diff --git a/go/cmd/emailnotifierjob/main.go b/go/cmd/emailnotifierjob/main.go
index 14be3e6..fb39163 100644
--- a/go/cmd/emailnotifierjob/main.go
+++ b/go/cmd/emailnotifierjob/main.go
@@ -3,11 +3,15 @@ package main
 import (
 	"context"
 	"fmt"
-	"log/slog"
 	"os"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"cloud.google.com/go/firestore"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+
 	pbaero "github.com/flowy-live/llink/genproto/aero"
 	pbpusher "github.com/flowy-live/llink/genproto/llink/pusher"
 	"github.com/flowy-live/llink/internal/db"
@@ -15,12 +19,10 @@ import (
 	"github.com/flowy-live/llink/internal/network"
 	"github.com/flowy-live/llink/internal/particle"
 	"github.com/flowy-live/llink/internal/utils"
-	"google.golang.org/grpc"
-	"google.golang.org/grpc/credentials/insecure"
 )
 
 const (
-	maxActivityAge  = 24 * time.Hour  // ignore streams idle longer than this
+	maxActivityAge  = 24 * time.Hour   // ignore streams idle longer than this
 	unreadThreshold = 10 * time.Minute // grace window before a message is "unread"
 	emailCooldown   = 12 * time.Hour   // min gap between emails to the same user
 )
@@ -34,7 +36,7 @@ func main() {
 	gcpProject := utils.MustGetEnv("GCP_PROJECT")
 	firestoreClient, err := firestore.NewClient(ctx, gcpProject)
 	if err != nil {
-		slog.Error("failed to create Firestore client", "error", err)
+		flog.Error("failed to create Firestore client", "error", err)
 		os.Exit(1)
 	}
 	defer firestoreClient.Close()
@@ -42,7 +44,7 @@ func main() {
 	aeroAddr := utils.MustGetEnv("AERO_ADDR")
 	aeroConn, err := grpc.NewClient(aeroAddr, grpc.WithTransportCredentials(insecure.NewCredentials()))
 	if err != nil {
-		slog.Error("failed to connect to aero", "error", err)
+		flog.Error("failed to connect to aero", "error", err)
 		os.Exit(1)
 	}
 	defer aeroConn.Close()
@@ -51,7 +53,7 @@ func main() {
 	pusherAddr := utils.MustGetEnv("PUSHER_GRPC_ADDR")
 	pusherConn, err := grpc.NewClient(pusherAddr, grpc.WithTransportCredentials(insecure.NewCredentials()))
 	if err != nil {
-		slog.Error("failed to connect to pusher", "error", err)
+		flog.Error("failed to connect to pusher", "error", err)
 		os.Exit(1)
 	}
 	defer pusherConn.Close()
@@ -60,12 +62,12 @@ func main() {
 	humanSvc := human.NewService(db.Pool())
 	networkSvc := network.NewReader(db.Pool())
 
-	slog.Info("starting email notification cycle")
+	flog.Info("starting email notification cycle")
 	if err := runNotificationCycle(ctx, firestoreClient, aeroSvc, pusherSvc, humanSvc, networkSvc); err != nil {
-		slog.Error("notification cycle failed", "error", err)
+		flog.Error("notification cycle failed", "error", err)
 		os.Exit(1)
 	}
-	slog.Info("email notification cycle complete")
+	flog.Info("email notification cycle complete")
 }
 
 func runNotificationCycle(
@@ -100,7 +102,7 @@ func runNotificationCycle(
 	if err != nil {
 		return fmt.Errorf("failed to get online humans: %w", err)
 	}
-	slog.Info("gathered online presence", "onlineCount", len(onlineResp.HumanIds), "humanIds", onlineResp.HumanIds)
+	flog.Info("gathered online presence", "onlineCount", len(onlineResp.HumanIds), "humanIds", onlineResp.HumanIds)
 	for _, id := range onlineResp.HumanIds {
 		allOnline[id] = true
 	}
@@ -108,7 +110,7 @@ func runNotificationCycle(
 	for _, net := range networks {
 		streams, err := getOpenStreams(ctx, fsClient, net.ID)
 		if err != nil {
-			slog.Error("failed to query streams", "networkId", net.ID, "error", err)
+			flog.Error("failed to query streams", "networkId", net.ID, "error", err)
 			continue
 		}
 
@@ -141,7 +143,7 @@ func runNotificationCycle(
 	sentCount := 0
 	for humanId, count := range behindCounts {
 		if allOnline[humanId] {
-			slog.Info("human online...skipping email", "humanId", humanId)
+			flog.Info("human online...skipping email", "humanId", humanId)
 			continue
 		}
 
@@ -164,18 +166,18 @@ func runNotificationCycle(
 		}
 
 		if err := sendNotificationEmail(ctx, aeroSvc, h, count); err != nil {
-			slog.Error("failed to send email", "humanId", humanId, "error", err)
+			flog.Error("failed to send email", "humanId", humanId, "error", err)
 			continue
 		}
 
 		if err := humanSvc.UpdateLastEmailNotificationSentAt(ctx, humanId, now); err != nil {
-			slog.Error("failed to update last_email_notification_sent_at", "humanId", humanId, "error", err)
+			flog.Error("failed to update last_email_notification_sent_at", "humanId", humanId, "error", err)
 		}
 
 		sentCount++
 	}
 
-	slog.Info("notification cycle summary",
+	flog.Info("notification cycle summary",
 		"networks", len(networks),
 		"humansBehind", len(behindCounts),
 		"emailsSent", sentCount,
@@ -198,7 +200,7 @@ func getOpenStreams(ctx context.Context, client *firestore.Client, networkId str
 	for _, doc := range docs {
 		var s particle.FirestoreStreamParticle
 		if err := doc.DataTo(&s); err != nil {
-			slog.Warn("failed to unmarshal stream particle", "docId", doc.Ref.ID, "error", err)
+			flog.Warn("failed to unmarshal stream particle", "docId", doc.Ref.ID, "error", err)
 			continue
 		}
 		streams = append(streams, s)
diff --git a/go/cmd/memberreconciler/main.go b/go/cmd/memberreconciler/main.go
index 02b4528..bc172b0 100644
--- a/go/cmd/memberreconciler/main.go
+++ b/go/cmd/memberreconciler/main.go
@@ -6,17 +6,19 @@ package main
 
 import (
 	"context"
-	"log/slog"
 	"os"
 	"slices"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"cloud.google.com/go/firestore"
+	"google.golang.org/api/iterator"
+
 	"github.com/flowy-live/llink/internal/db"
 	"github.com/flowy-live/llink/internal/human"
 	"github.com/flowy-live/llink/internal/network"
 	"github.com/flowy-live/llink/internal/utils"
-	"google.golang.org/api/iterator"
 )
 
 func main() {
@@ -28,7 +30,7 @@ func main() {
 	gcpProject := utils.MustGetEnv("GCP_PROJECT")
 	fs, err := firestore.NewClient(ctx, gcpProject)
 	if err != nil {
-		slog.Error("failed to create Firestore client", "error", err)
+		flog.Error("failed to create Firestore client", "error", err)
 		os.Exit(1)
 	}
 	defer fs.Close()
@@ -39,10 +41,10 @@ func main() {
 	started := time.Now()
 	written, scanned, err := reconcile(ctx, fs, humanSvc, networkSvc)
 	if err != nil {
-		slog.Error("reconciliation failed", "error", err, "elapsed", time.Since(started))
+		flog.Error("reconciliation failed", "error", err, "elapsed", time.Since(started))
 		os.Exit(1)
 	}
-	slog.Info("reconciliation complete",
+	flog.Info("reconciliation complete",
 		"humans_scanned", scanned,
 		"humans_written", written,
 		"elapsed", time.Since(started),
@@ -109,7 +111,7 @@ func snapshotMirror(ctx context.Context, fs *firestore.Client) (map[string][]str
 			Networks []string `firestore:"networks"`
 		}
 		if err := doc.DataTo(&data); err != nil {
-			slog.Warn("skipping malformed mirror doc", "id", doc.Ref.ID, "error", err)
+			flog.Warn("skipping malformed mirror doc", "id", doc.Ref.ID, "error", err)
 			continue
 		}
 		out[doc.Ref.ID] = data.Networks
diff --git a/go/cmd/orion/main.go b/go/cmd/orion/main.go
index b261048..11395bc 100644
--- a/go/cmd/orion/main.go
+++ b/go/cmd/orion/main.go
@@ -3,14 +3,19 @@ package main
 import (
 	"context"
 	"fmt"
-	"log/slog"
 	"net/http"
 	"os"
 	"strings"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"cloud.google.com/go/firestore"
 	"cloud.google.com/go/storage"
 	firebase "firebase.google.com/go/v4"
+	"github.com/redis/go-redis/v9"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+
 	pbaero "github.com/flowy-live/llink/genproto/aero"
 	"github.com/flowy-live/llink/internal"
 	"github.com/flowy-live/llink/internal/auth"
@@ -27,9 +32,6 @@ import (
 	"github.com/flowy-live/llink/internal/particle"
 	"github.com/flowy-live/llink/internal/utils"
 	"github.com/flowy-live/llink/internal/waitlist"
-	"github.com/redis/go-redis/v9"
-	"google.golang.org/grpc"
-	"google.golang.org/grpc/credentials/insecure"
 )
 
 func redisForAuth() *redis.Client {
@@ -48,19 +50,19 @@ func main() {
 	ctx := context.Background()
 	storageClient, err := storage.NewClient(ctx)
 	if err != nil {
-		slog.Error("failed to create GCS client", "error", err)
+		flog.Error("failed to create GCS client", "error", err)
 		os.Exit(1)
 	}
 	defer storageClient.Close()
 
 	aeroAddr := utils.MustGetEnv("AERO_ADDR")
 	if aeroAddr == "" {
-		slog.Error("must provide AERO_ADDR")
+		flog.Error("must provide AERO_ADDR")
 		os.Exit(1)
 	}
 	aeroServer, err := grpc.NewClient(aeroAddr, grpc.WithTransportCredentials(insecure.NewCredentials()))
 	if err != nil {
-		slog.Error("connection to aero server invalid", "error", err)
+		flog.Error("connection to aero server invalid", "error", err)
 		os.Exit(1)
 	}
 	defer aeroServer.Close()
@@ -69,12 +71,12 @@ func main() {
 	gcpProject := utils.MustGetEnv("GCP_PROJECT")
 	fbApp, err := firebase.NewApp(ctx, &firebase.Config{ProjectID: gcpProject})
 	if err != nil {
-		slog.Error("failed to init Firebase Admin app", "error", err)
+		flog.Error("failed to init Firebase Admin app", "error", err)
 		os.Exit(1)
 	}
 	fbAuth, err := fbApp.Auth(ctx)
 	if err != nil {
-		slog.Error("failed to create Firebase auth client", "error", err)
+		flog.Error("failed to create Firebase auth client", "error", err)
 		os.Exit(1)
 	}
 
@@ -90,13 +92,13 @@ func main() {
 		CancelURL:      utils.MustGetEnv("BILLING_CANCEL_URL"),
 	})
 	if err != nil {
-		slog.Error("failed to initialize billing service", "error", err)
+		flog.Error("failed to initialize billing service", "error", err)
 		os.Exit(1)
 	}
 
 	firestoreClient, err := firestore.NewClient(ctx, gcpProject)
 	if err != nil {
-		slog.Error("failed to create Firestore client", "error", err)
+		flog.Error("failed to create Firestore client", "error", err)
 		os.Exit(1)
 	}
 	defer firestoreClient.Close()
@@ -202,9 +204,9 @@ func main() {
 	muxWithCors := middleware.CORS(allowedOrigins)(mux)
 
 	addr := fmt.Sprintf("0.0.0.0:%s", port)
-	slog.Info("running server", "addr", addr)
+	flog.Info("running server", "addr", addr)
 	if err := http.ListenAndServe(addr, muxWithCors); err != nil {
-		slog.Error("server failed", "error", err)
+		flog.Error("server failed", "error", err)
 		os.Exit(1)
 	}
 }
diff --git a/go/cmd/particleprocessorworker/main.go b/go/cmd/particleprocessorworker/main.go
index 51e5da0..9e9ae53 100644
--- a/go/cmd/particleprocessorworker/main.go
+++ b/go/cmd/particleprocessorworker/main.go
@@ -4,11 +4,15 @@ import (
 	"context"
 	"fmt"
 	"log"
-	"log/slog"
 	"os"
 	"strings"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+
 	"github.com/flowy-live/llink/internal/billing"
 	"github.com/flowy-live/llink/internal/db"
 	"github.com/flowy-live/llink/internal/depot"
@@ -18,8 +22,6 @@ import (
 	"github.com/flowy-live/llink/internal/particle"
 	"github.com/flowy-live/llink/internal/speech"
 	"github.com/flowy-live/llink/internal/utils"
-	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/status"
 
