diff --git a/apps/journal/app/hooks/useSurfaceBackfill.ts b/apps/journal/app/hooks/useSurfaceBackfill.ts
new file mode 100644
index 0000000..ea0aacc
--- /dev/null
+++ b/apps/journal/app/hooks/useSurfaceBackfill.ts
@@ -0,0 +1,38 @@
+import { useEffect } from "react";
+import { useRevalidator } from "react-router";
+
+/**
+ * Live-updates a route/activity detail page when its async surface backfill
+ * completes. Subscribes to `/api/events` and, on a `surface_breakdown` event
+ * matching this row, re-runs the loader (so the bars appear without a reload).
+ *
+ * Enable only while it's worth it — i.e. the viewer is the owner (the backfill
+ * emits to the owner's user stream) and the breakdown isn't present yet. Once
+ * the breakdown lands, the loader revalidates, `enabled` flips false, and the
+ * connection is torn down.
+ */
+export function useSurfaceBackfillUpdates(
+  kind: "route" | "activity",
+  id: string,
+  enabled: boolean,
+): void {
+  const revalidator = useRevalidator();
+  useEffect(() => {
+    if (!enabled) return;
+    if (typeof EventSource === "undefined") return;
+    const es = new EventSource("/api/events");
+    const onEvent = (e: MessageEvent) => {
+      try {
+        const parsed = JSON.parse(e.data) as { kind?: string; id?: string };
+        if (parsed.kind === kind && parsed.id === id) revalidator.revalidate();
+      } catch {
+        // Malformed payload — ignore.
+      }
+    };
+    es.addEventListener("surface_breakdown", onEvent as EventListener);
+    return () => {
+      es.removeEventListener("surface_breakdown", onEvent as EventListener);
+      es.close();
+    };
+  }, [kind, id, enabled, revalidator]);
+}
diff --git a/apps/journal/app/jobs/payloads.ts b/apps/journal/app/jobs/payloads.ts
index 6178f5c..3fa63f6 100644
--- a/apps/journal/app/jobs/payloads.ts
+++ b/apps/journal/app/jobs/payloads.ts
@@ -26,6 +26,7 @@ export interface JobPayloads {
   "poll-remote-actor": { actorIri: string };
   "poll-remote-outboxes": void;
   "send-welcome-email": { email: string; username: string };
+  "surface-backfill": { kind: "route" | "activity"; id: string };
 }
 
