diff --git a/apps/journal/app/components/SurfaceBreakdown.test.tsx b/apps/journal/app/components/SurfaceBreakdown.test.tsx
new file mode 100644
index 0000000..521bbc0
--- /dev/null
+++ b/apps/journal/app/components/SurfaceBreakdown.test.tsx
@@ -0,0 +1,40 @@
+// @vitest-environment jsdom
+import { describe, it, expect, afterEach } from "vitest";
+import { render, cleanup } from "@testing-library/react";
+import { SurfaceBreakdown } from "./SurfaceBreakdown.tsx";
+
+afterEach(cleanup);
+
+describe("SurfaceBreakdown", () => {
+  it("renders nothing without a breakdown", () => {
+    const { container } = render(<SurfaceBreakdown breakdown={null} />);
+    expect(container.firstChild).toBeNull();
+  });
+
+  it("renders nothing when every bucket is zero", () => {
+    const { container } = render(<SurfaceBreakdown breakdown={{ surface: { asphalt: 0 }, highway: {} }} />);
+    expect(container.firstChild).toBeNull();
+  });
+
+  it("renders a legend item per non-zero category with its percentage", () => {
+    const { container, getByText } = render(
+      <SurfaceBreakdown breakdown={{ surface: { asphalt: 6000, gravel: 4000 }, highway: { residential: 10000 } }} />,
+    );
+    // 2 surface + 1 waytype = 3 legend entries
+    expect(container.querySelectorAll("li")).toHaveLength(3);
+    expect(getByText(/60% · 6\.0 km/)).toBeTruthy();
+    expect(getByText(/40% · 4\.0 km/)).toBeTruthy();
+    expect(getByText(/100% · 10\.0 km/)).toBeTruthy();
+  });
+
+  it("sorts segments largest-first within a dimension", () => {
+    const { container } = render(
+      <SurfaceBreakdown breakdown={{ surface: { gravel: 3000, asphalt: 7000 }, highway: {} }} />,
+    );
+    // first bar's first segment is the larger (asphalt 70%)
+    const firstBar = container.querySelector("div.flex.h-3");
+    const widths = [...firstBar!.querySelectorAll("div")].map((d) => (d as HTMLElement).style.width);
+    expect(widths[0]).toBe("70%");
+    expect(widths[1]).toBe("30%");
+  });
+});
diff --git a/apps/journal/app/components/SurfaceBreakdown.tsx b/apps/journal/app/components/SurfaceBreakdown.tsx
new file mode 100644
index 0000000..868e713
--- /dev/null
+++ b/apps/journal/app/components/SurfaceBreakdown.tsx
@@ -0,0 +1,99 @@
+import { useTranslation } from "react-i18next";
+import {
+  SURFACE_COLORS,
+  DEFAULT_SURFACE_COLOR,
+  HIGHWAY_COLORS,
+  DEFAULT_HIGHWAY_COLOR,
+} from "@trails-cool/map-core";
+import { formatDistanceKm } from "~/lib/stats";
+
+export interface SurfaceBreakdownData {
+  surface: Record<string, number>;
+  highway: Record<string, number>;
+}
+
+function Bar({
+  title,
+  data,
+  colorFor,
+}: {
+  title: string;
+  data: Record<string, number>;
+  colorFor: (category: string) => string;
+}) {
+  const { t } = useTranslation("journal");
+  const entries = Object.entries(data)
+    .filter(([, m]) => m > 0)
+    .sort((a, b) => b[1] - a[1]);
+  const total = entries.reduce((s, [, m]) => s + m, 0);
+  if (total <= 0) return null;
+
+  const label = (cat: string) =>
+    cat === "unknown"
+      ? t("surface.other")
