CUB-117: Port Moonraker + MQTT printer integrations to Go

- Add internal/clients/moonraker.go: HTTP client for Moonraker REST API
- Add internal/clients/mqtt.go: MQTT client via paho.mqtt.golang with TLS support
- Add internal/workers/moonraker_poller.go: background polling, usage logging, SSE broadcasts
- Add internal/workers/mqtt_subscriber.go: per-printer MQTT subscriber, Bambu telemetry parsing, SSE broadcasts
- Wire workers into cmd/server/main.go (Start/Stop with graceful shutdown)

Blocked at step 4: go toolchain not installed on build host

backend/cmd/server/main.go

@@ -11,7 +11,10 @@ import (
 
 	"github.com/CubeCraft-Creations/Extrudex/backend/internal/config"
 	"github.com/CubeCraft-Creations/Extrudex/backend/internal/db"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
 	"github.com/CubeCraft-Creations/Extrudex/backend/internal/router"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/sse"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/workers"
 )
 
 func main() {
@@ -39,15 +42,42 @@ func main() {
 
 	slog.Info("database connected")
 
+	// Repositories (for background workers)
+	printerRepo := repositories.NewPrinterRepository(dbPool)
+	jobRepo := repositories.NewPrintJobRepository(dbPool)
+	usageLogRepo := repositories.NewUsageLogRepository(dbPool)
+
+	// Create SSE broadcaster and start it
+	sseBC := sse.NewBroadcaster(128)
+	sseBC.Start()
+	defer sseBC.Stop()
+
+	slog.Info("sse broadcaster started")
+
+	// Start background workers
+	mrCfg := workers.DefaultMoonrakerPollerConfig()
+	mrPoller := workers.NewMoonrakerPoller(mrCfg, dbPool, printerRepo, jobRepo, usageLogRepo, sseBC)
+	mrPoller.Start()
+	defer mrPoller.Stop()
+
+	mqttCfg := workers.DefaultMQTTSubscriberConfig()
+	mqttSub := workers.NewMQTTSubscriber(mqttCfg, dbPool, printerRepo, usageLogRepo, sseBC)
+	mqttSub.Start()
+	defer mqttSub.Stop()
+
+	slog.Info("background workers started")
+
 	// Create router
-	r := router.New(cfg, dbPool)
+	r := router.New(cfg, dbPool, sseBC)
 
 	// Create HTTP server
+	// WriteTimeout is 0 for SSE support — the Chi middleware.Timeout(60s)
+	// handles request-level timeouts on non-SSE routes.
 	server := &http.Server{
 		Addr:         ":" + cfg.Port,
 		Handler:      r,
 		ReadTimeout:  15 * time.Second,
-		WriteTimeout: 15 * time.Second,
+		WriteTimeout: 0, // disabled for SSE long-lived connections
 		IdleTimeout:  60 * time.Second,
 	}
 

backend/internal/clients/moonraker.go

@@ -0,0 +1,161 @@
+// Package clients provides third-party printer integrations.
+package clients
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"time"
+)
+
+// MoonrakerPrinterInfo represents the response from /api/printer/info.
+type MoonrakerPrinterInfo struct {
+	State      string `json:"state"`
+	Hostname   string `json:"hostname,omitempty"`
+	SoftwareVersion string `json:"software_version,omitempty"`
+}
+
+// MoonrakerPrintStats represents the response from /api/printer/print_stats.
+type MoonrakerPrintStats struct {
+	State            string  `json:"state"`
+	Filename         string  `json:"filename,omitempty"`
+	FilamentUsedMm   float64 `json:"filament_used,omitempty"`
+	TotalDuration    float64 `json:"total_duration,omitempty"`
+	PrintDuration    float64 `json:"print_duration,omitempty"`
+	Message          string  `json:"message,omitempty"`
+}
+
+// MoonrakerPrintJob represents a single job from the history API.
+type MoonrakerPrintJob struct {
+	JobID          string    `json:"job_id,omitempty"`
+	Filename       string    `json:"filename"`
+	Status         string    `json:"status"`
+	StartTime      time.Time `json:"start_time"`
+	EndTime        time.Time `json:"end_time,omitempty"`
+	FilamentUsedMm float64   `json:"filament_used,omitempty"`
+	TotalDuration  float64   `json:"total_duration,omitempty"`
+}
+
+// MoonrakerHistoryResponse represents the response from /api/server/history/job.
+type MoonrakerHistoryResponse struct {
+	Items []MoonrakerPrintJob `json:"jobs"`
+}
+
+// MoonrakerClient is an HTTP client for the Moonraker API.
+type MoonrakerClient struct {
+	HTTPClient *http.Client
+}
+
+// NewMoonrakerClient creates a MoonrakerClient with the given request timeout.
+func NewMoonrakerClient(timeout time.Duration) *MoonrakerClient {
+	return &MoonrakerClient{
+		HTTPClient: &http.Client{Timeout: timeout},
+	}
+}
+
+// baseURL builds the Moonraker base URL from host and port.
+func (c *MoonrakerClient) baseURL(host string, port int) string {
+	if port == 0 {
+		port = 80
+	}
+	return fmt.Sprintf("http://%s:%d", host, port)
+}
+
+// GetPrinterInfo fetches printer info from Moonraker.
+func (c *MoonrakerClient) GetPrinterInfo(ctx context.Context, host string, port int, apiKey string) (*MoonrakerPrinterInfo, error) {
+	url := c.baseURL(host, port) + "/api/printer/info"
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	if apiKey != "" {
+		req.Header.Set("X-Api-Key", apiKey)
+	}
+
+	resp, err := c.HTTPClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("moonraker getPrinterInfo request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("moonraker getPrinterInfo returned status %d", resp.StatusCode)
+	}
+
+	var body struct {
+		Result MoonrakerPrinterInfo `json:"result"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&body); err != nil {
+		return nil, fmt.Errorf("moonraker getPrinterInfo decode failed: %w", err)
+	}
+
+	slog.Debug("moonraker printer info", "host", host, "state", body.Result.State)
+	return &body.Result, nil
+}
+
+// GetPrintStats fetches current print statistics from Moonraker.
+func (c *MoonrakerClient) GetPrintStats(ctx context.Context, host string, port int, apiKey string) (*MoonrakerPrintStats, error) {
+	url := c.baseURL(host, port) + "/api/printer/print_stats"
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	if apiKey != "" {
+		req.Header.Set("X-Api-Key", apiKey)
+	}
+
+	resp, err := c.HTTPClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("moonraker getPrintStats request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("moonraker getPrintStats returned status %d", resp.StatusCode)
+	}
+
+	var body struct {
+		Result MoonrakerPrintStats `json:"result"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&body); err != nil {
+		return nil, fmt.Errorf("moonraker getPrintStats decode failed: %w", err)
+	}
+
+	slog.Debug("moonraker print stats", "host", host, "state", body.Result.State, "filename", body.Result.Filename)
+	return &body.Result, nil
+}
+
+// GetPrintHistory fetches completed print job history from Moonraker.
+func (c *MoonrakerClient) GetPrintHistory(ctx context.Context, host string, port int, apiKey string, limit int) (*MoonrakerHistoryResponse, error) {
+	if limit <= 0 {
+		limit = 25
+	}
+	url := fmt.Sprintf("%s/api/server/history/job?limit=%d", c.baseURL(host, port), limit)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	if apiKey != "" {
+		req.Header.Set("X-Api-Key", apiKey)
+	}
+
+	resp, err := c.HTTPClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("moonraker getPrintHistory request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("moonraker getPrintHistory returned status %d", resp.StatusCode)
+	}
+
+	var body MoonrakerHistoryResponse
+	if err := json.NewDecoder(resp.Body).Decode(&body); err != nil {
+		return nil, fmt.Errorf("moonraker getPrintHistory decode failed: %w", err)
+	}
+
+	slog.Debug("moonraker print history", "host", host, "count", len(body.Items))
+	return &body, nil
+}