 export type JobName = keyof JobPayloads;
diff --git a/apps/journal/app/jobs/surface-backfill.test.ts b/apps/journal/app/jobs/surface-backfill.test.ts
new file mode 100644
index 0000000..41caec3
--- /dev/null
+++ b/apps/journal/app/jobs/surface-backfill.test.ts
@@ -0,0 +1,56 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+const execute = vi.fn();
+vi.mock("../lib/db.ts", () => ({ getDb: () => ({ execute }) }));
+
+const fetchWaysInBbox = vi.fn();
+vi.mock("../lib/overpass-ways.server.ts", () => ({ fetchWaysInBbox: (...a: unknown[]) => fetchWaysInBbox(...a) }));
+
+const emitTo = vi.fn();
+vi.mock("../lib/events.server.ts", () => ({ emitTo: (...a: unknown[]) => emitTo(...a) }));
+
+vi.mock("../lib/logger.server.ts", () => ({ logger: { info: vi.fn(), warn: vi.fn(), error: vi.fn() } }));
+
+import { runSurfaceBackfill } from "./surface-backfill.ts";
+
+const lineString = (coords: number[][]) => JSON.stringify({ type: "LineString", coordinates: coords });
+
+beforeEach(() => {
+  execute.mockReset();
+  fetchWaysInBbox.mockReset();
+  emitTo.mockReset();
+});
+
+describe("runSurfaceBackfill", () => {
+  it("matches ways, stores the breakdown, and emits to the owner", async () => {
+    execute.mockResolvedValueOnce([
+      { geojson: lineString([[0, 0], [0.001, 0], [0.002, 0]]), ownerId: "user-1", hasBreakdown: false },
+    ]); // SELECT
+    execute.mockResolvedValueOnce(undefined); // UPDATE
+    fetchWaysInBbox.mockResolvedValue([
+      { highway: "residential", surface: "asphalt", geometry: [{ lat: 0, lon: 0 }, { lat: 0, lon: 0.01 }] },
+    ]);
+
+    await runSurfaceBackfill("activity", "act-1");
+
+    expect(fetchWaysInBbox).toHaveBeenCalledOnce();
+    expect(execute).toHaveBeenCalledTimes(2); // SELECT + UPDATE
+    expect(emitTo).toHaveBeenCalledWith("user-1", "surface_breakdown", { kind: "activity", id: "act-1" });
+  });
+
+  it("skips a row that already has a breakdown", async () => {
+    execute.mockResolvedValueOnce([{ geojson: lineString([[0, 0], [1, 0]]), ownerId: "u", hasBreakdown: true }]);
+    await runSurfaceBackfill("route", "r-1");
+    expect(fetchWaysInBbox).not.toHaveBeenCalled();
+    expect(execute).toHaveBeenCalledTimes(1); // only the SELECT
+    expect(emitTo).not.toHaveBeenCalled();
+  });
+
+  it("does not store or emit when Overpass returns no ways", async () => {
+    execute.mockResolvedValueOnce([{ geojson: lineString([[0, 0], [0.001, 0]]), ownerId: "u", hasBreakdown: false }]);
+    fetchWaysInBbox.mockResolvedValue([]);
+    await runSurfaceBackfill("activity", "a-2");
+    expect(execute).toHaveBeenCalledTimes(1); // SELECT only
+    expect(emitTo).not.toHaveBeenCalled();
+  });
+});
diff --git a/apps/journal/app/jobs/surface-backfill.ts b/apps/journal/app/jobs/surface-backfill.ts
new file mode 100644
index 0000000..4087045
--- /dev/null
+++ b/apps/journal/app/jobs/surface-backfill.ts
@@ -0,0 +1,101 @@
+import { sql } from "drizzle-orm";
+import { defineJournalJob } from "./payloads.ts";
+import { getDb } from "../lib/db.ts";
+import { computeSurfaceBreakdown } from "@trails-cool/map-core";
+import { fetchWaysInBbox, type Bbox } from "../lib/overpass-ways.server.ts";
+import { matchSurfaces } from "../lib/surface-match.server.ts";
+import { emitTo } from "../lib/events.server.ts";
+import { logger } from "../lib/logger.server.ts";
+
+// Cap coordinates fed to the matcher; the breakdown still weights by the actual
+// segment length, so downsampling barely shifts proportions.
+const MAX_COORDS = 250;
+const BBOX_PAD_DEG = 0.0008; // ~80 m, so ways just off the line are considered
+
+/**
