diff --git a/next.config.ts b/next.config.ts
index fd22ff481..a279dd6e0 100644
--- a/next.config.ts
+++ b/next.config.ts
@@ -121,6 +121,15 @@ const nextConfig: NextConfig = {
         destination: "/coach",
         permanent: true,
       },
+      // v1.18.0 (S3) — Sources folded into Settings → Integrations as the
+      // "Sources" sub-tab; the standalone `/settings/sources` page is gone.
+      // 301-redirect so bookmarks, the PWA's cached navigation, and the old
+      // cross-links keep resolving.
+      {
+        source: "/settings/sources",
+        destination: "/settings/integrations",
+        permanent: true,
+      },
     ];
   },
   async headers() {
diff --git a/src/app/settings/[section]/page.tsx b/src/app/settings/[section]/page.tsx
index 645e28a1a..0d5e60a15 100644
--- a/src/app/settings/[section]/page.tsx
+++ b/src/app/settings/[section]/page.tsx
@@ -17,12 +17,10 @@ import { MoodSection } from "@/components/settings/mood-section";
 import { NotificationsSection } from "@/components/settings/notifications-section";
 import { RemindersSection } from "@/components/settings/reminders-section";
 import { SectionPlaceholder } from "@/components/settings/section-placeholder";
-// v1.8.7.1 — `thresholds` (Targets) and `sources` (Sources) are two
-// separate sections again. `ThresholdsSection` renders the target-range
-// editor; `SourcesSection` (standalone mode) renders the source-priority
-// ladders. Both are served by this dynamic route.
+// v1.18.0 (S3) — `sources` no longer has a standalone route; source priority
+// renders inside Settings → Integrations as the "Sources" sub-tab.
+// `/settings/sources` 301-redirects to `/settings/integrations` (next.config.ts).
 import { ThresholdsSection } from "@/components/settings/thresholds-section";
-import { SourcesSection } from "@/components/settings/sources-section";
 import {
   SETTINGS_SECTION_SLUGS,
   isSettingsSectionSlug,
@@ -32,7 +30,7 @@ import { SettingsShell } from "@/components/settings/settings-shell";
 
 /**
  * Dynamic settings section route. Each of the `SETTINGS_SECTION_SLUGS`
- * (16 today — 12 nav-visible sections plus the four routable-but-hidden
+ * (15 today — 11 nav-visible sections plus the four routable-but-hidden
  * Layout child editors) is pre-rendered at build via
  * `generateStaticParams()` so the URLs are
  * statically known to Next.js, while the `dynamicParams = false` flag below
@@ -64,7 +62,6 @@ const SECTION_COMPONENTS: Record<
   medications: MedicationsSection,
   mood: MoodSection,
   thresholds: ThresholdsSection,
-  sources: () => <SourcesSection />,
   api: ApiSection,
   export: ExportSection,
   advanced: AdvancedSection,
diff --git a/src/components/settings/__tests__/settings-shell.test.tsx b/src/components/settings/__tests__/settings-shell.test.tsx
index ddca9005d..e9513b823 100644
--- a/src/components/settings/__tests__/settings-shell.test.tsx
+++ b/src/components/settings/__tests__/settings-shell.test.tsx
@@ -45,9 +45,10 @@ describe("SETTINGS_SECTION_SLUGS", () => {
     // `api` and `advanced` so every "give me my data out" path lives in
     // one place.
     // v1.4.25 W5e added `sources` between `thresholds` and `ai`; v1.4.34
-    // IW-D merged it into `thresholds`.
-    // v1.8.7.1 — `sources` (Sources) is its own slug again, sitting
-    // between `thresholds` (Targets) and `ai`.
+    // IW-D merged it into `thresholds`; v1.8.7.1 split it back out.
+    // v1.18.0 (S3) — `sources` is no longer a standalone slug: source
+    // priority folded into Settings → Integrations as the "Sources"
+    // sub-tab. `/settings/sources` 301-redirects to `/settings/integrations`.
     // v1.15.18 — `insights` sits between `dashboard` and `thresholds`: the
     // overview-arrange + pill-sort customise surface for `/insights`.
     // v1.16.10 — `medications` sits between `insights` and `thresholds`:
@@ -77,7 +78,6 @@ describe("SETTINGS_SECTION_SLUGS", () => {
       "medications",
       "mood",
       "thresholds",
-      "sources",
       "ai",
       "api",
       "export",
@@ -211,13 +211,11 @@ describe("<SettingsShell>", () => {
     // About is back in the settings nav as the last entry (it also
     // stays linked from the sidebar user-card dropdown).
     expect(html).toContain('href="/settings/about"');
-    // v1.8.7.1 — Targets and Sources are two separate nav entries again.
+    // v1.18.0 (S3) — Targets keeps its own nav entry; Sources folded into
+    // Integrations as a sub-tab, so it is no longer a standalone nav entry.
     expect(html).toContain('href="/settings/thresholds"');
-    expect(html).toContain('href="/settings/sources"');
+    expect(html).not.toContain('href="/settings/sources"');
     expect(html).toContain("Targets");
-    // v1.12.0 — the source-priority entry adopts the canonical
-    // "Source priority" / "Quellen-Priorität" label (handover §5).
-    expect(html).toContain("Source priority");
   });
 
