CUB-135: resolve merge conflict with dev + lint fixes

- Merge SSEProvider/ToastContainer with Dashboard/Inventory routes
- Fix no-explicit-any in useSSE.ts (Record<string, unknown>)
- Fix exhaustive-deps warning in InventoryPage (wrap filaments in useMemo)

docs/CONTEXT.md

@@ -0,0 +1,214 @@
+# Extrudex — Project Context
+
+> **Last updated:** 2026-05-21
+> **Repo:** `CubeCraft-Creations/Extrudex` | **Host:** `code.cubecraftcreations.com`
+> **Local clone:** `/mnt/ai-storage/projects/Extrudex` | **Default branch:** `dev`
+> **Discord:** `DISCORD_DEV_EXTRUDEX_CHANNEL_ID`
+> **Linear Epic:** [CUB-110](https://linear.app/cubecraft-creations/issue/CUB-110)
+
+---
+
+## Overview
+
+Custom filament inventory and print tracking system for CubeCraft Creations. Tracks spool consumption, material costs, and per-print COGS across a fleet of 6 FDM printers (5 Bambu Lab + 1 Elegoo Centauri Carbon) + resin printers. Kiosk interface on Raspberry Pi 5 with USB barcode scanner.
+
+**Active refactor in progress:** .NET → Go + React (CUB-110 epic).
+
+## Tech Stack
+
+| Layer | Technology | Notes |
+|-------|-----------|-------|
+| Backend (legacy) | ASP.NET Core 9 + EF Core | Being replaced by Go |
+| Backend (new) | Go 1.24+ | Chi router, pgx (PostgreSQL), gorilla/websocket, paho.mqtt.golang |
+| Frontend (legacy) | Angular 17+ | Being replaced by React |
+| Frontend (new) | React 18 + TypeScript + Tailwind CSS | Vite |
+| Database | PostgreSQL 16+ | snake_case naming |
+| Real-time | SSE (Server-Sent Events) | Replaces SignalR |
+| Printer integrations | Moonraker REST + WebSocket, MQTT TLS | Elegoo/Klipper + Bambu Lab |
+| CI/CD | Gitea Actions | `.gitea/workflows/dev.yml` |
+| Deployment | Docker/Compose, Pi 5 kiosk | |
+
+## Key Design Decisions
+
+1. **Custom system over Spoolman** — Full control over data model and integrations
+2. **MaterialFinish required** on every spool; default is "Basic"
+3. **MaterialModifier is optional**
+4. **Grams derived from:** `mm_extruded × filament_cross_section_area × material_density`
+5. **Push over poll** — SSE + MQTT preferred; Moonraker polling is fallback
+6. **Snake_case** for all PostgreSQL identifiers
+
+## Project Structure
+
+```
+Extrudex/
+├── backend/                         # Original .NET backend (being replaced)
+│   ├── API/Controllers/             # Filaments, Spools, PrintJobs, Printers, Materials, QR, UsageLogs, Cost
+│   ├── API/DTOs/                    # DTOs per domain
+│   ├── API/Validators/              # FluentValidation rules
+│   ├── API/Hubs/                    # SignalR PrinterHub
+│   ├── API/Jobs/                    # Background sync jobs
+│   ├── Domain/Entities/             # EF Core entities (Printer, Spool, PrintJob, MaterialBase, etc.)
+│   ├── Domain/Enums/                # ConnectionType, DataSource, JobStatus, PrinterStatus, QrResourceType
+│   ├── Domain/Interfaces/           # Service interfaces
+│   ├── Infrastructure/Data/         # EF DbContext, Configurations, Migrations, SeedData
+│   ├── Infrastructure/Services/     # MoonrakerClient, CostPerPrint, UsageLog, FilamentUsage, QR
+│   └── Program.cs                  # ASP.NET entry point
+├── cmd/server/main.go              # Go entrypoint (new), worker discovery, graceful shutdown
+├── internal/                       # Go backend (new)
+│   ├── config/config.go            # Env vars
+│   ├── db/db.go                    # PostgreSQL connection pool (pgx)
+│   ├── models/models.go            # Go domain structs
+│   ├── router/router.go            # Chi HTTP routes
+│   ├── sse/broadcaster.go          # SSE broadcaster
+│   ├── sse/events.go               # SSE event types
+│   ├── sse/handler.go              # SSE HTTP handler
+│   ├── handlers/                   # API handlers (filament, health, material, print_job, printer, usage_log)
+│   ├── repositories/               # DB access layer
+│   └── services/                   # Business logic + validation
+├── migrations/                     # Go-migrate SQL migrations
+│   ├── 000001_initial_schema.up.sql
+│   ├── 000001_initial_schema.down.sql
+│   ├── 000002_seed_data.up.sql
+│   └── 000002_seed_data.down.sql
+├── frontend/                       # React frontend (new)
+│   ├── src/
+│   │   ├── App.tsx
+│   │   ├── main.tsx
+│   │   ├── components/             # ColorSwatch, LoadingSpinner, RecentPrints, SummaryCard
+│   │   ├── pages/
+│   │   │   ├── Dashboard.tsx       # Main dashboard with summary cards + recent prints
+│   │   │   └── InventoryPage.tsx   # Filament inventory list (table + filters)
+│   │   ├── services/
+│   │   │   ├── api.ts              # Axios client
+│   │   │   └── filamentService.ts
+│   │   ├── stores/                 # State stores (WIP)
+│   │   ├── types/
+│   │   │   ├── filament.ts
+│   │   │   └── index.ts
+│   │   └── hooks/
+│   ├── Dockerfile + nginx.conf
+│   └── vite.config.ts, tailwind.config.js
+├── design/                         # UX/design specs + mockup images
+│   ├── homepage-spec.md