backend/internal/clients/mqtt.go

@@ -0,0 +1,119 @@
+// Package clients provides third-party printer integrations.
+package clients
+
+import (
+	"context"
+	"crypto/tls"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"time"
+
+	mqtt "github.com/eclipse/paho.mqtt.golang"
+)
+
+// MQTTClient wraps the Eclipse Paho MQTT client for printer telemetry.
+type MQTTClient struct {
+	client mqtt.Client
+}
+
+// MQTTConfig holds per-printer MQTT connection settings.
+type MQTTConfig struct {
+	BrokerHost  string
+	BrokerPort  int
+	TopicPrefix string
+	TLSEnabled  bool
+	ClientID    string
+}
+
+// BambuPrintStatus is the known Bambu Lab print-status payload shape.
+type BambuPrintStatus struct {
+	Print struct {
+		GcodeFile       string  `json:"gcode_file,omitempty"`
+		Stage           int     `json:"stage,omitempty"`
+		SubTaskName     string  `json:"subtask_name,omitempty"`
+		PrintType       string  `json:"print_type,omitempty"`
+		FilamentUsedMm  float64 `json:"mc_percent,omitempty"` // placeholder; real telemetry varies
+	} `json:"print,omitempty"`
+}
+
+// NewMQTTClient creates an MQTT client connected to the given broker.
+func NewMQTTClient(cfg MQTTConfig) (*MQTTClient, error) {
+	if cfg.BrokerPort == 0 {
+		if cfg.TLSEnabled {
+			cfg.BrokerPort = 8883
+		} else {
+			cfg.BrokerPort = 1883
+		}
+	}
+	if cfg.ClientID == "" {
+		cfg.ClientID = fmt.Sprintf("extrudex-%d", time.Now().Unix())
+	}
+
+	opts := mqtt.NewClientOptions().
+		AddBroker(fmt.Sprintf("tcp://%s:%d", cfg.BrokerHost, cfg.BrokerPort)).
+		SetClientID(cfg.ClientID).
+		SetAutoReconnect(true).
+		SetConnectTimeout(10 * time.Second).
+		SetOrderMatters(false)
+
+	if cfg.TLSEnabled {
+		opts = opts.SetTLSConfig(&tls.Config{InsecureSkipVerify: false})
+	}
+
+	client := mqtt.NewClient(opts)
+	token := client.Connect()
+	if token.Wait() && token.Error() != nil {
+		return nil, fmt.Errorf("mqtt connect failed: %w", token.Error())
+	}
+
+	slog.Info("mqtt client connected", "broker", cfg.BrokerHost, "port", cfg.BrokerPort, "tls", cfg.TLSEnabled)
+	return &MQTTClient{client: client}, nil
+}
+
+// Subscribe registers a callback for messages matching topic.
+func (c *MQTTClient) Subscribe(topic string, qos byte, callback func([]byte)) error {
+	token := c.client.Subscribe(topic, qos, func(_ mqtt.Client, msg mqtt.Message) {
+		callback(msg.Payload())
+	})
+	if token.Wait() && token.Error() != nil {
+		return fmt.Errorf("mqtt subscribe failed: %w", token.Error())
+	}
+	slog.Info("mqtt subscribed", "topic", topic, "qos", qos)
+	return nil
+}
+
+// Unsubscribe removes a subscription.
+func (c *MQTTClient) Unsubscribe(topics ...string) error {
+	token := c.client.Unsubscribe(topics...)
+	if token.Wait() && token.Error() != nil {
+		return fmt.Errorf("mqtt unsubscribe failed: %w", token.Error())
+	}
+	return nil
+}
+
+// Disconnect cleanly disconnects the MQTT client.
+func (c *MQTTClient) Disconnect(quiesceMs uint) {
+	c.client.Disconnect(quiesceMs)
+}
+
+// IsConnected returns whether the underlying client is connected.
+func (c *MQTTClient) IsConnected() bool {
+	return c.client.IsConnected()
+}
+
+// ParseBambuTelemetry attempts to parse a Bambu Lab telemetry JSON payload.
+func ParseBambuTelemetry(payload []byte) (*BambuPrintStatus, error) {
+	var msg BambuPrintStatus
+	if err := json.Unmarshal(payload, &msg); err != nil {
+		return nil, fmt.Errorf("parse bambu telemetry failed: %w", err)
+	}
+	return &msg, nil
+}
+
+// DefaultBambuTopics returns the default topic patterns for Bambu Lab printers.
+func DefaultBambuTopics(topicPrefix string) []string {
+	return []string{
+		topicPrefix + "/report",
+	}
+}

backend/internal/router/router.go

@@ -8,13 +8,14 @@ import (
 	"github.com/CubeCraft-Creations/Extrudex/backend/internal/handlers"
 	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
 	"github.com/CubeCraft-Creations/Extrudex/backend/internal/services"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/sse"
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/jackc/pgx/v5/pgxpool"
 )
 
 // New creates and configures a Chi router with all middleware and handlers mounted.
-func New(cfg *config.Config, dbPool *pgxpool.Pool) chi.Router {
+func New(cfg *config.Config, dbPool *pgxpool.Pool, sseBC *sse.Broadcaster) chi.Router {
 	r := chi.NewRouter()
 
 	// Middleware
@@ -22,7 +23,7 @@ func New(cfg *config.Config, dbPool *pgxpool.Pool) chi.Router {
 	r.Use(middleware.RealIP)
 	r.Use(middleware.Logger)
 	r.Use(middleware.Recoverer)
-	r.Use(middleware.Timeout(60 * time.Second))
+	// Timeout middleware is applied per-route below to exclude SSE
 
 	// CORS
 	r.Use(func(next http.Handler) http.Handler {
@@ -38,9 +39,9 @@ func New(cfg *config.Config, dbPool *pgxpool.Pool) chi.Router {
 		})
 	})
 
-	// Health check
+	// Health check (with timeout)
 	healthHandler := handlers.NewHealthHandler(dbPool)
-	r.Get("/health", healthHandler.ServeHTTP)
+	r.With(middleware.Timeout(30 * time.Second)).Get("/health", healthHandler.ServeHTTP)
 
 	// ── Repositories ──────────────────────────────────────────────────────
 	materialRepo := repositories.NewMaterialRepository(dbPool)
@@ -61,8 +62,9 @@ func New(cfg *config.Config, dbPool *pgxpool.Pool) chi.Router {
 	printJobHandler := handlers.NewPrintJobHandler(printJobService)
 	usageLogHandler := handlers.NewUsageLogHandler(usageLogRepo)
 
-	// ── API Routes ────────────────────────────────────────────────────────
+	// ── API Routes (with timeout) ─────────────────────────────────────────
 	r.Route("/api", func(r chi.Router) {
+		r.Use(middleware.Timeout(60 * time.Second))
 		r.Get("/materials", materialHandler.List)
 
 		r.Route("/filaments", func(r chi.Router) {
@@ -78,6 +80,10 @@ func New(cfg *config.Config, dbPool *pgxpool.Pool) chi.Router {
 		r.Get("/printers", printerHandler.List)
 		r.Get("/print-jobs", printJobHandler.List)
 		r.Get("/usage-logs", usageLogHandler.List)
+
+		// SSE Events stream
+		sseHandler := sse.NewHandler(sseBC)
+		r.Get("/events", sseHandler.ServeHTTP)
 	})
 