   it("resolves every section title via the i18n provider — German", () => {
@@ -235,10 +233,9 @@ describe("<SettingsShell>", () => {
     expect(html).toContain("Layout &amp; Personalisierung");
     expect(html).not.toContain('href="/settings/medications"');
     expect(html).not.toContain('href="/settings/mood"');
-    // v1.8.7.1 — Targets and Sources are two separate German nav
-    // entries again: "Zielwerte" and "Quellen".
+    // v1.18.0 (S3) — Targets keeps its German nav entry ("Zielwerte");
+    // Sources folded into Integrations as a sub-tab.
     expect(html).toContain("Zielwerte");
-    expect(html).toContain("Quellen");
     // v1.8.7.1 — the AI Insights section is named "KI-Auswertungen" in
     // German (the "KI" prefix makes the AI nature explicit).
     expect(html).toContain("KI-Auswertungen");
@@ -248,8 +245,8 @@ describe("<SettingsShell>", () => {
     // "Über diese App" (About) is back as the last in-shell nav entry
     // (the sidebar user-card dropdown keeps its own link too).
     expect(html).toContain('href="/settings/about"');
-    // v1.8.7.1 — both Targets and Sources nav entries are present.
-    expect(html).toContain('href="/settings/sources"');
+    // v1.18.0 (S3) — Sources is no longer a standalone nav entry.
+    expect(html).not.toContain('href="/settings/sources"');
   });
 
   it("does NOT surface the raw key when a translation resolves — guards against missing JSON entries", () => {
diff --git a/src/components/settings/integrations-section.tsx b/src/components/settings/integrations-section.tsx
index dfebc9b88..86e6d5ad0 100644
--- a/src/components/settings/integrations-section.tsx
+++ b/src/components/settings/integrations-section.tsx
@@ -11,6 +11,10 @@
  *      per-channel status surface (moved here from Settings → Notifications,
  *      where it never belonged: channels are delivery providers, not
  *      reminder preferences). See `notification-channels-panel.tsx`.
+ *   3. Sources — the per-metric source-priority + device-type ladders that
+ *      decide which connection wins when two report the same metric. Folded in
+ *      from the former standalone `/settings/sources` page. See
+ *      `sources-section.tsx` (sub-tab mode).
  *
  * `parseOAuthOutcome` / `oauthReasonKey` are re-exported from
  * `connections-panel.tsx` so existing unit-test imports keep resolving.
@@ -21,6 +25,7 @@ import { useState } from "react";
 import { Tabs, TabsContent, TabsList, TabsTrigger } from "@/components/ui/tabs";
 import { ConnectionsPanel } from "@/components/settings/integrations/connections-panel";
 import { NotificationChannelsPanel } from "@/components/settings/integrations/notification-channels-panel";
+import { SourcesSection } from "@/components/settings/sources-section";
 import { useTranslations } from "@/lib/i18n/context";
 
 export {
@@ -28,7 +33,7 @@ export {
   oauthReasonKey,
 } from "@/components/settings/integrations/connections-panel";
 
-type IntegrationsTab = "connections" | "channels";
+type IntegrationsTab = "connections" | "channels" | "sources";
 
 export function IntegrationsSection() {
   const { t } = useTranslations();
@@ -59,6 +64,9 @@ export function IntegrationsSection() {
           <TabsTrigger value="channels">
             {t("settings.sections.integrations.tabs.channels")}
           </TabsTrigger>
+          <TabsTrigger value="sources">
+            {t("settings.sections.integrations.tabs.sources")}
+          </TabsTrigger>
         </TabsList>
 