+      : t(`surface.cat.${cat}`, { defaultValue: cat.replace(/_/g, " ") });
+
+  return (
+    <div className="mt-3 first:mt-0">
+      <p className="mb-1 text-xs font-medium text-gray-500">{title}</p>
+      <div className="flex h-3 w-full overflow-hidden rounded">
+        {entries.map(([cat, m]) => (
+          <div
+            key={cat}
+            style={{ width: `${(m / total) * 100}%`, backgroundColor: colorFor(cat) }}
+            title={`${label(cat)} · ${formatDistanceKm(m)}`}
+          />
+        ))}
+      </div>
+      <ul className="mt-2 flex flex-wrap gap-x-4 gap-y-1 text-xs text-gray-600">
+        {entries.map(([cat, m]) => (
+          <li key={cat} className="flex items-center gap-1.5">
+            <span
+              className="inline-block h-2.5 w-2.5 rounded-sm"
+              style={{ backgroundColor: colorFor(cat) }}
+              aria-hidden
+            />
+            <span>{label(cat)}</span>
+            <span className="tabular-nums text-gray-400">
+              {Math.round((m / total) * 100)}% · {formatDistanceKm(m)}
+            </span>
+          </li>
+        ))}
+      </ul>
+    </div>
+  );
+}
+
+/**
+ * Surface + waytype proportion bars (route-surface-breakdown). Renders nothing
+ * when there's no breakdown data. Colours come from the shared map-core
+ * palettes; unknown tags collapse into "other".
+ */
+export function SurfaceBreakdown({
+  breakdown,
+  className,
+}: {
+  breakdown: SurfaceBreakdownData | null | undefined;
+  className?: string;
+}) {
+  const { t } = useTranslation("journal");
+  if (!breakdown) return null;
+  const hasSurface = Object.values(breakdown.surface).some((m) => m > 0);
+  const hasHighway = Object.values(breakdown.highway).some((m) => m > 0);
+  if (!hasSurface && !hasHighway) return null;
+
+  return (
+    <div className={className}>
+      <Bar
+        title={t("surface.surface")}
+        data={breakdown.surface}
+        colorFor={(c) => SURFACE_COLORS[c] ?? DEFAULT_SURFACE_COLOR}
+      />
+      <Bar
+        title={t("surface.waytype")}
+        data={breakdown.highway}
+        colorFor={(c) => HIGHWAY_COLORS[c] ?? DEFAULT_HIGHWAY_COLOR}
+      />
+    </div>
+  );
+}
diff --git a/apps/journal/app/lib/routes.server.ts b/apps/journal/app/lib/routes.server.ts
index 406113e..4e2a31a 100644
--- a/apps/journal/app/lib/routes.server.ts
+++ b/apps/journal/app/lib/routes.server.ts
@@ -2,7 +2,7 @@ import { randomUUID } from "node:crypto";
 import { eq, desc, and, inArray, isNotNull } from "drizzle-orm";
 import { getDb } from "./db.ts";
 import { routes, routeVersions } from "@trails-cool/db/schema/journal";
-import type { Visibility } from "@trails-cool/db/schema/journal";
+import type { Visibility, SurfaceBreakdown } from "@trails-cool/db/schema/journal";
 import { sql } from "drizzle-orm";
 import { processGpx, writeGeom } from "./gpx-save.server.ts";
 import type { ProcessedGpx } from "./gpx-save.server.ts";
@@ -20,6 +20,7 @@ export interface RouteInput {
   elevationLoss?: number | null;
   dayBreaks?: number[];
   synthetic?: boolean;
+  surfaceBreakdown?: SurfaceBreakdown;
 }
 