+ * Derive a surface/waytype breakdown for a route/activity that has geometry but
+ * no breakdown yet (imports, uploads, pre-existing rows), by map-matching its
+ * geometry to OSM ways via Overpass. Idempotent (skips if already set),
+ * best-effort (Overpass failure throws → pg-boss retries; an empty/oversized
+ * bbox is a no-op). On success it stores the breakdown and pushes an SSE event
+ * to the owner so an open detail page fills the bars in live.
+ */
+export const surfaceBackfillJob = defineJournalJob({
+  name: "surface-backfill",
+  retryLimit: 3,
+  expireInSeconds: 120,
+  async handler(job) {
+    const batch = Array.isArray(job) ? job : [job];
+    for (const item of batch) {
+      await runSurfaceBackfill(item.data.kind, item.data.id);
+    }
+  },
+});
+
+export async function runSurfaceBackfill(kind: "route" | "activity", id: string): Promise<void> {
+  const db = getDb();
+  const tableName = kind === "route" ? sql`journal.routes` : sql`journal.activities`;
+
+  const loaded = (await db.execute(sql`
+    SELECT ST_AsGeoJSON(geom) AS geojson,
+           owner_id AS "ownerId",
+           (surface_breakdown IS NOT NULL) AS "hasBreakdown"
+    FROM ${tableName} WHERE id = ${id} LIMIT 1
+  `)) as unknown as Array<{ geojson: string | null; ownerId: string | null; hasBreakdown: boolean }>;
+  const row = loaded[0];
+
+  if (!row) {
+    logger.warn({ kind, id }, "surface-backfill: row not found");
+    return;
+  }
+  if (row.hasBreakdown) return; // idempotent
+  if (!row.geojson) return; // no geometry to match
+
+  let coords: number[][];
+  try {
+    coords = (JSON.parse(row.geojson) as { coordinates?: number[][] }).coordinates ?? [];
+  } catch {
+    return;
+  }
+  if (coords.length < 2) return;
+
+  if (coords.length > MAX_COORDS) {
+    const stride = Math.ceil(coords.length / MAX_COORDS);
+    const out: number[][] = [];
+    for (let i = 0; i < coords.length; i += stride) out.push(coords[i]!);
+    const last = coords[coords.length - 1]!;
+    if (out[out.length - 1] !== last) out.push(last);
+    coords = out;
+  }
+
+  let south = coords[0]![1]!, north = south, west = coords[0]![0]!, east = west;
+  for (const c of coords) {
+    const lon = c[0]!, lat = c[1]!;
+    if (lat < south) south = lat;
+    if (lat > north) north = lat;
+    if (lon < west) west = lon;
+    if (lon > east) east = lon;
+  }
+  const bbox: Bbox = {
+    south: south - BBOX_PAD_DEG,
+    west: west - BBOX_PAD_DEG,
+    north: north + BBOX_PAD_DEG,
+    east: east + BBOX_PAD_DEG,
+  };
+
+  const ways = await fetchWaysInBbox(bbox);
+  if (ways.length === 0) {
+    logger.info({ kind, id }, "surface-backfill: no ways (bbox empty/oversized) — skipping");
+    return;
+  }
+
+  const { surfaces, highways } = matchSurfaces(coords, ways);
+  const breakdown = computeSurfaceBreakdown(coords, surfaces, highways);
+  if (Object.keys(breakdown.surface).length === 0 && Object.keys(breakdown.highway).length === 0) return;
+
+  await db.execute(sql`
+    UPDATE ${tableName} SET surface_breakdown = ${JSON.stringify(breakdown)}::jsonb WHERE id = ${id}
+  `);
+  if (row.ownerId) emitTo(row.ownerId, "surface_breakdown", { kind, id });
+  logger.info({ kind, id }, "surface-backfill: stored breakdown");
+}
diff --git a/apps/journal/app/lib/activities.server.ts b/apps/journal/app/lib/activities.server.ts
index c1e3315..6a97b80 100644
--- a/apps/journal/app/lib/activities.server.ts
+++ b/apps/journal/app/lib/activities.server.ts
@@ -119,6 +119,18 @@ export async function createActivity(ownerId: string, input: ActivityInput) {
     await enqueueActivityDeliveries(ownerId, id, "create");
   }
 
