diff --git a/.env.example b/.env.example
index 755b4bc..c333141 100644
--- a/.env.example
+++ b/.env.example
@@ -5,6 +5,13 @@ MYSQL_DATABASE=ik_kontroll
 MYSQL_USER=ik_user
 MYSQL_PASSWORD=ik_pass
 
+# ── Spring datasource overrides ───────────────────────────────────────────────
+# Optional when running locally outside Docker Compose. Docker Compose sets these
+# automatically for the backend container.
+SPRING_DATASOURCE_URL=jdbc:mysql://localhost:3306/ik_kontroll?allowPublicKeyRetrieval=true&useSSL=false&serverTimezone=UTC&characterEncoding=UTF-8&useUnicode=true
+SPRING_DATASOURCE_USERNAME=ik_user
+SPRING_DATASOURCE_PASSWORD=ik_pass
+
 # ── JWT secret ────────────────────────────────────────────────────────────────
 # Must be at least 32 characters. Change this to something random in production.
 JWT_SECRET=local-dev-secret-please-change-this-for-production-use-only
diff --git a/backend/src/main/resources/application-dev.properties b/backend/src/main/resources/application-dev.properties
index 1e22cf6..39bd8ff 100644
--- a/backend/src/main/resources/application-dev.properties
+++ b/backend/src/main/resources/application-dev.properties
@@ -1,6 +1,14 @@
 # Flyway in dev: run normal schema migrations + dev-only seed migrations
 spring.flyway.locations=classpath:db/migration,classpath:db/migration-dev
 
+# Local datasource defaults for IDE runs. Docker Compose overrides these with
+# SPRING_DATASOURCE_* environment variables when the app runs in containers.
+spring.datasource.url=${SPRING_DATASOURCE_URL:jdbc:mysql://localhost:3306/${MYSQL_DATABASE:ik_kontroll}?allowPublicKeyRetrieval=true&useSSL=false&serverTimezone=UTC&characterEncoding=UTF-8&useUnicode=true}
+spring.datasource.username=${SPRING_DATASOURCE_USERNAME:${MYSQL_USER:ik_user}}
+spring.datasource.password=${SPRING_DATASOURCE_PASSWORD:${MYSQL_PASSWORD:ik_pass}}
+spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
+spring.jpa.database-platform=org.hibernate.dialect.MySQLDialect
+
 # Allow Flyway to wipe and rebuild schema if it finds a failed migration record
 spring.flyway.clean-disabled=false
 spring.flyway.clean-on-validation-error=true
diff --git a/frontend/src/views/GraphView.vue b/frontend/src/views/GraphView.vue
index 61c0b7a..793816e 100644
--- a/frontend/src/views/GraphView.vue
+++ b/frontend/src/views/GraphView.vue
@@ -163,7 +163,7 @@ const lineChartOptions = computed(() => ({
       callbacks: {
         label: (ctx: any) => {
           const ds = visibleDatasets.value[ctx.datasetIndex]
-          if (!ds || ctx.parsed.y == null) return null
+          if (!ds || ctx.parsed.y == null) return undefined
           const val: number = ctx.parsed.y
           const hasThresholds = ds.minThreshold != null && ds.maxThreshold != null
           const isOut = hasThresholds && (val < ds.minThreshold || val > ds.maxThreshold)
@@ -171,7 +171,7 @@ const lineChartOptions = computed(() => ({
         },
         afterLabel: (ctx: any) => {
           const ds = visibleDatasets.value[ctx.datasetIndex]
-          if (!ds || ctx.parsed.y == null || ds.minThreshold == null || ds.maxThreshold == null) return null
+          if (!ds || ctx.parsed.y == null || ds.minThreshold == null || ds.maxThreshold == null) return undefined
           return `  Grense: ${ds.minThreshold}°C – ${ds.maxThreshold}°C`
         },
       },