 export async function createRoute(ownerId: string, input: RouteInput) {
@@ -139,6 +140,7 @@ export async function updateRoute(route: OwnedRef, input: Partial<RouteInput>) {
   if (input.name !== undefined) updateData.name = input.name;
   if (input.description !== undefined) updateData.description = input.description;
   if (input.visibility !== undefined) updateData.visibility = input.visibility;
+  if (input.surfaceBreakdown !== undefined) updateData.surfaceBreakdown = input.surfaceBreakdown;
 
   if (input.gpx && processed) {
     const { stats } = processed;
diff --git a/apps/journal/app/routes/activities.$id.server.ts b/apps/journal/app/routes/activities.$id.server.ts
index b5d0562..a39ef32 100644
--- a/apps/journal/app/routes/activities.$id.server.ts
+++ b/apps/journal/app/routes/activities.$id.server.ts
@@ -65,6 +65,7 @@ export async function loadActivityDetail(request: Request, id: string | undefine
       duration: activity.duration,
       movingTimeSec,
       elevation,
+      surfaceBreakdown: activity.surfaceBreakdown ?? null,
       routeId: activity.routeId,
       hasGpx: !!activity.gpx,
       geojson: activity.geojson ?? null,
diff --git a/apps/journal/app/routes/activities.$id.tsx b/apps/journal/app/routes/activities.$id.tsx
index 7ade93c..86cb03f 100644
--- a/apps/journal/app/routes/activities.$id.tsx
+++ b/apps/journal/app/routes/activities.$id.tsx
@@ -7,6 +7,7 @@ import { ClientMap } from "~/components/ClientMap";
 import { SportBadge } from "~/components/SportBadge";
 import { StatRow } from "~/components/StatRow";
 import { ElevationProfile } from "~/components/ElevationProfile";
+import { SurfaceBreakdown } from "~/components/SurfaceBreakdown";
 import { activityStatItems } from "~/lib/stats";
 import { loadActivityDetail, activityDetailAction } from "./activities.$id.server";
 import {
@@ -142,6 +143,8 @@ export default function ActivityDetailPage({ loaderData }: Route.ComponentProps)
         />
       )}
 
+      <SurfaceBreakdown breakdown={activity.surfaceBreakdown} className="mt-6" />
+
       {activity.routeId && (
         <div className="mt-6">
           <a href={`/routes/${activity.routeId}`} className="text-blue-600 hover:underline">
diff --git a/apps/journal/app/routes/api.routes.$id.callback.ts b/apps/journal/app/routes/api.routes.$id.callback.ts
index 98f814c..091ca67 100644
--- a/apps/journal/app/routes/api.routes.$id.callback.ts
+++ b/apps/journal/app/routes/api.routes.$id.callback.ts
@@ -1,4 +1,5 @@
 import { data } from "react-router";
+import { SurfaceBreakdownSchema } from "@trails-cool/api";
 import type { Route } from "./+types/api.routes.$id.callback";
 import { verifyRouteToken } from "~/lib/jwt.server";
 import { updateRoute, getRoute } from "~/lib/routes.server";
@@ -56,16 +57,23 @@ export async function action({ params, request }: Route.ActionArgs) {
 
     // Parse GPX from request body
     const body = await request.json();
-    const { gpx } = body as { gpx: string };
+    const { gpx, surfaceBreakdown } = body as { gpx: string; surfaceBreakdown?: unknown };
 
     if (!gpx) {
       return data({ error: "Missing GPX data" }, { status: 400, headers: corsHeaders() });
     }
 
+    // Optional, best-effort surface/waytype breakdown from the Planner's BRouter
+    // waytags (route-surface-breakdown, Path 1) — stored if well-formed, ignored otherwise.
+    const sb = SurfaceBreakdownSchema.safeParse(surfaceBreakdown);
+
     // Update route with new GPX (creates new version). Authorization
     // here comes from the verified single-use route token, not a
     // session — vouchOwnership marks that explicitly.
-    await updateRoute(vouchOwnership(route), { gpx });
+    await updateRoute(vouchOwnership(route), {
+      gpx,
+      ...(sb.success ? { surfaceBreakdown: sb.data } : {}),
+    });
 
     return data({ success: true, routeId: params.id }, { headers: corsHeaders() });
   } catch (e) {
diff --git a/apps/journal/app/routes/routes.$id.server.ts b/apps/journal/app/routes/routes.$id.server.ts
index 3c2340b..749d1be 100644
--- a/apps/journal/app/routes/routes.$id.server.ts
+++ b/apps/journal/app/routes/routes.$id.server.ts
@@ -126,6 +126,7 @@ export async function loadRouteDetail(request: Request, id: string | undefined)
       hasGpx: !!route.gpx,
       dayBreaks: route.dayBreaks ?? [],
       elevation,
+      surfaceBreakdown: route.surfaceBreakdown ?? null,
       geojson: routeWithGeojson?.geojson ?? null,
       visibility: route.visibility,
       createdAt: route.createdAt.toISOString(),
diff --git a/apps/journal/app/routes/routes.$id.tsx b/apps/journal/app/routes/routes.$id.tsx
index bf4fe9d..fdeae34 100644
--- a/apps/journal/app/routes/routes.$id.tsx
+++ b/apps/journal/app/routes/routes.$id.tsx
@@ -6,6 +6,7 @@ import { ClientDate } from "~/components/ClientDate";
 import { ClientMap } from "~/components/ClientMap";
 import { StatRow } from "~/components/StatRow";
 import { ElevationProfile } from "~/components/ElevationProfile";
+import { SurfaceBreakdown } from "~/components/SurfaceBreakdown";
 import { activityStatItems } from "~/lib/stats";
 import { loadRouteDetail, routeDetailAction } from "./routes.$id.server";
 
