diff --git a/changelog/unreleased/fix-wopi-lock-read-only-view-mode.md b/changelog/unreleased/fix-wopi-lock-read-only-view-mode.md
new file mode 100644
index 00000000000..2442f03e21f
--- /dev/null
+++ b/changelog/unreleased/fix-wopi-lock-read-only-view-mode.md
@@ -0,0 +1,11 @@
+Bugfix: Return 200 OK for WOPI Lock requests in read-only and view-only modes
+
+OnlyOffice sends a WOPI Lock request when opening any document, even when
+the user only has read access. The WOPI Lock handler was attempting to acquire
+a CS3 write lock regardless of the view mode, causing a permission error for
+read-only tokens that OnlyOffice displayed as an error message on load.
+
+The Lock handler now returns 200 OK immediately for READ_ONLY and VIEW_ONLY
+view modes without attempting to acquire a lock, consistent with the WOPI spec.
+
+https://github.com/owncloud/ocis/pull/12257
diff --git a/services/collaboration/pkg/connector/fileconnector.go b/services/collaboration/pkg/connector/fileconnector.go
index ddef048147f..a9915588abd 100644
--- a/services/collaboration/pkg/connector/fileconnector.go
+++ b/services/collaboration/pkg/connector/fileconnector.go
@@ -212,6 +212,16 @@ func (f *FileConnector) Lock(ctx context.Context, lockID, oldLockID string) (*Co
 		return NewResponse(400), nil
 	}
 
+	// For read-only and view-only modes, the user has no write access.
+	// OnlyOffice sends a Lock request even for view-only documents, but
+	// attempting SetLock with a read-only token would fail at the CS3 layer.
+	// Return 200 OK immediately without acquiring a lock.
+	if wopiContext.ViewMode == appproviderv1beta1.ViewMode_VIEW_MODE_READ_ONLY ||
+		wopiContext.ViewMode == appproviderv1beta1.ViewMode_VIEW_MODE_VIEW_ONLY {
+		logger.Debug().Msg("Lock: view-only mode, skipping lock")
+		return NewResponseWithVersion(nil), nil
+	}
+
 	var setOrRefreshStatus *rpcv1beta1.Status
 	if oldLockID == "" {
 		// If the oldLockID is empty, this is a "LOCK" request
diff --git a/services/collaboration/pkg/connector/fileconnector_test.go b/services/collaboration/pkg/connector/fileconnector_test.go
index 8096856a06b..ca49d5f9514 100644
--- a/services/collaboration/pkg/connector/fileconnector_test.go
+++ b/services/collaboration/pkg/connector/fileconnector_test.go
@@ -178,6 +178,28 @@ var _ = Describe("FileConnector", func() {
 				Expect(response.Headers).To(BeNil())
 			})
 
+			It("Read-only view mode returns 200 without locking", func() {
+				gatewaySelector.EXPECT().Next().Unset()
+				readOnlyCtx := wopiCtx
+				readOnlyCtx.ViewMode = appproviderv1beta1.ViewMode_VIEW_MODE_READ_ONLY
+				ctx := middleware.WopiContextToCtx(context.Background(), readOnlyCtx)
+
+				response, err := fc.Lock(ctx, "abcdef123", "")
+				Expect(err).ToNot(HaveOccurred())
+				Expect(response.Status).To(Equal(200))
+			})
+
+			It("View-only mode returns 200 without locking", func() {
+				gatewaySelector.EXPECT().Next().Unset()
+				viewOnlyCtx := wopiCtx
+				viewOnlyCtx.ViewMode = appproviderv1beta1.ViewMode_VIEW_MODE_VIEW_ONLY
+				ctx := middleware.WopiContextToCtx(context.Background(), viewOnlyCtx)
+
+				response, err := fc.Lock(ctx, "abcdef123", "")
+				Expect(err).ToNot(HaveOccurred())
+				Expect(response.Status).To(Equal(200))
+			})
+
 			It("Set lock failed", func() {
 				ctx := middleware.WopiContextToCtx(context.Background(), wopiCtx)
 
@@ -2166,5 +2188,6 @@ var _ = Describe("FileConnector", func() {
 			// so we can't compare the whole url
 			Expect(templateSource).To(HavePrefix(expectedTemplateSource))
 		})
+
 	})
 })