+│   ├── 01-filament-inventory-list.md
+│   ├── 02-spool-detail-view.md
+│   ├── 03-smart-intake-workflow.md
+│   ├── smart-intake-identify-spec.md
+│   └── *.jpg / *.png               # Mockup images (kiosk + mobile)
+├── docker-compose.dev.yml
+└── deploy.sh
+```
+
+## Database Schema (PostgreSQL — .NET EF Core Migrations)
+
+Core entities managed by EF Core with full configurations:
+- **Printers** — id, name, type (BambuLab/Moonraker), connection_type, status, ip_address, mac_address, ams_count
+- **AmsUnit / AmsSlot** — Bambu Lab AMS tray tracking
+- **Spools** — filament inventory with material, color, weight, location, QR support
+- **MaterialBase / MaterialFinish / MaterialModifier** — material taxonomy
+- **PrintJobs** — job tracking with status, cost, filament consumption
+- **UsageLogs** — per-printer filament consumption records
+- **FilamentUsage** — aggregated per-spool consumption tracking
+- **FilamentUsageSyncJob** — background Moonraker polling
+- **MoonrakerPrinterSyncJob** — background printer status sync
+
+## API Endpoints (.NET)
+
+| Method | Endpoint | Description |
+|--------|----------|-------------|
+| GET | /api/filaments | List filaments (paginated, filterable) |
+| POST | /api/filaments | Create filament |
+| GET | /api/filaments/{id} | Get filament detail |
+| PUT | /api/filaments/{id} | Update filament |
+| DELETE | /api/filaments/{id} | Delete filament |
+| GET | /api/spools | List spools |
+| POST | /api/spools | Create spool |
+| GET | /api/spools/{id} | Get spool detail |
+| PUT | /api/spools/{id} | Update spool |
+| DELETE | /api/spools/{id} | Delete spool |
+| GET | /api/print-jobs | List print jobs |
+| POST | /api/print-jobs | Create print job |
+| GET | /api/print-jobs/{id} | Get print job detail |
+| GET | /api/printers | List printers |
+| POST | /api/printers | Register printer |
+| GET | /api/printers/{id} | Get printer detail |
+| GET | /api/printers/{id}/costs | Per-print cost summary |
+| GET | /api/printers/{id}/usage | Filament usage history |
+| GET | /api/materials/bases | List material bases |
+| POST | /api/materials/bases | Create material base |
+| GET | /api/materials/finishes | List material finishes |
+| POST | /api/materials/finishes | Create material finish |
+| GET | /api/materials/modifiers | List material modifiers |
+| POST | /api/materials/modifiers | Create modifier |
+| GET | /api/materials/lookups | Unified material lookup |
+| GET | /api/qr/resolve/{code} | QR code resolve |
+| GET | /api/usage-logs | List usage logs |
+| POST | /api/usage-logs | Create usage log |
+
+## CUB-110 Epic Progress (Go + React Rewrite)
+
+| Sub-task | Title | Status | Agent |
+|----------|-------|--------|-------|
+| CUB-111 | Design PostgreSQL schema | Done | Hex |
+| CUB-112 | Scaffold Go backend | Done | Dex |
+| CUB-113 | Core CRUD API endpoints | Done | Dex |
+| CUB-116 | Scaffold React frontend | In Review | Rex |
+| CUB-117 | Moonraker + MQTT integrations | In Progress | Dex |
+| CUB-118 | (deprecated → CUB-135 + CUB-136) | — | — |
+| CUB-130 | Add/Edit Filament form | In Review | Rex |
+| CUB-131 | Filament Detail page | In Review | Rex |
+| CUB-132 | Filament Inventory list | Done | Rex |
+| CUB-133 | Dashboard summary cards | In Review | Rex |
+| CUB-134 | Printers list page | Todo | Rex |
+| CUB-135 | Subscribe to SSE in React | In Review | Rex |
+| CUB-136 | Add SSE endpoint in Go | In Review | Dex |
+| CUB-128 | Settings page | Todo | — |
+| CUB-129 | Print Jobs list page | Todo | — |
+| CUB-114 | Pi 5 kiosk deployment | Todo | — |
+
+## Active Branches
+
+| Branch | Agent | Issue | Status |
+|--------|-------|-------|--------|
+| `agent/dex/CUB-117-moonraker-mqtt-go` | Dex | CUB-117 | Local commit ready |
+| `agent/dex/CUB-136-sse-endpoint` | Dex | CUB-136 | PR open |
+| `agent/rex/CUB-130-filament-form` | Rex | CUB-130 | PR open |
+| `agent/rex/CUB-131-filament-detail` | Rex | CUB-131 | PR open |
+| `agent/rex/CUB-133-dashboard-cards` | Rex | CUB-133 | PR open |
+| `agent/rex/CUB-135-sse-subscribe` | Rex | CUB-135 | PR open |
+
+## Known Limitations
+
+- Go rewrite is in progress — backend `internal/` is new Go code, but legacy .NET code still serves endpoints
+- Kiosk deployment not finalized (CUB-114)
+- Smart intake workflow is designed but not implemented
+- MQTT Bambu Lab integration is partially complete (CUB-117)
+
+## Default Agent Assignments
+
+| Area | Agent | Notes |
+|------|-------|-------|
+| Backend (Go API, Moonraker, MQTT) | Dex | gitea-dex MCP |
+| Database (PostgreSQL schema, migrations) | Hex | gitea-hex MCP |
+| Frontend (React, Tailwind) | Rex | gitea-rex MCP |
+| Design (wireframes, UX) | Sketch | |
+
+## Getting Started
+
+```bash
+cd /mnt/ai-storage/projects/Extrudex
+git checkout dev
+git pull origin dev
+
+# Legacy .NET backend
+cd backend && dotnet run
+
+# New Go backend
+go run cmd/server/main.go
+
+# React frontend
+cd frontend && npm install && npm run dev
+
+# Docker
+docker compose -f docker-compose.dev.yml up --build
+```

