feat(dashboard): add A2A audit page, stats bar on MCP audit, fix sidebar duplicates

- Add /dashboard/audit/a2a page with A2aAuditTab: lists tasks with skill/state
  filters, colored state badges, duration, events and artifacts counts
- Add "A2A Audit" item to Audit sidebar group (Monitoring section)
- Remove duplicate "MCP Audit" from MCP Server sidebar group — it stays
  only in the Audit group under Monitoring
- Improve McpAuditTab: fetch /api/mcp/audit/stats and show 4-card stat bar
  (calls 24h, success rate, avg duration, top tool) above the filters
- Add audit-a2a to HIDEABLE_SIDEBAR_ITEM_IDS
- Add i18n keys: auditA2a in sidebar + header sections, a2a* in compliance namespace

src/app/(dashboard)/dashboard/audit/A2aAuditTab.tsx

@@ -0,0 +1,217 @@
+"use client";
+
+import { useCallback, useEffect, useState } from "react";
+import { useTranslations } from "next-intl";
+import { Card } from "@/shared/components";
+import type { A2ATask, TaskState } from "@/lib/a2a/taskManager";
+
+type TaskListResponse = {
+  tasks: A2ATask[];
+  total: number;
+  limit: number;
+  offset: number;
+};
+
+const A2A_PAGE_SIZE = 25;
+
+const STATE_STYLES: Record<TaskState, string> = {
+  submitted: "border-amber-500/30 bg-amber-500/10 text-amber-600",
+  working: "border-blue-500/30 bg-blue-500/10 text-blue-600",
+  completed: "border-emerald-500/30 bg-emerald-500/10 text-emerald-600",
+  failed: "border-red-500/30 bg-red-500/10 text-red-600",
+  cancelled: "border-border bg-sidebar/40 text-text-muted",
+};
+
+function taskDuration(task: A2ATask): string {
+  const ms = new Date(task.updatedAt).getTime() - new Date(task.createdAt).getTime();
+  if (ms < 1000) return `${ms}ms`;
+  return `${(ms / 1000).toFixed(1)}s`;
+}
+
+export default function A2aAuditTab() {
+  const t = useTranslations("compliance");
+  const [data, setData] = useState<TaskListResponse>({
+    tasks: [],
+    total: 0,
+    limit: A2A_PAGE_SIZE,
+    offset: 0,
+  });
+  const [loading, setLoading] = useState(true);
+  const [skillFilter, setSkillFilter] = useState("");
+  const [stateFilter, setStateFilter] = useState<TaskState | "all">("all");
+  const [offset, setOffset] = useState(0);
+
+  const fetchTasks = useCallback(async () => {
+    setLoading(true);
+    try {
+      const params = new URLSearchParams();
+      params.set("limit", String(A2A_PAGE_SIZE));
+      params.set("offset", String(offset));
+      if (skillFilter) params.set("skill", skillFilter);
+      if (stateFilter !== "all") params.set("state", stateFilter);
+
+      const response = await fetch(`/api/a2a/tasks?${params.toString()}`);
+      const json = (await response.json().catch(() => ({}))) as Partial<TaskListResponse>;
+      setData({
+        tasks: Array.isArray(json.tasks) ? json.tasks : [],
+        total: Number(json.total || 0),
+        limit: Number(json.limit || A2A_PAGE_SIZE),
+        offset: Number(json.offset || offset),
+      });
+    } finally {
+      setLoading(false);
+    }
+  }, [offset, skillFilter, stateFilter]);
+
+  useEffect(() => {
+    void fetchTasks();
+  }, [fetchTasks]);
+
+  return (
+    <div className="space-y-5">
+      <Card className="p-5">
+        <div className="flex flex-col gap-4 lg:flex-row lg:items-start lg:justify-between">
+          <div>
+            <h2 className="text-xl font-semibold text-text-main">{t("a2aAudit")}</h2>
+            <p className="mt-1 text-sm text-text-muted">{t("a2aAuditDesc")}</p>
+            <p className="mt-2 text-xs text-text-muted">
+              {t("a2aShowingTasks", { count: data.tasks.length, total: data.total })}
+            </p>
+          </div>
+          <button
+            onClick={() => void fetchTasks()}
+            disabled={loading}
+            className="inline-flex items-center gap-2 rounded-lg border border-border px-3 py-2 text-sm font-medium text-text-main transition-colors hover:bg-sidebar disabled:opacity-40"
+          >
+            <span
+              className={`material-symbols-outlined text-[16px] ${loading ? "animate-spin" : ""}`}
+            >
+              refresh
+            </span>
+            {t("refresh")}
+          </button>
+        </div>
+      </Card>
+
+      <Card className="p-4">
+        <div className="grid gap-3 md:grid-cols-3">
+          <label className="space-y-1">
+            <span className="text-xs font-medium uppercase tracking-wider text-text-muted">
+              {t("a2aSkill")}
+            </span>
+            <input
+              value={skillFilter}
+              onChange={(e) => {
+                setOffset(0);
+                setSkillFilter(e.target.value);
+              }}
+              placeholder={t("a2aSkillPlaceholder")}