 	return r

backend/internal/sse/broadcaster.go

@@ -0,0 +1,133 @@
+package sse
+
+import (
+	"log/slog"
+	"sync"
+)
+
+// client represents a single SSE subscriber — identified by its send channel.
+type client struct {
+	ch chan string
+}
+
+// Broadcaster receives Events on its input channel and fans them out to every
+// connected client. Subscribe adds a new client; Unsubscribe removes one.
+// Start must be called before the broadcaster accepts events.
+type Broadcaster struct {
+	input       chan Event
+	subscribe   chan client
+	unsubscribe chan client
+	clients     map[chan string]struct{}
+	done        chan struct{}
+	once        sync.Once
+}
+
+// NewBroadcaster creates a Broadcaster. bufSize controls the buffer depth for
+// the input channel as well as for each per-client outbound channel.
+func NewBroadcaster(bufSize int) *Broadcaster {
+	if bufSize <= 0 {
+		bufSize = 64
+	}
+	return &Broadcaster{
+		input:       make(chan Event, bufSize),
+		subscribe:   make(chan client),
+		unsubscribe: make(chan client),
+		clients:     make(map[chan string]struct{}),
+		done:        make(chan struct{}),
+	}
+}
+
+// Publish pushes an event into the broadcaster. Safe for concurrent use.
+func (b *Broadcaster) Publish(ev Event) {
+	select {
+	case b.input <- ev:
+	case <-b.done:
+		// Silently drop during shutdown.
+	}
+}
+
+// Start launches the broadcaster's fan-out loop in a goroutine.
+// It must be called before Publish is used.
+func (b *Broadcaster) Start() {
+	go b.loop()
+}
+
+// Stop terminates the fan-out loop and closes all client channels.
+// It is safe to call multiple times.
+func (b *Broadcaster) Stop() {
+	b.once.Do(func() {
+		close(b.done)
+	})
+}
+
+// Subscribe returns a new client channel that receives SSE-formatted strings.
+func (b *Broadcaster) Subscribe() chan string {
+	c := client{ch: make(chan string, 64)}
+	select {
+	case b.subscribe <- c:
+	case <-b.done:
+		// Broadcaster already stopped — return a closed chan so the handler
+		// can bail out quickly.
+		ch := make(chan string)
+		close(ch)
+		return ch
+	}
+	return c.ch
+}
+
+// Unsubscribe removes a client channel and closes it.
+func (b *Broadcaster) Unsubscribe(ch chan string) {
+	c := client{ch: ch}
+	select {
+	case b.unsubscribe <- c:
+	case <-b.done:
+		// Already shutting down — channels will be cleaned up by Stop.
+	}
+}
+
+// loop is the core fan-out goroutine.
+func (b *Broadcaster) loop() {
+	for {
+		select {
+		case ev := <-b.input:
+			sse := ev.toSSE()
+			for ch := range b.clients {
+				// Non-blocking send — slow clients are dropped.
+				select {
+				case ch <- sse:
+				default:
+					slog.Warn("sse broadcaster: dropping event for slow client", "type", ev.Type)
+				}
+			}
+
+		case c := <-b.subscribe:
+			b.clients[c.ch] = struct{}{}
+			slog.Debug("sse broadcaster: client connected", "total_clients", len(b.clients))
+
+		case c := <-b.unsubscribe:
+			if _, ok := b.clients[c.ch]; ok {
+				delete(b.clients, c.ch)
+				close(c.ch)
+				slog.Debug("sse broadcaster: client disconnected", "total_clients", len(b.clients))
+			}
+
+		case <-b.done:
+			// Drain remaining events in input before shutting down.
+			for ev := range b.input {
+				sse := ev.toSSE()
+				for ch := range b.clients {
+					select {
+					case ch <- sse:
+					default:
+					}
+				}
+			}
+			// Close all remaining client channels.
+			for ch := range b.clients {
+				close(ch)
+			}
+			b.clients = nil
+			return
+		}
+	}
+}

backend/internal/sse/events.go

@@ -0,0 +1,92 @@
+// Package sse provides Server-Sent Events infrastructure for real-time updates.
+// Includes event types, a central broadcaster, and an HTTP handler.
+package sse
+
+import (
+	"encoding/json"
+	"time"
+)
+
+// EventType identifies the category of an SSE event.
+type EventType string
+
+const (
+	EventPrinterStatus  EventType = "printer.status"
+	EventJobStarted     EventType = "job.started"
+	EventJobCompleted   EventType = "job.completed"
+	EventFilamentLow    EventType = "filament.low"
+)
+
+// Event is a JSON-serializable SSE event pushed through the broadcaster.
+type Event struct {
+	Type      EventType       `json:"type"`
+	Payload   json.RawMessage `json:"payload"`
+	Timestamp time.Time       `json:"timestamp"`
+}
+
+// PrinterStatusPayload carries printer online/offline/printing state.
+type PrinterStatusPayload struct {
+	PrinterID   int    `json:"printer_id"`
+	PrinterName string `json:"printer_name"`
+	Status      string `json:"status"` // "online", "offline", "printing"
+}
+
+// JobStartedPayload carries initial print job info.
+type JobStartedPayload struct {
+	JobID      int    `json:"job_id"`
+	JobName    string `json:"job_name"`
+	PrinterID  int    `json:"printer_id"`
+	SpoolID    *int   `json:"spool_id,omitempty"`
+}
+
+// JobCompletedPayload carries final print job data including usage.
+type JobCompletedPayload struct {
+	JobID           int     `json:"job_id"`
+	JobName         string  `json:"job_name"`
+	PrinterID       int     `json:"printer_id"`
+	DurationSeconds *int    `json:"duration_seconds,omitempty"`
+	TotalGramsUsed  *float64 `json:"total_grams_used,omitempty"`
+	TotalCostUSD    *float64 `json:"total_cost_usd,omitempty"`
+}
+
+// FilamentLowPayload alerts that a spool is below its threshold.
+type FilamentLowPayload struct {
+	SpoolID       int    `json:"spool_id"`
+	SpoolName     string `json:"spool_name"`
+	RemainingGrams int   `json:"remaining_grams"`
+	ThresholdGrams int   `json:"threshold_grams"`
+}
+
+// NewEvent creates an Event with the current timestamp from a typed payload.
+func NewEvent(eventType EventType, payload any) (Event, error) {
+	raw, err := json.Marshal(payload)
+	if err != nil {
+		return Event{}, err
+	}
+	return Event{
+		Type:      eventType,
+		Payload:   raw,
+		Timestamp: time.Now().UTC(),
+	}, nil
+}
+
+// MustEvent creates an Event and panics on marshal failure (for use with
+// known-good payloads in tests and internal wiring).
+func MustEvent(eventType EventType, payload any) Event {
+	ev, err := NewEvent(eventType, payload)
+	if err != nil {
+		panic("sse.MustEvent: failed to marshal payload: " + err.Error())
+	}
+	return ev
+}
+
+// toSSE formats this Event as a standard SSE message string ready to be
+// written to a response writer. The format is:
+//
+//	event: <type>
+//	data: <json>
+//
+func (e Event) toSSE() string {
+	data, _ := json.Marshal(e)
+	return "event: " + string(e.Type) + "\n" + "data: " + string(data) + "\n\n"
+}

backend/internal/sse/handler.go

@@ -0,0 +1,59 @@
+package sse
+
+import (
+	"net/http"
+)
+
+// Handler is the HTTP handler for the GET /api/events SSE stream.
+// It registers a client with the broadcaster, streams events as they arrive,
+// and unregisters on disconnect.
+type Handler struct {
+	bc *Broadcaster
+}
+
+// NewHandler creates a Handler backed by the given Broadcaster.
+func NewHandler(bc *Broadcaster) *Handler {
+	return &Handler{bc: bc}
+}
+
+// ServeHTTP implements the SSE streaming endpoint.
+// Flusher is required; clients that do not support flushing receive a 501.
+func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	flusher, ok := w.(http.Flusher)
+	if !ok {
+		http.Error(w, "streaming not supported", http.StatusNotImplemented)
+		return
+	}
+
+	// SSE-specific headers
+	w.Header().Set("Content-Type", "text/event-stream")
+	w.Header().Set("Cache-Control", "no-cache")
+	w.Header().Set("Connection", "keep-alive")
+	w.Header().Set("X-Accel-Buffering", "no") // Disable nginx buffering
+
+	// Write headers immediately
+	flusher.Flush()
+
+	// Subscribe to the broadcaster
+	ch := h.bc.Subscribe()
+	defer h.bc.Unsubscribe(ch)
+
+	// Use request context for cancellation when the client disconnects.
+	ctx := r.Context()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case msg, ok := <-ch:
+			if !ok {
+				return
+			}
+			_, err := w.Write([]byte(msg))
+			if err != nil {
+				return
+			}
+			flusher.Flush()
+		}
+	}
+}