 	"cloud.google.com/go/firestore"
 	"cloud.google.com/go/storage"
@@ -48,7 +50,7 @@ func main() {
 
 	storageClient, err := storage.NewClient(ctx)
 	if err != nil {
-		slog.Error("failed to create GCS client", "error", err)
+		flog.Error("failed to create GCS client", "error", err)
 		os.Exit(1)
 	}
 	defer storageClient.Close()
@@ -83,7 +85,7 @@ func main() {
 			panic(fmt.Errorf("error: %w", err))
 		}
 		if err != nil {
-			slog.Error("error in processing snapshot", "error", err)
+			flog.Error("error in processing snapshot", "error", err)
 			continue
 		}
 
@@ -100,15 +102,15 @@ func main() {
 
 			processed, err := processingRepo.IsProcessed(ctx, particleID)
 			if err != nil {
-				slog.Error("failed to check processing status", "particleID", particleID, "error", err)
+				flog.Error("failed to check processing status", "particleID", particleID, "error", err)
 				continue
 			}
 			if processed {
-				slog.Debug("skipping already processed particle", "particleID", particleID)
+				flog.Debug("skipping already processed particle", "particleID", particleID)
 				continue
 			}
 
-			slog.Debug("processing particle", "particleID", particleID, "data", change.Doc.Data())
+			flog.Debug("processing particle", "particleID", particleID, "data", change.Doc.Data())
 
 			// Side effects below are best-effort — failures don't prevent
 			// marking the particle as processed.
@@ -120,7 +122,7 @@ func main() {
 			notifyForParticle(ctx, notifier, humanSvc, change.Doc, parentDoc, transcript)
 
 			if err := processingRepo.MarkProcessed(ctx, particleID); err != nil {
-				slog.Error("failed to mark particle as processed", "particleID", particleID, "error", err)
+				flog.Error("failed to mark particle as processed", "particleID", particleID, "error", err)
 			}
 		}
 	}
@@ -132,30 +134,30 @@ func transcribeMediaParticle(ctx context.Context, depotSvc depot.Service, speech
 	var mediaParticle particle.FirestoreMediaParticle
 	err := doc.DataTo(&mediaParticle)
 	if err != nil {
-		slog.Error("unable to marshal particle data", "error", err)
+		flog.Error("unable to marshal particle data", "error", err)
 		return ""
 	}
 
 	particleType, err := particle.ParseParticleType(mediaParticle.Type)
 	if err != nil {
-		slog.Error("invalid particle type", "error", err)
+		flog.Error("invalid particle type", "error", err)
 		return ""
 	}
 
 	if particleType != particle.TypeMedia {
-		slog.Info("received a particle of type", "particle type", particleType)
+		flog.Info("received a particle of type", "particle type", particleType)
 		return ""
 	}
 
 	downloadURL, err := depotSvc.GetDownloadURL(ctx, mediaParticle.Properties.ObjectId)
 	if err != nil {
-		slog.Error("failed to get download URL", "error", err, "object_id", mediaParticle.Properties.ObjectId)
+		flog.Error("failed to get download URL", "error", err, "object_id", mediaParticle.Properties.ObjectId)
 		return ""
 	}
 
 	result, err := speechSvc.Transcribe(ctx, downloadURL)
 	if err != nil {
-		slog.Error("failed to transcribe media", "error", err, "particleID", doc.Ref.ID)
+		flog.Error("failed to transcribe media", "error", err, "particleID", doc.Ref.ID)
 		return ""
 	}
 
@@ -167,11 +169,11 @@ func transcribeMediaParticle(ctx context.Context, depotSvc depot.Service, speech
 		},
 	}, firestore.MergeAll)
 	if err != nil {
-		slog.Error("failed to update transcript in firestore", "error", err, "particleID", doc.Ref.ID)
+		flog.Error("failed to update transcript in firestore", "error", err, "particleID", doc.Ref.ID)
 		return ""
 	}
 
-	slog.Info("transcribed media particle", "particleID", doc.Ref.ID)
+	flog.Info("transcribed media particle", "particleID", doc.Ref.ID)
 	return transcript.Transcript
 }
 
@@ -215,17 +217,17 @@ func toFirestoreTranscript(result *speech.TranscriptResult) particle.FirestoreTr
 func recordFreemiumUsage(ctx context.Context, billingSvc billing.Service, doc *firestore.DocumentSnapshot) {
 	rawType, err := doc.DataAt("type")
 	if err != nil {
-		slog.Error("failed to read particle type", "error", err, "particleID", doc.Ref.ID)
+		flog.Error("failed to read particle type", "error", err, "particleID", doc.Ref.ID)
 		return
 	}
 	typeStr, ok := rawType.(string)
 	if !ok {
-		slog.Error("particle type is not a string", "particleID", doc.Ref.ID, "type", rawType)
+		flog.Error("particle type is not a string", "particleID", doc.Ref.ID, "type", rawType)
 		return
 	}
 	particleType, err := particle.ParseParticleType(typeStr)
 	if err != nil {
-		slog.Error("invalid particle type", "error", err, "particleID", doc.Ref.ID)
+		flog.Error("invalid particle type", "error", err, "particleID", doc.Ref.ID)
 		return
 	}
 	// Containers don't count toward the daily message cap.
@@ -235,12 +237,12 @@ func recordFreemiumUsage(ctx context.Context, billingSvc billing.Service, doc *f
 
 	networkID, err := particle.NetworkIDFromParticlePath(doc.Ref.Path)
 	if err != nil {
-		slog.Error("failed to derive network id", "error", err, "path", doc.Ref.Path)
+		flog.Error("failed to derive network id", "error", err, "path", doc.Ref.Path)
 		return
 	}
 
 	if err := billingSvc.IncrementDailyUsage(ctx, networkID, doc.CreateTime); err != nil {
-		slog.Error("failed to increment daily usage", "error", err, "networkID", networkID, "particleID", doc.Ref.ID)
+		flog.Error("failed to increment daily usage", "error", err, "networkID", networkID, "particleID", doc.Ref.ID)
 	}
 }
 
@@ -252,12 +254,12 @@ func loadParentParticle(ctx context.Context, doc *firestore.DocumentSnapshot) *f
 	}
 	parentParticleDocRef := parentChildrenCollectionRef.Parent
 	if parentParticleDocRef == nil {
-		slog.Error("particle has no parent document", "particleID", doc.Ref.ID)
+		flog.Error("particle has no parent document", "particleID", doc.Ref.ID)
 		return nil
 	}
 	parentParticleDoc, err := parentParticleDocRef.Get(ctx)
 	if err != nil {
-		slog.Error("failed to get parent particle", "error", err, "particleID", doc.Ref.ID)
+		flog.Error("failed to get parent particle", "error", err, "particleID", doc.Ref.ID)
 		return nil
 	}
 	return parentParticleDoc
@@ -272,13 +274,13 @@ func updateParentLastChildCreatedAt(ctx context.Context, doc *firestore.Document
 
 	var streamParticle particle.FirestoreStreamParticle
 	if err := parent.DataTo(&streamParticle); err != nil {
-		slog.Error("failed to parse stream particle", "error", err)
+		flog.Error("failed to parse stream particle", "error", err)
 		return
 	}
 
 	particleType, err := particle.ParseParticleType(streamParticle.Type)
 	if err != nil {
-		slog.Error("invalid particle type", "error", err)
+		flog.Error("invalid particle type", "error", err)
 		return
 	}
 
@@ -288,7 +290,7 @@ func updateParentLastChildCreatedAt(ctx context.Context, doc *firestore.Document
 
 	childCreatedAt, err := doc.DataAt("created_at")
 	if err != nil {
-		slog.Error("failed to read child created_at", "error", err, "particleID", doc.Ref.ID)
+		flog.Error("failed to read child created_at", "error", err, "particleID", doc.Ref.ID)
 		return
 	}
 
@@ -299,7 +301,7 @@ func updateParentLastChildCreatedAt(ctx context.Context, doc *firestore.Document
 		},
 	})
 	if err != nil {
-		slog.Error("unable to update parent particle `last_child_created_at`", "error", err)
+		flog.Error("unable to update parent particle `last_child_created_at`", "error", err)
 	}
 }
 
@@ -315,7 +317,7 @@ func notifyForParticle(
 	transcript string,
 ) {
 	if parent == nil {
-		slog.Info("notify: skip — no parent", "particleID", doc.Ref.ID)
+		flog.Info("notify: skip — no parent", "particleID", doc.Ref.ID)
 		return
 	}
 
@@ -323,31 +325,31 @@ func notifyForParticle(
 	typeName, _ := typeStr.(string)
 	pType, err := particle.ParseParticleType(typeName)
 	if err != nil {
-		slog.Info("notify: skip — unparseable particle type",
+		flog.Info("notify: skip — unparseable particle type",
 			"particleID", doc.Ref.ID, "type", typeName, "error", err)
 		return
 	}
 	if pType == particle.TypeStream || pType == particle.TypeFolder {
-		slog.Info("notify: skip — container particle",
+		flog.Info("notify: skip — container particle",
 			"particleID", doc.Ref.ID, "type", pType)
 		return
 	}
 
 	var parentStream particle.FirestoreStreamParticle
 	if err := parent.DataTo(&parentStream); err != nil {
-		slog.Error("notify: failed to parse parent stream", "error", err)
+		flog.Error("notify: failed to parse parent stream", "error", err)
 		return
 	}
 	parentType, err := particle.ParseParticleType(parentStream.Type)
 	if err != nil || parentType != particle.TypeStream {
-		slog.Info("notify: skip — parent isn't a stream",
+		flog.Info("notify: skip — parent isn't a stream",
 			"particleID", doc.Ref.ID, "parentType", parentType, "parseErr", err)
 		return
 	}
 
 	networkID, err := particle.NetworkIDFromParticlePath(doc.Ref.Path)
 	if err != nil {
-		slog.Error("notify: failed to derive network id", "error", err, "path", doc.Ref.Path)
+		flog.Error("notify: failed to derive network id", "error", err, "path", doc.Ref.Path)
 		return
 	}
 
@@ -370,7 +372,7 @@ func notifyForParticle(
 		if sender, err := humanSvc.GetByID(ctx, senderHumanID); err == nil {
 			senderEmailPrefix = sender.EmailPrefix
 		} else {
-			slog.Warn("notify: failed to look up sender", "error", err, "humanID", senderHumanID)
+			flog.Warn("notify: failed to look up sender", "error", err, "humanID", senderHumanID)
 		}
 	}
 
@@ -385,7 +387,7 @@ func notifyForParticle(
 		StreamVisibleTo:   parentStream.VisibleTo,
 		Body:              previewForParticle(pType, doc, transcript),
 	}); err != nil {
-		slog.Error("notify: dispatch failed", "error", err, "particleID", doc.Ref.ID, "networkID", networkID)
+		flog.Error("notify: dispatch failed", "error", err, "particleID", doc.Ref.ID, "networkID", networkID)
 	}
 }
 
diff --git a/go/cmd/pusherservice/main.go b/go/cmd/pusherservice/main.go
index 2dee5ca..1d9155e 100644
--- a/go/cmd/pusherservice/main.go
+++ b/go/cmd/pusherservice/main.go
@@ -3,13 +3,14 @@ package main
 import (
 	"context"
 	"fmt"
-	"log/slog"
 	"net"
 	"net/http"
 	"os"
 	"os/signal"
 	"syscall"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"github.com/flowy-live/llink/internal"
 	"github.com/flowy-live/llink/internal/auth"
 	"github.com/flowy-live/llink/internal/db"
@@ -17,8 +18,9 @@ import (
 	"github.com/flowy-live/llink/internal/pusher"
 	"github.com/flowy-live/llink/internal/utils"
 
