diff --git a/app/src/handlers/demo-plc.ts b/app/src/handlers/demo-plc.ts
index 968f6ef..ea44cba 100644
--- a/app/src/handlers/demo-plc.ts
+++ b/app/src/handlers/demo-plc.ts
@@ -12,24 +12,11 @@ type DemoPlcPayload = {
   value: number
 }
 
-type DemoPlcMetric = DemoPlcPayload & {
+type DemoPlcMetric = {
   edge: string
   timestamp: number
-}
-
-function isDemoPlcPayload(value: unknown): value is DemoPlcPayload {
-  if (!value || typeof value !== 'object') {
-    return false
-  }
-
-  const candidate = value as Partial<DemoPlcPayload>
-
-  return (
-    typeof candidate.tag === 'string' &&
-    candidate.tag.length > 0 &&
-    typeof candidate.value === 'number' &&
-    Number.isFinite(candidate.value)
-  )
+  tag: string
+  value: number
 }
 
 function toMetric(payload: DemoPlcPayload, timestamp: number): DemoPlcMetric {
@@ -52,12 +39,7 @@ async function postMetric(metric: DemoPlcMetric): Promise<void> {
 
   if (!response.ok) {
     const text = await response.text()
-    console.error('demo.plc.post_error', {
-      status: response.status,
-      statusText: response.statusText,
-      body: text.slice(0, 500),
-    })
-    return
+    throw new Error(text)
   }
 
   console.log('demo.plc.posted', { tag: metric.tag })
@@ -66,20 +48,7 @@ async function postMetric(metric: DemoPlcMetric): Promise<void> {
 export const handleDemoPlc: TopicHandler = async (topic, payload) => {
   console.log('demo.plc.received', { topic, bytes: payload.length })
 
-  let value: unknown
-
-  try {
-    value = parseJson(payload)
-  } catch (err) {
-    console.warn('demo.plc.invalid_json', { topic, err })
-    return
-  }
-
-  if (!isDemoPlcPayload(value)) {
-    console.warn('demo.plc.invalid_payload', { topic })
-    return
-  }
-
+  const value = parseJson<DemoPlcPayload>(payload)
   const metric = toMetric(value, Date.now())
   await postMetric(metric)
 }
diff --git a/app/src/handlers/edge5-modbus-v2.ts b/app/src/handlers/edge5-modbus-v2.ts
index 0897155..cd69336 100644
--- a/app/src/handlers/edge5-modbus-v2.ts
+++ b/app/src/handlers/edge5-modbus-v2.ts
@@ -43,12 +43,7 @@ async function postMetrics(metrics: MappedMetric[]): Promise<void> {
 
   if (!response.ok) {
     const text = await response.text()
-    console.error('edge5.modbus.v2.post_error', {
-      status: response.status,
-      statusText: response.statusText,
-      body: text.slice(0, 500),
-    })
-    return
+    throw new Error(text)
   }
 
   console.log('edge5.modbus.v2.posted', { count: metrics.length })
@@ -57,15 +52,7 @@ async function postMetrics(metrics: MappedMetric[]): Promise<void> {
 export const handleEdge5ModbusV2: TopicHandler = async (topic, payload) => {
   console.log('edge5.modbus.v2.received', { topic, bytes: payload.length })
 
-  let values: number[]
-
-  try {
-    values = parseValues(payload)
-  } catch (err) {
-    console.warn('edge5.modbus.v2.invalid_payload', { topic, err })
-    return
-  }
-
+  const values = parseValues(payload)
   const metrics = mapper.mapValues(values, Date.now())
   await postMetrics(metrics)
 }
diff --git a/app/src/mapping.ts b/app/src/mapping.ts
index 11b113d..c08300c 100644
--- a/app/src/mapping.ts
+++ b/app/src/mapping.ts
@@ -1,6 +1,4 @@
 import { readFileSync } from 'node:fs'
-import { isAbsolute, resolve } from 'node:path'
-import { fileURLToPath } from 'node:url'
 
 export type MappedMetric = {
   edge: string
@@ -23,88 +21,30 @@ export type MetricMapper = {
 }
 
 type MetricMapperOptions = {
+  // filePath is set as a URL from import.meta.url for bundled mappings,
+  // or as a path string resolved by Node from the process working directory.
   filePath: string | URL
 }
 
-function resolveMappingPath(filePath: string | URL): string {
-  if (filePath instanceof URL) {
-    return fileURLToPath(filePath)
-  }
-
-  return isAbsolute(filePath) ? filePath : resolve(process.cwd(), filePath)
-}
-
 function readMappingConfig(filePath: string | URL): MappingConfig {
-  const resolvedPath = resolveMappingPath(filePath)
-  let raw: unknown
-
-  try {
-    raw = JSON.parse(readFileSync(resolvedPath, 'utf8')) as unknown
-  } catch (err) {
-    throw new Error(`Failed to read mapping file ${resolvedPath}: ${String(err)}`)
-  }
-
-  if (!isMappingConfig(raw)) {
-    throw new Error(`Invalid mapping file ${resolvedPath}`)
-  }
-
-  return raw
-}
-
-function isMappingConfig(value: unknown): value is MappingConfig {
-  if (!value || typeof value !== 'object') {
-    return false
-  }
-
-  const candidate = value as Partial<MappingConfig>
-
-  return (
-    typeof candidate.edge === 'string' &&
-    candidate.edge.length > 0 &&
-    Array.isArray(candidate.tags) &&
-    candidate.tags.length > 0 &&
-    candidate.tags.every(isMappingTagEntry)
-  )
-}
-
-function isMappingTagEntry(value: unknown): value is MappingTagEntry {
-  return (
-    (typeof value === 'string' && value.length > 0) ||
-    (Boolean(value) &&
-      typeof value === 'object' &&
-      ((typeof (value as { tag?: unknown }).tag === 'string' &&
-        (value as { tag: string }).tag.length > 0) ||
-        (typeof (value as { key?: unknown }).key === 'string' &&
-          (value as { key: string }).key.length > 0)))
-  )
-}
-
-function getTag(entry: MappingTagEntry): string {
-  if (typeof entry === 'string') {
-    return entry
-  }
-
-  return 'tag' in entry ? entry.tag : entry.key
+  return JSON.parse(readFileSync(filePath, 'utf8')) as MappingConfig
 }
 
 export function createMetricMapper(options: MetricMapperOptions): MetricMapper {
   const config = readMappingConfig(options.filePath)
-  const tags = config.tags.map(getTag)
+  const tags = config.tags.map((entry) =>
+    typeof entry === 'string' ? entry : 'tag' in entry ? entry.tag : entry.key,
+  )
 
   return {
     edge: config.edge,
     tagCount: tags.length,
-    mapValues: (values, timestamp) => {
-      if (values.length !== tags.length) {
-        throw new Error(`Expected ${tags.length} values, got ${values.length}`)
-      }
-
-      return values.map((value, index) => ({
+    mapValues: (values, timestamp) =>
+      values.map((value, index) => ({
         edge: config.edge,
         timestamp,
         tag: tags[index],
         value,
-      }))
-    },
+      })),
   }
 }