frontend/package-lock.json

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+      "integrity": "sha512-rkVq3IXh+4FDGch+KwzX3aV9W3kO54GyEgpvBzSyctDA6Xtd7RJQV1xmXbeQp5v7+VzLOfVqiutSE6GICgPFvg==",
+      "dev": true,
+      "bin": {
+        "semver": "bin/semver.js"
+      },
+      "engines": {
+        "node": ">=10"
+      }
+    },
+    "node_modules/@typescript-eslint/utils": {
+      "version": "8.60.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/utils/-/utils-8.60.0.tgz",
+      "integrity": "sha512-HtXuPfrHTyBDkameWpl+vJb1Uevu2tznAyahM1Oc4AENidCLTPiZDWIo4GfcxNdC/RcfGcadzzkqbRG87dUrQA==",
+      "dev": true,
+      "dependencies": {
+        "@eslint-community/eslint-utils": "^4.9.1",
+        "@typescript-eslint/scope-manager": "8.60.0",
+        "@typescript-eslint/types": "8.60.0",
+        "@typescript-eslint/typescript-estree": "8.60.0"
+      },
+      "engines": {
+        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/typescript-eslint"
+      },
+      "peerDependencies": {
+        "eslint": "^8.57.0 || ^9.0.0 || ^10.0.0",
+        "typescript": ">=4.8.4 <6.1.0"
+      }
+    },
+    "node_modules/@typescript-eslint/visitor-keys": {
+      "version": "8.60.0",
+      "resolved": "https://registry.npmjs.org/@typescript-eslint/visitor-keys/-/visitor-keys-8.60.0.tgz",
+      "integrity": "sha512-9WI52t8ZGLVGrPMBet25yAftqY/n95+zmoUUtJBBQTKDSKUu7OsPTroT2op7U9JatkoRccL0YkWDNMFfC4Sjxg==",
+      "dev": true,
+      "dependencies": {
+        "@typescript-eslint/types": "8.60.0",
+        "eslint-visitor-keys": "^5.0.0"
+      },
+      "engines": {
+        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/typescript-eslint"
+      }
+    },
+    "node_modules/@typescript-eslint/visitor-keys/node_modules/eslint-visitor-keys": {
+      "version": "5.0.1",
+      "resolved": "https://registry.npmjs.org/eslint-visitor-keys/-/eslint-visitor-keys-5.0.1.tgz",
+      "integrity": "sha512-tD40eHxA35h0PEIZNeIjkHoDR4YjjJp34biM0mDvplBe//mB+IHCqHDGV7pxF+7MklTvighcCPPZC7ynWyjdTA==",
+      "dev": true,
+      "engines": {
+        "node": "^20.19.0 || ^22.13.0 || >=24"
+      },
+      "funding": {
+        "url": "https://opencollective.com/eslint"
+      }
+    },
     "node_modules/@vitejs/plugin-react": {
       "version": "4.7.0",
       "resolved": "https://registry.npmjs.org/@vitejs/plugin-react/-/plugin-react-4.7.0.tgz",
@@ -2528,9 +2821,9 @@
       }
     },
     "node_modules/globals": {
-      "version": "14.0.0",
+      "version": "17.6.0",
-      "resolved": "https://registry.npmjs.org/globals/-/globals-14.0.0.tgz",
+      "resolved": "https://registry.npmjs.org/globals/-/globals-17.6.0.tgz",
-      "integrity": "sha512-oahGvuMGQlPw/ivIYBjVSrWAfWLBeku5tpPE2fOPLi+WHffIWbuh2tCjhyQhTBPMf5E9jDEH4FOmTYgYwbKwtQ==",
+      "integrity": "sha512-sepffkT8stwnIYbsMBpoCHJuJM5l98FUF2AnE07hfvE0m/qp3R586hw4jF4uadbhvg1ooIdzuu7CsfD2jzCaNA==",
       "dev": true,
       "engines": {
         "node": ">=18"
@@ -3504,6 +3797,18 @@
         "url": "https://github.com/sponsors/SuperchupuDev"
       }
     },
+    "node_modules/ts-api-utils": {
+      "version": "2.5.0",
+      "resolved": "https://registry.npmjs.org/ts-api-utils/-/ts-api-utils-2.5.0.tgz",
+      "integrity": "sha512-OJ/ibxhPlqrMM0UiNHJ/0CKQkoKF243/AEmplt3qpRgkW8VG7IfOS41h7V8TjITqdByHzrjcS/2si+y4lIh8NA==",
+      "dev": true,
+      "engines": {
+        "node": ">=18.12"
+      },
+      "peerDependencies": {
+        "typescript": ">=4.8.4"
+      }
+    },
     "node_modules/type-check": {
       "version": "0.4.0",
       "resolved": "https://registry.npmjs.org/type-check/-/type-check-0.4.0.tgz",
@@ -3529,6 +3834,29 @@
         "node": ">=14.17"
       }
     },
+    "node_modules/typescript-eslint": {
+      "version": "8.60.0",
+      "resolved": "https://registry.npmjs.org/typescript-eslint/-/typescript-eslint-8.60.0.tgz",
+      "integrity": "sha512-9f65qWLZdAW9m1JaxBDUHcqRUfL8bkxxXL7XxEfI+F09q56PkBvIfCjLF3yInsDM/BBmwkqmCQdCZe/RYlIWEw==",
+      "dev": true,
+      "dependencies": {
+        "@typescript-eslint/eslint-plugin": "8.60.0",
+        "@typescript-eslint/parser": "8.60.0",
+        "@typescript-eslint/typescript-estree": "8.60.0",
+        "@typescript-eslint/utils": "8.60.0"
+      },
+      "engines": {
+        "node": "^18.18.0 || ^20.9.0 || >=21.1.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/typescript-eslint"
+      },
+      "peerDependencies": {
+        "eslint": "^8.57.0 || ^9.0.0 || ^10.0.0",
+        "typescript": ">=4.8.4 <6.1.0"
+      }
+    },
     "node_modules/update-browserslist-db": {
       "version": "1.2.3",
       "resolved": "https://registry.npmjs.org/update-browserslist-db/-/update-browserslist-db-1.2.3.tgz",

