From fc8bfb669122058ca339072d5bc6b96623e63636 Mon Sep 17 00:00:00 2001
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Date: Tue, 7 Jul 2026 01:27:07 +0300
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---
 app/src/index.ts          |  1 +
 app/src/process-errors.ts | 57 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 app/src/process-errors.ts

diff --git a/app/src/index.ts b/app/src/index.ts
index 9fbd394..1cd4f4e 100644
--- a/app/src/index.ts
+++ b/app/src/index.ts
@@ -1,3 +1,4 @@
+import './process-errors.js'
 import './handlers/index.js'
 import './http/server.js'
 import './mqtt.js'
diff --git a/app/src/process-errors.ts b/app/src/process-errors.ts
new file mode 100644
index 0000000..4b33394
--- /dev/null
+++ b/app/src/process-errors.ts
@@ -0,0 +1,57 @@
+type ErrorWithCause = Error & {
+  cause?: unknown
+}
+
+type NodeError = Error & {
+  code?: string
+  address?: string
+  port?: number
+}
+
+// Undici кладёт системную ошибку соединения внутрь error.cause.
+function getFetchCause(error: unknown): NodeError | null {
+  if (!(error instanceof Error)) {
+    return null
+  }
+
+  const cause = (error as ErrorWithCause).cause
+  return cause instanceof Error ? (cause as NodeError) : null
+}
+
+// Обрабатываем только подсвеченный кейс: backend отказал в TCP-соединении.
+function isFetchConnectionRefused(error: unknown): boolean {
+  if (!(error instanceof Error)) {
+    return false
+  }
+
+  const cause = getFetchCause(error)
+  return error.message === 'fetch failed' && cause?.code === 'ECONNREFUSED'
+}
+
+// Логируем короткую диагностическую форму без огромного stack trace.
+function formatFetchError(error: unknown): object {
+  if (!(error instanceof Error)) {
+    return { message: String(error) }
+  }
+
+  const cause = getFetchCause(error)
+  return {
+    message: error.message,
+    cause: cause?.message,
+    code: cause?.code,
+    address: cause?.address,
+    port: cause?.port,
+  }
+}
+
+// Последний рубеж защиты для fire-and-forget fetch-запросов.
+// Если backend недоступен, Node.js 22 может превратить незахваченный
+// fetch failed / ECONNREFUSED в падение всего процесса mqtt-worker.
+process.on('unhandledRejection', (error) => {
+  if (isFetchConnectionRefused(error)) {
+    console.error('process.unhandled_fetch_refused', formatFetchError(error))
+    return
+  }
+
+  console.error('process.unhandled_rejection', error)
+})
-- 
2.49.1