backend/internal/workers/moonraker_poller.go

@@ -0,0 +1,321 @@
+// Package workers provides background goroutines for printer telemetry.
+package workers
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"strconv"
+	"time"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/clients"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/sse"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// MoonrakerPollerConfig controls the background polling behaviour.
+type MoonrakerPollerConfig struct {
+	PollInterval   time.Duration
+	RequestTimeout time.Duration
+}
+
+// DefaultMoonrakerPollerConfig returns sensible defaults.
+func DefaultMoonrakerPollerConfig() MoonrakerPollerConfig {
+	return MoonrakerPollerConfig{
+		PollInterval:   30 * time.Second,
+		RequestTimeout: 10 * time.Second,
+	}
+}
+
+// MoonrakerPoller periodically polls Moonraker printers for status and usage.
+type MoonrakerPoller struct {
+	cfg         MoonrakerPollerConfig
+	client      *clients.MoonrakerClient
+	printerRepo *repositories.PrinterRepository
+	jobRepo     *repositories.PrintJobRepository
+	usageRepo   *repositories.UsageLogRepository
+	sseBC       *sse.Broadcaster
+	pool        *pgxpool.Pool
+	stop        chan struct{}
+}
+
+// NewMoonrakerPoller creates a poller. It uses the pool directly for
+// transaction-scoped writes that the repository layer cannot span.
+func NewMoonrakerPoller(
+	cfg MoonrakerPollerConfig,
+	pool *pgxpool.Pool,
+	printerRepo *repositories.PrinterRepository,
+	jobRepo *repositories.PrintJobRepository,
+	usageRepo *repositories.UsageLogRepository,
+	sseBC *sse.Broadcaster,
+) *MoonrakerPoller {
+	return &MoonrakerPoller{
+		cfg:         cfg,
+		client:      clients.NewMoonrakerClient(cfg.RequestTimeout),
+		printerRepo: printerRepo,
+		jobRepo:     jobRepo,
+		usageRepo:   usageRepo,
+		sseBC:       sseBC,
+		pool:        pool,
+		stop:        make(chan struct{}),
+	}
+}
+
+// Start begins the polling loop in a goroutine.
+func (p *MoonrakerPoller) Start() {
+	go p.loop()
+}
+
+// Stop signals the loop to exit.
+func (p *MoonrakerPoller) Stop() {
+	close(p.stop)
+}
+
+func (p *MoonrakerPoller) loop() {
+	ticker := time.NewTicker(p.cfg.PollInterval)
+	defer ticker.Stop()
+
+	// Immediate first tick.
+	p.pollCycle()
+
+	for {
+		select {
+		case <-ticker.C:
+			p.pollCycle()
+		case <-p.stop:
+			slog.Info("moonraker poller stopped")
+			return
+		}
+	}
+}
+
+func (p *MoonrakerPoller) pollCycle() {
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	defer cancel()
+
+	printers, err := p.printerRepo.GetAll(ctx)
+	if err != nil {
+		slog.Error("moonraker poller: failed to list printers", "error", err)
+		return
+	}
+
+	for _, printer := range printers {
+		if !printer.IsActive || printer.MoonrakerURL == nil || *printer.MoonrakerURL == "" {
+			continue
+		}
+
+		if err := p.pollPrinter(ctx, printer); err != nil {
+			slog.Warn("moonraker poller: poll failed",
+				"printer", printer.Name,
+				"error", err,
+			)
+		}
+	}
+}
+
+// pollPrinter performs a single Moonraker poll for a printer.
+func (p *MoonrakerPoller) pollPrinter(ctx context.Context, printer models.Printer) error {
+	host := *printer.MoonrakerURL
+	var apiKey string
+	if printer.MoonrakerAPIKey != nil {
+		apiKey = *printer.MoonrakerAPIKey
+	}
+
+	// Fetch printer info (status)
+	info, err := p.client.GetPrinterInfo(ctx, host, 80, apiKey)
+	if err != nil {
+		p.broadcastStatus(printer.ID, printer.Name, "offline")
+		return err
+	}
+
+	status := mapMoonrakerState(info.State)
+	p.broadcastStatus(printer.ID, printer.Name, status)
+
+	// Fetch print stats
+	stats, err := p.client.GetPrintStats(ctx, host, 80, apiKey)
+	if err != nil {
+		return fmt.Errorf("getPrintStats failed: %w", err)
+	}
+
+	if status == "printing" && stats.Filename != "" {
+		p.broadcastJobStarted(printer.ID, stats.Filename)
+	}
+
+	if isCompleteState(stats.State) && stats.FilamentUsedMm > 0 {
+		// Record usage
+		if err := p.recordUsage(ctx, printer, stats); err != nil {
+			slog.Error("moonraker poller: record usage failed",
+				"printer", printer.Name, "error", err)
+		} else {
+			p.broadcastJobCompleted(printer.ID, stats.Filename, stats.FilamentUsedMm)
+		}
+	}
+
+	return nil
+}
+
+func (p *MoonrakerPoller) recordUsage(ctx context.Context, printer models.Printer, stats *clients.MoonrakerPrintStats) error {
+	// Find active spool for printer — for now use the first active spool
+	// or fallback to the one referenced by the printer if available.
+	// In a real scenario we'd query AMS slots or fallback logic.
+	// Here we simply look for the most recently used spool in usage_logs.
+	var spoolID int
+	row := p.pool.QueryRow(ctx, `
+		SELECT filament_spool_id FROM usage_logs
+		WHERE print_job_id IN (
+			SELECT id FROM print_jobs WHERE printer_id = $1
+		)
+		ORDER BY logged_at DESC LIMIT 1
+	`, printer.ID)
+	_ = row.Scan(&spoolID)
+
+	if spoolID == 0 {
+		// No prior usage — skip recording (no known spool to deduct from)
+		slog.Warn("moonraker poller: no known spool for printer; skipping usage record",
+			"printer", printer.Name)
+		return nil
+	}
+
+	// Compute grams from mm extruded using defaults (1.75mm diameter, PLA density 1.24)
+	grams := calculateGrams(stats.FilamentUsedMm, 1.75, 1.24)
+
+	// Create a print job record
+	var jobID int
+	err := p.pool.QueryRow(ctx, `
+		INSERT INTO print_jobs (printer_id, filament_spool_id, job_name, file_name, job_status_id,
+			started_at, completed_at, duration_seconds, total_mm_extruded, total_grams_used)
+		VALUES ($1, $2, $3, $4, 4, $5, $6, $7, $8, $9)
+		RETURNING id
+	`, printer.ID, spoolID, stats.Filename, stats.Filename,
+		time.Now().Add(-time.Duration(stats.TotalDuration)*time.Second),
+		time.Now(),
+		int(stats.TotalDuration),
+		stats.FilamentUsedMm,
+		grams,
+	).Scan(&jobID)
+
+	if err != nil {
+		return fmt.Errorf("insert print_job failed: %w", err)
+	}
+
+	// Create usage_log
+	_, err = p.pool.Exec(ctx, `
+		INSERT INTO usage_logs (print_job_id, filament_spool_id, mm_extruded, grams_used, logged_at)
+		VALUES ($1, $2, $3, $4, NOW())
+	`, jobID, spoolID, stats.FilamentUsedMm, grams)
+
+	if err != nil {
+		return fmt.Errorf("insert usage_log failed: %w", err)
+	}
+
+	slog.Info("moonraker poller: recorded usage",
+		"printer", printer.Name,
+		"job", stats.Filename,
+		"mm", stats.FilamentUsedMm,
+		"grams", grams,
+	)
+	return nil
+}
+
+func (p *MoonrakerPoller) broadcastStatus(printerID int, name, status string) {
+	if p.sseBC == nil {
+		return
+	}
+	ev, err := sse.NewEvent(sse.EventPrinterStatus, sse.PrinterStatusPayload{
+		PrinterID:   printerID,
+		PrinterName: name,
+		Status:      status,
+	})
+	if err != nil {
+		return
+	}
+	p.sseBC.Publish(ev)
+}
+
+func (p *MoonrakerPoller) broadcastJobStarted(printerID int, jobName string) {
+	if p.sseBC == nil {
+		return
+	}
+	ev, err := sse.NewEvent(sse.EventJobStarted, sse.JobStartedPayload{
+		JobName:   jobName,
+		PrinterID: printerID,
+	})
+	if err != nil {
+		return
+	}
+	p.sseBC.Publish(ev)
+}
+
+func (p *MoonrakerPoller) broadcastJobCompleted(printerID int, jobName string, mmExtruded float64) {
+	if p.sseBC == nil {
+		return
+	}
+	grams := calculateGrams(mmExtruded, 1.75, 1.24)
+	gramsInt := int(grams)
+	ev, err := sse.NewEvent(sse.EventJobCompleted, sse.JobCompletedPayload{
+		JobName:        jobName,
+		PrinterID:      printerID,
+		TotalGramsUsed: &gramsInt,
+	})
+	if err != nil {
+		return
+	}
+	p.sseBC.Publish(ev)
+}
+
+func mapMoonrakerState(state string) string {
+	switch state {
+	case "printing":
+		return "printing"
+	case "paused":
+		return "paused"
+	case "complete", "standby", "cancelled":
+		return "idle"
+	case "error":
+		return "error"
+	default:
+		return "offline"
+	}
+}
+
+func isCompleteState(state string) bool {
+	return state == "complete" || state == "completed"
+}
+
+func calculateGrams(mmExtruded, diameterMm, densityGcm3 float64) float64 {
+	if mmExtruded <= 0 {
+		return 0
+	}
+	radiusCm := diameterMm / 2.0 / 10.0
+	crossSection := 3.141592653589793 * radiusCm * radiusCm
+	volumeCm3 := (mmExtruded / 10.0) * crossSection
+	return volumeCm3 * densityGcm3
+}
+
+// ---------------------------------------------------------------------------
+// Helper for port parsing (Moonraker URL may contain port)
+// ---------------------------------------------------------------------------
+
+func extractHostPort(rawURL string) (string, int) {
+	// Very simplistic: if rawURL contains ":" after a dot, parse host:port.
+	// Otherwise assume host only and return port 80.
+	if rawURL == "" {
+		return "", 80
+	}
+	for i := len(rawURL) - 1; i >= 0; i-- {
+		if rawURL[i] == ':' {
+			portStr := rawURL[i+1:]
+			port, err := strconv.Atoi(portStr)
+			if err == nil {
+				return rawURL[:i], port
+			}
+			break
+		}
+		if rawURL[i] == '/' {
+			break
+		}
+	}
+	return rawURL, 80
+}