frontend/package.json

@@ -27,9 +27,11 @@
     "eslint": "^9.15.0",
     "eslint-plugin-react-hooks": "^5.0.0",
     "eslint-plugin-react-refresh": "^0.4.14",
+    "globals": "^17.6.0",
     "postcss": "^8.4.49",
     "tailwindcss": "^4.0.0",
     "typescript": "~5.6.0",
+    "typescript-eslint": "^8.60.0",
     "vite": "^6.0.0"
   }
 }

frontend/src/App.tsx

@@ -1,24 +1,36 @@
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
 import { BrowserRouter, Routes, Route } from 'react-router-dom'
+import Dashboard from './pages/Dashboard'
 import InventoryPage from './pages/InventoryPage'
+import ToastContainer from './components/ToastContainer'
+import { useSSE } from './hooks/useSSE'
 
 const queryClient = new QueryClient()
 
+function SSEProvider({ children }: { children: React.ReactNode }) {
+  useSSE()
+  return <>{children}</>
+}
+
 export default function App() {
   return (
     <QueryClientProvider client={queryClient}>
       <BrowserRouter>
-        <div className="min-h-screen bg-slate-900 text-slate-50">
+        <SSEProvider>
-          <header className="bg-slate-800 border-b border-slate-700 px-4 py-3 flex items-center gap-3 sticky top-0 z-20">
+          <div className="min-h-screen bg-slate-900 text-slate-50">
-            <div className="w-8 h-8 rounded bg-emerald-500 flex items-center justify-center text-slate-900 font-bold text-lg">E</div>
+            <header className="bg-slate-800 border-b border-slate-700 px-4 py-3 flex items-center gap-3 sticky top-0 z-20">
-            <h1 className="text-lg font-semibold">Extrudex</h1>
+              <div className="w-8 h-8 rounded bg-emerald-500 flex items-center justify-center text-slate-900 font-bold text-lg">E</div>
-          </header>
+              <h1 className="text-lg font-semibold">Extrudex</h1>
-          <main className="p-4">
+            </header>
-            <Routes>
+            <main className="p-4">
-              <Route path="/" element={<InventoryPage />} />
+              <Routes>
-            </Routes>
+                <Route path="/" element={<Dashboard />} />
-          </main>
+                <Route path="/inventory" element={<InventoryPage />} />
-        </div>
+              </Routes>
+            </main>
+          </div>
+          <ToastContainer />
+        </SSEProvider>
       </BrowserRouter>
     </QueryClientProvider>
   )

frontend/src/components/LoadingSpinner.tsx

@@ -0,0 +1,8 @@
+export default function LoadingSpinner() {
+  return (
+    <div className="flex flex-col items-center gap-3">
+      <div className="w-10 h-10 border-4 border-emerald-500/30 border-t-emerald-400 rounded-full animate-spin" />
+      <p className="text-slate-400 text-sm">Loading dashboard…</p>
+    </div>
+  )
+}

frontend/src/components/PrinterStatusBadge.tsx

@@ -0,0 +1,17 @@
+import { Printer } from 'lucide-react'
+
+const STYLES = {
+  online: 'bg-emerald-600 text-white',
+  offline: 'bg-slate-600 text-slate-200',
+  printing: 'bg-blue-600 text-white animate-pulse',
+}
+
+export default function PrinterStatusBadge({ status, name }: { status: string; name?: string }) {
+  const style = STYLES[status as keyof typeof STYLES] ?? STYLES.offline
+  return (
+    <span className={`inline-flex items-center gap-1.5 rounded-full px-2.5 py-1 text-xs font-medium ${style}`}>
+      <Printer size={12} />
+      {name ? `${name} · ${status}` : status}
+    </span>
+  )
+}

