diff --git a/src/lib/logging/context.ts b/src/lib/logging/context.ts
index 1ed5e019c..5ff165dff 100644
--- a/src/lib/logging/context.ts
+++ b/src/lib/logging/context.ts
@@ -1,6 +1,7 @@
 import { AsyncLocalStorage } from "node:async_hooks";
 import type { WideEvent } from "./types";
 import { WideEventBuilder } from "./event-builder";
+import { registerSourcePriorityParseObserver } from "@/lib/validations/source-priority";
 
 /** AsyncLocalStorage fuer den aktuellen Request-Kontext */
 export const eventStorage = new AsyncLocalStorage<WideEventBuilder>();
@@ -27,3 +28,12 @@ export function annotate(fields: {
     }
   }
 }
+
+// v1.4.25 Fix-G — wire the schema-parser breadcrumb into the
+// AsyncLocalStorage-backed `annotate()` only on the server. The
+// validations module stays bundle-safe for client imports; this side
+// effect runs the first time any server module imports the logging
+// context.
+registerSourcePriorityParseObserver((fields) => {
+  annotate(fields);
+});
diff --git a/src/lib/validations/source-priority.ts b/src/lib/validations/source-priority.ts
index 0afafe2aa..896650d35 100644
--- a/src/lib/validations/source-priority.ts
+++ b/src/lib/validations/source-priority.ts
@@ -34,12 +34,41 @@
  */
 import { z } from "zod/v4";
 
-import { annotate } from "@/lib/logging/context";
 import {
   measurementSourceEnum,
   measurementTypeEnum,
 } from "@/lib/validations/measurement";
 
+// v1.4.25 Fix-G — `annotate` from `@/lib/logging/context` was the
+// canonical breadcrumb for a parse failure, but the helper pulls
+// `node:async_hooks` via `AsyncLocalStorage`. Any client component that
+// reaches for a type-only export here (e.g.
+// `src/components/settings/sources-section.tsx` importing
+// `DEFAULT_SOURCE_PRIORITY`) used to drag `node:async_hooks` into the
+// browser bundle and break the Turbopack build. The parser stays in the
+// shared module — splitting it out would ripple through every callsite —
+// so the breadcrumb path now goes through a runtime-resolved callback.
+// The server logging module registers the real `annotate` on first import
+// (via `registerSourcePriorityParseObserver`); the browser leaves it as
+// the no-op default and never traces `node:async_hooks`.
+type ParseFailureObserver = (entry: {
+  meta: Record<string, unknown>;
+}) => void;
+let parseFailureObserver: ParseFailureObserver = () => {};
+
+/**
+ * Server-side opt-in for the parse-failure breadcrumb. Called once from
+ * `@/lib/logging/context` so a buggy schema-tightening that silently
+ * wipes a saved ladder still surfaces in ops dashboards. The client
+ * bundle never imports the logging module, so the observer stays the
+ * no-op default in the browser.
+ */
+export function registerSourcePriorityParseObserver(
+  observer: ParseFailureObserver,
+): void {
+  parseFailureObserver = observer;
+}
+
 /**
  * Device-type tag attached to a `Measurement` row. Mirrors
  * open-wearables (`watch | band | ring | phone | scale | other`) plus
@@ -280,7 +309,7 @@ export function parseSourcePriority(raw: unknown): ResolvedSourcePriority {
     // priorities reset?" user report. `annotate()` is a no-op outside a
     // request context, so the static settings-page render and tests
     // remain side-effect-free.
-    annotate({
+    parseFailureObserver({
       meta: {
         sourcePriority: {
           parse: "failed",