@@ -332,6 +333,8 @@ export default function RouteDetailPage({ loaderData }: Route.ComponentProps) {
         />
       )}
 
+      <SurfaceBreakdown breakdown={route.surfaceBreakdown} className="mt-6" />
+
       {isEmpty && (
         <div className="mt-6 flex flex-col items-center rounded-lg border border-dashed border-gray-300 bg-gray-50 px-6 py-12 text-center">
           <div className="text-4xl" aria-hidden="true">🗺️</div>
diff --git a/apps/journal/package.json b/apps/journal/package.json
index 6e33431..b54967d 100644
--- a/apps/journal/package.json
+++ b/apps/journal/package.json
@@ -27,6 +27,7 @@
     "@trails-cool/gpx": "workspace:*",
     "@trails-cool/i18n": "workspace:*",
     "@trails-cool/jobs": "workspace:*",
+    "@trails-cool/map-core": "workspace:*",
     "@trails-cool/sentry-config": "workspace:*",
     "@trails-cool/types": "workspace:*",
     "drizzle-orm": "catalog:",
diff --git a/apps/planner/app/components/SaveToJournalButton.tsx b/apps/planner/app/components/SaveToJournalButton.tsx
index 056d4bc..d464cf4 100644
--- a/apps/planner/app/components/SaveToJournalButton.tsx
+++ b/apps/planner/app/components/SaveToJournalButton.tsx
@@ -1,7 +1,9 @@
 import { useState, useCallback } from "react";
 import { useTranslation } from "react-i18next";
+import { computeSurfaceBreakdown } from "@trails-cool/map-core";
 import type { YjsState } from "~/lib/use-yjs";
 import { buildPlanGpx } from "~/lib/gpx-export";
+import { readComputedRoute } from "~/lib/route-data";
 
 interface SaveToJournalButtonProps {
   yjs: YjsState;
@@ -24,6 +26,19 @@ export function SaveToJournalButton({ yjs, sessionId, returnUrl }: SaveToJournal
       // route round-trips correctly through the journal.
       const gpx = buildPlanGpx(yjs);
 
+      // Distance-weighted surface/waytype breakdown from the BRouter waytags
+      // already in routeData — sent alongside the GPX so the journal can show
+      // it without re-deriving (route-surface-breakdown, Path 1).
+      const route = readComputedRoute(yjs.routeData);
+      const breakdown =
+        route.coordinates && route.coordinates.length > 1
+          ? computeSurfaceBreakdown(route.coordinates, route.surfaces, route.highways)
+          : null;
+      const surfaceBreakdown =
+        breakdown && (Object.keys(breakdown.surface).length > 0 || Object.keys(breakdown.highway).length > 0)
+          ? breakdown
+          : undefined;
+
       // POST to the planner's server-side proxy. The proxy attaches the
       // journal Bearer token (stored on the session row) and forwards
       // the GPX. Token never leaves the planner server — see
@@ -31,7 +46,7 @@ export function SaveToJournalButton({ yjs, sessionId, returnUrl }: SaveToJournal
       const response = await fetch("/api/save-to-journal", {
         method: "POST",
         headers: { "Content-Type": "application/json" },
-        body: JSON.stringify({ sessionId, gpx }),
+        body: JSON.stringify({ sessionId, gpx, ...(surfaceBreakdown ? { surfaceBreakdown } : {}) }),
       });
 
       if (!response.ok) {
diff --git a/apps/planner/app/routes/api.save-to-journal.ts b/apps/planner/app/routes/api.save-to-journal.ts
index 29ac08e..1f4e2b9 100644
--- a/apps/planner/app/routes/api.save-to-journal.ts
+++ b/apps/planner/app/routes/api.save-to-journal.ts
@@ -21,6 +21,7 @@ import { validateFetchUrl, getCallbackAllowedHosts } from "~/lib/url-validation.
 interface SaveRequestBody {
   sessionId?: unknown;
   gpx?: unknown;
+  surfaceBreakdown?: unknown;
 }
 
