## QA PASSED (Code Review) Browser testing was blocked by authentication and dev server HMR instability. Verification completed via code review as permitted. **Findings:** All requirements verified correct in source code: 1. **Power/Current Toggle Buttons** - PASS - State variables default: Power=ON, Current=OFF (lines 138-139) - Toggle buttons with ToggleRight/ToggleLeft icons - Conditional chart line rendering 2. **Multi-Device Comparison** - PASS - Toggle selection handler allows multi-select - Check icons on selected devices - Chart title shows 'Comparing N Devices' - Multiple colored lines per device No issues found. Implementation matches all requirements. See QA report document: ca67fc50-8f6e-4b7a-9819-2b466cd3e4fa

## Implementation Complete ### Changes Made **1. Power/Current Toggle Feature** (`frontend/src/components/historical-power-chart.tsx`) - Added `showPower` (default: true) and `showCurrent` (default: false) state variables - Added toggle buttons in the chart header with ToggleLeft/ToggleRight icons - Conditionally render Power and Current Y-axis based on toggle state - Conditionally render Power and Current Line components in chart - Updated tooltip to only show enabled metrics - Toggle controls hidden in multi-device mode (power comparison only) **2. Multi-Device Comparison Feature** - Changed props from `deviceId?: number` to `deviceIds?: number[]` and `deviceNames?: Map<number, string>` - Added `isMultiDeviceMode` check when `deviceIds.length > 1` - Fetch data in parallel with `Promise.all` for all selected devices - Combined data structure with timestamp-aligned points containing `power_${deviceId}` fields - DEVICE_COLORS array provides 8 distinct colors for device lines - Legend shows device names from the `deviceNames` map **3. History Page Updates** (`frontend/src/app/history/page.tsx`) - Changed `selectedDevice: RackDevice` to `selectedDevices: RackDevice[]` - Device buttons now toggle selection (click to add/remove) - Checkmark icon shows on selected devices - "Select Device(s) (click multiple to compare)" helper text - Dynamic chart title: single device name, or "Comparing N Devices" - `deviceNamesMap` useMemo creates Map for chart legend labels ### Testing - All 111 frontend tests pass - Build completes successfully - TypeScript compiles without errors ### Files Modified - `/home/gateway/gitea/apc-controller/frontend/src/components/historical-power-chart.tsx` - `/home/gateway/gitea/apc-controller/frontend/src/app/history/page.tsx`