Improve xDS web UI: navigation, pagination, history diff, and client subscriptions

Motivation:
- Selecting a group landed on the Listeners page instead of the Overview page,
  making it hard to get a quick summary of the group at a glance.
- The Resources and History pages had no pagination, making large groups hard to
  browse.
- The group-wide History page showed commit summaries as plain text with no way
  to inspect what actually changed in a commit.
- The References page gave no indication that inbound references from other groups
  are not shown, which could be confusing.
- The control plane Clients table had no visibility into what resource names each
  client subscribed to.

Modifications:
- Change the default navigation target when selecting a group (group list,
  sidebar dropdown, breadcrumb, and the `useXdsRoute` fallback) from `listeners`
  to `overview`.
- Add client-side pagination (default 10 rows) to the Resources and History pages.
- Add a Subscriptions column to the Clients table.
- Track subscribed resource names in `XdsClientStatusTracker`.

Result:
- Selecting a group now lands on the Overview page.
- Resources and History pages are paginated.
- Every commit in the group-wide History is inspectable with a before/after diff.
- The References page clearly communicates its cross-group limitation.

Author: minwoox

webapp/.gitignore

@@ -2,3 +2,4 @@
 /playwright-report/
 /blob-report/
 /playwright/.cache/
+tsconfig.tsbuildinfo

webapp/src/dogma/common/components/JsonDiffEditor.tsx

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2026 LY Corporation
+ *
+ * LY Corporation licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+import { DiffEditor, loader } from '@monaco-editor/react';
+import { useColorMode } from '@chakra-ui/react';
+import { useEffect, useState } from 'react';
+import { Loading } from 'dogma/common/components/Loading';
+
+interface JsonDiffEditorProps {
+  // The left-hand (baseline) document, e.g. the content before a change.
+  original: string;
+  // The right-hand (compared) document, e.g. the content after a change.
+  modified: string;
+  height?: string | number;
+}
+
+// Wraps the Monaco diff editor and configures it to use the locally bundled `monaco-editor` package (provided
+// by MonacoWebpackPlugin) instead of a CDN, mirroring {@link JsonEditor}.
+export const JsonDiffEditor = ({ original, modified, height = '60vh' }: JsonDiffEditorProps) => {
+  const { colorMode } = useColorMode();
+  const [ready, setReady] = useState(false);
+
+  useEffect(() => {
+    let active = true;
+    (async () => {
+      const monaco = await import('monaco-editor');
+      loader.config({ monaco });
+      await loader.init();
+      if (active) {
+        setReady(true);
+      }
+    })();
+    return () => {
+      active = false;
+    };
+  }, []);
+
+  if (!ready) {
+    return <Loading />;
+  }
+
+  return (
+    <DiffEditor
+      height={height}
+      language="json"
+      theme={colorMode === 'light' ? 'light' : 'vs-dark'}
+      original={original}
+      modified={modified}
+      options={{
+        readOnly: true,
+        renderSideBySide: true,
+        minimap: { enabled: false },
+        automaticLayout: true,
+        scrollBeyondLastLine: false,
+        lineNumbersMinChars: 4,
+      }}
+    />
+  );
+};

webapp/src/dogma/features/api/apiSlice.ts

@@ -47,6 +47,7 @@ import {
 } from 'dogma/features/settings/server-status/ServerStatusDto';
 import Router from 'next/router';
 import { VariableDto } from 'dogma/features/project/settings/variables/VariableDto';
+import { XdsApp, XdsClientStatus, XdsSnapshot } from 'dogma/features/xds/ControlPlaneStatusDto';
 
 export type ApiAction<Arg, Result> = {
   (arg: Arg): { unwrap: () => Promise<Result> };
@@ -598,6 +599,21 @@ export const apiSlice = createApi({
       }),
       transformResponse: () => true,
     }),
+    // System-administrator-only views of the xDS control plane runtime state.
+    getXdsClients: builder.query<XdsClientStatus[], void>({
+      query: () => '/api/v1/xds/clients',
+    }),
+    getXdsApps: builder.query<XdsApp[], void>({
+      query: () => '/api/v1/xds/apps',
+    }),
+    getXdsSnapshot: builder.query<XdsSnapshot, { group?: string; appId?: string }>({
+      query: ({ group, appId }) => {
+        if (appId) {
+          return `/api/v1/xds/snapshot?appId=${encodeURIComponent(appId)}`;
+        }
+        return group ? `/api/v1/xds/snapshot?group=${encodeURIComponent(group)}` : '/api/v1/xds/snapshot';
+      },
+    }),
   }),
 });
 