 const MAX_GPX_BYTES = 5 * 1024 * 1024; // 5 MB — same ceiling as the Yjs doc cap
@@ -39,6 +40,12 @@ export async function action({ request }: Route.ActionArgs) {
 
   const sessionId = typeof body.sessionId === "string" ? body.sessionId : "";
   const gpx = typeof body.gpx === "string" ? body.gpx : "";
+  // Optional, best-effort decoration — forwarded as-is; the journal callback is
+  // the authoritative validator (planner doesn't depend on @trails-cool/api).
+  const surfaceBreakdown =
+    body.surfaceBreakdown && typeof body.surfaceBreakdown === "object"
+      ? body.surfaceBreakdown
+      : undefined;
 
   if (!sessionId) return data({ error: "sessionId required" }, { status: 400 });
   if (!gpx) return data({ error: "gpx required" }, { status: 400 });
@@ -69,7 +76,7 @@ export async function action({ request }: Route.ActionArgs) {
         "Content-Type": "application/json",
         Authorization: `Bearer ${session.callbackToken}`,
       },
-      body: JSON.stringify({ gpx }),
+      body: JSON.stringify({ gpx, ...(surfaceBreakdown ? { surfaceBreakdown } : {}) }),
     });
   } catch {
     return data({ error: "journal unreachable" }, { status: 502 });
diff --git a/openspec/changes/route-surface-breakdown/tasks.md b/openspec/changes/route-surface-breakdown/tasks.md
index 68d50a6..55a0a52 100644
--- a/openspec/changes/route-surface-breakdown/tasks.md
+++ b/openspec/changes/route-surface-breakdown/tasks.md
@@ -1,24 +1,27 @@
+<!-- PHASE 1 (this PR): synchronous Planner path + bars. PHASE 2 (follow-up):
+     async Overpass backfill + SSE (sections 5–6, e2e in 7.3). -->
+
 ## 1. Shared derivation + shape
 
-- [ ] 1.1 Pure `surfaceBreakdown(coordinates, surfaces, highways)` helper: haversine-weight each segment into per-surface + per-waytype buckets → `{ surface: Record<string, number>, highway: Record<string, number> }` (metres). Unit-test.
-- [ ] 1.2 `SurfaceBreakdownSchema` (Zod) in `@trails-cool/api` (record of category → metres ≥ 0, surface + highway).
+- [x] 1.1 `computeSurfaceBreakdown(coordinates, surfaces, highways)` in `@trails-cool/map-core` → `{ surface, highway }` metres; unit-tested.
+- [x] 1.2 `SurfaceBreakdownSchema` (Zod) in `@trails-cool/api`.
 
 ## 2. Schema
 
-- [ ] 2.1 Nullable `surfaceBreakdown` jsonb on `journal.routes` **and** `journal.activities`; `pnpm db:push`.
+- [x] 2.1 Nullable `surfaceBreakdown` jsonb on `journal.routes` **and** `journal.activities`; pushed to dev + e2e DBs.
 
 ## 3. Path 1 — synchronous (Planner routes)
 
-- [ ] 3.1 `apps/planner/.../api.save-to-journal`: compute the breakdown from the session `EnrichedRoute` (coords + surfaces + highways) and add `surfaceBreakdown` to the POST body.
-- [ ] 3.2 Journal route callback validates the optional field and persists it (overwrite on re-save).
+- [x] 3.1 `SaveToJournalButton` computes the breakdown from `readComputedRoute` and sends it; `api.save-to-journal` forwards it (journal is the authoritative validator — planner has no `@trails-cool/api` dep).
+- [x] 3.2 Journal route callback validates the optional field with `SurfaceBreakdownSchema` and persists via `updateRoute` (overwrite on re-save).
 
