diff --git a/internal/service/service.go b/internal/service/service.go
index de8d99e..b53ebe9 100644
--- a/internal/service/service.go
+++ b/internal/service/service.go
@@ -33,6 +33,15 @@ import (
 	openai "github.com/sashabaranov/go-openai"
 )
 
+// Context keys for request-scoped values.
+type key string
+
+const (
+	logKey key = "log"
+	idKey  key = "id"
+	ipKey  key = "ip"
+)
+
 //go:embed all:static/*
 var static embed.FS
 
@@ -189,9 +198,9 @@ func (svc *Service) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 	// Enrich context with request-scoped values.
 	ctx := r.Context()
-	ctx = context.WithValue(ctx, "log", log)
-	ctx = context.WithValue(ctx, "id", id)
-	ctx = context.WithValue(ctx, "ip", ip)
+	ctx = context.WithValue(ctx, logKey, log)
+	ctx = context.WithValue(ctx, idKey, id)
+	ctx = context.WithValue(ctx, ipKey, ip)
 	r = r.WithContext(ctx)
 
 	log.InfoContext(ctx, "handling")
@@ -346,7 +355,7 @@ func (svc *Service) JobCount() int {
 func (svc *Service) home(w http.ResponseWriter, r *http.Request) {
 	var (
 		ctx = r.Context()
-		log = ctx.Value("log").(*slog.Logger)
+		log = ctx.Value(logKey).(*slog.Logger)
 	)
 
 	if r.URL.Path != "/" {
@@ -408,7 +417,7 @@ type Response struct {
 func (svc *Service) voice(w http.ResponseWriter, r *http.Request) {
 	var (
 		ctx = r.Context()
-		log = ctx.Value("log").(*slog.Logger)
+		log = ctx.Value(logKey).(*slog.Logger)
 	)
 
 	// Parse request.
@@ -619,7 +628,7 @@ type StreamMessage struct {
 func (svc *Service) voiceStream(w http.ResponseWriter, r *http.Request) {
 	var (
 		ctx = r.Context()
-		log = ctx.Value("log").(*slog.Logger)
+		log = ctx.Value(logKey).(*slog.Logger)
 	)
 
 	// Check that the response writer supports flushing.
@@ -848,7 +857,7 @@ func (svc *Service) voiceStream(w http.ResponseWriter, r *http.Request) {
 func (svc *Service) models(w http.ResponseWriter, r *http.Request) {
 	var (
 		ctx = r.Context()
-		log = ctx.Value("log").(*slog.Logger)
+		log = ctx.Value(logKey).(*slog.Logger)
 	)
 
 	models, err := svc.llm.ListModels(ctx)
@@ -886,7 +895,7 @@ func (svc *Service) models(w http.ResponseWriter, r *http.Request) {
 func (svc *Service) voices(w http.ResponseWriter, r *http.Request) {
 	var (
 		ctx = r.Context()
-		log = ctx.Value("log").(*slog.Logger)
+		log = ctx.Value(logKey).(*slog.Logger)
 	)
 
 	voices, err := svc.tts.ListVoices(ctx)