backend/internal/workers/mqtt_subscriber.go

@@ -0,0 +1,223 @@
+// Package workers provides background goroutines for printer telemetry.
+package workers
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"time"
+
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/clients"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/models"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/repositories"
+	"github.com/CubeCraft-Creations/Extrudex/backend/internal/sse"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// MQTTSubscriberConfig controls MQTT background worker behaviour.
+type MQTTSubscriberConfig struct {
+	ReconnectInterval time.Duration
+}
+
+// DefaultMQTTSubscriberConfig returns sensible defaults.
+func DefaultMQTTSubscriberConfig() MQTTSubscriberConfig {
+	return MQTTSubscriberConfig{
+		ReconnectInterval: 30 * time.Second,
+	}
+}
+
+// MQTTSubscriber manages per-printer MQTT connections and telemetry ingestion.
+type MQTTSubscriber struct {
+	cfg         MQTTSubscriberConfig
+	printerRepo *repositories.PrinterRepository
+	usageRepo   *repositories.UsageLogRepository
+	sseBC       *sse.Broadcaster
+	pool        *pgxpool.Pool
+	clients     map[int]*clients.MQTTClient // keyed by printer ID
+	stop        chan struct{}
+}
+
+// NewMQTTSubscriber creates a new subscriber worker.
+func NewMQTTSubscriber(
+	cfg MQTTSubscriberConfig,
+	pool *pgxpool.Pool,
+	printerRepo *repositories.PrinterRepository,
+	usageRepo *repositories.UsageLogRepository,
+	sseBC *sse.Broadcaster,
+) *MQTTSubscriber {
+	return &MQTTSubscriber{
+		cfg:         cfg,
+		printerRepo: printerRepo,
+		usageRepo:   usageRepo,
+		sseBC:       sseBC,
+		pool:        pool,
+		clients:     make(map[int]*clients.MQTTClient),
+		stop:        make(chan struct{}),
+	}
+}
+
+// Start begins the connection manager loop.
+func (s *MQTTSubscriber) Start() {
+	go s.loop()
+}
+
+// Stop signals the loop to exit and disconnects all clients.
+func (s *MQTTSubscriber) Stop() {
+	close(s.stop)
+}
+
+func (s *MQTTSubscriber) loop() {
+	// Initial connect attempt.
+	s.connectAll()
+
+	ticker := time.NewTicker(s.cfg.ReconnectInterval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			s.connectAll()
+		case <-s.stop:
+			slog.Info("mqtt subscriber stopped")
+			for _, c := range s.clients {
+				c.Disconnect(1000)
+			}
+			return
+		}
+	}
+}
+
+func (s *MQTTSubscriber) connectAll() {
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
+	printers, err := s.printerRepo.GetAll(ctx)
+	if err != nil {
+		slog.Error("mqtt subscriber: failed to list printers", "error", err)
+		return
+	}
+
+	for _, printer := range printers {
+		if !printer.IsActive || printer.MQTTBrokerHost == nil || *printer.MQTTBrokerHost == "" {
+			// Disconnect if previously connected and now inactive
+			if existing, ok := s.clients[printer.ID]; ok {
+				existing.Disconnect(1000)
+				delete(s.clients, printer.ID)
+			}
+			continue
+		}
+
+		if _, ok := s.clients[printer.ID]; ok {
+			// Already connected — skip
+			continue
+		}
+
+		topicPrefix := ""
+		if printer.MQTTTopicPrefix != nil {
+			topicPrefix = *printer.MQTTTopicPrefix
+		}
+
+		cfg := clients.MQTTConfig{
+			BrokerHost:  *printer.MQTTBrokerHost,
+			TopicPrefix: topicPrefix,
+			TLSEnabled:  printer.MQTTTLSEnabled,
+			ClientID:    fmt.Sprintf("extrudex-printer-%d", printer.ID),
+		}
+
+		c, err := clients.NewMQTTClient(cfg)
+		if err != nil {
+			slog.Warn("mqtt subscriber: connect failed",
+				"printer", printer.Name,
+				"broker", cfg.BrokerHost,
+				"error", err,
+			)
+			continue
+		}
+
+		s.clients[printer.ID] = c
+
+		// Subscribe to telemetry topics
+		topics := clients.DefaultBambuTopics(topicPrefix)
+		for _, topic := range topics {
+			if err := c.Subscribe(topic, 0, s.makeHandler(printer)); err != nil {
+				slog.Warn("mqtt subscriber: subscribe failed",
+					"printer", printer.Name,
+					"topic", topic,
+					"error", err,
+				)
+			}
+		}
+
+		slog.Info("mqtt subscriber: connected",
+			"printer", printer.Name,
+			"broker", cfg.BrokerHost,
+			"topics", topics,
+		)
+	}
+}
+
+func (s *MQTTSubscriber) makeHandler(printer models.Printer) func([]byte) {
+	return func(payload []byte) {
+		slog.Debug("mqtt subscriber: message received",
+			"printer", printer.Name,
+			"size", len(payload),
+		)
+
+		// Attempt Bambu Lab parse
+		telemetry, err := clients.ParseBambuTelemetry(payload)
+		if err != nil {
+			slog.Debug("mqtt subscriber: not Bambu telemetry; discarding",
+				"printer", printer.Name, "error", err)
+			return
+		}
+
+		// Determine status from telemetry
+		status := "idle"
+		if telemetry.Print.Stage > 0 {
+			status = "printing"
+		}
+		s.broadcastStatus(printer.ID, printer.Name, status)
+
+		// If a print just completed, record usage when we see a completed event.
+		// Bambu telemetry does not carry mm_extruded directly; we approximate
+		// or skip if not present.  Here we broadcast completion if stage == 0
+		// and a gcode file was present (naive heuristic).
+		if telemetry.Print.GcodeFile != "" && telemetry.Print.Stage == 0 {
+			// In a real implementation we'd extract mm_extruded from Bambu telemetry
+			// or query the printer after completion.  For now broadcast completion.
+			s.broadcastJobCompleted(printer.ID, telemetry.Print.GcodeFile, 0)
+		}
+	}
+}
+
+func (s *MQTTSubscriber) broadcastStatus(printerID int, name, status string) {
+	if s.sseBC == nil {
+		return
+	}
+	ev, err := sse.NewEvent(sse.EventPrinterStatus, sse.PrinterStatusPayload{
+		PrinterID:   printerID,
+		PrinterName: name,
+		Status:      status,
+	})
+	if err != nil {
+		return
+	}
+	s.sseBC.Publish(ev)
+}
+
+func (s *MQTTSubscriber) broadcastJobCompleted(printerID int, jobName string, mmExtruded float64) {
+	if s.sseBC == nil {
+		return
+	}
+	grams := calculateGrams(mmExtruded, 1.75, 1.24)
+	gramsInt := int(grams)
+	ev, err := sse.NewEvent(sse.EventJobCompleted, sse.JobCompletedPayload{
+		JobName:        jobName,
+		PrinterID:      printerID,
+		TotalGramsUsed: &gramsInt,
+	})
+	if err != nil {
+		return
+	}
+	s.sseBC.Publish(ev)
+}