 ## 4. Render
 
-- [ ] 4.1 Route + activity detail loaders expose `surfaceBreakdown`.
-- [ ] 4.2 `SurfaceBreakdown` component: stacked bar per dimension (surface, waytype), `map-core` `SURFACE_COLORS`/`HIGHWAY_COLORS` (DEFAULT → "other"), legend category · km · % (largest first), hidden when empty. Mount on `routes.$id.tsx` and `activities.$id.tsx`.
-- [ ] 4.3 i18n `journal.surface.*` (label + category names + "other") en + de.
+- [x] 4.1 Route + activity detail loaders expose `surfaceBreakdown`.
+- [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
+## 5. Path 2 — async backfill + SSE  (PHASE 2 — follow-up 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.
@@ -32,7 +35,7 @@
 
 ## 7. Tests & checks
 
-- [ ] 7.1 Unit: `surfaceBreakdown` weighting; map-matcher nearest-way + unknown bucket.
-- [ ] 7.2 Component (jsdom): bars/proportions, "other" bucket, hidden when empty.
-- [ ] 7.3 E2E: a route/activity with a stored breakdown shows the bars (seed the breakdown to avoid a live Overpass call in CI).
-- [ ] 7.4 `pnpm typecheck && pnpm lint && pnpm test && pnpm test:e2e` green.
+- [x] 7.1 Unit: `computeSurfaceBreakdown` weighting + unknown bucket (map-matcher unit is Phase 2).
+- [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.
diff --git a/packages/api/src/index.ts b/packages/api/src/index.ts
index b8b4a2d..b157e77 100644
--- a/packages/api/src/index.ts
+++ b/packages/api/src/index.ts
@@ -42,6 +42,9 @@ export {
   type ComputeRouteRequest,
 } from "./routes.ts";
 
+// Surface / waytype breakdown
+export { SurfaceBreakdownSchema, type SurfaceBreakdown } from "./surface-breakdown.ts";
+
 // Activities
 export {
   ActivitySummarySchema, ActivityDetailSchema,
diff --git a/packages/api/src/surface-breakdown.ts b/packages/api/src/surface-breakdown.ts
new file mode 100644
index 0000000..1587f34
--- /dev/null
+++ b/packages/api/src/surface-breakdown.ts
@@ -0,0 +1,15 @@
+import { z } from "zod";
+
+/**
+ * Distance-weighted surface/waytype breakdown (metres per category). Shared
+ * wire shape for the planner→journal handoff and the route/activity read APIs.
+ * Mirrors `SurfaceBreakdown` in `@trails-cool/map-core`.
+ */
+const MetresByCategory = z.record(z.string(), z.number().min(0));
+
+export const SurfaceBreakdownSchema = z.object({
+  surface: MetresByCategory,
+  highway: MetresByCategory,
+});
+
+export type SurfaceBreakdown = z.infer<typeof SurfaceBreakdownSchema>;
diff --git a/packages/db/src/schema/journal.ts b/packages/db/src/schema/journal.ts
index a3c99b2..b13c46c 100644
--- a/packages/db/src/schema/journal.ts
+++ b/packages/db/src/schema/journal.ts
@@ -91,6 +91,15 @@ export const magicTokens = journalSchema.table("magic_tokens", {
  */
 export type Visibility = "private" | "unlisted" | "public";
 