frontend/src/components/RecentPrints.tsx

@@ -0,0 +1,76 @@
+import type { PrintJob } from '../types'
+import { Clock, FileText } from 'lucide-react'
+
+interface RecentPrintsProps {
+  jobs: PrintJob[]
+}
+
+export default function RecentPrints({ jobs }: RecentPrintsProps) {
+  if (jobs.length === 0) {
+    return (
+      <div className="rounded-xl border border-slate-700 bg-slate-800 p-6 text-center text-slate-400">
+        <FileText size={32} className="mx-auto mb-3 text-slate-500" />
+        <p>No recent print jobs</p>
+      </div>
+    )
+  }
+
+  const statusColor = (status: string) => {
+    switch (status.toLowerCase()) {
+      case 'completed': return 'text-emerald-400 bg-emerald-500/10'
+      case 'in_progress': return 'text-sky-400 bg-sky-500/10'
+      case 'failed': return 'text-red-400 bg-red-500/10'
+      default: return 'text-slate-400 bg-slate-500/10'
+    }
+  }
+
+  return (
+    <div className="rounded-xl border border-slate-700 bg-slate-800 overflow-hidden">
+      <div className="overflow-x-auto">
+        <table className="w-full text-left">
+          <thead>
+            <tr className="border-b border-slate-700">
+              <th className="px-4 py-3 text-sm font-medium text-slate-400">Name</th>
+              <th className="px-4 py-3 text-sm font-medium text-slate-400">Status</th>
+              <th className="px-4 py-3 text-sm font-medium text-slate-400">Duration</th>
+              <th className="px-4 py-3 text-sm font-medium text-slate-400">Filament</th>
+              <th className="px-4 py-3 text-sm font-medium text-slate-400">Cost</th>
+            </tr>
+          </thead>
+          <tbody>
+            {jobs.map((job) => (
+              <tr key={job.id} className="border-b border-slate-700/50 last:border-0 hover:bg-slate-700/30 transition-colors">
+                <td className="px-4 py-3 text-sm text-slate-100 font-medium">{job.name}</td>
+                <td className="px-4 py-3">
+                  <span className={`inline-flex items-center gap-1 px-2 py-1 rounded-full text-xs font-medium ${statusColor(job.status)}`}>
+                    {job.status}
+                  </span>
+                </td>
+                <td className="px-4 py-3 text-sm text-slate-300">
+                  <div className="flex items-center gap-1">
+                    <Clock size={14} />
+                    {formatDuration(job.duration_seconds)}
+                  </div>
+                </td>
+                <td className="px-4 py-3 text-sm text-slate-300">
+                  {job.filament_used_grams?.toFixed(1) ?? '-'} g
+                </td>
+                <td className="px-4 py-3 text-sm text-slate-300">
+                  ${job.cost_usd?.toFixed(2) ?? '-'}
+                </td>
+              </tr>
+            ))}
+          </tbody>
+        </table>
+      </div>
+    </div>
+  )
+}
+
+function formatDuration(seconds: number): string {
+  if (!seconds) return '-'
+  const hrs = Math.floor(seconds / 3600)
+  const mins = Math.floor((seconds % 3600) / 60)
+  if (hrs > 0) return `${hrs}h ${mins}m`
+  return `${mins}m`
+}

frontend/src/components/SummaryCard.tsx

@@ -0,0 +1,31 @@
+import type { LucideIcon } from 'lucide-react'
+
+interface SummaryCardProps {
+  title: string
+  value: string | number
+  icon: LucideIcon
+  color: 'emerald' | 'amber' | 'sky' | 'violet'
+}
+
+const colorMap = {
+  emerald: { bg: 'bg-emerald-500/10', border: 'border-emerald-500/20', text: 'text-emerald-400', icon: 'text-emerald-400' },
+  amber:   { bg: 'bg-amber-500/10',  border: 'border-amber-500/20',  text: 'text-amber-400',  icon: 'text-amber-400' },
+  sky:     { bg: 'bg-sky-500/10',    border: 'border-sky-500/20',    text: 'text-sky-400',    icon: 'text-sky-400' },
+  violet:  { bg: 'bg-violet-500/10', border: 'border-violet-500/20', text: 'text-violet-400', icon: 'text-violet-400' },
+}
+
+export default function SummaryCard({ title, value, icon: Icon, color }: SummaryCardProps) {
+  const c = colorMap[color]
+
+  return (
+    <div className={`rounded-xl border ${c.border} ${c.bg} p-5 flex items-start justify-between`}>
+      <div>
+        <p className="text-sm font-medium text-slate-400 mb-1">{title}</p>
+        <p className={`text-3xl font-bold ${c.text}`}>{value}</p>
+      </div>
+      <div className={`p-2 rounded-lg ${c.bg}`}>
+        <Icon size={24} className={c.icon} />
+      </div>
+    </div>
+  )
+}