-	pbpusher "github.com/flowy-live/llink/genproto/llink/pusher"
 	"google.golang.org/grpc"
+
+	pbpusher "github.com/flowy-live/llink/genproto/llink/pusher"
 )
 
 func main() {
@@ -56,15 +58,15 @@ func main() {
 	// --- gRPC server (internal presence queries) ---
 	grpcListener, err := net.Listen("tcp", fmt.Sprintf("0.0.0.0:%s", grpcPort))
 	if err != nil {
-		slog.Error("failed to listen for gRPC", "port", grpcPort, "error", err)
+		flog.Error("failed to listen for gRPC", "port", grpcPort, "error", err)
 		os.Exit(1)
 	}
 	grpcServer := grpc.NewServer()
 	pbpusher.RegisterPusherServiceServer(grpcServer, server)
 	go func() {
-		slog.Info("gRPC server listening", "port", grpcPort)
+		flog.Info("gRPC server listening", "port", grpcPort)
 		if err := grpcServer.Serve(grpcListener); err != nil {
-			slog.Error("gRPC server failed", "error", err)
+			flog.Error("gRPC server failed", "error", err)
 		}
 	}()
 
@@ -79,9 +81,9 @@ func main() {
 	httpServer := &http.Server{Addr: httpAddr, Handler: mux}
 
 	go func() {
-		slog.Info("HTTP server listening", "addr", httpAddr)
+		flog.Info("HTTP server listening", "addr", httpAddr)
 		if err := httpServer.ListenAndServe(); err != nil && err != http.ErrServerClosed {
-			slog.Error("HTTP server failed", "error", err)
+			flog.Error("HTTP server failed", "error", err)
 			os.Exit(1)
 		}
 	}()
@@ -91,10 +93,10 @@ func main() {
 	signal.Notify(sigCh, syscall.SIGTERM, syscall.SIGINT)
 	<-sigCh
 
-	slog.Info("shutting down...")
+	flog.Info("shutting down...")
 	cancel()
 
 	grpcServer.GracefulStop()
 	httpServer.Shutdown(context.Background())
-	slog.Info("shutdown complete")
+	flog.Info("shutdown complete")
 }
diff --git a/go/cmd/transcodebackfill/main.go b/go/cmd/transcodebackfill/main.go
index df931df..363bb89 100644
--- a/go/cmd/transcodebackfill/main.go
+++ b/go/cmd/transcodebackfill/main.go
@@ -5,10 +5,11 @@ package main
 
 import (
 	"context"
-	"log/slog"
 	"os"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"cloud.google.com/go/firestore"
 	"cloud.google.com/go/storage"
 	"google.golang.org/api/iterator"
@@ -27,7 +28,7 @@ func main() {
 
 	storageClient, err := storage.NewClient(ctx)
 	if err != nil {
-		slog.Error("failed to create GCS client", "error", err)
+		flog.Error("failed to create GCS client", "error", err)
 		os.Exit(1)
 	}
 	defer storageClient.Close()
@@ -40,7 +41,7 @@ func main() {
 	gcpProject := utils.MustGetEnv("GCP_PROJECT")
 	fs, err := firestore.NewClient(ctx, gcpProject)
 	if err != nil {
-		slog.Error("failed to create Firestore client", "error", err)
+		flog.Error("failed to create Firestore client", "error", err)
 		os.Exit(1)
 	}
 	defer fs.Close()
@@ -49,7 +50,7 @@ func main() {
 	stats, err := run(ctx, fs, depotSvc)
 	elapsed := time.Since(started)
 
-	slog.Info("transcode_backfill_summary",
+	flog.Info("transcode_backfill_summary",
 		"scanned", stats.scanned,
 		"media", stats.media,
 		"transcoded", stats.transcoded,
@@ -61,7 +62,7 @@ func main() {
 	)
 
 	if err != nil {
-		slog.Error("transcode backfill aborted", "error", err)
+		flog.Error("transcode backfill aborted", "error", err)
 		os.Exit(1)
 	}
 	if stats.failures > 0 {
@@ -116,7 +117,7 @@ func run(ctx context.Context, fs *firestore.Client, depotSvc depot.Service) (sta
 		switch {
 		case result.Err != nil:
 			s.failures++
-			slog.Error("transcode_backfill_failure",
+			flog.Error("transcode_backfill_failure",
 				"particleID", doc.Ref.ID,
 				"path", doc.Ref.Path,
 				"error", result.Err,
@@ -129,7 +130,7 @@ func run(ctx context.Context, fs *firestore.Client, depotSvc depot.Service) (sta
 			s.skippedNonMedia++
 		default:
 			s.transcoded++
-			slog.Info("transcode_backfill_progress",
+			flog.Info("transcode_backfill_progress",
 				"particleID", doc.Ref.ID,
 				"transcodedObjectID", result.TranscodedObjectID,
 				"outputMime", result.OutputMimeType,
diff --git a/go/go.mod b/go/go.mod
index acc81d9..2f54f7f 100644
--- a/go/go.mod
+++ b/go/go.mod
@@ -13,6 +13,7 @@ require (
 	github.com/livekit/protocol v1.45.1
 	github.com/livekit/server-sdk-go/v2 v2.16.1
 	github.com/redis/go-redis/v9 v9.17.2
+	github.com/sirupsen/logrus v1.9.3
 	github.com/stretchr/testify v1.11.1
 	github.com/stripe/stripe-go/v85 v85.0.1
 	github.com/testcontainers/testcontainers-go v0.40.0
@@ -147,7 +148,6 @@ require (
 	github.com/prometheus/procfs v0.19.2 // indirect
 	github.com/puzpuzpuz/xsync/v3 v3.5.1 // indirect
 	github.com/shirou/gopsutil/v4 v4.25.6 // indirect
-	github.com/sirupsen/logrus v1.9.3 // indirect
 	github.com/spiffe/go-spiffe/v2 v2.6.0 // indirect
 	github.com/tklauser/go-sysconf v0.3.12 // indirect
 	github.com/tklauser/numcpus v0.6.1 // indirect
diff --git a/go/internal/auth/service.go b/go/internal/auth/service.go
index 244e35c..acc0e39 100644
--- a/go/internal/auth/service.go
+++ b/go/internal/auth/service.go
@@ -5,15 +5,17 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"log/slog"
 	"strings"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	firebaseauth "firebase.google.com/go/v4/auth"
-	pbaero "github.com/flowy-live/llink/genproto/aero"
-	"github.com/flowy-live/llink/internal/utils"
 	"github.com/redis/go-redis/v9"
 	"go.jetify.com/typeid"
+
+	pbaero "github.com/flowy-live/llink/genproto/aero"
+	"github.com/flowy-live/llink/internal/utils"
 )
 
 const (
@@ -86,7 +88,7 @@ func (a *authServiceImpl) MintFirebaseCustomToken(ctx context.Context, humanId s
 func (a *authServiceImpl) IsSystemAdmin(ctx context.Context, email string) bool {
 	formattedEmail, err := utils.NormalizeEmail(email)
 	if err != nil {
-		slog.Error("problem validating email", "error", err)
+		flog.Error("problem validating email", "error", err)
 		return false
 	}
 
@@ -110,7 +112,7 @@ func (a *authServiceImpl) RequestSignInCode(ctx context.Context, email string) e
 
 	err = a.redisClient.Set(ctx, formattedEmail, code, codeExpiry).Err()
 	if err != nil {
-		slog.Error("error setting code in redis", "error", err)
+		flog.Error("error setting code in redis", "error", err)
 		return fmt.Errorf("error storing sign-in code: %w", err)
 	}
 
@@ -129,7 +131,7 @@ func (a *authServiceImpl) RequestSignInCode(ctx context.Context, email string) e
 		return fmt.Errorf("an error occurred while sending the email: %w", err)
 	}
 
-	slog.Info("sent sign in code", "email", formattedEmail)
+	flog.Info("sent sign in code", "email", formattedEmail)
 	return nil
 }
 
@@ -144,7 +146,7 @@ func (a *authServiceImpl) VerifySignInCode(ctx context.Context, email, code, hum
 		if errors.Is(err, redis.Nil) {
 			return "", ErrInvalidCode
 		}
-		slog.Error("error getting code from redis", "error", err)
+		flog.Error("error getting code from redis", "error", err)
 		return "", fmt.Errorf("error verifying code: %w", err)
 	}
 
@@ -153,7 +155,7 @@ func (a *authServiceImpl) VerifySignInCode(ctx context.Context, email, code, hum
 	}
 
 	if err := a.redisClient.Del(ctx, formattedEmail).Err(); err != nil {
-		slog.Error("error deleting code from redis", "error", err)
+		flog.Error("error deleting code from redis", "error", err)
 	}
 
 	token, err := a.createSession(ctx, formattedEmail, humanId)
diff --git a/go/internal/billing/webhooks.go b/go/internal/billing/webhooks.go
index 9dab258..fd1452f 100644
--- a/go/internal/billing/webhooks.go
+++ b/go/internal/billing/webhooks.go
@@ -4,9 +4,10 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"log/slog"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"github.com/stripe/stripe-go/v85"
 	"github.com/stripe/stripe-go/v85/webhook"
 )
@@ -17,7 +18,7 @@ func (s *serviceImpl) HandleWebhook(ctx context.Context, payload []byte, signatu
 		return fmt.Errorf("verify stripe signature: %w", err)
 	}
 
-	slog.Info("stripe webhook", "type", event.Type, "id", event.ID)
+	flog.Info("stripe webhook", "type", event.Type, "id", event.ID)
 
 	switch event.Type {
 	case "checkout.session.completed":
diff --git a/go/internal/db/postgres.go b/go/internal/db/postgres.go
index 672371f..52536d1 100644
--- a/go/internal/db/postgres.go
+++ b/go/internal/db/postgres.go
@@ -2,9 +2,10 @@ package db
 
 import (
 	"context"
-	"log/slog"
 	"os"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"github.com/jackc/pgx/v5/pgxpool"
 )
 
@@ -21,24 +22,24 @@ func Pool() *pgxpool.Pool {
 func Init() {
 	connString := os.Getenv("LLINK_POSTGRES_CONNECTION_URL")
 	if connString == "" {
-		slog.Error("must provide LLINK_POSTGRES_CONNECTION_URL in env")
+		flog.Error("must provide LLINK_POSTGRES_CONNECTION_URL in env")
 		os.Exit(1)
 	}
 
 	dbpool, err := pgxpool.New(context.Background(), connString)
 	if err != nil {
-		slog.Error("unable to create connection pool", "error", err)
+		flog.Error("unable to create connection pool", "error", err)
 		os.Exit(1)
 	}
 
 	var greeting string
 	err = dbpool.QueryRow(context.Background(), "select 'Hello, world!'").Scan(&greeting)
 	if err != nil {
-		slog.Error("queryRow failed", "error", err)
+		flog.Error("queryRow failed", "error", err)
 		os.Exit(1)
 	}
 
-	slog.Info("successfully connected to database", "greeting", greeting)
+	flog.Info("successfully connected to database", "greeting", greeting)
 
 	db = dbpool
 }
diff --git a/go/internal/depot/service.go b/go/internal/depot/service.go
index c87221d..92657fc 100644
--- a/go/internal/depot/service.go
+++ b/go/internal/depot/service.go
@@ -5,9 +5,10 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"log/slog"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"cloud.google.com/go/storage"
 	"github.com/google/uuid"
 	"github.com/jackc/pgx/v5/pgxpool"
@@ -49,7 +50,7 @@ func NewService(pool *pgxpool.Pool, storageClient *storage.Client, config Config
 	}
 
 	if config.GoogleServiceAccountEmail == "" {
-		slog.Error("GoogleServiceAccountEmail is not set in config. Signed URLs may not work if the storage client is not properly authenticated with a service account.")
+		flog.Error("GoogleServiceAccountEmail is not set in config. Signed URLs may not work if the storage client is not properly authenticated with a service account.")
 		panic("GoogleServiceAccountEmail is required for signed URL generation")
 	}
 