+/**
+ * Distance-weighted surface/waytype breakdown (metres per category), derived
+ * from BRouter waytags at Planner save or backfilled via Overpass.
+ */
+export type SurfaceBreakdown = {
+  surface: Record<string, number>;
+  highway: Record<string, number>;
+};
+
 export const routes = journalSchema.table("routes", {
   id: text("id").primaryKey(),
   ownerId: text("owner_id")
@@ -106,6 +115,7 @@ export const routes = journalSchema.table("routes", {
   elevationLoss: real("elevation_loss"),
   dayBreaks: jsonb("day_breaks").$type<number[]>(),
   tags: jsonb("tags").$type<string[]>(),
+  surfaceBreakdown: jsonb("surface_breakdown").$type<SurfaceBreakdown>(),
   plannerState: bytea("planner_state"),
   visibility: text("visibility").$type<Visibility>().notNull().default("private"),
   /**
@@ -173,6 +183,9 @@ export const activities = journalSchema.table("activities", {
   description: text("description").default(""),
   // Sport / activity type (NULL = unspecified). See SPORT_TYPES above.
   sportType: text("sport_type").$type<SportType>(),
+  // Distance-weighted surface/waytype breakdown (backfilled via Overpass for
+  // imported/uploaded activities). NULL until derived.
+  surfaceBreakdown: jsonb("surface_breakdown").$type<SurfaceBreakdown>(),
   gpx: text("gpx"),
   geom: lineString("geom"),
   startedAt: timestamp("started_at", { withTimezone: true }),
diff --git a/packages/i18n/src/locales/de.ts b/packages/i18n/src/locales/de.ts
index f2200fd..3dcd4fc 100644
--- a/packages/i18n/src/locales/de.ts
+++ b/packages/i18n/src/locales/de.ts
@@ -418,6 +418,38 @@ export default {
       weeklyDistance: "Wochendistanz (letzte 12 Wochen)",
       weekOf: "Woche vom {{date}}",
     },
+    surface: {
+      surface: "Oberfläche",
+      waytype: "Wegtyp",
+      other: "Sonstige",
+      cat: {
+        asphalt: "Asphalt",
+        paved: "Befestigt",
+        concrete: "Beton",
+        paving_stones: "Pflastersteine",
+        cobblestone: "Kopfsteinpflaster",
+        gravel: "Schotter",
+        fine_gravel: "Feinschotter",
+        compacted: "Verdichtet",
+        ground: "Naturboden",
+        dirt: "Erde",
+        grass: "Gras",
+        sand: "Sand",
+        unpaved: "Unbefestigt",
+        path: "Pfad",
+        track: "Wirtschaftsweg",
+        residential: "Wohnstraße",
+        cycleway: "Radweg",
+        footway: "Fußweg",
+        primary: "Hauptstraße",
+        secondary: "Landstraße",
+        tertiary: "Nebenstraße",
+        service: "Erschließungsweg",
+        unclassified: "Kleine Straße",
+        bridleway: "Reitweg",
+        steps: "Treppe",
+      },
+    },
     settings: {
       title: "Einstellungen",
       nav: {
diff --git a/packages/i18n/src/locales/en.ts b/packages/i18n/src/locales/en.ts
index 16d3eb5..83493f35 100644
--- a/packages/i18n/src/locales/en.ts
+++ b/packages/i18n/src/locales/en.ts
@@ -418,6 +418,38 @@ export default {
       weeklyDistance: "Weekly distance (last 12 weeks)",
       weekOf: "Week of {{date}}",
     },
+    surface: {
+      surface: "Surface",
+      waytype: "Way type",
+      other: "other",
+      cat: {
+        asphalt: "Asphalt",
+        paved: "Paved",
+        concrete: "Concrete",
+        paving_stones: "Paving stones",
+        cobblestone: "Cobblestone",
+        gravel: "Gravel",
+        fine_gravel: "Fine gravel",
+        compacted: "Compacted",
+        ground: "Ground",
+        dirt: "Dirt",
+        grass: "Grass",
+        sand: "Sand",
+        unpaved: "Unpaved",
+        path: "Path",
+        track: "Track",
+        residential: "Residential road",
+        cycleway: "Cycleway",
+        footway: "Footway",
+        primary: "Primary road",
+        secondary: "Secondary road",
+        tertiary: "Tertiary road",
+        service: "Service road",
+        unclassified: "Minor road",
+        bridleway: "Bridleway",
+        steps: "Steps",
+      },
+    },
     settings: {
       title: "Settings",
       nav: {
diff --git a/packages/map-core/src/index.ts b/packages/map-core/src/index.ts
index 48939dd..821e82e 100644
--- a/packages/map-core/src/index.ts
+++ b/packages/map-core/src/index.ts
@@ -21,3 +21,6 @@ export {
 } from "./z-index.ts";
 