         <TabsContent value="connections">
@@ -67,6 +75,9 @@ export function IntegrationsSection() {
         <TabsContent value="channels">
           <NotificationChannelsPanel />
         </TabsContent>
+        <TabsContent value="sources">
+          <SourcesSection variant="subtab" />
+        </TabsContent>
       </Tabs>
     </section>
   );
diff --git a/src/components/settings/section-placeholder.tsx b/src/components/settings/section-placeholder.tsx
index 846d3c3af..9bf8765b0 100644
--- a/src/components/settings/section-placeholder.tsx
+++ b/src/components/settings/section-placeholder.tsx
@@ -18,7 +18,6 @@ import {
   Download,
   Info,
   KeyRound,
-  Layers,
   LayoutDashboard,
   Link2,
   Pill,
@@ -47,7 +46,6 @@ const SLUG_ICON: Record<SettingsSectionSlug, LucideIcon> = {
   medications: Pill,
   mood: Smile,
   thresholds: SlidersHorizontal,
-  sources: Layers,
   ai: Sparkles,
   api: KeyRound,
   export: Download,
diff --git a/src/components/settings/section-slugs.ts b/src/components/settings/section-slugs.ts
index b2e65c233..96dc02271 100644
--- a/src/components/settings/section-slugs.ts
+++ b/src/components/settings/section-slugs.ts
@@ -6,13 +6,12 @@
  * graph.
  */
 
-// v1.8.7.1 — `thresholds` (Targets) and `sources` (Sources) are again two
-// separate settings pages, each its own left-nav entry and route. They were
-// merged into one "Targets & Sources" page in v1.4.34 IW-D, but the two
-// editors drive distinct mutation flows (`/api/user/thresholds` vs
-// `/api/auth/me/source-priority`) and reading them as one page made the
-// surface long; splitting them back keeps each concern self-contained.
-// Both slugs are served by the dynamic `[section]` route below.
+// v1.18.0 (S3) — `sources` is no longer a standalone slug. Source priority
+// folded into Settings → Integrations as the "Sources" sub-tab (deciding which
+// connection wins when two report the same metric is an Integrations concern).
+// `/settings/sources` 301-redirects to `/settings/integrations` (next.config.ts).
+// `thresholds` (Targets) keeps its own left-nav entry + route, served by the
+// dynamic `[section]` route below.
 // v1.16.10 — `medications` sits after `insights`: the customise surface
 // for the /medications list (view preference + manual order), following
 // the dashboard / insights pattern of a dedicated settings section
@@ -46,7 +45,6 @@ export const SETTINGS_SECTION_SLUGS = [
   "medications",
   "mood",
   "thresholds",
-  "sources",
   "ai",
   "api",
   "export",
diff --git a/src/components/settings/settings-shell.tsx b/src/components/settings/settings-shell.tsx
index 1c5c14309..12f28598a 100644
--- a/src/components/settings/settings-shell.tsx
+++ b/src/components/settings/settings-shell.tsx
@@ -24,7 +24,6 @@ import {
   Download,
   Info,
   KeyRound,
-  Layers,
   LayoutDashboard,
   Link2,
   Settings2,
@@ -74,10 +73,10 @@ interface SettingsSection {
  * settings navigation. It is now both a regular (last) shell entry and
  * a user-card dropdown item ("Über HealthLog" / "About HealthLog").
  *
- * v1.8.7.1 — `thresholds` (Targets) and `sources` (Sources) are two
- * separate sidebar entries again (merged into a single "Targets &
- * Sources" page in v1.4.34 IW-D, split back here). Both are served by
- * the dynamic `[section]` route.
+ * v1.18.0 (S3) — `sources` is no longer a sidebar entry: source priority
+ * folded into Settings → Integrations as the "Sources" sub-tab.
+ * `thresholds` (Targets) keeps its own entry, served by the dynamic
+ * `[section]` route.
  */
 export const SETTINGS_SECTIONS: readonly SettingsSection[] = [
   { slug: "account", titleKey: "settings.sections.account.title", icon: User },
@@ -122,11 +121,6 @@ export const SETTINGS_SECTIONS: readonly SettingsSection[] = [
     titleKey: "settings.sections.thresholds.title",
     icon: SlidersHorizontal,
   },
-  {
-    slug: "sources",
-    titleKey: "settings.sections.sources.title",
-    icon: Layers,
-  },
   { slug: "ai", titleKey: "settings.sections.ai.title", icon: Sparkles },
   { slug: "api", titleKey: "settings.sections.api.title", icon: KeyRound },
   {
diff --git a/src/components/settings/sources-section.tsx b/src/components/settings/sources-section.tsx
index eb5b44310..e490ae727 100644
--- a/src/components/settings/sources-section.tsx
+++ b/src/components/settings/sources-section.tsx
@@ -111,18 +111,31 @@ const DEVICE_TYPE_LABEL_KEYS: Record<DeviceType, string> = {
   unknown: "settings.sections.sources.deviceLabels.unknown",
 };
 