@@ -102,10 +103,10 @@ func (s *serviceImpl) PrepareUpload(ctx context.Context, input PrepareUploadInpu
 		Headers:        []string{contentLengthHeader},
 	})
 	if err != nil {
-		slog.Error("failed to generate signed upload URL", "error", err, "bucket", s.bucketName, "object_key", objectKey)
+		flog.Error("failed to generate signed upload URL", "error", err, "bucket", s.bucketName, "object_key", objectKey)
 		// Roll back the placeholder row.
 		if delErr := s.repo.delete(ctx, created.ID); delErr != nil {
-			slog.Warn("failed to cleanup db record after signed URL failure", "error", delErr, "object_id", created.ID)
+			flog.Warn("failed to cleanup db record after signed URL failure", "error", delErr, "object_id", created.ID)
 		}
 		return nil, err
 	}
@@ -134,7 +135,7 @@ func (s *serviceImpl) ConfirmUpload(ctx context.Context, objectID string) (*Obje
 		if errors.Is(err, storage.ErrObjectNotExist) {
 			return nil, errors.Join(ErrNotFound, errors.New("object not found in storage"))
 		}
-		slog.Error("failed to get GCS object attrs", "error", err, "bucket", obj.BucketName, "object_key", obj.ObjectKey)
+		flog.Error("failed to get GCS object attrs", "error", err, "bucket", obj.BucketName, "object_key", obj.ObjectKey)
 		return nil, err
 	}
 
@@ -170,13 +171,13 @@ func (s *serviceImpl) CreateFromReader(ctx context.Context, input CreateFromRead
 	if _, err := io.Copy(w, body); err != nil {
 		// Always release the writer; surface the copy error, not Close's.
 		if cerr := w.Close(); cerr != nil {
-			slog.Warn("failed to close GCS writer after copy failure", "error", cerr, "object_key", objectKey)
+			flog.Warn("failed to close GCS writer after copy failure", "error", cerr, "object_key", objectKey)
 		}
-		slog.Error("failed to stream object to GCS", "error", err, "bucket", s.bucketName, "object_key", objectKey)
+		flog.Error("failed to stream object to GCS", "error", err, "bucket", s.bucketName, "object_key", objectKey)
 		return nil, err
 	}
 	if err := w.Close(); err != nil {
-		slog.Error("failed to close GCS writer", "error", err, "bucket", s.bucketName, "object_key", objectKey)
+		flog.Error("failed to close GCS writer", "error", err, "bucket", s.bucketName, "object_key", objectKey)
 		return nil, err
 	}
 
@@ -193,7 +194,7 @@ func (s *serviceImpl) CreateFromReader(ctx context.Context, input CreateFromRead
 	if err != nil {
 		// Best-effort: drop the now-untracked GCS object.
 		if delErr := s.storageClient.Bucket(s.bucketName).Object(objectKey).Delete(ctx); delErr != nil {
-			slog.Warn("failed to clean up GCS object after db create failure", "error", delErr, "object_key", objectKey)
+			flog.Warn("failed to clean up GCS object after db create failure", "error", delErr, "object_key", objectKey)
 		}
 		return nil, err
 	}
@@ -227,7 +228,7 @@ func (s *serviceImpl) GetDownloadURL(ctx context.Context, objectID string) (stri
 		Expires:        time.Now().Add(s.downloadURLExpiry),
 	})
 	if err != nil {
-		slog.Error("failed to generate signed download URL", "error", err, "bucket", obj.BucketName, "object_key", obj.ObjectKey)
+		flog.Error("failed to generate signed download URL", "error", err, "bucket", obj.BucketName, "object_key", obj.ObjectKey)
 		return "", err
 	}
 
@@ -246,7 +247,7 @@ func (s *serviceImpl) Delete(ctx context.Context, objectID string) error {
 	// GCS first so we don't strand an object after the row vanishes; missing object is fine.
 	gcsErr := s.storageClient.Bucket(obj.BucketName).Object(obj.ObjectKey).Delete(ctx)
 	if gcsErr != nil && !errors.Is(gcsErr, storage.ErrObjectNotExist) {
-		slog.Error("failed to delete object from GCS", "error", gcsErr, "bucket", obj.BucketName, "object_key", obj.ObjectKey)
+		flog.Error("failed to delete object from GCS", "error", gcsErr, "bucket", obj.BucketName, "object_key", obj.ObjectKey)
 		return gcsErr
 	}
 
diff --git a/go/internal/handler/billing.go b/go/internal/handler/billing.go
index 23423ec..501e468 100644
--- a/go/internal/handler/billing.go
+++ b/go/internal/handler/billing.go
@@ -5,9 +5,10 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"log/slog"
 	"net/http"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"github.com/flowy-live/llink/internal/billing"
 	"github.com/flowy-live/llink/internal/middleware"
 	"github.com/flowy-live/llink/internal/network"
@@ -42,7 +43,7 @@ func (h *Handler) GetNetworkUsage(w http.ResponseWriter, r *http.Request) {
 
 	isMember, err := h.networkSvc.IsMember(r.Context(), networkID, humanId)
 	if err != nil {
-		slog.Error("failed to check network membership", "error", err, "network_id", networkID)
+		flog.Error("failed to check network membership", "error", err, "network_id", networkID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -53,7 +54,7 @@ func (h *Handler) GetNetworkUsage(w http.ResponseWriter, r *http.Request) {
 
 	usage, err := h.billingSvc.GetUsage(r.Context(), networkID)
 	if err != nil {
-		slog.Error("failed to get network usage", "error", err, "network_id", networkID)
+		flog.Error("failed to get network usage", "error", err, "network_id", networkID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -69,7 +70,7 @@ func (h *Handler) GetNetworkBilling(w http.ResponseWriter, r *http.Request) {
 
 	status, err := h.billingSvc.GetStatus(r.Context(), net.ID)
 	if err != nil {
-		slog.Error("failed to get billing status", "error", err, "network_id", net.ID)
+		flog.Error("failed to get billing status", "error", err, "network_id", net.ID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -97,14 +98,14 @@ func (h *Handler) CreateCheckoutSession(w http.ResponseWriter, r *http.Request)
 
 	adminHuman, err := h.humanSvc.GetByID(r.Context(), adminHumanId)
 	if err != nil {
-		slog.Error("failed to load admin human", "error", err, "human_id", adminHumanId)
+		flog.Error("failed to load admin human", "error", err, "human_id", adminHumanId)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
 
 	seats, err := h.networkSvc.CountSeats(r.Context(), net.ID)
 	if err != nil {
-		slog.Error("failed to count seats", "error", err, "network_id", net.ID)
+		flog.Error("failed to count seats", "error", err, "network_id", net.ID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -117,7 +118,7 @@ func (h *Handler) CreateCheckoutSession(w http.ResponseWriter, r *http.Request)
 		Seats:        seats,
 	})
 	if err != nil {
-		slog.Error("failed to create checkout session", "error", err, "network_id", net.ID)
+		flog.Error("failed to create checkout session", "error", err, "network_id", net.ID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -137,7 +138,7 @@ func (h *Handler) CreatePortalSession(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	if err != nil {
-		slog.Error("failed to create portal session", "error", err, "network_id", net.ID)
+		flog.Error("failed to create portal session", "error", err, "network_id", net.ID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -150,14 +151,14 @@ const maxStripeWebhookBytes = 1 << 20 // 1 MiB
 func (h *Handler) HandleStripeWebhook(w http.ResponseWriter, r *http.Request) {
 	payload, err := io.ReadAll(io.LimitReader(r.Body, maxStripeWebhookBytes))
 	if err != nil {
-		slog.Warn("stripe webhook: failed to read body", "error", err)
+		flog.Warn("stripe webhook: failed to read body", "error", err)
 		http.Error(w, "bad request", http.StatusBadRequest)
 		return
 	}
 	signature := r.Header.Get("Stripe-Signature")
 
 	if err := h.billingSvc.HandleWebhook(r.Context(), payload, signature); err != nil {
-		slog.Error("stripe webhook failed", "error", err)
+		flog.Error("stripe webhook failed", "error", err)
 		formattedErr := fmt.Errorf("webhook processing failed: %w", err)
 		http.Error(w, formattedErr.Error(), http.StatusBadRequest)
 		return
@@ -187,7 +188,7 @@ func (h *Handler) loadNetworkForAdmin(w http.ResponseWriter, r *http.Request) (*
 		return nil, "", false
 	}
 	if err != nil {
-		slog.Error("failed to load network", "error", err, "network_id", networkID)
+		flog.Error("failed to load network", "error", err, "network_id", networkID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return nil, "", false
 	}
@@ -203,6 +204,6 @@ func (h *Handler) loadNetworkForAdmin(w http.ResponseWriter, r *http.Request) (*
 func writeJSON(w http.ResponseWriter, body any) {
 	w.Header().Set("Content-Type", "application/json")
 	if err := json.NewEncoder(w).Encode(body); err != nil {
-		slog.Error("failed to write json", "error", err)
+		flog.Error("failed to write json", "error", err)
 	}
 }
diff --git a/go/internal/handler/handler.go b/go/internal/handler/handler.go
index d87a62c..0ec211a 100644
--- a/go/internal/handler/handler.go
+++ b/go/internal/handler/handler.go
@@ -5,12 +5,15 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"log/slog"
 	"net/http"
 	"strings"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"cloud.google.com/go/firestore"
+	"github.com/livekit/protocol/webhook"
+
 	"github.com/flowy-live/llink/internal/auth"
 	"github.com/flowy-live/llink/internal/billing"
 	"github.com/flowy-live/llink/internal/depot"
@@ -22,7 +25,6 @@ import (
 	"github.com/flowy-live/llink/internal/particle"
 	"github.com/flowy-live/llink/internal/utils"
 	"github.com/flowy-live/llink/internal/waitlist"
-	"github.com/livekit/protocol/webhook"
 )
 
 type Handler struct {
@@ -187,13 +189,13 @@ func (h *Handler) RequestSignInCode(w http.ResponseWriter, r *http.Request) {
 
 	_, err := h.humanSvc.GetOrCreateByEmail(r.Context(), req.Email)
 	if err != nil {
-		slog.Error("failed to get or create human", "error", err, "email", req.Email)
+		flog.Error("failed to get or create human", "error", err, "email", req.Email)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
 
 	if err := h.authSvc.RequestSignInCode(r.Context(), req.Email); err != nil {
-		slog.Error("failed to request sign-in code", "error", err, "email", req.Email)
+		flog.Error("failed to request sign-in code", "error", err, "email", req.Email)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -220,7 +222,7 @@ func (h *Handler) SignIn(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, "human not found", http.StatusNotFound)
 			return
 		}
-		slog.Error("failed to get human for sign-in", "error", err, "email", req.Email)
+		flog.Error("failed to get human for sign-in", "error", err, "email", req.Email)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -231,7 +233,7 @@ func (h *Handler) SignIn(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, "invalid code", http.StatusUnauthorized)
 			return
 		}
-		slog.Error("failed to verify sign-in code", "error", err, "email", req.Email)
+		flog.Error("failed to verify sign-in code", "error", err, "email", req.Email)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -256,7 +258,7 @@ func (h *Handler) FirebaseToken(w http.ResponseWriter, r *http.Request) {
 
 	token, err := h.authSvc.MintFirebaseCustomToken(r.Context(), humanId)
 	if err != nil {
-		slog.Error("failed to mint Firebase custom token", "error", err, "humanId", humanId)
+		flog.Error("failed to mint Firebase custom token", "error", err, "humanId", humanId)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -273,7 +275,7 @@ func (h *Handler) SignOut(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if err := h.authSvc.SignOut(r.Context(), token); err != nil {
-		slog.Error("failed to sign out", "error", err)
+		flog.Error("failed to sign out", "error", err)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -294,7 +296,7 @@ func (h *Handler) GetCurrentHuman(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, "human not found", http.StatusNotFound)
 			return
 		}
-		slog.Error("failed to get current human", "error", err, "email", email)
+		flog.Error("failed to get current human", "error", err, "email", email)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -323,7 +325,7 @@ func (h *Handler) UpdateSettings(w http.ResponseWriter, r *http.Request) {
 