frontend/src/App.tsx

@@ -1,28 +1,25 @@
-import { useState, useEffect } from 'react'
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import { BrowserRouter, Routes, Route } from 'react-router-dom'
+import InventoryPage from './pages/InventoryPage'
 
-function App() {
+const queryClient = new QueryClient()
-  const [health, setHealth] = useState<any>(null)
-
-  useEffect(() => {
-    fetch('/api/health')
-      .then(r => r.json())
-      .then(setHealth)
-      .catch(console.error)
-  }, [])
 
+export default function App() {
   return (
-    <div className="min-h-screen flex items-center justify-center">
+    <QueryClientProvider client={queryClient}>
-      <div className="p-6 rounded-lg bg-slate-800 shadow-xl max-w-md w-full">
+      <BrowserRouter>
-        <h1 className="text-2xl font-bold mb-4 text-emerald-400">Extrudex</h1>
+        <div className="min-h-screen bg-slate-900 text-slate-50">
-        <p className="text-slate-300 mb-4">React frontend scaffold</p>
+          <header className="bg-slate-800 border-b border-slate-700 px-4 py-3 flex items-center gap-3 sticky top-0 z-20">
-        {health && (
+            <div className="w-8 h-8 rounded bg-emerald-500 flex items-center justify-center text-slate-900 font-bold text-lg">E</div>
-          <pre className="text-xs bg-slate-900 p-3 rounded overflow-auto">
+            <h1 className="text-lg font-semibold">Extrudex</h1>
-            {JSON.stringify(health, null, 2)}
+          </header>
-          </pre>
+          <main className="p-4">
-        )}
+            <Routes>
-      </div>
+              <Route path="/" element={<InventoryPage />} />
+            </Routes>
+          </main>
         </div>
+      </BrowserRouter>
+    </QueryClientProvider>
   )
 }
-
-export default App

frontend/src/components/ColorSwatch.tsx

@@ -0,0 +1,18 @@
+interface ColorSwatchProps {
+  colorHex: string
+  size?: number
+}
+
+export default function ColorSwatch({ colorHex, size = 24 }: ColorSwatchProps) {
+  return (
+    <div
+      className="rounded-full border border-slate-600 shadow-sm inline-block"
+      style={{
+        backgroundColor: colorHex.startsWith('#') ? colorHex : `#${colorHex}`,
+        width: size,
+        height: size,
+      }}
+      title={colorHex}
+    />
+  )
+}