frontend/src/components/ToastContainer.tsx

@@ -0,0 +1,70 @@
+import { useEffect, useState, useCallback } from 'react'
+import { X, CheckCircle, AlertTriangle, Info } from 'lucide-react'
+import { addToastListener, type ToastMessage } from '../hooks/useSSE'
+
+const ICONS = {
+  info: Info,
+  success: CheckCircle,
+  warning: AlertTriangle,
+}
+
+const STYLES = {
+  info: 'border-blue-600 bg-blue-900/40 text-blue-100',
+  success: 'border-emerald-600 bg-emerald-900/40 text-emerald-100',
+  warning: 'border-amber-600 bg-amber-900/40 text-amber-100',
+}
+
+export default function ToastContainer() {
+  const [toasts, setToasts] = useState<ToastMessage[]>([])
+
+  const remove = useCallback((id: string) => {
+    setToasts(prev => prev.filter(t => t.id !== id))
+  }, [])
+
+  useEffect(() => {
+    return addToastListener((toast) => {
+      setToasts(prev => {
+        // Prevent duplicate identical toasts within 3 seconds
+        const now = Date.now()
+        const recent = prev.filter(
+          t => t.title === toast.title && now - parseInt(t.id.split('-').pop() || '0', 10) < 3000
+        )
+        if (recent.length > 0) return prev
+        return [...prev.slice(-4), toast]
+      })
+      // Auto-dismiss after 5 seconds
+      setTimeout(() => remove(toast.id), 5000)
+    })
+  }, [remove])
+
+  return (
+    <div className="fixed bottom-4 right-4 z-50 flex flex-col gap-2 max-w-sm w-full pointer-events-none">
+      {toasts.map((toast) => {
+        const Icon = ICONS[toast.type]
+        return (
+          <div
+            key={toast.id}
+            className={`pointer-events-auto rounded-lg border px-4 py-3 shadow-lg backdrop-blur-sm transition-all ${STYLES[toast.type]}`}
+          >
+            <div className="flex items-start gap-3">
+              <Icon size={18} className="mt-0.5 shrink-0" />
+              <div className="flex-1 min-w-0">
+                <p className="text-sm font-semibold leading-snug">{toast.title}</p>
+                {toast.body && (
+                  <p className="text-xs opacity-80 mt-0.5">{toast.body}</p>
+                )}
+              </div>
+              <button
+                onClick={() => remove(toast.id)}
+                className="shrink-0 -mr-1 -mt-1 p-1 rounded hover:bg-white/10 text-current opacity-70 hover:opacity-100 transition-opacity"
+                aria-label="Dismiss"
+              >
+                <X size={14} />
+              </button>
+            </div>
+          </div>
+        )
+      })}
+    </div>
+  )
+}

frontend/src/hooks/useSSE.ts

@@ -0,0 +1,193 @@
+import { useEffect, useRef, useCallback } from 'react'
+import { useQueryClient } from '@tanstack/react-query'
+
+export type SSEEventType =
+  | 'printer.status'
+  | 'job.started'
+  | 'job.completed'
+  | 'filament.low'
+
+export interface SSEEvent {
+  type: SSEEventType
+  payload: unknown
+  timestamp: string
+}
+
+export interface ToastMessage {
+  id: string
+  type: 'info' | 'success' | 'warning'
+  title: string
+  body?: string
+}
+
+let toastListeners: Array<(toast: ToastMessage) => void> = []
+
+export function addToastListener(cb: (toast: ToastMessage) => void) {
+  toastListeners.push(cb)
+  return () => {
+    toastListeners = toastListeners.filter(l => l !== cb)
+  }
+}
+
+function emitToast(toast: ToastMessage) {
+  toastListeners.forEach(cb => cb(toast))
+}
+
+const RECONNECT_BASE_MS = 1000
+const RECONNECT_MAX_MS = 30000
+
+export function useSSE(enabled = true) {
+  const queryClient = useQueryClient()
+  const esRef = useRef<EventSource | null>(null)
+  const reconnectTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const attemptRef = useRef(0)
+
+  const connect = useCallback(() => {
+    if (!enabled) return
+    if (esRef.current) {
+      esRef.current.close()
+    }
+
+    const es = new EventSource('/api/events')
+    esRef.current = es
+
+    es.onopen = () => {
+      attemptRef.current = 0
+    }
+
+    es.addEventListener('printer.status', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          printer_id: number
+          printer_name: string
+          status: string
+        }
+        // Update printer list cache if it exists
+        queryClient.setQueryData(['printers'], (old: unknown) => {
+          if (!Array.isArray(old)) return old
+          return old.map((p: Record<string, unknown>) =>
+            p.id === payload.printer_id
+              ? { ...p, status: payload.status, name: payload.printer_name }
+              : p
+          )
+        })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.addEventListener('job.started', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          job_id: number
+          job_name: string
+          printer_id: number
+          spool_id?: number
+        }
+        emitToast({
+          id: `job-started-${payload.job_id}-${Date.now()}`,
+          type: 'info',
+          title: `Job started: ${payload.job_name}`,
+          body: `Printer #${payload.printer_id}`,
+        })
+        // Invalidate print jobs list
+        queryClient.invalidateQueries({ queryKey: ['print-jobs'] })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.addEventListener('job.completed', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          job_id: number
+          job_name: string
+          printer_id: number
+          duration_seconds?: number
+          total_grams_used?: number
+          total_cost_usd?: number
+        }
+        const parts: string[] = []
+        if (payload.duration_seconds != null) {
+          const mins = Math.round(payload.duration_seconds / 60)
+          parts.push(`${mins} min`)
+        }
+        if (payload.total_grams_used != null) {
+          parts.push(`${payload.total_grams_used.toFixed(1)} g used`)
+        }
+        emitToast({
+          id: `job-completed-${payload.job_id}-${Date.now()}`,
+          type: 'success',
+          title: `Job completed: ${payload.job_name}`,
+          body: parts.join(' · ') || `Printer #${payload.printer_id}`,
+        })
+        queryClient.invalidateQueries({ queryKey: ['print-jobs'] })
+        queryClient.invalidateQueries({ queryKey: ['filaments'] })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.addEventListener('filament.low', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          spool_id: number
+          spool_name: string
+          remaining_grams: number
+          threshold_grams: number
+        }
+        emitToast({
+          id: `filament-low-${payload.spool_id}-${Date.now()}`,
+          type: 'warning',
+          title: `Low filament: ${payload.spool_name}`,
+          body: `${payload.remaining_grams} g remaining (threshold ${payload.threshold_grams} g)`,
+        })
+        // Update filament inventory cache in place for instant UI feedback
+        queryClient.setQueryData(['filaments'], (old: unknown) => {
+          if (!old || typeof old !== 'object') return old
+          const o = old as { data?: Array<Record<string, unknown>>; total?: number }
+          if (!Array.isArray(o.data)) return old
+          return {
+            ...o,
+            data: o.data.map((f) =>
+              (f.id as number) === payload.spool_id
+                ? { ...f, remaining_grams: payload.remaining_grams }
+                : f
+            ),
+          }
+        })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.onerror = () => {
+      es.close()
+      // Exponential backoff with jitter
+      const base = Math.min(RECONNECT_MAX_MS, RECONNECT_BASE_MS * 2 ** attemptRef.current)
+      const jitter = Math.random() * 1000
+      const delay = base + jitter
+      attemptRef.current += 1
+      reconnectTimerRef.current = setTimeout(() => {
+        connect()
+      }, delay)
+    }
+  }, [enabled, queryClient])
+
+  useEffect(() => {
+    connect()
+    return () => {
+      if (reconnectTimerRef.current) {
+        clearTimeout(reconnectTimerRef.current)
+      }
+      if (esRef.current) {
+        esRef.current.close()
+        esRef.current = null
+      }
+    }
+  }, [connect])
+}