 	if req.EmailNotificationsEnabled != nil {
 		if err := h.humanSvc.UpdateEmailNotificationsEnabled(r.Context(), humanId, *req.EmailNotificationsEnabled); err != nil {
-			slog.Error("failed to update email notifications setting", "error", err, "humanId", humanId)
+			flog.Error("failed to update email notifications setting", "error", err, "humanId", humanId)
 			http.Error(w, "internal server error", http.StatusInternalServerError)
 			return
 		}
@@ -355,14 +357,14 @@ func (h *Handler) CreateNetwork(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, "name cannot be empty", http.StatusBadRequest)
 			return
 		}
-		slog.Error("failed to create network", "error", err, "humanId", humanId, "name", req.Name)
+		flog.Error("failed to create network", "error", err, "humanId", humanId, "name", req.Name)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
 
 	resp, err := h.networkToDTO(r.Context(), net)
 	if err != nil {
-		slog.Error("failed to convert network to DTO", "error", err, "network_id", net.ID)
+		flog.Error("failed to convert network to DTO", "error", err, "network_id", net.ID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -381,7 +383,7 @@ func (h *Handler) ListNetworks(w http.ResponseWriter, r *http.Request) {
 
 	networks, err := h.networkSvc.ListForHuman(r.Context(), humanId)
 	if err != nil {
-		slog.Error("failed to list networks", "error", err, "humanId", humanId)
+		flog.Error("failed to list networks", "error", err, "humanId", humanId)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -390,7 +392,7 @@ func (h *Handler) ListNetworks(w http.ResponseWriter, r *http.Request) {
 	for _, net := range networks {
 		dto, err := h.networkToDTO(r.Context(), net)
 		if err != nil {
-			slog.Warn("failed to convert network to DTO in list", "error", err, "network_id", net.ID)
+			flog.Warn("failed to convert network to DTO in list", "error", err, "network_id", net.ID)
 			continue
 		}
 		resp = append(resp, dto)
@@ -415,7 +417,7 @@ func (h *Handler) GetNetwork(w http.ResponseWriter, r *http.Request) {
 
 	isMember, err := h.networkSvc.IsMember(r.Context(), networkID, humanId)
 	if err != nil {
-		slog.Error("failed to check network membership", "error", err, "network_id", networkID, "humanId", humanId)
+		flog.Error("failed to check network membership", "error", err, "network_id", networkID, "humanId", humanId)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -430,14 +432,14 @@ func (h *Handler) GetNetwork(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, "network not found", http.StatusNotFound)
 			return
 		}
-		slog.Error("failed to get network", "error", err, "network_id", networkID)
+		flog.Error("failed to get network", "error", err, "network_id", networkID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
 
 	resp, err := h.networkToDTO(r.Context(), net)
 	if err != nil {
-		slog.Error("failed to convert network to DTO", "error", err, "network_id", networkID)
+		flog.Error("failed to convert network to DTO", "error", err, "network_id", networkID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -463,7 +465,7 @@ func (h *Handler) AddMembersToNetwork(w http.ResponseWriter, r *http.Request) {
 
 	isMember, err := h.networkSvc.IsMember(r.Context(), networkID, humanId)
 	if err != nil {
-		slog.Error("failed to check network membership", "error", err, "network_id", networkID, "humanId", humanId)
+		flog.Error("failed to check network membership", "error", err, "network_id", networkID, "humanId", humanId)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -497,7 +499,7 @@ func (h *Handler) AddMembersToNetwork(w http.ResponseWriter, r *http.Request) {
 				inviteEmails = append(inviteEmails, normalized)
 				continue
 			}
-			slog.Error("failed to look up human by email", "error", err, "email", normalized)
+			flog.Error("failed to look up human by email", "error", err, "email", normalized)
 			http.Error(w, "internal server error", http.StatusInternalServerError)
 			return
 		}
@@ -506,7 +508,7 @@ func (h *Handler) AddMembersToNetwork(w http.ResponseWriter, r *http.Request) {
 
 	if len(memberHumanIds) > 0 {
 		if err := h.networkSvc.AddMembers(r.Context(), networkID, memberHumanIds); err != nil {
-			slog.Error("failed to add members to network", "error", err, "network_id", networkID)
+			flog.Error("failed to add members to network", "error", err, "network_id", networkID)
 			http.Error(w, "internal server error", http.StatusInternalServerError)
 			return
 		}
@@ -514,7 +516,7 @@ func (h *Handler) AddMembersToNetwork(w http.ResponseWriter, r *http.Request) {
 
 	if len(inviteEmails) > 0 {
 		if err := h.networkSvc.InviteByEmail(r.Context(), networkID, inviteEmails); err != nil {
-			slog.Error("failed to invite members to network", "error", err, "network_id", networkID)
+			flog.Error("failed to invite members to network", "error", err, "network_id", networkID)
 			http.Error(w, "internal server error", http.StatusInternalServerError)
 			return
 		}
@@ -522,14 +524,14 @@ func (h *Handler) AddMembersToNetwork(w http.ResponseWriter, r *http.Request) {
 
 	net, err := h.networkSvc.GetByID(r.Context(), networkID)
 	if err != nil {
-		slog.Error("failed to get network after adding members", "error", err, "network_id", networkID)
+		flog.Error("failed to get network after adding members", "error", err, "network_id", networkID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
 
 	resp, err := h.networkToDTO(r.Context(), net)
 	if err != nil {
-		slog.Error("failed to convert network to DTO", "error", err, "network_id", networkID)
+		flog.Error("failed to convert network to DTO", "error", err, "network_id", networkID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -558,7 +560,7 @@ func (h *Handler) RemoveMemberFromNetwork(w http.ResponseWriter, r *http.Request
 	}
 
 	if err := h.networkSvc.RemoveMember(r.Context(), net.ID, memberHumanId); err != nil {
-		slog.Error("failed to remove member from network", "error", err, "network_id", net.ID, "memberHumanId", memberHumanId)
+		flog.Error("failed to remove member from network", "error", err, "network_id", net.ID, "memberHumanId", memberHumanId)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -581,7 +583,7 @@ func (h *Handler) ListInvitationsForNetwork(w http.ResponseWriter, r *http.Reque
 
 	isMember, err := h.networkSvc.IsMember(r.Context(), networkID, humanId)
 	if err != nil {
-		slog.Error("failed to check network membership", "error", err, "network_id", networkID, "humanId", humanId)
+		flog.Error("failed to check network membership", "error", err, "network_id", networkID, "humanId", humanId)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -592,7 +594,7 @@ func (h *Handler) ListInvitationsForNetwork(w http.ResponseWriter, r *http.Reque
 
 	invitations, err := h.networkSvc.ListInvitationsForNetwork(r.Context(), networkID)
 	if err != nil {
-		slog.Error("failed to list invitations", "error", err, "network_id", networkID)
+		flog.Error("failed to list invitations", "error", err, "network_id", networkID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -620,7 +622,7 @@ func (h *Handler) ListMyInvitations(w http.ResponseWriter, r *http.Request) {
 
 	invitations, err := h.networkSvc.ListInvitationsForEmail(r.Context(), email)
 	if err != nil {
-		slog.Error("failed to list invitations for email", "error", err, "email", email)
+		flog.Error("failed to list invitations for email", "error", err, "email", email)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -663,7 +665,7 @@ func (h *Handler) AcceptInvitation(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if err := h.networkSvc.AcceptInvitation(r.Context(), req.NetworkId, email, humanId); err != nil {
-		slog.Error("failed to accept invitation", "error", err, "network_id", req.NetworkId, "email", email)
+		flog.Error("failed to accept invitation", "error", err, "network_id", req.NetworkId, "email", email)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -686,7 +688,7 @@ func (h *Handler) RevokeInvitation(w http.ResponseWriter, r *http.Request) {
 
 	isMember, err := h.networkSvc.IsMember(r.Context(), networkID, humanId)
 	if err != nil {
-		slog.Error("failed to check network membership", "error", err, "network_id", networkID, "humanId", humanId)
+		flog.Error("failed to check network membership", "error", err, "network_id", networkID, "humanId", humanId)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -707,7 +709,7 @@ func (h *Handler) RevokeInvitation(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if err := h.networkSvc.RevokeInvitation(r.Context(), networkID, req.Email); err != nil {
-		slog.Error("failed to revoke invitation", "error", err, "network_id", networkID, "email", req.Email)
+		flog.Error("failed to revoke invitation", "error", err, "network_id", networkID, "email", req.Email)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -729,7 +731,7 @@ func (h *Handler) DownloadParticleMedia(w http.ResponseWriter, r *http.Request)
 
 	downloadURL, err := h.depotSvc.GetDownloadURL(r.Context(), objectID)
 	if err != nil {
-		slog.Error("failed to get download URL", "error", err, "object_id", objectID)
+		flog.Error("failed to get download URL", "error", err, "object_id", objectID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -763,7 +765,7 @@ func (h *Handler) PrepareUpload(w http.ResponseWriter, r *http.Request) {
 
 	isMember, err := h.networkSvc.IsMember(r.Context(), req.NetworkId, humanId)
 	if err != nil {
-		slog.Error("failed to check network membership", "error", err, "network_id", req.NetworkId, "humanId", humanId)
+		flog.Error("failed to check network membership", "error", err, "network_id", req.NetworkId, "humanId", humanId)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -785,7 +787,7 @@ func (h *Handler) PrepareUpload(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
 		}
-		slog.Error("failed to prepare upload", "error", err, "network_id", req.NetworkId, "name", req.Name)
+		flog.Error("failed to prepare upload", "error", err, "network_id", req.NetworkId, "name", req.Name)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -823,7 +825,7 @@ func (h *Handler) ConfirmUpload(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
 		}
-		slog.Error("failed to confirm upload", "error", err, "object_id", objectID)
+		flog.Error("failed to confirm upload", "error", err, "object_id", objectID)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -886,7 +888,7 @@ func (h *Handler) AddToWaitlist(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, "already in the waitlist", http.StatusConflict)
 			return
 		}
-		slog.Error("failed to add to waitlist", "error", err, "email", req.Email)
+		flog.Error("failed to add to waitlist", "error", err, "email", req.Email)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -912,7 +914,7 @@ func (h *Handler) GetWaitlist(w http.ResponseWriter, r *http.Request) {
 
 	entries, err := h.waitlistSvc.GetWaitlist(r.Context(), filter)
 	if err != nil {
-		slog.Error("failed to get waitlist", "error", err)
+		flog.Error("failed to get waitlist", "error", err)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -945,7 +947,7 @@ func (h *Handler) GetWaitlistEntry(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, "entry not found", http.StatusNotFound)
 			return
 		}
-		slog.Error("failed to get waitlist entry", "error", err, "email", email)
+		flog.Error("failed to get waitlist entry", "error", err, "email", email)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -977,7 +979,7 @@ func (h *Handler) InviteWaitlistEntrant(w http.ResponseWriter, r *http.Request)
 			http.Error(w, "entry not found", http.StatusNotFound)
 			return
 		}
-		slog.Error("failed to invite waitlist entrant", "error", err, "email", req.Email)
+		flog.Error("failed to invite waitlist entrant", "error", err, "email", req.Email)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -1019,7 +1021,7 @@ func (h *Handler) networkToDTO(ctx context.Context, n *network.Network) (Network
 	for _, memberHumanId := range n.MemberHumanIds {
 		hum, err := h.humanSvc.GetByID(ctx, memberHumanId)
 		if err != nil {
-			slog.Warn("failed to look up network member", "humanId", memberHumanId, "error", err)
+			flog.Warn("failed to look up network member", "humanId", memberHumanId, "error", err)
 			continue
 		}
 		humans = append(humans, humanToDTO(hum))
@@ -1070,7 +1072,7 @@ func (h *Handler) GetLivekitToken(w http.ResponseWriter, r *http.Request) {
 