frontend/src/pages/InventoryPage.tsx

@@ -0,0 +1,339 @@
+import { useState, useMemo } from 'react'
+import { useQuery } from '@tanstack/react-query'
+import { Search, Filter, ChevronLeft, ChevronRight, Trash2, Pencil, Plus, AlertTriangle } from 'lucide-react'
+import ColorSwatch from '../components/ColorSwatch'
+import { fetchFilaments, deleteFilament } from '../services/filamentService'
+import type { FilamentSpool, FilamentFilter } from '../types/filament'
+
+const PAGE_SIZE = 20
+
+type SortField = 'name' | 'remaining_grams' | 'cost_usd'
+type SortDir = 'asc' | 'desc'
+
+export default function InventoryPage() {
+  const [search, setSearch] = useState('')
+  const [material, setMaterial] = useState('')
+  const [finish, setFinish] = useState('')
+  const [lowStockOnly, setLowStockOnly] = useState(false)
+  const [sortBy, setSortBy] = useState<SortField>('name')
+  const [sortDir, setSortDir] = useState<SortDir>('asc')
+  const [page, setPage] = useState(0)
+  const [deleteId, setDeleteId] = useState<number | null>(null)
+
+  const filter: FilamentFilter = useMemo(() => ({
+    material: material || undefined,
+    finish: finish || undefined,
+    low_stock: lowStockOnly,
+    sort_by: sortBy,
+    sort_dir: sortDir,
+    limit: PAGE_SIZE,
+    offset: page * PAGE_SIZE,
+  }), [material, finish, lowStockOnly, sortBy, sortDir, page])
+
+  const { data, isLoading, error, refetch } = useQuery({
+    queryKey: ['filaments', filter],
+    queryFn: () => fetchFilaments(filter),
+  })
+
+  const filaments = data?.data ?? []
+  const total = data?.total ?? 0
+  const totalPages = Math.max(1, Math.ceil(total / PAGE_SIZE))
+
+  // Client-side search filter (name/barcode) since backend may not support it yet.
+  const filtered = useMemo(() => {
+    if (!search.trim()) return filaments
+    const q = search.toLowerCase()
+    return filaments.filter(
+      (f: FilamentSpool) =>
+        f.name.toLowerCase().includes(q) ||
+        (f.barcode && f.barcode.toLowerCase().includes(q))
+    )
+  }, [filaments, search])
+
+  const handleSort = (field: SortField) => {
+    if (sortBy === field) {
+      setSortDir(prev => (prev === 'asc' ? 'desc' : 'asc'))
+    } else {
+      setSortBy(field)
+      setSortDir('asc')
+    }
+    setPage(0)
+  }
+
+  const handleDelete = async (id: number) => {
+    await deleteFilament(id)
+    setDeleteId(null)
+    refetch()
+  }
+
+  const SortIndicator = ({ field }: { field: SortField }) => {
+    if (sortBy !== field) return <span className="text-slate-600 ml-1">↕</span>
+    return <span className="text-emerald-400 ml-1">{sortDir === 'asc' ? '↑' : '↓'}</span>
+  }
+
+  return (
+    <div className="space-y-4">
+      {/* Header */}
+      <div className="flex flex-col sm:flex-row sm:items-center sm:justify-between gap-3">
+        <div>
+          <h2 className="text-xl font-bold text-slate-100">Filament Inventory</h2>
+          <p className="text-sm text-slate-400">{total} spool(s) total</p>
+        </div>
+        <button className="inline-flex items-center gap-2 rounded-lg bg-emerald-600 px-4 py-2 text-sm font-semibold text-white hover:bg-emerald-500 active:bg-emerald-700 transition-colors">
+          <Plus size={16} /> Add Spool
+        </button>
+      </div>
+
+      {/* Filters */}
+      <div className="flex flex-col lg:flex-row gap-3">
+        {/* Search */}
+        <div className="relative flex-1">
+          <Search size={16} className="absolute left-3 top-1/2 -translate-y-1/2 text-slate-400" />
+          <input
+            type="text"
+            placeholder="Search by name or barcode…"
+            value={search}
+            onChange={e => { setSearch(e.target.value); setPage(0) }}
+            className="w-full rounded-lg bg-slate-800 border border-slate-700 pl-9 pr-3 py-2 text-sm text-slate-100 placeholder-slate-500 focus:outline-none focus:ring-2 focus:ring-emerald-500 focus:border-emerald-500"
+          />
+        </div>
+
+        {/* Material filter */}
+        <select
+          value={material}
+          onChange={e => { setMaterial(e.target.value); setPage(0) }}
+          className="rounded-lg bg-slate-800 border border-slate-700 px-3 py-2 text-sm text-slate-100 focus:outline-none focus:ring-2 focus:ring-emerald-500"
+        >
+          <option value="">All Materials</option>
+          <option value="PLA">PLA</option>
+          <option value="PETG">PETG</option>
+          <option value="ABS">ABS</option>
+          <option value="TPU">TPU</option>
+          <option value="ASA">ASA</option>
+          <option value="Nylon">Nylon</option>
+          <option value="PC">PC</option>
+        </select>
+
+        {/* Finish filter */}
+        <select
+          value={finish}
+          onChange={e => { setFinish(e.target.value); setPage(0) }}
+          className="rounded-lg bg-slate-800 border border-slate-700 px-3 py-2 text-sm text-slate-100 focus:outline-none focus:ring-2 focus:ring-emerald-500"
+        >
+          <option value="">All Finishes</option>
+          <option value="Basic">Basic</option>
+          <option value="Silk">Silk</option>
+          <option value="Matte">Matte</option>
+          <option value="Glossy">Glossy</option>
+          <option value="Wood">Wood</option>
+          <option value="Marble">Marble</option>
+        </select>
+
+        {/* Low stock toggle */}
+        <label className="inline-flex items-center gap-2 rounded-lg bg-slate-800 border border-slate-700 px-3 py-2 text-sm text-slate-100 cursor-pointer select-none hover:bg-slate-750">
+          <Filter size={14} className="text-amber-400" />
+          <input
+            type="checkbox"
+            checked={lowStockOnly}
+            onChange={e => { setLowStockOnly(e.target.checked); setPage(0) }}
+            className="accent-amber-500"
+          />
+          Low Stock Only
+        </label>
+      </div>
+
+      {/* Loading / Error */}
+      {isLoading && (
+        <div className="text-center py-12 text-slate-400">Loading spools…</div>
+      )}
+      {error && (
+        <div className="text-center py-12 text-red-400">
+          Failed to load inventory.
+          <button onClick={() => refetch()} className="ml-2 underline hover:text-red-300">Retry</button>
+        </div>
+      )}
+
+      {/* Desktop Table */}
+      {!isLoading && !error && (
+        <>
+          <div className="hidden md:block overflow-x-auto rounded-lg border border-slate-700">
+            <table className="w-full text-sm">
+              <thead className="bg-slate-800 text-slate-300">
+                <tr>
+                  <th className="px-4 py-3 text-left font-semibold cursor-pointer select-none hover:text-slate-100" onClick={() => handleSort('name')}>
+                    Name <SortIndicator field="name" />
+                  </th>
+                  <th className="px-4 py-3 text-left font-semibold">Material</th>
+                  <th className="px-4 py-3 text-left font-semibold">Finish</th>
+                  <th className="px-4 py-3 text-left font-semibold">Color</th>
+                  <th className="px-4 py-3 text-right font-semibold cursor-pointer select-none hover:text-slate-100" onClick={() => handleSort('remaining_grams')}>
+                    Remaining <SortIndicator field="remaining_grams" />
+                  </th>
+                  <th className="px-4 py-3 text-right font-semibold cursor-pointer select-none hover:text-slate-100" onClick={() => handleSort('cost_usd')}>
+                    Cost <SortIndicator field="cost_usd" />
+                  </th>
+                  <th className="px-4 py-3 text-center font-semibold">Status</th>
+                  <th className="px-4 py-3 text-right font-semibold">Actions</th>
+                </tr>
+              </thead>
+              <tbody className="divide-y divide-slate-700">
+                {filtered.length === 0 && (
+                  <tr>
+                    <td colSpan={8} className="px-4 py-8 text-center text-slate-500">No spools found.</td>
+                  </tr>
+                )}
+                {filtered.map((spool: FilamentSpool) => {
+                  const isLow = spool.remaining_grams <= spool.low_stock_threshold_grams
+                  return (
+                    <tr key={spool.id} className={`${isLow ? 'bg-red-900/20' : 'bg-slate-800/50'} hover:bg-slate-700/50 transition-colors`}>
+                      <td className="px-4 py-3 font-medium text-slate-100">{spool.name}</td>
+                      <td className="px-4 py-3 text-slate-300">{spool.material_base?.name ?? '—'}</td>
+                      <td className="px-4 py-3 text-slate-300">{spool.material_finish?.name ?? '—'}</td>
+                      <td className="px-4 py-3">
+                        <div className="flex items-center gap-2">
+                          <ColorSwatch colorHex={spool.color_hex} size={20} />
+                          <span className="text-xs text-slate-400 uppercase">{spool.color_hex}</span>
+                        </div>
+                      </td>
+                      <td className="px-4 py-3 text-right tabular-nums text-slate-200">{spool.remaining_grams.toLocaleString()} g</td>
+                      <td className="px-4 py-3 text-right tabular-nums text-slate-300">{spool.cost_usd != null ? `$${spool.cost_usd.toFixed(2)}` : '—'}</td>
+                      <td className="px-4 py-3 text-center">
+                        {isLow ? (
+                          <span className="inline-flex items-center gap-1 rounded-full bg-red-900/50 border border-red-700 px-2 py-0.5 text-xs font-medium text-red-300">
+                            <AlertTriangle size={12} /> Low
+                          </span>
+                        ) : (
+                          <span className="inline-flex items-center rounded-full bg-emerald-900/30 border border-emerald-700 px-2 py-0.5 text-xs font-medium text-emerald-300">OK</span>
+                        )}
+                      </td>
+                      <td className="px-4 py-3 text-right">
+                        <div className="flex items-center justify-end gap-2">
+                          <button className="p-1.5 rounded hover:bg-slate-600 text-slate-400 hover:text-blue-400 transition-colors" title="Edit">
+                            <Pencil size={14} />
+                          </button>
+                          <button
+                            onClick={() => setDeleteId(spool.id)}
+                            className="p-1.5 rounded hover:bg-slate-600 text-slate-400 hover:text-red-400 transition-colors"
+                            title="Delete"
+                          >
+                            <Trash2 size={14} />
+                          </button>
+                        </div>
+                      </td>
+                    </tr>
+                  )
+                })}
+              </tbody>
+            </table>
+          </div>
+
+          {/* Mobile Cards */}
+          <div className="md:hidden space-y-3">
+            {filtered.length === 0 && (
+              <div className="text-center py-12 text-slate-500">No spools found.</div>
+            )}
+            {filtered.map((spool: FilamentSpool) => {
+              const isLow = spool.remaining_grams <= spool.low_stock_threshold_grams
+              return (
+                <div key={spool.id} className={`rounded-lg border ${isLow ? 'border-red-700 bg-red-900/10' : 'border-slate-700 bg-slate-800'} p-4 space-y-2`}>
+                  <div className="flex items-start justify-between">
+                    <div>
+                      <div className="font-semibold text-slate-100">{spool.name}</div>
+                      <div className="text-xs text-slate-400 mt-0.5">{spool.material_base?.name ?? '—'} · {spool.material_finish?.name ?? '—'}</div>
+                    </div>
+                    {isLow ? (
+                      <span className="inline-flex items-center gap-1 rounded-full bg-red-900/50 border border-red-700 px-2 py-0.5 text-xs font-medium text-red-300">
+                        <AlertTriangle size={12} /> Low
+                      </span>
+                    ) : (
+                      <span className="inline-flex items-center rounded-full bg-emerald-900/30 border border-emerald-700 px-2 py-0.5 text-xs font-medium text-emerald-300">OK</span>
+                    )}
+                  </div>
+
+                  <div className="flex items-center gap-3 text-sm">
+                    <div className="flex items-center gap-2">
+                      <ColorSwatch colorHex={spool.color_hex} size={20} />
+                      <span className="text-slate-400 uppercase text-xs">{spool.color_hex}</span>
+                    </div>
+                  </div>
+
+                  <div className="flex items-center justify-between text-sm">
+                    <span className="text-slate-400">Remaining: <span className="text-slate-200 font-medium tabular-nums">{spool.remaining_grams.toLocaleString()} g</span></span>
+                    <span className="text-slate-400">{spool.cost_usd != null ? `$${spool.cost_usd.toFixed(2)}` : '—'}</span>
+                  </div>
+
+                  <div className="flex items-center justify-end gap-2 pt-1">
+                    <button className="flex items-center gap-1 rounded-md bg-slate-700 px-3 py-1.5 text-xs font-medium text-slate-200 hover:bg-slate-600">
+                      <Pencil size={12} /> Edit
+                    </button>
+                    <button
+                      onClick={() => setDeleteId(spool.id)}
+                      className="flex items-center gap-1 rounded-md bg-red-900/30 border border-red-700 px-3 py-1.5 text-xs font-medium text-red-300 hover:bg-red-900/50"
+                    >
+                      <Trash2 size={12} /> Delete
+                    </button>
+                  </div>
+                </div>
+              )
+            })}
+          </div>
+
+          {/* Pagination */}
+          <div className="flex items-center justify-between pt-2">
+            <span className="text-sm text-slate-400">
+              Showing {page * PAGE_SIZE + 1}–{Math.min((page + 1) * PAGE_SIZE, total)} of {total}
+            </span>
+            <div className="flex items-center gap-2">
+              <button
+                onClick={() => setPage(p => Math.max(0, p - 1))}
+                disabled={page === 0}
+                className="p-2 rounded-lg bg-slate-800 border border-slate-700 text-slate-300 hover:bg-slate-700 disabled:opacity-40 disabled:cursor-not-allowed transition-colors"
+              >
+                <ChevronLeft size={16} />
+              </button>
+              <span className="text-sm text-slate-300 tabular-nums">{page + 1} / {totalPages}</span>
+              <button
+                onClick={() => setPage(p => Math.min(totalPages - 1, p + 1))}
+                disabled={page >= totalPages - 1}
+                className="p-2 rounded-lg bg-slate-800 border border-slate-700 text-slate-300 hover:bg-slate-700 disabled:opacity-40 disabled:cursor-not-allowed transition-colors"
+              >
+                <ChevronRight size={16} />
+              </button>
+            </div>
+          </div>
+        </>
+      )}
+
+      {/* Delete confirmation modal */}
+      {deleteId !== null && (
+        <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/60 backdrop-blur-sm p-4">
+          <div className="w-full max-w-sm rounded-xl bg-slate-800 border border-slate-700 p-6 shadow-2xl space-y-4">
+            <div className="flex items-center gap-3">
+              <div className="flex h-10 w-10 items-center justify-center rounded-full bg-red-900/30">
+                <AlertTriangle size={20} className="text-red-400" />
+              </div>
+              <div>
+                <h3 className="text-lg font-semibold text-slate-100">Delete Spool?</h3>
+                <p className="text-sm text-slate-400">This action cannot be undone.</p>
+              </div>
+            </div>
+            <div className="flex justify-end gap-3">
+              <button
+                onClick={() => setDeleteId(null)}
+                className="rounded-lg bg-slate-700 px-4 py-2 text-sm font-medium text-slate-200 hover:bg-slate-600 transition-colors"
+              >
+                Cancel
+              </button>
+              <button
+                onClick={() => handleDelete(deleteId)}
+                className="rounded-lg bg-red-600 px-4 py-2 text-sm font-medium text-white hover:bg-red-500 transition-colors"
+              >
+                Delete
+              </button>
+            </div>
+          </div>
+        </div>
+      )}
+    </div>
+  )
+}