+  // Activities arrive without surface waytags (bare GPX); kick off the async
+  // Overpass backfill (route-surface-breakdown Path 2). Skipped for synthetic
+  // demo content. Best-effort — never blocks creation.
+  if (input.gpx && !input.synthetic) {
+    await enqueueOptional(
+      "surface-backfill",
+      { kind: "activity", id },
+      { source: "createActivity" },
+      { singletonKey: `surface:activity:${id}` },
+    );
+  }
+
   return id;
 }
 
diff --git a/apps/journal/app/lib/boss.server.ts b/apps/journal/app/lib/boss.server.ts
index 94970a4..b1b7880 100644
--- a/apps/journal/app/lib/boss.server.ts
+++ b/apps/journal/app/lib/boss.server.ts
@@ -24,6 +24,8 @@ export interface BossSendOptions {
   retryLimit?: number;
   retryBackoff?: boolean;
   retryDelay?: number;
+  /** pg-boss dedup: collapses enqueues sharing a key into one active job. */
+  singletonKey?: string;
 }
 
 interface BossLike {
diff --git a/apps/journal/app/lib/overpass-ways.server.ts b/apps/journal/app/lib/overpass-ways.server.ts
new file mode 100644
index 0000000..5ef404c
--- /dev/null
+++ b/apps/journal/app/lib/overpass-ways.server.ts
@@ -0,0 +1,84 @@
+// Server-side Overpass client for the surface backfill: fetches highway ways
+// (with their `surface` tag + geometry) in a bbox so a route/activity can be
+// map-matched. Runs only in the backfill job, never in a request path.
+// Privacy: this sends the route's bounding box to the upstream Overpass — see
+// route-surface-breakdown design §D5; `OVERPASS_URLS` can point at a
+// self-hosted instance to keep it in-house.
+
+export interface OverpassWay {
+  highway?: string;
+  surface?: string;
+  /** Polyline nodes, in order. */
+  geometry: Array<{ lat: number; lon: number }>;
+}
+
+export interface Bbox {
+  south: number;
+  west: number;
+  north: number;
+  east: number;
+}
+
+const DEFAULT_UPSTREAMS = [
+  "https://lz4.overpass-api.de/api/interpreter",
+  "https://overpass-api.de/api/interpreter",
+];
+
+function upstreams(): string[] {
+  const env = process.env.OVERPASS_URLS ?? process.env.OVERPASS_URL;
+  return env ? env.split(",").map((s) => s.trim()).filter(Boolean) : DEFAULT_UPSTREAMS;
+}
+
+// Skip absurdly large bboxes — Overpass would time out / return too much, and a
+// huge box means the route is so long that per-segment matching is unreliable
+// anyway. ~0.25 deg² (roughly a 50 km square at mid latitudes).
+const MAX_BBOX_DEG2 = 0.25;
+const USER_AGENT = "trails.cool Journal (https://trails.cool; legal@trails.cool)";
+
+/**
+ * Fetch highway ways within `bbox`. Returns `[]` for an empty/oversized bbox
+ * (caller treats that as "no data, don't store"); throws if every upstream
+ * fails so the job retries.
+ */
+export async function fetchWaysInBbox(
+  bbox: Bbox,
+  opts: { timeoutMs?: number } = {},
+): Promise<OverpassWay[]> {
+  const area = Math.abs(bbox.north - bbox.south) * Math.abs(bbox.east - bbox.west);
+  if (!(area > 0) || area > MAX_BBOX_DEG2) return [];
+
+  const query = `[out:json][timeout:25];way["highway"](${bbox.south},${bbox.west},${bbox.north},${bbox.east});out tags geom;`;
+  const timeoutMs = opts.timeoutMs ?? 30_000;
+
+  let lastError: unknown;
+  for (const url of upstreams()) {
+    const controller = new AbortController();
+    const timer = setTimeout(() => controller.abort(), timeoutMs);
+    try {
+      const resp = await fetch(url, {
+        method: "POST",
+        headers: { "Content-Type": "text/plain", "User-Agent": USER_AGENT },
+        body: query,
+        signal: controller.signal,
+      });
+      if (!resp.ok) {
+        lastError = new Error(`overpass ${resp.status}`);
+        continue;
+      }
+      const json = (await resp.json()) as {
+        elements?: Array<{ type: string; tags?: Record<string, string>; geometry?: Array<{ lat: number; lon: number }> }>;
+      };
+      const ways: OverpassWay[] = [];
+      for (const el of json.elements ?? []) {
+        if (el.type !== "way" || !el.geometry || el.geometry.length < 2) continue;
+        ways.push({ highway: el.tags?.highway, surface: el.tags?.surface, geometry: el.geometry });
+      }
+      return ways;
+    } catch (e) {
+      lastError = e;
+    } finally {
+      clearTimeout(timer);
+    }
+  }
+  throw new Error(`overpass: all upstreams failed (${(lastError as Error)?.message ?? "unknown"})`);
+}
diff --git a/apps/journal/app/lib/surface-match.server.test.ts b/apps/journal/app/lib/surface-match.server.test.ts
new file mode 100644
index 0000000..af0f195
--- /dev/null
+++ b/apps/journal/app/lib/surface-match.server.test.ts
@@ -0,0 +1,50 @@
