pages won't refresh" despite confirmed deploys
- `curl` returns HTTP 200 with correct content, but browser shows old version
- JS changes (401 redirect fix, new endpoint calls) don't take effect
- User has to manually Ctrl+Shift+R every page

**Fix:** Add `Cache-Control: no-cache, no-store, must-revalidate` headers to all `FileResponse` calls in `server.py`:

```python
return FileResponse(str(fpath), headers={"Cache-Control": "no-cache, no-store, must-revalidate"})
```

This applies to HTML pages, CSS, and JS. After adding headers, restart the service:
```bash
systemctl restart ops-portal
```

**Why this matters for ops:** The portal uses vanilla HTML/JS with no framework, no bundler, and no cache-busting hashes. Every file edit requires either a cache-control header or manual browser refresh. The header approach is reliable across all users.

**Files affected:**
- `/opt/ops-portal/server.py` — `serve_css()`, `serve_js()`, `serve_index()`, `serve_html_page()`
- Any `@app.get("/{page}.html")` handler