+export interface SourcesSectionProps {
+  /**
+   * `"standalone"` (the default) renders the full page header + the
+   * cross-link back to Integrations — the shape used while Sources had its
+   * own `/settings/sources` route. `"subtab"` (v1.18.0 S3) suppresses both:
+   * Sources now renders inside the Integrations → Sources sub-tab, so the
+   * page header is the parent section's and a cross-link back to the page
+   * that already contains it would be circular.
+   */
+  variant?: "standalone" | "subtab";
+}
+
 /**
- * `<SourcesSection>` — route-level wrapper for `/settings/sources`
- * (the "Sources" / "Quellen" page).
+ * `<SourcesSection>` — the per-metric source-priority + device-type ladders.
  *
- * v1.8.7.1 — Sources is its own settings page again (it was merged into
- * the combined "Targets & Sources" page under `/settings/thresholds` in
- * v1.4.34 IW-D). The section renders its own page header (h1 + subtitle)
- * and owns the per-metric source-priority + device-type ladders.
+ * v1.18.0 (S3) — Sources folded into Settings → Integrations as the "Sources"
+ * sub-tab (`variant="subtab"`), since deciding which connection wins when two
+ * report the same metric is an Integrations concern. The standalone
+ * `/settings/sources` route is gone; `/settings/sources` 301-redirects to
+ * `/settings/integrations` (see `next.config.ts`).
  */
-export function SourcesSection() {
+export function SourcesSection({ variant = "standalone" }: SourcesSectionProps = {}) {
   const { t } = useTranslations();
   const queryClient = useQueryClient();
+  const isSubtab = variant === "subtab";
 
   const { data: remote, isLoading } = useQuery({
     queryKey: queryKeys.sourcePriority(),
@@ -285,26 +298,35 @@ export function SourcesSection() {
       aria-labelledby="settings-section-sources-title"
       className="space-y-6"
     >
-      <header className="space-y-1">
-        <h1 id="settings-section-sources-title" className="sr-only">
-          {t("settings.sections.sources.title")}
-        </h1>
+      {isSubtab ? (
+        // Sub-tab mode: the Integrations section owns the page header, and a
+        // cross-link back to the page that already contains this tab would be
+        // circular. Surface only the one-line description.
         <p className="text-muted-foreground text-sm">
           {t("settings.sections.sources.description")}
         </p>
-        {/* Cross-link back to Settings → Integrations — the page that
-            actually adds / removes the sources this ladder ranks. */}
-        <p className="text-muted-foreground text-xs">
-          {t("settings.sections.sources.integrationsHint")}{" "}
-          <Link
-            href="/settings/integrations"
-            className="text-primary underline underline-offset-2"
-            data-slot="sources-integrations-cross-link"
-          >
-            {t("settings.sections.sources.integrationsHintLink")}
-          </Link>
-        </p>
-      </header>
+      ) : (
+        <header className="space-y-1">
+          <h1 id="settings-section-sources-title" className="sr-only">
+            {t("settings.sections.sources.title")}
+          </h1>
+          <p className="text-muted-foreground text-sm">
+            {t("settings.sections.sources.description")}
+          </p>
+          {/* Cross-link back to Settings → Integrations — the page that
+              actually adds / removes the sources this ladder ranks. */}
+          <p className="text-muted-foreground text-xs">
+            {t("settings.sections.sources.integrationsHint")}{" "}
+            <Link
+              href="/settings/integrations"
+              className="text-primary underline underline-offset-2"
+              data-slot="sources-integrations-cross-link"
+            >
+              {t("settings.sections.sources.integrationsHintLink")}
+            </Link>
+          </p>
+        </header>
+      )}
 
       <div className="bg-card border-border space-y-4 rounded-xl border p-4 sm:p-6">
         <SettingsCardHeader