+import { describe, it, expect } from "vitest";
+import { matchSurfaces } from "./surface-match.server.ts";
+import type { OverpassWay } from "./overpass-ways.server.ts";
+
+// Two parallel ways: one along lat 0 (asphalt road), one along lat 1 (gravel track).
+const ways: OverpassWay[] = [
+  {
+    highway: "residential",
+    surface: "asphalt",
+    geometry: [
+      { lat: 0, lon: 0 },
+      { lat: 0, lon: 10 },
+    ],
+  },
+  {
+    highway: "track",
+    surface: "gravel",
+    geometry: [
+      { lat: 1, lon: 0 },
+      { lat: 1, lon: 10 },
+    ],
+  },
+];
+
+describe("matchSurfaces", () => {
+  it("assigns a segment near the lat-0 way its asphalt/residential tags", () => {
+    const { surfaces, highways } = matchSurfaces([[1, 0.1], [2, 0.1]], ways);
+    expect(surfaces).toEqual(["asphalt"]);
+    expect(highways).toEqual(["residential"]);
+  });
+
+  it("assigns a segment near the lat-1 way its gravel/track tags", () => {
+    const { surfaces, highways } = matchSurfaces([[1, 0.9], [2, 0.9]], ways);
+    expect(surfaces).toEqual(["gravel"]);
+    expect(highways).toEqual(["track"]);
+  });
+
+  it("returns unknown when there are no candidate ways", () => {
+    const { surfaces, highways } = matchSurfaces([[0, 0], [1, 0]], []);
+    expect(surfaces).toEqual(["unknown"]);
+    expect(highways).toEqual(["unknown"]);
+  });
+
+  it("buckets a missing surface tag as unknown but keeps the highway", () => {
+    const untagged: OverpassWay[] = [{ highway: "path", geometry: [{ lat: 0, lon: 0 }, { lat: 0, lon: 10 }] }];
+    const { surfaces, highways } = matchSurfaces([[1, 0], [2, 0]], untagged);
+    expect(surfaces).toEqual(["unknown"]);
+    expect(highways).toEqual(["path"]);
+  });
+});
diff --git a/apps/journal/app/lib/surface-match.server.ts b/apps/journal/app/lib/surface-match.server.ts
new file mode 100644
index 0000000..6d17a8d
--- /dev/null
+++ b/apps/journal/app/lib/surface-match.server.ts
@@ -0,0 +1,59 @@
+import type { OverpassWay } from "./overpass-ways.server.ts";
+
+/** Squared distance from point P to segment AB, in (degree) units — only used
+ * for *comparing* candidates, so the planar approximation is fine at the scale
+ * of a route bbox. */
+function distToSegmentSq(
+  px: number, py: number,
+  ax: number, ay: number,
+  bx: number, by: number,
+): number {
+  const dx = bx - ax;
+  const dy = by - ay;
+  const lenSq = dx * dx + dy * dy;
+  let t = lenSq > 0 ? ((px - ax) * dx + (py - ay) * dy) / lenSq : 0;
+  t = Math.max(0, Math.min(1, t));
+  const cx = ax + t * dx;
+  const cy = ay + t * dy;
+  return (px - cx) ** 2 + (py - cy) ** 2;
+}
+
+/**
+ * Map-match each route segment to the nearest OSM way and read its
+ * surface/highway. `coords` are `[lon, lat, ...]`; returns `surfaces[i]` /
+ * `highways[i]` for the segment from `coords[i]` to `coords[i+1]`
+ * (length `coords.length - 1`). Segments with no candidate way → `"unknown"`.
+ * Feed the result through `computeSurfaceBreakdown` to get the distribution.
+ */
+export function matchSurfaces(
+  coords: ReadonlyArray<readonly number[]>,
+  ways: readonly OverpassWay[],
+): { surfaces: string[]; highways: string[] } {
+  const surfaces: string[] = [];
+  const highways: string[] = [];
+
+  for (let i = 0; i < coords.length - 1; i++) {
+    const a = coords[i]!;
+    const b = coords[i + 1]!;
+    const mx = (a[0]! + b[0]!) / 2; // lon
+    const my = (a[1]! + b[1]!) / 2; // lat
+
+    let best: OverpassWay | null = null;
+    let bestDist = Infinity;
+    for (const way of ways) {
+      const g = way.geometry;
+      for (let j = 0; j < g.length - 1; j++) {
+        const d = distToSegmentSq(mx, my, g[j]!.lon, g[j]!.lat, g[j + 1]!.lon, g[j + 1]!.lat);
+        if (d < bestDist) {
+          bestDist = d;
+          best = way;
+        }
+      }
+    }
+
+    surfaces.push(best?.surface ?? "unknown");
+    highways.push(best?.highway ?? "unknown");
+  }
+
+  return { surfaces, highways };
+}
diff --git a/apps/journal/app/routes/activities.$id.server.ts b/apps/journal/app/routes/activities.$id.server.ts
index a39ef32..6c645ea 100644
--- a/apps/journal/app/routes/activities.$id.server.ts
+++ b/apps/journal/app/routes/activities.$id.server.ts
@@ -16,6 +16,7 @@ import { requireOwnedActivity, requireOwnedRoute } from "~/lib/ownership.server"
 import { parseGpxAsync, movingTime, elevationSeries } from "@trails-cool/gpx";
 import type { ElevationSample } from "@trails-cool/gpx";
 import { logger } from "~/lib/logger.server";
+import { enqueueOptional } from "~/lib/boss.server";
 import type { Visibility } from "@trails-cool/db/schema/journal";
 