frontend/src/services/filamentService.ts

@@ -0,0 +1,24 @@
+import axios from 'axios'
+import type { FilamentSpool, ListResponse, FilamentFilter } from '../types/filament'
+
+const API_BASE = '/api'
+
+export async function fetchFilaments(filter: FilamentFilter): Promise<ListResponse<FilamentSpool>> {
+  const params = new URLSearchParams()
+  if (filter.material) params.set('material', filter.material)
+  if (filter.finish) params.set('finish', filter.finish)
+  if (filter.color) params.set('color', filter.color)
+  if (filter.low_stock) params.set('low_stock', 'true')
+  if (filter.search) params.set('search', filter.search)
+  if (filter.sort_by) params.set('sort_by', filter.sort_by)
+  if (filter.sort_dir) params.set('sort_dir', filter.sort_dir)
+  if (filter.limit !== undefined) params.set('limit', String(filter.limit))
+  if (filter.offset !== undefined) params.set('offset', String(filter.offset))
+
+  const res = await axios.get<ListResponse<FilamentSpool>>(`${API_BASE}/filaments?${params.toString()}`)
+  return res.data
+}
+
+export async function deleteFilament(id: number): Promise<void> {
+  await axios.delete(`${API_BASE}/filaments/${id}`)
+}

frontend/src/types/filament.ts

@@ -0,0 +1,72 @@
+// Extrudex domain types
+
+export interface MaterialBase {
+  id: number
+  name: string
+  density_g_cm3: number
+  extrusion_temp_min?: number
+  extrusion_temp_max?: number
+  bed_temp_min?: number
+  bed_temp_max?: number
+  created_at: string
+  updated_at: string
+}
+
+export interface MaterialFinish {
+  id: number
+  name: string
+  description?: string
+  created_at: string
+  updated_at: string
+}
+
+export interface MaterialModifier {
+  id: number
+  name: string
+  description?: string
+  created_at: string
+  updated_at: string
+}
+
+export interface FilamentSpool {
+  id: number
+  name: string
+  material_base_id: number
+  material_base?: MaterialBase
+  material_finish_id: number
+  material_finish?: MaterialFinish
+  material_modifier_id?: number
+  material_modifier?: MaterialModifier
+  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
+  deleted_at?: string
+  created_at: string
+  updated_at: string
+}
+
+export interface ListResponse<T> {
+  data: T[]
+  total: number
+  limit: number
+  offset: number
+}
+
+export interface FilamentFilter {
+  material?: string
+  finish?: string
+  color?: string
+  low_stock?: boolean
+  search?: string
+  sort_by?: string
+  sort_dir?: 'asc' | 'desc'
+  limit?: number
+  offset?: number
+}