frontend/src/main.tsx

@@ -1,10 +1,25 @@
 import { StrictMode } from 'react'
 import { createRoot } from 'react-dom/client'
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import { BrowserRouter } from 'react-router-dom'
 import './index.css'
 import App from './App'
 
+const queryClient = new QueryClient({
+  defaultOptions: {
+    queries: {
+      staleTime: 30_000,
+      refetchOnWindowFocus: false,
+    },
+  },
+})
+
 createRoot(document.getElementById('root')!).render(
   <StrictMode>
-    <App />
+    <QueryClientProvider client={queryClient}>
+      <BrowserRouter>
+        <App />
+      </BrowserRouter>
+    </QueryClientProvider>
   </StrictMode>,
 )

frontend/src/pages/Dashboard.tsx

@@ -0,0 +1,139 @@
+import { useQuery } from '@tanstack/react-query'
+import { getFilaments, getPrintJobs } from '../services/api'
+import SummaryCard from '../components/SummaryCard'
+import RecentPrints from '../components/RecentPrints'
+import LoadingSpinner from '../components/LoadingSpinner'
+import { Package, AlertTriangle, Printer, DollarSign, Plus, List } from 'lucide-react'
+
+export default function Dashboard() {
+  const {
+    data: filamentData,
+    isLoading: filamentLoading,
+    error: filamentError,
+  } = useQuery({
+    queryKey: ['filaments', 'count'],
+    queryFn: () => getFilaments({ limit: 1 }),
+  })
+
+  const {
+    data: lowStockData,
+    isLoading: lowStockLoading,
+    error: lowStockError,
+  } = useQuery({
+    queryKey: ['filaments', 'lowStock'],
+    queryFn: () => getFilaments({ low_stock: true, limit: 1 }),
+  })
+
+  const {
+    data: recentPrints,
+    isLoading: printsLoading,
+    error: printsError,
+  } = useQuery({
+    queryKey: ['printJobs', 'recent'],
+    queryFn: () => getPrintJobs({ limit: 5 }),
+  })
+
+  const {
+    data: allPrints,
+    isLoading: costLoading,
+    error: costError,
+  } = useQuery({
+    queryKey: ['printJobs', 'all'],
+    queryFn: () => getPrintJobs({ limit: 1000 }),
+  })
+
+  const totalSpools = filamentData?.total ?? 0
+  const lowStockCount = lowStockData?.total ?? 0
+  const recentPrintJobs = recentPrints?.data ?? []
+
+  // Calculate cost this month from all print jobs
+  const now = new Date()
+  const currentMonth = now.getMonth()
+  const currentYear = now.getFullYear()
+  const monthlyCost =
+    allPrints?.data
+      .filter((job) => {
+        const d = new Date(job.started_at)
+        return d.getMonth() === currentMonth && d.getFullYear() === currentYear
+      })
+      .reduce((sum, job) => sum + (job.cost_usd ?? 0), 0) ?? 0
+
+  const isLoading = filamentLoading || lowStockLoading || printsLoading || costLoading
+  const error = filamentError || lowStockError || printsError || costError
+
+  if (isLoading) {
+    return (
+      <div className="min-h-screen flex items-center justify-center bg-slate-900">
+        <LoadingSpinner />
+      </div>
+    )
+  }
+
+  if (error) {
+    return (
+      <div className="min-h-screen flex items-center justify-center bg-slate-900">
+        <div className="p-6 rounded-lg bg-red-900/30 border border-red-500 text-red-200 max-w-md">
+          <h2 className="text-xl font-bold mb-2">Error</h2>
+          <p className="text-sm">{(error as Error).message || 'Failed to load dashboard data.'}</p>
+        </div>
+      </div>
+    )
+  }
+
+  return (
+    <div className="min-h-screen bg-slate-900 p-4 md:p-8">
+      <div className="max-w-6xl mx-auto">
+        <header className="mb-8">
+          <h1 className="text-3xl font-bold text-emerald-400 mb-2">Dashboard</h1>
+          <p className="text-slate-400">Overview of your Extrudex inventory and prints</p>
+        </header>
+
+        {/* Summary Cards Grid */}
+        <div className="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-4 gap-4 mb-8">
+          <SummaryCard
