diff --git a/backend/app/api/export.py b/backend/app/api/export.py
index c3a9a6a..1c04c01 100644
--- a/backend/app/api/export.py
+++ b/backend/app/api/export.py
@@ -9,7 +9,7 @@ from app.core.config import settings
 from app.core.rate_limit import limiter
 from app.db.models import Publication, PublicationDownload, Researcher
 from app.db.session import get_db
-from app.security.api_key import get_api_key_optional
+from app.security.api_key import get_api_key
 from app.security.jwt import get_optional_current_researcher
 from app.services.sword_generator import SWORDGenerator
 from app.services.zip_generator import ZIPGenerator
@@ -19,11 +19,6 @@ from app.utils.orcid_validator import ORCID_PATTERN, is_valid_orcid
 router = APIRouter(prefix="/export")
 
 
-def _ensure_credentials(api_key: str | None, current: Researcher | None) -> None:
-    if not api_key and not current:
-        raise HTTPException(status_code=401, detail="Authentication required")
-
-
 def _record_downloads(db: Session, current: Researcher, pubs: Iterable[Publication]) -> None:
     """
     Inserta marcadores de descarga (researcher_id, publication_id).
@@ -94,10 +89,9 @@ async def export_multiple_sword(
     request: Request,
     pub_ids: List[UUID] = Body(..., min_length=1, max_length=settings.MAX_PUB_IDS_BATCH),
     db: Session = Depends(get_db),
-    api_key: str | None = Depends(get_api_key_optional),
+    _: str = Depends(get_api_key),
     current: Researcher | None = Depends(get_optional_current_researcher),
 ):
-    _ensure_credentials(api_key, current)
     _validate_pub_ids(pub_ids)
 
     pubs = db.query(Publication).filter(Publication.id.in_(pub_ids)).all()
@@ -124,10 +118,9 @@ async def export_researcher_sword(
     request: Request,
     orcid_id: str = Path(min_length=19, max_length=19, pattern=ORCID_PATTERN),
     db: Session = Depends(get_db),
-    api_key: str | None = Depends(get_api_key_optional),
+    _: str = Depends(get_api_key),
     current: Researcher | None = Depends(get_optional_current_researcher),
 ):
-    _ensure_credentials(api_key, current)
     if not is_valid_orcid(orcid_id):
         raise HTTPException(status_code=400, detail="Invalid ORCID iD")
 
@@ -156,10 +149,9 @@ async def export_multiple_zip(
     request: Request,
     pub_ids: List[UUID] = Body(..., min_length=1, max_length=settings.MAX_PUB_IDS_BATCH),
     db: Session = Depends(get_db),
-    api_key: str | None = Depends(get_api_key_optional),
+    _: str = Depends(get_api_key),
     current: Researcher | None = Depends(get_optional_current_researcher),
 ):
-    _ensure_credentials(api_key, current)
     _validate_pub_ids(pub_ids)
 
     pubs = db.query(Publication).filter(Publication.id.in_(pub_ids)).all()
@@ -186,10 +178,9 @@ async def export_researcher_zip(
     request: Request,
     orcid_id: str = Path(min_length=19, max_length=19, pattern=ORCID_PATTERN),
     db: Session = Depends(get_db),
-    api_key: str | None = Depends(get_api_key_optional),
+    _: str = Depends(get_api_key),
     current: Researcher | None = Depends(get_optional_current_researcher),
 ):
-    _ensure_credentials(api_key, current)
     if not is_valid_orcid(orcid_id):
         raise HTTPException(status_code=400, detail="Invalid ORCID iD")
 
@@ -205,4 +196,4 @@ async def export_researcher_zip(
     if current:
         _record_downloads(db, current, pubs)
 
-    return Response(content=zip_bytes, media_type="application/zip")
+    return Response(content=zip_bytes, media_type="application/zip")
\ No newline at end of file
diff --git a/frontend/src/services/api.js b/frontend/src/services/api.js
index 390987e..443cad2 100644
--- a/frontend/src/services/api.js
+++ b/frontend/src/services/api.js
@@ -17,10 +17,10 @@
  *   - GET    /researchers/search                          → buscador grupal (todo en uno)
  *   - GET    /researchers/search/{orcid_id}               → buscador individual (todo en uno)
  *   - POST   /researchers/{orcid_id}/sync                 → re-sync manual
- *   - POST   /export/sword/publications  body=[ids]       → SWORD XML de selección
- *   - POST   /export/zip/publications    body=[ids]       → ZIP de selección
- *   - GET    /export/sword/researcher/{orcid_id}          → SWORD XML de todo el investigador
- *   - GET    /export/zip/researcher/{orcid_id}            → ZIP de todo el investigador
+ *   - POST   /export/sword/publications  body=[ids]       → SWORD XML de selección (requiere X-API-Key)
+ *   - POST   /export/zip/publications    body=[ids]       → ZIP de selección (requiere X-API-Key)
+ *   - GET    /export/sword/researcher/{orcid_id}          → SWORD XML de todo el investigador (requiere X-API-Key)
+ *   - GET    /export/zip/researcher/{orcid_id}            → ZIP de todo el investigador (requiere X-API-Key)
  */
 
 import {
@@ -390,9 +390,9 @@ function exportSegmentFor(format) {
  * dato meramente informativo en los toasts de éxito; las descargas
  * reales se disparan vía blob para poder forzar el download.
  *
- * Ojo: estas URLs requieren `X-API-Key`, así que NO sirven como link
- * directo en una etiqueta `<a href>`; las exponemos para mostrarlas o
- * loguearlas, no para navegar.
+ * El backend exige la cabecera `X-API-Key` (misma que `VITE_API_KEY` en el
+ * front). No sirven como `<a href>` simple: hay que descargar con `fetch`
+ * (p. ej. `downloadExport`) o añadir la cabecera de otro modo.
  */
 export function getExportUrl(orcidId, format) {
   const segment = exportSegmentFor(format);
@@ -420,6 +420,13 @@ export async function downloadExport(
     return { blob: null, url: getExportUrl(orcidId, format) };
   }
 
+  if (!API_KEY) {
+    throw new ApiError(
+      "Configura VITE_API_KEY (debe coincidir con API_KEY_VALUE del backend): las exportaciones exigen la cabecera X-API-Key.",
+      { status: 401, payload: { missingApiKey: true } },
+    );
+  }
+
   const segment = exportSegmentFor(format);
   const ids =
     Array.isArray(publicationIds) && publicationIds.length > 0
@@ -468,4 +475,4 @@ export async function downloadExport(
   }
   const blob = await response.blob();
   return { blob, url };
-}
+}
\ No newline at end of file