diff --git a/server/src/app-config/derive.ts b/server/src/app-config/derive.ts
index ec444b9cc..793d0e86f 100644
--- a/server/src/app-config/derive.ts
+++ b/server/src/app-config/derive.ts
@@ -245,7 +245,9 @@ export function deriveIntegrations(raw: RawEnv) {
     unsplashAccessKey: raw.UNSPLASH_ACCESS_KEY?.trim(),
     transitApiBase: stripTrailingSlashes(raw.TRANSIT_API_URL || 'https://api.transitous.org'),
     overpassUrl: raw.OVERPASS_URL,
-    overpassTimeoutMs: positiveNumberOr(raw.OVERPASS_TIMEOUT_MS, 12000),
+    // Longer than the `[timeout:20]` the query itself carries, or we abort an answer the
+    // mirror was still allowed to be working on. See OVERPASS_QUERY_TIMEOUT_S.
+    overpassTimeoutMs: positiveNumberOr(raw.OVERPASS_TIMEOUT_MS, 25000),
     kitineraryExtractorPath: raw.KITINERARY_EXTRACTOR_PATH,
     /**
      * One ceiling for a model call, replacing the three per-client constants
diff --git a/server/src/nest/maps/maps.helpers.ts b/server/src/nest/maps/maps.helpers.ts
index 588f419e5..07b9d1f01 100644
--- a/server/src/nest/maps/maps.helpers.ts
+++ b/server/src/nest/maps/maps.helpers.ts
@@ -362,10 +362,24 @@ export function resolveOverpassEndpoints(raw: string | undefined = readEnv().int
 // slow self-hosted endpoint can raise it via OVERPASS_TIMEOUT_MS. A non-positive or
 // non-numeric value falls back to the default — a 0/negative cap would abort every
 // request immediately and 502 the search.
+/**
+ * How long Overpass is allowed to spend on one query, in seconds.
+ *
+ * Sent inside the query as `[timeout:N]`, so the mirror itself enforces it. Anything we
+ * wait client-side has to be longer than this or we hang up on an answer that was still
+ * coming — which is exactly what used to happen: the query asked for twenty seconds of
+ * work and the fetch was aborted after twelve, so a mirror under load never got to
+ * finish and a corridor search reported half its stretches as unsearchable.
+ */
+export const OVERPASS_QUERY_TIMEOUT_S = 20;
+
+/** The client-side budget: the mirror's own, plus room to hand the answer back. */
+export const OVERPASS_TIMEOUT_DEFAULT_MS = (OVERPASS_QUERY_TIMEOUT_S + 5) * 1000;
+
 export function resolveOverpassTimeoutMs(raw?: string): number {
   if (raw === undefined) return readEnv().integrations.overpassTimeoutMs;
   const n = Number(raw);
-  return Number.isFinite(n) && n > 0 ? n : 12000;
+  return Number.isFinite(n) && n > 0 ? n : OVERPASS_TIMEOUT_DEFAULT_MS;
 }
 
 // ── Opening hours parsing ────────────────────────────────────────────────────
diff --git a/server/src/nest/maps/maps.service.ts b/server/src/nest/maps/maps.service.ts
index 52ce87aee..bf022ef51 100644
--- a/server/src/nest/maps/maps.service.ts
+++ b/server/src/nest/maps/maps.service.ts
@@ -39,6 +39,7 @@ import {
   parsePoiCategories,
   resolveOverpassEndpoints,
   resolveOverpassTimeoutMs,
+  OVERPASS_QUERY_TIMEOUT_S,
   stripWikiMarkup,
   parseWikipediaTag,
   toWikiLang,
@@ -1224,7 +1225,7 @@ export class MapsService {
       .join('\n');
     // `out center tags <n>` returns ways/relations with a computed center and caps
     // the result count in one round-trip.
-    const query = `[out:json][timeout:20];\n(\n${selectors}\n);\nout center tags ${cap + 25};`;
+    const query = `[out:json][timeout:${OVERPASS_QUERY_TIMEOUT_S}];\n(\n${selectors}\n);\nout center tags ${cap + 25};`;
 
     const elements = await overpassFetch(query);
 
diff --git a/server/tests/unit/nest/maps.service.test.ts b/server/tests/unit/nest/maps.service.test.ts
index a78b437e1..d148beef1 100644
--- a/server/tests/unit/nest/maps.service.test.ts
+++ b/server/tests/unit/nest/maps.service.test.ts
@@ -20,6 +20,8 @@ import {
   buildUserAgent,
   resolveOverpassEndpoints,
   resolveOverpassTimeoutMs,
+  OVERPASS_QUERY_TIMEOUT_S,
+  OVERPASS_TIMEOUT_DEFAULT_MS,
   stripWikiMarkup,
   parseWikipediaTag,
   rankCommonsCandidates,
@@ -2487,10 +2489,10 @@ describe('resolveOverpassEndpoints', () => {
 // ── resolveOverpassTimeoutMs (OVERPASS_TIMEOUT_MS override, #1309) ─────────────
 
 describe('resolveOverpassTimeoutMs', () => {
-  it('MAPS-104: falls back to the 12s default for unset / empty / non-numeric values', () => {
-    expect(resolveOverpassTimeoutMs(undefined)).toBe(12000);
-    expect(resolveOverpassTimeoutMs('')).toBe(12000);
-    expect(resolveOverpassTimeoutMs('abc')).toBe(12000);
+  it('MAPS-104: falls back to the default for unset / empty / non-numeric values', () => {
+    expect(resolveOverpassTimeoutMs(undefined)).toBe(OVERPASS_TIMEOUT_DEFAULT_MS);
+    expect(resolveOverpassTimeoutMs('')).toBe(OVERPASS_TIMEOUT_DEFAULT_MS);
+    expect(resolveOverpassTimeoutMs('abc')).toBe(OVERPASS_TIMEOUT_DEFAULT_MS);
   });
 
   it('MAPS-105: honours a positive numeric override', () => {
@@ -2498,9 +2500,17 @@ describe('resolveOverpassTimeoutMs', () => {
   });
 
   it('MAPS-106: rejects 0, negative and Infinity — a non-positive cap would 502 every search', () => {
-    expect(resolveOverpassTimeoutMs('0')).toBe(12000);
-    expect(resolveOverpassTimeoutMs('-5')).toBe(12000);
-    expect(resolveOverpassTimeoutMs('Infinity')).toBe(12000);
+    expect(resolveOverpassTimeoutMs('0')).toBe(OVERPASS_TIMEOUT_DEFAULT_MS);
+    expect(resolveOverpassTimeoutMs('-5')).toBe(OVERPASS_TIMEOUT_DEFAULT_MS);
+    expect(resolveOverpassTimeoutMs('Infinity')).toBe(OVERPASS_TIMEOUT_DEFAULT_MS);
+  });
+
+  it('MAPS-107: we wait longer than the query we sent is allowed to take', () => {
+    // The query carries `[timeout:N]`, which the mirror enforces itself. Hanging up
+    // before that expires aborts an answer that was still legitimately being computed —
+    // which is how a corridor search came to report half its stretches as unsearchable
+    // while every mirror was in fact working on them.
+    expect(OVERPASS_TIMEOUT_DEFAULT_MS).toBeGreaterThan(OVERPASS_QUERY_TIMEOUT_S * 1000);
   });
 });