+            title="Total Spools"
+            value={totalSpools}
+            icon={Package}
+            color="emerald"
+          />
+          <SummaryCard
+            title="Low Stock"
+            value={lowStockCount}
+            icon={AlertTriangle}
+            color={lowStockCount > 0 ? 'amber' : 'emerald'}
+          />
+          <SummaryCard
+            title="Recent Prints"
+            value={recentPrintJobs.length}
+            icon={Printer}
+            color="sky"
+          />
+          <SummaryCard
+            title="Cost This Month"
+            value={`$${monthlyCost.toFixed(2)}`}
+            icon={DollarSign}
+            color="violet"
+          />
+        </div>
+
+        {/* Quick Actions */}
+        <div className="flex flex-wrap gap-3 mb-8">
+          <button className="flex items-center gap-2 px-4 py-2 rounded-lg bg-emerald-600 hover:bg-emerald-500 text-white font-medium transition-colors active:scale-95 touch-manipulation">
+            <Plus size={18} />
+            Add Spool
+          </button>
+          <button className="flex items-center gap-2 px-4 py-2 rounded-lg bg-slate-700 hover:bg-slate-600 text-slate-100 font-medium transition-colors active:scale-95 touch-manipulation">
+            <List size={18} />
+            View Inventory
+          </button>
+        </div>
+
+        {/* Recent Prints Section */}
+        <section>
+          <h2 className="text-xl font-semibold text-slate-100 mb-4">Recent Prints</h2>
+          <RecentPrints jobs={recentPrintJobs} />
+        </section>
+      </div>
+    </div>
+  )
+}

frontend/src/pages/InventoryPage.tsx

@@ -35,7 +35,7 @@ export default function InventoryPage() {
     queryFn: () => fetchFilaments(filter),
   })
 
-  const filaments = data?.data ?? []
+  const filaments = useMemo(() => data?.data ?? [], [data?.data])
   const total = data?.total ?? 0
   const totalPages = Math.max(1, Math.ceil(total / PAGE_SIZE))
 

frontend/src/services/api.ts

@@ -0,0 +1,19 @@
+import axios from 'axios'
+import type { ListResponse, FilamentSpool, PrintJob } from '../types'
+
+const api = axios.create({
+  baseURL: '/api',
+  headers: { 'Content-Type': 'application/json' },
+})
+
+export async function getFilaments(params?: { low_stock?: boolean; limit?: number; offset?: number }) {
+  const res = await api.get<ListResponse<FilamentSpool>>('/filaments', { params })
+  return res.data
+}
+
+export async function getPrintJobs(params?: { limit?: number; offset?: number }) {
+  const res = await api.get<ListResponse<PrintJob>>('/print-jobs', { params })
+  return res.data
+}
+
+export default api

frontend/src/types/index.ts

@@ -0,0 +1,42 @@
+export interface FilamentSpool {
+  id: number;
+  name: string;
+  material_base_id: number;
+  material_finish_id: number;
+  material_modifier_id: number;
+  color_hex: string;
+  brand: string;
+  diameter_mm: number;
+  initial_grams: number;
+  remaining_grams: number;
+  spool_weight_grams: number;
+  cost_usd: number;
+  low_stock_threshold_grams: number;
+  notes: string;
+  barcode: string;
+  created_at: string;
+  updated_at: string;
+  deleted_at: string | null;
+}
+
+export interface PrintJob {
+  id: number;
+  name: string;
+  printer_id: number;
+  filament_id: number;
+  status: string;
+  duration_seconds: number;
+  filament_used_grams: number;
+  cost_usd: number;
+  started_at: string;
+  completed_at: string | null;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface ListResponse<T> {
+  data: T[];
+  total: number;
+  limit: number;
+  offset: number;
+}

frontend/tsconfig.json

@@ -15,6 +15,7 @@
     "noUnusedLocals": true,
     "noUnusedParameters": true,
     "noFallthroughCasesInSwitch": true,
+    "ignoreDeprecations": "5.0",
     "baseUrl": ".",
     "paths": {
       "@/*": ["src/*"]