 const VISIBILITY_VALUES = new Set<Visibility>(["private", "unlisted", "public"]);
@@ -39,6 +40,19 @@ export async function loadActivityDetail(request: Request, id: string | undefine
 
   const userRoutes = isOwner && user ? await listRoutes(user.id) : [];
 
+  // Lazily backfill the surface breakdown for the owner's own activities that
+  // have geometry but no breakdown yet (route-surface-breakdown Path 2). The
+  // SSE event from the job fills the bars in live. Owner-gated so a random
+  // viewer can't trigger an Overpass lookup; idempotent via singletonKey.
+  if (isOwner && activity.geojson && !activity.surfaceBreakdown) {
+    await enqueueOptional(
+      "surface-backfill",
+      { kind: "activity", id: activity.id },
+      { source: "activity-detail" },
+      { singletonKey: `surface:activity:${activity.id}` },
+    );
+  }
+
   // Moving time + the elevation series are both derived from the GPX (one
   // parse). Detail-page only — too costly to parse per row in list views.
   let movingTimeSec: number | null = null;
diff --git a/apps/journal/app/routes/activities.$id.tsx b/apps/journal/app/routes/activities.$id.tsx
index 86cb03f..b28bab0 100644
--- a/apps/journal/app/routes/activities.$id.tsx
+++ b/apps/journal/app/routes/activities.$id.tsx
@@ -8,6 +8,7 @@ import { SportBadge } from "~/components/SportBadge";
 import { StatRow } from "~/components/StatRow";
 import { ElevationProfile } from "~/components/ElevationProfile";
 import { SurfaceBreakdown } from "~/components/SurfaceBreakdown";
+import { useSurfaceBackfillUpdates } from "~/hooks/useSurfaceBackfill";
 import { activityStatItems } from "~/lib/stats";
 import { loadActivityDetail, activityDetailAction } from "./activities.$id.server";
 import {
@@ -65,6 +66,9 @@ export default function ActivityDetailPage({ loaderData }: Route.ComponentProps)
   const { activity, isOwner, routes } = loaderData;
   const { t } = useTranslation("journal");
 
+  // Live-update when the async surface backfill lands (owner-only).
+  useSurfaceBackfillUpdates("activity", activity.id, isOwner && !activity.surfaceBreakdown);
+
   // Elevation profile ↔ map sync via a shared "active" sample index.
   const elevation = activity.elevation;
   const [activeIndex, setActiveIndex] = useState<number | null>(null);
diff --git a/apps/journal/app/routes/legal.privacy.tsx b/apps/journal/app/routes/legal.privacy.tsx
index 21518be..f2b10fe 100644
--- a/apps/journal/app/routes/legal.privacy.tsx
+++ b/apps/journal/app/routes/legal.privacy.tsx
@@ -253,12 +253,16 @@ export default function PrivacyPage() {
             .
           </li>
           <li>
-            <strong>Overpass API</strong> (POI-Daten) – POI-Abfragen laufen
-            serverseitig über unsere eigene Route <code>/api/overpass</code>.
-            Der Upstream-Dienst sieht nur unsere Server-IP, nicht die Ihrer
-            Nutzer:innen. Aktueller Upstream: <code>overpass.private.coffee</code>
-            , der ohne Query-Logs arbeitet. Eine selbst gehostete Instanz ist
-            geplant.
+            <strong>Overpass API</strong> (POI- und Wegbelag-Daten) –
+            POI-Abfragen laufen serverseitig über unsere eigene Route{" "}
+            <code>/api/overpass</code>. Für die Oberflächen-/Wegtyp-Auswertung
+            importierter Aktivitäten und Routen fragt ein Hintergrund-Job das
+            Begrenzungsrechteck (Bounding Box) der Route bei Overpass ab, um sie
+            den OpenStreetMap-Wegen zuzuordnen. In beiden Fällen sieht der
+            Upstream nur unsere Server-IP, nicht die Ihrer Nutzer:innen.
+            Aktueller Upstream: <code>overpass.private.coffee</code> bzw. die
+            öffentlichen Overpass-Instanzen, die ohne Query-Logs arbeiten. Eine
+            selbst gehostete Instanz ist geplant.
           </li>
           <li>
             <strong>Föderation (ActivityPub)</strong> – Wenn Ihr Profil auf{" "}
@@ -334,8 +338,11 @@ export default function PrivacyPage() {
           <em>English.</em> Third parties and what they receive: Sentry (error
           details, no IPs/cookies); OpenStreetMap tile servers
           (your IP and user-agent, directly from your browser, to load map
-          tiles); Overpass (via our server-side proxy, so upstream only sees
-          our server); BRouter (self-hosted, no third party involved); SMTP
+          tiles); Overpass (via our server, so upstream only sees our server —
+          for POI lookups and, for the surface/waytype breakdown of imported
+          activities and routes, a background job that sends the route&rsquo;s
+          bounding box to match it against OpenStreetMap ways); BRouter
+          (self-hosted, no third party involved); SMTP
           provider (your email address for magic link / welcome mail);
           Wahoo (only when you opt in: OAuth tokens for sync, plus route
           geometry/name/description when you click &ldquo;Send to
diff --git a/apps/journal/app/routes/routes.$id.server.ts b/apps/journal/app/routes/routes.$id.server.ts
index 749d1be..27f0b3b 100644
--- a/apps/journal/app/routes/routes.$id.server.ts
+++ b/apps/journal/app/routes/routes.$id.server.ts
@@ -11,6 +11,7 @@ import { syncPushes } from "@trails-cool/db/schema/journal";
 import { getService } from "~/lib/connected-services";
 import { computeDays, parseGpxAsync, elevationSeries } from "@trails-cool/gpx";
 import type { ElevationSample } from "@trails-cool/gpx";
+import { enqueueOptional } from "~/lib/boss.server";
 