@@ -613,6 +629,9 @@ function variableApiPrefix(projectName: string, repoName?: string): string {
 export const {
   // xDS
   useIsXdsWebEnabledQuery,
+  useGetXdsClientsQuery,
+  useGetXdsAppsQuery,
+  useGetXdsSnapshotQuery,
   // Project
   useGetProjectsQuery,
   useRestoreProjectMutation,

webapp/src/dogma/features/xds/ClientStatusTable.tsx

@@ -0,0 +1,190 @@
+/*
+ * Copyright 2026 LY Corporation
+ *
+ * LY Corporation licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+import { Badge, Box, Code, HStack, Tag, Text, VStack, Wrap, WrapItem } from '@chakra-ui/react';
+import {
+  ColumnDef,
+  createColumnHelper,
+  getCoreRowModel,
+  getSortedRowModel,
+  useReactTable,
+} from '@tanstack/react-table';
+import { useMemo } from 'react';
+import { DataTable } from 'dogma/features/xds/DataTable';
+import { XdsAckStatus, XdsClientStatus, xdsTypeOf } from 'dogma/features/xds/ControlPlaneStatusDto';
+
+// One row per (stream, resource type). A single ADS stream multiplexes several types, so it produces several
+// rows.
+interface ClientRow {
+  streamId: number;
+  nodeId: string;
+  nodeCluster: string;
+  appId: string;
+  acronym: string;
+  status: XdsAckStatus;
+  nackReason: string;
+  lastSeen: number;
+  resourceNames: string[];
+}
+
+const columnHelper = createColumnHelper<ClientRow>();
+
+function statusColorScheme(status: XdsAckStatus): string {
+  switch (status) {
+    case 'ACKED':
+      return 'green';
+    case 'NACKED':
+      return 'red';
+    default:
+      return 'gray';
+  }
+}
+
+function formatTime(millis: number): string {
+  return millis > 0 ? new Date(millis).toLocaleString() : '-';
+}
+
+export const ClientStatusTable = ({ clients }: { clients: XdsClientStatus[] }) => {
+  const rows = useMemo<ClientRow[]>(
+    () =>
+      clients.flatMap((client) =>
+        client.types.map((type) => ({
+          streamId: client.streamId,
+          nodeId: client.nodeId,
+          nodeCluster: client.nodeCluster,
+          appId: client.appId,
+          acronym: xdsTypeOf(type.typeUrl).acronym,
+          status: type.status,
+          nackReason: type.nackReason,
+          lastSeen: type.lastSeen,
+          resourceNames: type.resourceNames ?? [],
+        })),
+      ),
+    [clients],
+  );
+
+  const columns = useMemo(() => {
+    const cols: ColumnDef<ClientRow, string>[] = [
+      columnHelper.accessor('nodeId', {
+        header: 'Node',
+        cell: (info) => (
+          <VStack align="start" spacing={0}>
+            <Text fontWeight="semibold">{info.getValue() || '(unknown)'}</Text>
+            {info.row.original.nodeCluster && (
+              <Text fontSize="xs" color="gray.500">
+                {info.row.original.nodeCluster}
+              </Text>
+            )}
+            <Text fontSize="xs" color="gray.400">
+              stream #{info.row.original.streamId}
+            </Text>
+          </VStack>
+        ),
+      }),
+      columnHelper.accessor('appId', {
+        header: 'App ID',
+        cell: (info) =>
+          info.getValue() ? (
+            <Code>{info.getValue()}</Code>
+          ) : (
+            <Text fontSize="sm" color="gray.400">
+              anonymous
+            </Text>
+          ),
+      }),
+      columnHelper.accessor('acronym', {
+        header: 'Type',
+        cell: (info) => (
+          <Tag colorScheme="purple" size="sm">
+            {info.getValue()}
+          </Tag>
+        ),
+      }),
+      columnHelper.accessor((row) => row.resourceNames.join(','), {
+        id: 'subscriptions',
+        header: 'Subscriptions',
+        enableSorting: false,
+        cell: (info) => {
+          const names = info.row.original.resourceNames;
+          if (names.length === 0) {
+            return (
+              <Badge colorScheme="gray" variant="subtle">
+                wildcard
+              </Badge>
+            );
+          }
+          return (
+            <Wrap spacing={1}>
+              {names.map((name) => (
+                <WrapItem key={name}>
+                  <Code fontSize="xs">{name}</Code>
+                </WrapItem>
+              ))}
+            </Wrap>
+          );
+        },
+      }),
+      columnHelper.accessor('status', {
+        header: 'Status',
+        cell: (info) => (
+          <Badge colorScheme={statusColorScheme(info.getValue() as XdsAckStatus)}>{info.getValue()}</Badge>
+        ),
+      }),
+      columnHelper.accessor('nackReason', {
+        header: 'NACK reason',
+        enableSorting: false,
+        cell: (info) =>
+          info.getValue() ? (
+            <Text color="red.500" fontSize="sm" maxW="md" whiteSpace="pre-wrap">
+              {info.getValue()}
+            </Text>
+          ) : (
+            <Text color="gray.400" fontSize="sm">
+              -
+            </Text>
+          ),
+      }),
+      columnHelper.accessor((row) => String(row.lastSeen), {
+        id: 'lastSeen',
+        header: 'Last seen',
+        cell: (info) => (
+          <Text fontSize="sm" color="gray.600">
+            {formatTime(info.row.original.lastSeen)}
+          </Text>
+        ),
+      }),
+    ];
+    return cols;
+  }, []);
+
+  const table = useReactTable({
+    data: rows,
+    columns,
+    getCoreRowModel: getCoreRowModel(),
+    getSortedRowModel: getSortedRowModel(),
+  });
+
+  if (rows.length === 0) {
+    return (
+      <Box mt={4}>
+        <HStack color="gray.500">
+          <Text>No xDS clients are currently connected to this server.</Text>
+        </HStack>
+      </Box>
+    );
+  }
+
+  return <DataTable table={table} />;
+};