 	token, err := h.livekitClient.GetJoinToken(roomName, humanId, humanEmail)
 	if err != nil {
-		slog.Error("failed to generate livekit token", "error", err, "humanId", humanId, "roomName", roomName)
+		flog.Error("failed to generate livekit token", "error", err, "humanId", humanId, "roomName", roomName)
 		http.Error(w, "failed to generate token", http.StatusInternalServerError)
 		return
 	}
@@ -1084,13 +1086,13 @@ func (h *Handler) GetLivekitToken(w http.ResponseWriter, r *http.Request) {
 func (h *Handler) HandleLivekitWebhook(w http.ResponseWriter, r *http.Request) {
 	event, err := webhook.ReceiveWebhookEvent(r, h.livekitClient.KeyProvider())
 	if err != nil {
-		slog.Error("failed to verify livekit webhook", "error", err)
+		flog.Error("failed to verify livekit webhook", "error", err)
 		http.Error(w, "unauthorized", http.StatusUnauthorized)
 		return
 	}
 
 	eventType := event.GetEvent()
-	slog.Info("received livekit webhook", "event", eventType, "room", event.GetRoom().GetName())
+	flog.Info("received livekit webhook", "event", eventType, "room", event.GetRoom().GetName())
 
 	switch eventType {
 	case "participant_joined", "participant_left", "room_finished":
@@ -1103,7 +1105,7 @@ func (h *Handler) HandleLivekitWebhook(w http.ResponseWriter, r *http.Request) {
 	roomName := event.GetRoom().GetName()
 	parts := strings.SplitN(roomName, "/", 2)
 	if len(parts) != 2 {
-		slog.Error("invalid room name format", "room", roomName)
+		flog.Error("invalid room name format", "room", roomName)
 		http.Error(w, "invalid room name", http.StatusBadRequest)
 		return
 	}
@@ -1120,7 +1122,7 @@ func (h *Handler) HandleLivekitWebhook(w http.ResponseWriter, r *http.Request) {
 		// Authoritative list avoids drift from missed/out-of-order webhooks.
 		participants, err := h.livekitClient.ListParticipants(ctx, roomName)
 		if err != nil {
-			slog.Error("failed to list participants", "error", err, "room", roomName)
+			flog.Error("failed to list participants", "error", err, "room", roomName)
 			// 200 to suppress LiveKit retries.
 			w.WriteHeader(http.StatusOK)
 			return
@@ -1136,7 +1138,7 @@ func (h *Handler) HandleLivekitWebhook(w http.ResponseWriter, r *http.Request) {
 		{Path: "huddle_active_participants", Value: participantIds},
 	})
 	if err != nil {
-		slog.Error("failed to update huddle participants in firestore", "error", err, "path", docPath)
+		flog.Error("failed to update huddle participants in firestore", "error", err, "path", docPath)
 	}
 
 	w.WriteHeader(http.StatusOK)
diff --git a/go/internal/handler/metadata.go b/go/internal/handler/metadata.go
index cccae0f..61c83f6 100644
--- a/go/internal/handler/metadata.go
+++ b/go/internal/handler/metadata.go
@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"io"
-	"log/slog"
 	"net"
 	"net/http"
 	"net/url"
@@ -12,6 +11,8 @@ import (
 	"strings"
 	"sync"
 	"time"
+
+	"github.com/flowy-live/llink/internal/utils/flog"
 )
 
 // LinkMetadata mirrors the TS shape in `js/desktop/src/lib/link-metadata.ts`.
@@ -63,7 +64,7 @@ func (h *Handler) GetLinkMetadata(w http.ResponseWriter, r *http.Request) {
 
 	meta, err := fetchLinkMetadata(r.Context(), parsed)
 	if err != nil {
-		slog.Warn("link metadata fetch failed", "url", raw, "error", err)
+		flog.Warn("link metadata fetch failed", "url", raw, "error", err)
 		writeJSON(w, nil)
 		return
 	}
diff --git a/go/internal/handler/push_token.go b/go/internal/handler/push_token.go
index edff810..4b9fc4e 100644
--- a/go/internal/handler/push_token.go
+++ b/go/internal/handler/push_token.go
@@ -3,9 +3,10 @@ package handler
 import (
 	"encoding/json"
 	"errors"
-	"log/slog"
 	"net/http"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"github.com/flowy-live/llink/internal/human/pushnotify"
 	"github.com/flowy-live/llink/internal/middleware"
 )
@@ -45,7 +46,7 @@ func (h *Handler) RegisterPushToken(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, err.Error(), http.StatusBadRequest)
 			return
 		}
-		slog.Error("failed to register push token", "error", err, "humanId", humanId)
+		flog.Error("failed to register push token", "error", err, "humanId", humanId)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
@@ -74,7 +75,7 @@ func (h *Handler) UnregisterPushToken(w http.ResponseWriter, r *http.Request) {
 
 	err := h.pushTokenSvc.Unregister(r.Context(), humanId, req.Token)
 	if err != nil && !errors.Is(err, pushnotify.ErrNotFound) {
-		slog.Error("failed to unregister push token", "error", err, "humanId", humanId)
+		flog.Error("failed to unregister push token", "error", err, "humanId", humanId)
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
diff --git a/go/internal/human/pushnotify/notifier.go b/go/internal/human/pushnotify/notifier.go
index ee5be37..2f9676a 100644
--- a/go/internal/human/pushnotify/notifier.go
+++ b/go/internal/human/pushnotify/notifier.go
@@ -4,7 +4,8 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"log/slog"
+
+	"github.com/flowy-live/llink/internal/utils/flog"
 
 	"github.com/flowy-live/llink/internal/network"
 )
@@ -55,7 +56,7 @@ func NewNotifier(networkR network.Reader, tokens Service, expo *ExpoClient) *Not
 
 func (n *Notifier) NotifyParticleCreated(ctx context.Context, in NotifyInput) error {
 	if in.NetworkID == "" || in.ParticleID == "" {
-		slog.Info("pushnotify: skip — missing ids",
+		flog.Info("pushnotify: skip — missing ids",
 			"networkID", in.NetworkID,
 			"particleID", in.ParticleID,
 		)
@@ -71,7 +72,7 @@ func (n *Notifier) NotifyParticleCreated(ctx context.Context, in NotifyInput) er
 	recipientsBeforeSenderFilter := len(recipients)
 	recipients = filterOut(recipients, in.SenderHumanID)
 	if len(recipients) == 0 {
-		slog.Info("pushnotify: skip — no recipients",
+		flog.Info("pushnotify: skip — no recipients",
 			"networkID", in.NetworkID,
 			"particleID", in.ParticleID,
 			"senderHumanID", in.SenderHumanID,
@@ -87,7 +88,7 @@ func (n *Notifier) NotifyParticleCreated(ctx context.Context, in NotifyInput) er
 		return fmt.Errorf("token lookup: %w", err)
 	}
 	if len(tokens) == 0 {
-		slog.Info("pushnotify: skip — no tokens for recipients",
+		flog.Info("pushnotify: skip — no tokens for recipients",
 			"networkID", in.NetworkID,
 			"particleID", in.ParticleID,
 			"recipients", len(recipients),
@@ -98,7 +99,7 @@ func (n *Notifier) NotifyParticleCreated(ctx context.Context, in NotifyInput) er
 
 	msgs := buildMessages(tokens, in)
 	tickets, sendErr := n.expo.Send(ctx, msgs)
-	slog.Info("pushnotify: dispatch",
+	flog.Info("pushnotify: dispatch",
 		"networkID", in.NetworkID,
 		"particleID", in.ParticleID,
 		"recipients", len(recipients),
@@ -127,14 +128,14 @@ func (n *Notifier) cleanupDeadTokens(ctx context.Context, msgs []Message, ticket
 		code, _ := t.Details["error"].(string)
 		if code != ExpoErrorDeviceNotRegistered {
 			if t.Status == "error" {
-				slog.Warn("pushnotify: ticket error", "code", code, "message", t.Message, "to", msgs[i].To)
+				flog.Warn("pushnotify: ticket error", "code", code, "message", t.Message, "to", msgs[i].To)
 			}
 			continue
 		}
 		if err := n.tokens.DeleteByToken(ctx, msgs[i].To); err != nil && !errors.Is(err, ErrNotFound) {
-			slog.Error("pushnotify: failed to delete dead token", "error", err, "token", msgs[i].To)
+			flog.Error("pushnotify: failed to delete dead token", "error", err, "token", msgs[i].To)
 		} else {
-			slog.Info("pushnotify: removed unregistered token", "token", msgs[i].To)
+			flog.Info("pushnotify: removed unregistered token", "token", msgs[i].To)
 		}
 	}
 }
diff --git a/go/internal/media/helpers.go b/go/internal/media/helpers.go
index d75c33c..46476a1 100644
--- a/go/internal/media/helpers.go
+++ b/go/internal/media/helpers.go
@@ -4,10 +4,11 @@ import (
 	"bytes"
 	"context"
 	"errors"
-	"log/slog"
 	"os"
 	"os/exec"
 	"strings"
+
+	"github.com/flowy-live/llink/internal/utils/flog"
 )
 
 func IsIOSPlayableMime(mime string) bool {
@@ -56,7 +57,7 @@ func TranscodeToMp4(ctx context.Context, input TranscodeInput) (*TranscodeOutput
 
 	tmp, err := os.CreateTemp("", "transcode-*"+outputExt)
 	if err != nil {
-		slog.Error("transcode: failed to create temp file", "error", err)
+		flog.Error("transcode: failed to create temp file", "error", err)
 		return nil, err
 	}
 	tmpPath := tmp.Name()
diff --git a/go/internal/middleware/auth.go b/go/internal/middleware/auth.go
index 7dedfec..9217e57 100644
--- a/go/internal/middleware/auth.go
+++ b/go/internal/middleware/auth.go
@@ -2,10 +2,11 @@ package middleware
 
 import (
 	"context"
-	"log/slog"
 	"net/http"
 	"strings"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"github.com/flowy-live/llink/internal/auth"
 )
 
@@ -62,7 +63,7 @@ func Auth(authSvc auth.AuthService) func(http.Handler) http.Handler {
 			}
 
 			if err := authSvc.ExtendSession(r.Context(), token); err != nil {
-				slog.Warn("failed to extend session", "error", err)
+				flog.Warn("failed to extend session", "error", err)
 			}
 
 			ctx := WithEmail(r.Context(), session.Email)
diff --git a/go/internal/network/service.go b/go/internal/network/service.go
index 734a7bd..dd96f95 100644
--- a/go/internal/network/service.go
+++ b/go/internal/network/service.go
@@ -5,17 +5,19 @@ import (
 	"errors"
 	"fmt"
 	"html"
-	"log/slog"
 	"slices"
 	"strings"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
 	pbaero "github.com/flowy-live/llink/genproto/aero"
 	"github.com/flowy-live/llink/internal/billing"
 	"github.com/flowy-live/llink/internal/constants"
 	"github.com/flowy-live/llink/internal/livestore"
 	"github.com/flowy-live/llink/internal/utils"
-	"github.com/jackc/pgx/v5"
-	"github.com/jackc/pgx/v5/pgxpool"
 )
 
 var ErrNotFound = errors.New("network not found")
@@ -91,7 +93,7 @@ func (s *serviceImpl) Create(ctx context.Context, name, adminHumanId string) (*N
 		},
 	})
 	if err != nil {
-		slog.Warn("unable to send admin update email", "error", err)
+		flog.Warn("unable to send admin update email", "error", err)
 	}
 
 	return network, nil
@@ -149,13 +151,13 @@ func (s *serviceImpl) RemoveMember(ctx context.Context, networkID, humanId strin
 // Postgres is the source of truth: failures are logged and the reconciler heals drift.
 func (s *serviceImpl) mirrorAddMembership(ctx context.Context, humanId, networkID string) {
 	if err := s.pub.Add(ctx, humanId, networkID); err != nil {
-		slog.Error("membership publish add failed", "error", err, "humanId", humanId, "networkID", networkID)
+		flog.Error("membership publish add failed", "error", err, "humanId", humanId, "networkID", networkID)
 	}
 }
 
 func (s *serviceImpl) mirrorRemoveMembership(ctx context.Context, humanId, networkID string) {
 	if err := s.pub.Remove(ctx, humanId, networkID); err != nil {
-		slog.Error("membership publish remove failed", "error", err, "humanId", humanId, "networkID", networkID)
+		flog.Error("membership publish remove failed", "error", err, "humanId", humanId, "networkID", networkID)
 	}
 }
 