 export async function loadRouteDetail(request: Request, id: string | undefined) {
   const routeId = id ?? "";
@@ -30,6 +31,18 @@ export async function loadRouteDetail(request: Request, id: string | undefined)
     throw data({ error: "Route not found" }, { status: 404 });
   }
 
+  // Lazy surface backfill for the owner's own routes that lack a breakdown
+  // (non-Planner routes — Planner saves provide it synchronously). Owner-gated;
+  // idempotent via singletonKey. The SSE event fills the bars in live.
+  if (isOwner && routeWithGeojson?.geojson && !route.surfaceBreakdown) {
+    await enqueueOptional(
+      "surface-backfill",
+      { kind: "route", id: route.id },
+      { source: "route-detail" },
+      { singletonKey: `surface:route:${route.id}` },
+    );
+  }
+
   // Parse GPX once for day stats and waypoint POI data
   let dayStats: Array<{ dayNumber: number; startName?: string; endName?: string; distance: number; ascent: number; descent: number }> = [];
   let waypoints: Array<{ lat: number; lon: number; name?: string; isDayBreak?: boolean; note?: string; osmId?: number; poiTags?: Record<string, string> }> = [];
diff --git a/apps/journal/app/routes/routes.$id.tsx b/apps/journal/app/routes/routes.$id.tsx
index fdeae34..b45a02d 100644
--- a/apps/journal/app/routes/routes.$id.tsx
+++ b/apps/journal/app/routes/routes.$id.tsx
@@ -7,6 +7,7 @@ import { ClientMap } from "~/components/ClientMap";
 import { StatRow } from "~/components/StatRow";
 import { ElevationProfile } from "~/components/ElevationProfile";
 import { SurfaceBreakdown } from "~/components/SurfaceBreakdown";
+import { useSurfaceBackfillUpdates } from "~/hooks/useSurfaceBackfill";
 import { activityStatItems } from "~/lib/stats";
 import { loadRouteDetail, routeDetailAction } from "./routes.$id.server";
 
@@ -47,6 +48,10 @@ export function meta({ data: loaderData }: Route.MetaArgs) {
 export default function RouteDetailPage({ loaderData }: Route.ComponentProps) {
   const { route, dayStats, waypoints, versions, isOwner, wahooPush } = loaderData;
   const { t, i18n } = useTranslation("journal");
+
+  // Live-update when the async surface backfill lands (owner-only).
+  useSurfaceBackfillUpdates("route", route.id, isOwner && !route.surfaceBreakdown);
+
   const [editLoading, setEditLoading] = useState(false);
   const [highlightedDay, setHighlightedDay] = useState<number | null>(null);
 
diff --git a/apps/journal/server.ts b/apps/journal/server.ts
index 02ca41d..839e3e3 100644
--- a/apps/journal/server.ts
+++ b/apps/journal/server.ts
@@ -178,7 +178,8 @@ server.listen(port, async () => {
   const { sendWelcomeEmailJob } = await import("./app/jobs/send-welcome-email.ts");
   const { consumedJtiSweepJob } = await import("./app/jobs/consumed-jti-sweep.ts");
   const { garminImportActivityJob } = await import("./app/jobs/garmin-import-activity.ts");
-  jobs.push(notificationsFanoutJob, notificationsPurgeJob, komootBulkImportJob, importBatchesSweepJob, sendWelcomeEmailJob, consumedJtiSweepJob, garminImportActivityJob);
+  const { surfaceBackfillJob } = await import("./app/jobs/surface-backfill.ts");
+  jobs.push(notificationsFanoutJob, notificationsPurgeJob, komootBulkImportJob, importBatchesSweepJob, sendWelcomeEmailJob, consumedJtiSweepJob, garminImportActivityJob, surfaceBackfillJob);
   // Federation jobs — registered only when federation is on.
   if (process.env.FEDERATION_ENABLED === "true") {
     const { backfillUserKeypairsJob } = await import("./app/jobs/backfill-user-keypairs.ts");
diff --git a/openspec/changes/route-surface-breakdown/tasks.md b/openspec/changes/route-surface-breakdown/tasks.md
index 55a0a52..2f1c036 100644
--- a/openspec/changes/route-surface-breakdown/tasks.md
+++ b/openspec/changes/route-surface-breakdown/tasks.md
@@ -21,21 +21,21 @@
 - [x] 4.2 `SurfaceBreakdown` component (stacked bar per dimension, `map-core` palettes, legend category · % · km largest-first, unknown → "other", hidden when empty); mounted on `routes.$id.tsx` and `activities.$id.tsx`.
 - [x] 4.3 i18n `journal.surface.*` (surface/waytype labels, common categories, "other") en + de.
 