 export { SNAP_DISTANCE_METERS } from "./snap.ts";
+
+export { computeSurfaceBreakdown } from "./surface-breakdown.ts";
+export type { SurfaceBreakdown } from "./surface-breakdown.ts";
diff --git a/packages/map-core/src/surface-breakdown.test.ts b/packages/map-core/src/surface-breakdown.test.ts
new file mode 100644
index 0000000..1ef157e
--- /dev/null
+++ b/packages/map-core/src/surface-breakdown.test.ts
@@ -0,0 +1,34 @@
+import { describe, it, expect } from "vitest";
+import { computeSurfaceBreakdown } from "./surface-breakdown.ts";
+
+// ~0.001° lon at the equator ≈ 111 m; exact value doesn't matter, only ratios.
+const coords: [number, number][] = [
+  [0, 0],
+  [0.001, 0],
+  [0.002, 0],
+  [0.003, 0],
+];
+
+describe("computeSurfaceBreakdown", () => {
+  it("weights segments by distance into surface and waytype buckets", () => {
+    const { surface, highway } = computeSurfaceBreakdown(
+      coords,
+      ["asphalt", "asphalt", "gravel"],
+      ["residential", "residential", "track"],
+    );
+    // segments 0,1 asphalt; segment 2 gravel — equal lengths → 2:1
+    expect(surface.asphalt! / surface.gravel!).toBeCloseTo(2, 5);
+    expect(highway.residential! / highway.track!).toBeCloseTo(2, 5);
+    expect(Object.keys(surface)).toEqual(["asphalt", "gravel"]);
+  });
+
+  it("buckets missing/empty values as unknown", () => {
+    const { surface } = computeSurfaceBreakdown(coords, ["asphalt", "", "asphalt"], ["", "", ""]);
+    expect(surface.asphalt).toBeGreaterThan(0);
+    expect(surface.unknown).toBeGreaterThan(0);
+  });
+
+  it("returns empty buckets for a degenerate track", () => {
+    expect(computeSurfaceBreakdown([[0, 0]], [], [])).toEqual({ surface: {}, highway: {} });
+  });
+});
diff --git a/packages/map-core/src/surface-breakdown.ts b/packages/map-core/src/surface-breakdown.ts
new file mode 100644
index 0000000..86d6773
--- /dev/null
+++ b/packages/map-core/src/surface-breakdown.ts
@@ -0,0 +1,52 @@
+/**
+ * Distance-weighted surface / waytype breakdown for a route. Both derivation
+ * paths (BRouter waytags at Planner save, and the async Overpass backfill) feed
+ * their per-segment `surfaces`/`highways` arrays through this to produce the
+ * same compact summary that gets stored and rendered.
+ */
+export interface SurfaceBreakdown {
+  /** metres per surface category (e.g. asphalt, gravel, path) */
+  surface: Record<string, number>;
+  /** metres per waytype/highway category */
+  highway: Record<string, number>;
+}
+
+function haversineMeters(lat1: number, lon1: number, lat2: number, lon2: number): number {
+  const R = 6371000;
+  const toRad = (d: number) => (d * Math.PI) / 180;
+  const dLat = toRad(lat2 - lat1);
+  const dLon = toRad(lon2 - lon1);
+  const a =
+    Math.sin(dLat / 2) ** 2 +
+    Math.cos(toRad(lat1)) * Math.cos(toRad(lat2)) * Math.sin(dLon / 2) ** 2;
+  return R * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
+}
+
+/**
+ * Sum each coordinate segment's length into its surface and waytype buckets.
+ * `coordinates` are `[lon, lat, ...]` (GeoJSON axis order); `surfaces[i]` /
+ * `highways[i]` describe the segment from point `i` to `i+1`. Missing/empty
+ * values bucket as `"unknown"`. Returns metres per category.
+ */
+export function computeSurfaceBreakdown(
+  coordinates: ReadonlyArray<readonly number[]>,
+  surfaces: readonly string[],
+  highways: readonly string[],
+): SurfaceBreakdown {
+  const surface: Record<string, number> = {};
+  const highway: Record<string, number> = {};
+
+  for (let i = 0; i < coordinates.length - 1; i++) {
+    const a = coordinates[i];
+    const b = coordinates[i + 1];
+    if (!a || !b || a.length < 2 || b.length < 2) continue;
+    const d = haversineMeters(a[1]!, a[0]!, b[1]!, b[0]!);
+    if (!(d > 0)) continue;
+    const s = surfaces[i] || "unknown";
+    const h = highways[i] || "unknown";
+    surface[s] = (surface[s] ?? 0) + d;
+    highway[h] = (highway[h] ?? 0) + d;
+  }
+
+  return { surface, highway };
+}
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 22a205a..8f5cad2 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -241,6 +241,9 @@ importers:
       '@trails-cool/jobs':
         specifier: workspace:*
         version: link:../../packages/jobs
+      '@trails-cool/map-core':
+        specifier: workspace:*
+        version: link:../../packages/map-core
       '@trails-cool/sentry-config':
         specifier: workspace:*
         version: link:../../packages/sentry-config