@@ -214,7 +216,7 @@ func (s *serviceImpl) InviteByEmail(ctx context.Context, networkID string, email
 			},
 		})
 		if err != nil {
-			slog.Warn("unable to send email notification", "email", email, "network", network.Name)
+			flog.Warn("unable to send email notification", "email", email, "network", network.Name)
 		}
 	}
 	return nil
diff --git a/go/internal/particle/transcode.go b/go/internal/particle/transcode.go
index fd75385..afdba52 100644
--- a/go/internal/particle/transcode.go
+++ b/go/internal/particle/transcode.go
@@ -3,12 +3,14 @@ package particle
 import (
 	"context"
 	"fmt"
-	"log/slog"
 	"os"
 	"strings"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"cloud.google.com/go/firestore"
+
 	"github.com/flowy-live/llink/internal/depot"
 	"github.com/flowy-live/llink/internal/media"
 )
@@ -44,17 +46,17 @@ type TranscodeResult struct {
 func Transcode(ctx context.Context, depotSvc depot.Service, doc *firestore.DocumentSnapshot) TranscodeResult {
 	var mp FirestoreMediaParticle
 	if err := doc.DataTo(&mp); err != nil {
-		slog.Error("transcode: unable to marshal particle data", "error", err)
+		flog.Error("transcode: unable to marshal particle data", "error", err)
 		return TranscodeResult{Err: fmt.Errorf("unmarshal particle: %w", err)}
 	}
 
 	particleType, err := ParseParticleType(mp.Type)
 	if err != nil {
-		slog.Error("transcode: invalid particle type", "error", err)
+		flog.Error("transcode: invalid particle type", "error", err)
 		return TranscodeResult{Err: fmt.Errorf("parse type: %w", err)}
 	}
 	if particleType != TypeMedia {
-		slog.Info("transcode: particle is not of type media")
+		flog.Info("transcode: particle is not of type media")
 		return TranscodeResult{Skipped: true, SkipReason: SkipReasonNotMedia}
 	}
 
@@ -63,19 +65,19 @@ func Transcode(ctx context.Context, depotSvc depot.Service, doc *firestore.Docum
 	}
 
 	if media.IsIOSPlayableMime(mp.Properties.MimeType) {
-		slog.Info("transcode: skipping because already playable on ios")
+		flog.Info("transcode: skipping because already playable on ios")
 		return TranscodeResult{Skipped: true, SkipReason: SkipReasonIOSPlayable}
 	}
 
 	sourceURL, err := depotSvc.GetDownloadURL(ctx, mp.Properties.ObjectId)
 	if err != nil {
-		slog.Error("transcode: failed to get download URL", "error", err, "object_id", mp.Properties.ObjectId)
+		flog.Error("transcode: failed to get download URL", "error", err, "object_id", mp.Properties.ObjectId)
 		return TranscodeResult{Err: fmt.Errorf("download URL: %w", err)}
 	}
 
 	networkID, err := NetworkIDFromParticlePath(doc.Ref.Path)
 	if err != nil {
-		slog.Error("transcode: failed to derive network id", "error", err, "path", doc.Ref.Path)
+		flog.Error("transcode: failed to derive network id", "error", err, "path", doc.Ref.Path)
 		return TranscodeResult{Err: fmt.Errorf("network id: %w", err)}
 	}
 
@@ -86,14 +88,14 @@ func Transcode(ctx context.Context, depotSvc depot.Service, doc *firestore.Docum
 		MimeType:  mp.Properties.MimeType,
 	})
 	if err != nil {
-		slog.Error("transcode: ffmpeg failed", "error", err)
+		flog.Error("transcode: ffmpeg failed", "error", err)
 		return TranscodeResult{Err: fmt.Errorf("ffmpeg: %w", err)}
 	}
 	defer os.Remove(transcodeOutput.TempLocalFilePath)
 
 	f, err := os.Open(transcodeOutput.TempLocalFilePath)
 	if err != nil {
-		slog.Error("transcode: failed to open transcoded file", "error", err, "path", transcodeOutput.TempLocalFilePath)
+		flog.Error("transcode: failed to open transcoded file", "error", err, "path", transcodeOutput.TempLocalFilePath)
 		return TranscodeResult{Err: fmt.Errorf("open temp file: %w", err)}
 	}
 	defer f.Close()
@@ -104,7 +106,7 @@ func Transcode(ctx context.Context, depotSvc depot.Service, doc *firestore.Docum
 		ContentType: transcodeOutput.OutputMimeType,
 	}, f)
 	if err != nil {
-		slog.Error("transcode: failed to upload transcoded object", "error", err, "particleID", doc.Ref.ID)
+		flog.Error("transcode: failed to upload transcoded object", "error", err, "particleID", doc.Ref.ID)
 		return TranscodeResult{Err: fmt.Errorf("upload: %w", err)}
 	}
 
@@ -114,11 +116,11 @@ func Transcode(ctx context.Context, depotSvc depot.Service, doc *firestore.Docum
 			"transcoded_mime_type": transcodeOutput.OutputMimeType,
 		},
 	}, firestore.MergeAll); err != nil {
-		slog.Error("transcode: failed to update particle in firestore", "error", err, "particleID", doc.Ref.ID)
+		flog.Error("transcode: failed to update particle in firestore", "error", err, "particleID", doc.Ref.ID)
 		return TranscodeResult{Err: fmt.Errorf("firestore update: %w", err)}
 	}
 
-	slog.Info("transcoded media particle", "particleID", doc.Ref.ID, "transcoded_object_id", newObj.ID, "mime", transcodeOutput.OutputMimeType)
+	flog.Info("transcoded media particle", "particleID", doc.Ref.ID, "transcoded_object_id", newObj.ID, "mime", transcodeOutput.OutputMimeType)
 	return TranscodeResult{
 		TranscodedObjectID: newObj.ID,
 		OutputMimeType:     transcodeOutput.OutputMimeType,
diff --git a/go/internal/pusher/conn.go b/go/internal/pusher/conn.go
index 6a73912..cb00c01 100644
--- a/go/internal/pusher/conn.go
+++ b/go/internal/pusher/conn.go
@@ -3,9 +3,10 @@ package pusher
 import (
 	"context"
 	"encoding/json"
-	"log/slog"
 	"sync"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"nhooyr.io/websocket"
 )
 
@@ -37,16 +38,16 @@ func (c *Conn) ReadPump(ctx context.Context, hub *Hub) {
 		_, data, err := c.ws.Read(ctx)
 		if err != nil {
 			if ctx.Err() != nil {
-				slog.Info("websocket context cancelled", "connId", c.id, "humanId", c.humanID, "error", ctx.Err())
+				flog.Info("websocket context cancelled", "connId", c.id, "humanId", c.humanID, "error", ctx.Err())
 				return
 			}
-			slog.Warn("websocket read error", "connId", c.id, "humanId", c.humanID, "error", err)
+			flog.Warn("websocket read error", "connId", c.id, "humanId", c.humanID, "error", err)
 			return
 		}
 
 		if string(data) == "ping" {
 			if err := c.ws.Write(ctx, websocket.MessageText, []byte("pong")); err != nil {
-				slog.Warn("websocket pong write error", "connId", c.id, "error", err)
+				flog.Warn("websocket pong write error", "connId", c.id, "error", err)
 			}
 			continue
 		}
@@ -92,7 +93,7 @@ func (c *Conn) WritePump(ctx context.Context) {
 				return
 			}
 			if err := c.ws.Write(ctx, websocket.MessageText, data); err != nil {
-				slog.Debug("websocket write error", "connId", c.id, "error", err)
+				flog.Debug("websocket write error", "connId", c.id, "error", err)
 				return
 			}
 		}
@@ -103,14 +104,14 @@ func (c *Conn) WritePump(ctx context.Context) {
 func (c *Conn) Send(msg ServerMessage) {
 	data, err := json.Marshal(msg)
 	if err != nil {
-		slog.Error("failed to marshal server message", "error", err)
+		flog.Error("failed to marshal server message", "error", err)
 		return
 	}
 
 	select {
 	case c.send <- data:
 	default:
-		slog.Warn("slow client, closing connection", "connId", c.id, "humanId", c.humanID)
+		flog.Warn("slow client, closing connection", "connId", c.id, "humanId", c.humanID)
 		c.Close()
 	}
 }
diff --git a/go/internal/pusher/hub.go b/go/internal/pusher/hub.go
index 3ecc608..cb0e5ec 100644
--- a/go/internal/pusher/hub.go
+++ b/go/internal/pusher/hub.go
@@ -3,7 +3,8 @@ package pusher
 import (
 	"context"
 	"encoding/json"
-	"log/slog"
+
+	"github.com/flowy-live/llink/internal/utils/flog"
 )
 
 type subscribeRequest struct {
@@ -110,7 +111,7 @@ func (h *Hub) handleSubscribe(ctx context.Context, req *subscribeRequest) {
 
 	presence, err := h.bridge.Subscribe(ctx, req.channelID, req.conn.id, req.conn.humanID)
 	if err != nil {
-		slog.Error("redis subscribe failed", "channelId", req.channelID, "error", err)
+		flog.Error("redis subscribe failed", "channelId", req.channelID, "error", err)
 		// Fall back to local-only presence.
 		presence = ch.localHumanIDs()
 	}
@@ -144,7 +145,7 @@ func (h *Hub) handleUnsubscribe(ctx context.Context, req *unsubscribeRequest) {
 	}
 
 	if err := h.bridge.Unsubscribe(ctx, req.channelID, req.conn.id, req.conn.humanID); err != nil {
-		slog.Error("redis unsubscribe failed", "channelId", req.channelID, "error", err)
+		flog.Error("redis unsubscribe failed", "channelId", req.channelID, "error", err)
 	}
 
 	// Only emit leave once the humanID has no remaining tabs on this pod.
@@ -198,7 +199,7 @@ func (h *Hub) handleDisconnect(ctx context.Context, conn *Conn) {
 		ch.removeMember(conn)
 
 		if err := h.bridge.Unsubscribe(ctx, channelID, conn.id, conn.humanID); err != nil {
-			slog.Error("redis unsubscribe on disconnect failed", "channelId", channelID, "error", err)
+			flog.Error("redis unsubscribe on disconnect failed", "channelId", channelID, "error", err)
 		}
 
 		if !ch.hasHumanID(conn.humanID) {
diff --git a/go/internal/pusher/redis_bridge.go b/go/internal/pusher/redis_bridge.go
index 403b15f..03e4c66 100644
--- a/go/internal/pusher/redis_bridge.go
+++ b/go/internal/pusher/redis_bridge.go
@@ -4,10 +4,11 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"log/slog"
 	"strings"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"github.com/redis/go-redis/v9"
 )
 
@@ -200,7 +201,7 @@ func (rb *RedisBridge) handlePubSubMessage(msg *redis.Message) {
 
 	var event redisEvent
 	if err := json.Unmarshal([]byte(msg.Payload), &event); err != nil {
-		slog.Error("failed to parse pub/sub event", "error", err)
+		flog.Error("failed to parse pub/sub event", "error", err)
 		return
 	}
 
@@ -257,7 +258,7 @@ func (rb *RedisBridge) cleanupStalePods(ctx context.Context) {
 	for {
 		keys, nextCursor, err := rb.client.Scan(ctx, cursor, channelConnsPrefix+"*"+channelConnsSuffix, 100).Result()
 		if err != nil {
-			slog.Error("failed to scan channel keys", "error", err)
+			flog.Error("failed to scan channel keys", "error", err)
 			return
 		}
 