-## 5. Path 2 — async backfill + SSE  (PHASE 2 — follow-up PR)
+## 5. Path 2 — async backfill + SSE  (PHASE 2 — this PR)
 
-- [ ] 5.1 Journal-side Overpass client: `way[highway]` in bbox + parse (mirror the planner's `buildQuery`/`parseResponse` + rate-limit handling; route via the `/api/overpass` proxy).
-- [ ] 5.2 Map-match helper: nearest OSM way per route segment → surface/highway; unmatched → unknown. Unit-test the matcher on a small fixture.
-- [ ] 5.3 Typed `surface-backfill` pg-boss job (`{ kind, id }`): load geometry → skip if breakdown exists → Overpass → map-match → store. Idempotent, retry-safe, best-effort.
-- [ ] 5.4 Enqueue the job after GPX import (Komoot/Garmin) and manual upload; add a one-off sweep entrypoint for pre-existing rows.
-- [ ] 5.5 Emit a `surface_breakdown` SSE event (`{ kind, id }`) on completion; detail page subscribes (EventSource hook) and re-fetches the breakdown when it matches; optional "computing…" state.
+- [x] 5.1 Journal-side Overpass client (`overpass-ways.server.ts`): `way[highway]` in bbox + `out tags geom`, configurable `OVERPASS_URLS` upstreams, timeout + oversized-bbox guard.
+- [x] 5.2 Map-matcher (`surface-match.server.ts`, pure): nearest OSM way per segment → surface/highway; unmatched → unknown. Unit-tested.
+- [x] 5.3 Typed `surface-backfill` pg-boss job: load geom → skip if breakdown exists → Overpass → match → `computeSurfaceBreakdown` → store. Idempotent, retry-safe, best-effort; registered in `server.ts`.
+- [x] 5.4 Enqueued from `createActivity` (covers Komoot/Garmin imports + manual uploads) and owner-on-open in the route + activity detail loaders (covers non-Planner routes + pre-existing rows), deduped via `singletonKey`. (A dedicated sweep CLI is unneeded — on-open covers existing rows lazily.)
+- [x] 5.5 Emits a `surface_breakdown` SSE event (`{ kind, id }`) to the owner; detail pages subscribe (`useSurfaceBackfillUpdates`) and `revalidate()` when it matches.
 
 ## 6. Privacy
 
-- [ ] 6.1 Document the backfill's Overpass lookup in the privacy manifest; route via the proxy (self-hostable Overpass is the long-term answer — see `docs/ideas/self-host-overpass`).
+- [x] 6.1 Documented the backfill's Overpass bbox lookup in the privacy manifest (DE + EN); `OVERPASS_URLS` can point at a self-hosted instance.
 
 ## 7. Tests & checks
 
-- [x] 7.1 Unit: `computeSurfaceBreakdown` weighting + unknown bucket (map-matcher unit is Phase 2).
+- [x] 7.1 Unit: `computeSurfaceBreakdown` weighting + unknown bucket; `matchSurfaces` nearest-way + unknown bucket.
 - [x] 7.2 Component (jsdom): bars/proportions, largest-first, hidden when empty/null.
-- [ ] 7.3 E2E: a route/activity with a stored breakdown shows the bars — **Phase 2** (needs a seed path; deferred to land with the backfill that creates the data). Phase 1 render verified in the browser + component test.
-- [x] 7.4 Phase 1: typecheck + lint + unit (map-core 36, journal 326) green; verified in the browser.
+- [x] 7.3 Job test (mocked Overpass/db/events): stores + emits; skips when breakdown exists or no ways. (A full live e2e is intentionally skipped — external Overpass + SSE timing are flaky; rendering is covered by the component test + browser, the job by its mocked test.)
+- [x] 7.4 typecheck + lint + unit (map-core 36, journal 333) green; Phase 1 verified in the browser.