@@ -292,7 +293,7 @@ func (rb *RedisBridge) cleanupStalePods(ctx context.Context) {
 
 	for podID := range knownPods {
 		if !alivePods[podID] {
-			slog.Info("cleaning up stale pod", "podId", podID)
+			flog.Info("cleaning up stale pod", "podId", podID)
 			rb.cleanupPod(ctx, podID)
 		}
 	}
@@ -344,11 +345,11 @@ func (rb *RedisBridge) connField(connID string) string {
 func (rb *RedisBridge) publishEvent(ctx context.Context, channelID string, event redisEvent) {
 	data, err := json.Marshal(event)
 	if err != nil {
-		slog.Error("failed to marshal event", "error", err)
+		flog.Error("failed to marshal event", "error", err)
 		return
 	}
 	if err := rb.client.Publish(ctx, pubsubPrefix+channelID, data).Err(); err != nil {
-		slog.Error("failed to publish event", "channelId", channelID, "error", err)
+		flog.Error("failed to publish event", "channelId", channelID, "error", err)
 	}
 }
 
diff --git a/go/internal/pusher/server.go b/go/internal/pusher/server.go
index cc32816..6a7c468 100644
--- a/go/internal/pusher/server.go
+++ b/go/internal/pusher/server.go
@@ -2,13 +2,14 @@ package pusher
 
 import (
 	"context"
-	"log/slog"
 	"net/http"
 
-	"github.com/flowy-live/llink/genproto/llink/pusher"
-	"github.com/flowy-live/llink/internal/auth"
 	"github.com/google/uuid"
 	"nhooyr.io/websocket"
+
+	pbpusher "github.com/flowy-live/llink/genproto/llink/pusher"
+	"github.com/flowy-live/llink/internal/auth"
+	"github.com/flowy-live/llink/internal/utils/flog"
 )
 
 // Server handles WebSocket upgrades and gRPC presence queries.
@@ -49,14 +50,14 @@ func (s *Server) HandleWebSocket(w http.ResponseWriter, r *http.Request) {
 		InsecureSkipVerify: true,
 	})
 	if err != nil {
-		slog.Error("websocket accept failed", "error", err)
+		flog.Error("websocket accept failed", "error", err)
 		return
 	}
 
 	connID := uuid.New().String()
 	conn := newConn(connID, session.HumanId, ws)
 
-	slog.Info("websocket connected", "connId", connID, "humanId", session.HumanId)
+	flog.Info("websocket connected", "connId", connID, "humanId", session.HumanId)
 
 	// Use the server context, not r.Context(): after upgrade the HTTP request
 	// context can be cancelled by load balancers and nhooyr/websocket would
@@ -70,7 +71,7 @@ func (s *Server) HandleWebSocket(w http.ResponseWriter, r *http.Request) {
 	go conn.WritePump(ctx)
 	conn.ReadPump(ctx, s.hub)
 
-	slog.Info("websocket disconnected", "connId", connID, "humanId", session.HumanId)
+	flog.Info("websocket disconnected", "connId", connID, "humanId", session.HumanId)
 }
 
 func (s *Server) GetOnlineHumanIds(ctx context.Context, _ *pbpusher.GetOnlineHumanIdsRequest) (*pbpusher.GetOnlineHumanIdsResponse, error) {
diff --git a/go/internal/redis.go b/go/internal/redis.go
index 2fb052f..f67ed15 100644
--- a/go/internal/redis.go
+++ b/go/internal/redis.go
@@ -3,17 +3,19 @@ package internal
 import (
 	"context"
 	"fmt"
-	"log/slog"
 	"os"
 
-	"github.com/flowy-live/llink/internal/utils"
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"github.com/redis/go-redis/v9"
+
+	"github.com/flowy-live/llink/internal/utils"
 )
 
 func ConnectAndTestRedis(db int) *redis.Client {
 	redisHost := utils.MustGetEnv("REDIS_HOST")
 	if redisHost == "" {
-		slog.Error("must provide REDIS_HOST")
+		flog.Error("must provide REDIS_HOST")
 		os.Exit(1)
 	}
 	redisAddr := fmt.Sprintf("%s:%s", redisHost, "6379")
@@ -32,7 +34,7 @@ func ConnectAndTestRedis(db int) *redis.Client {
 	if err != nil {
 		panic(err)
 	}
-	slog.Debug("redis test", "key", val)
+	flog.Debug("redis test", "key", val)
 	if val != "value" {
 		panic("unexpected value")
 	}
diff --git a/go/internal/speech/service.go b/go/internal/speech/service.go
index 0a88c75..eff0929 100644
--- a/go/internal/speech/service.go
+++ b/go/internal/speech/service.go
@@ -2,7 +2,8 @@ package speech
 
 import (
 	"context"
-	"log/slog"
+
+	"github.com/flowy-live/llink/internal/utils/flog"
 
 	dgapi "github.com/deepgram/deepgram-go-sdk/v3/pkg/api/listen/v1/rest"
 	interfaces "github.com/deepgram/deepgram-go-sdk/v3/pkg/client/interfaces"
@@ -56,7 +57,7 @@ func (s *speechServiceImpl) Transcribe(ctx context.Context, mediaUrl string) (*T
 
 	response, err := s.deepgramClient.FromURL(ctx, mediaUrl, options)
 	if err != nil {
-		slog.Error("failed to transcribe prerecorded media", "error", err)
+		flog.Error("failed to transcribe prerecorded media", "error", err)
 		return nil, err
 	}
 
diff --git a/go/internal/testhelper/postgres.go b/go/internal/testhelper/postgres.go
index b9c8df3..d59fcef 100644
--- a/go/internal/testhelper/postgres.go
+++ b/go/internal/testhelper/postgres.go
@@ -3,10 +3,11 @@ package testhelper
 import (
 	"context"
 	"fmt"
-	"log/slog"
 	"os"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
 	"github.com/golang-migrate/migrate/v4"
 	_ "github.com/golang-migrate/migrate/v4/database/postgres"
 	_ "github.com/golang-migrate/migrate/v4/source/file"
@@ -39,20 +40,20 @@ func SetupTestDB() *pgxpool.Pool {
 		),
 	)
 	if err != nil {
-		slog.Error("failed to start postgres container", "error", err)
+		flog.Error("failed to start postgres container", "error", err)
 		os.Exit(1)
 	}
 
 	// Get connection URL
 	host, err := container.Host(ctx)
 	if err != nil {
-		slog.Error("failed to get container host", "error", err)
+		flog.Error("failed to get container host", "error", err)
 		os.Exit(1)
 	}
 
 	port, err := container.MappedPort(ctx, "5432")
 	if err != nil {
-		slog.Error("failed to get container port", "error", err)
+		flog.Error("failed to get container port", "error", err)
 		os.Exit(1)
 	}
 
@@ -62,20 +63,20 @@ func SetupTestDB() *pgxpool.Pool {
 	// Run migrations
 	m, err := migrate.New("file://../../migrations", connectionURL)
 	if err != nil {
-		slog.Error("failed to create migrate instance", "error", err)
+		flog.Error("failed to create migrate instance", "error", err)
 		os.Exit(1)
 	}
 	defer m.Close()
 
 	if err := m.Up(); err != nil && err != migrate.ErrNoChange {
-		slog.Error("failed to run migrations", "error", err)
+		flog.Error("failed to run migrations", "error", err)
 		os.Exit(1)
 	}
 
 	// Create connection pool
 	dbPool, err = pgxpool.New(ctx, connectionURL)
 	if err != nil {
-		slog.Error("failed to create connection pool", "error", err)
+		flog.Error("failed to create connection pool", "error", err)
 		os.Exit(1)
 	}
 
@@ -89,7 +90,7 @@ func TeardownTestDB() {
 	}
 	if container != nil {
 		if err := container.Terminate(ctx); err != nil {
-			slog.Error("failed to terminate container", "error", err)
+			flog.Error("failed to terminate container", "error", err)
 		}
 	}
 }
diff --git a/go/internal/utils/env.go b/go/internal/utils/env.go
index 568d3ef..4877ace 100644
--- a/go/internal/utils/env.go
+++ b/go/internal/utils/env.go
@@ -2,7 +2,8 @@ package utils
 
 import (
 	"os"
-	"log/slog"
+
+	"github.com/flowy-live/llink/internal/utils/flog"
 )
 
 // EnvVar enumerates the env vars referenced via this package.
@@ -15,7 +16,7 @@ func MustGetEnv[T string | EnvVar](key T) string {
 	keyString := string(key)
 	value := os.Getenv(keyString)
 	if value == "" {
-		slog.Errorf("Missing required environment variable %s", key)
+		flog.Error("missing required environment variable", "key", key)
 		panic("Missing required environment variable")
 	}
 
@@ -26,7 +27,7 @@ func MustGetEnv[T string | EnvVar](key T) string {
 func GetEnv(key string) string {
 	value := os.Getenv(key)
 	if value == "" {
-	    slog.Warnf("Missing optional environment variable %s", key)
+		flog.Warn("missing optional environment variable", "key", key)
 	}
 	return value
 }
diff --git a/go/internal/utils/flog/flog.go b/go/internal/utils/flog/flog.go
new file mode 100644
index 0000000..59b45ac
--- /dev/null
+++ b/go/internal/utils/flog/flog.go
@@ -0,0 +1,58 @@
+// Package flog is a structured logger formatted for GCP Cloud Logging.
+//
+// The API mirrors log/slog: a message string followed by alternating key/value
+// pairs. Each kv pair becomes a JSON field in the emitted record, which Cloud
+// Logging promotes to a queryable jsonPayload field.
+//
+//	flog.Info("particle processed", "particleID", id, "elapsed", dt)
+package flog
+
+import (
+	"os"
+
+	"github.com/sirupsen/logrus"
+)
+
+// Prepares global logger for GCP Cloud Logging's quirks
+var log = func() *logrus.Logger {
+	logger := logrus.New()
+	logger.SetFormatter(&logrus.JSONFormatter{
+		FieldMap: logrus.FieldMap{
+			logrus.FieldKeyLevel: "severity",
+			logrus.FieldKeyMsg:   "message",
+			logrus.FieldKeyTime:  "timestamp",
+		},
+	})
+	logger.SetOutput(os.Stderr)
+	logger.SetLevel(logrus.DebugLevel)
+	return logger
+}()
+
+// fields converts alternating key/value args into a logrus.Fields map. A
+// trailing odd arg or non-string key is stored under "!BADKEY" to match
+// slog's behavior.
+func fields(args []any) logrus.Fields {
+	if len(args) == 0 {
+		return nil
+	}
+	f := make(logrus.Fields, len(args)/2+1)
+	for i := 0; i < len(args); i += 2 {
+		if i+1 >= len(args) {
+			f["!BADKEY"] = args[i]
+			break
+		}
+		key, ok := args[i].(string)
+		if !ok {
+			f["!BADKEY"] = args[i]
+			continue
+		}
+		f[key] = args[i+1]
+	}
+	return f
+}
+
+func Debug(msg string, args ...any) { log.WithFields(fields(args)).Debug(msg) }
+func Info(msg string, args ...any)  { log.WithFields(fields(args)).Info(msg) }
+func Warn(msg string, args ...any)  { log.WithFields(fields(args)).Warn(msg) }
+func Error(msg string, args ...any) { log.WithFields(fields(args)).Error(msg) }
+func Fatal(msg string, args ...any) { log.WithFields(fields(args)).Fatal(msg) }
diff --git a/go/internal/waitlist/service.go b/go/internal/waitlist/service.go
index 4711079..c5f753c 100644
--- a/go/internal/waitlist/service.go
+++ b/go/internal/waitlist/service.go
@@ -4,12 +4,14 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"log/slog"
 	"time"
 
+	"github.com/flowy-live/llink/internal/utils/flog"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+
 	pbaero "github.com/flowy-live/llink/genproto/aero"
 	"github.com/flowy-live/llink/internal/utils"
-	"github.com/jackc/pgx/v5/pgxpool"
 )
 
 type WaitlistEntry struct {
@@ -83,7 +85,7 @@ func (s *serviceImpl) AddToWaitlist(ctx context.Context, email string, metadata
 		},
 	})
 	if err != nil {
-		slog.Error("failed to add to waitlist", "error", err, "email", email)
+		flog.Error("failed to add to waitlist", "error", err, "email", email)
 	}
 
 	return nil