+              className="w-full rounded-lg border border-border bg-surface px-3 py-2 text-sm text-text-main focus:outline-none focus:ring-2 focus:ring-primary/40"
+            />
+          </label>
+          <label className="space-y-1">
+            <span className="text-xs font-medium uppercase tracking-wider text-text-muted">
+              {t("a2aState")}
+            </span>
+            <select
+              value={stateFilter}
+              onChange={(e) => {
+                setOffset(0);
+                setStateFilter(e.target.value as TaskState | "all");
+              }}
+              className="w-full rounded-lg border border-border bg-surface px-3 py-2 text-sm text-text-main focus:outline-none focus:ring-2 focus:ring-primary/40"
+            >
+              <option value="all">{t("a2aAllStates")}</option>
+              <option value="submitted">{t("a2aStateSubmitted")}</option>
+              <option value="working">{t("a2aStateWorking")}</option>
+              <option value="completed">{t("a2aStateCompleted")}</option>
+              <option value="failed">{t("a2aStateFailed")}</option>
+              <option value="cancelled">{t("a2aStateCancelled")}</option>
+            </select>
+          </label>
+          <div className="flex items-end">
+            <button
+              onClick={() => {
+                setSkillFilter("");
+                setStateFilter("all");
+                setOffset(0);
+              }}
+              className="w-full rounded-lg border border-border px-3 py-2 text-sm font-medium text-text-main transition-colors hover:bg-sidebar"
+            >
+              {t("clearFilters")}
+            </button>
+          </div>
+        </div>
+      </Card>
+
+      <Card className="overflow-hidden">
+        {loading ? (
+          <div className="p-8 text-center text-sm text-text-muted">{t("a2aLoadingTasks")}</div>
+        ) : data.tasks.length === 0 ? (
+          <div className="p-10 text-center">
+            <span className="material-symbols-outlined text-[40px] text-text-muted">
+              device_hub
+            </span>
+            <p className="mt-3 text-sm text-text-muted">{t("a2aNoTasks")}</p>
+          </div>
+        ) : (
+          <div className="overflow-x-auto">
+            <table className="w-full min-w-[760px] text-left text-sm">
+              <thead className="border-b border-border bg-sidebar/40 text-xs uppercase tracking-wider text-text-muted">
+                <tr>
+                  <th className="px-4 py-3 font-medium">{t("timestamp")}</th>
+                  <th className="px-4 py-3 font-medium">{t("a2aTaskId")}</th>
+                  <th className="px-4 py-3 font-medium">{t("a2aSkill")}</th>
+                  <th className="px-4 py-3 font-medium">{t("a2aState")}</th>
+                  <th className="px-4 py-3 font-medium">{t("duration")}</th>
+                  <th className="px-4 py-3 font-medium">{t("a2aEvents")}</th>
+                  <th className="px-4 py-3 font-medium">{t("a2aArtifacts")}</th>
+                </tr>
+              </thead>
+              <tbody className="divide-y divide-border">
+                {data.tasks.map((task) => (
+                  <tr key={task.id} className="transition-colors hover:bg-sidebar/30">
+                    <td className="whitespace-nowrap px-4 py-3 font-mono text-xs text-text-muted">
+                      {new Date(task.createdAt).toLocaleString()}
+                    </td>
+                    <td className="px-4 py-3 font-mono text-xs text-text-muted">
+                      {task.id.slice(0, 8)}&hellip;
+                    </td>
+                    <td className="px-4 py-3 font-mono text-xs text-text-main">{task.skill}</td>
+                    <td className="px-4 py-3">
+                      <span
+                        className={`rounded-full border px-2 py-1 text-xs font-medium ${STATE_STYLES[task.state]}`}
+                      >
+                        {task.state}
+                      </span>
+                    </td>
+                    <td className="px-4 py-3 text-text-muted">{taskDuration(task)}</td>
+                    <td className="px-4 py-3 text-text-muted">{task.events.length}</td>
+                    <td className="px-4 py-3 text-text-muted">{task.artifacts.length}</td>
+                  </tr>
+                ))}
+              </tbody>
+            </table>
+          </div>
+        )}
+      </Card>
+
+      <div className="flex items-center justify-end gap-2">
+        <button
+          onClick={() => setOffset((c) => Math.max(0, c - A2A_PAGE_SIZE))}
+          disabled={offset === 0 || loading}
+          className="rounded-lg border border-border px-3 py-2 text-sm font-medium text-text-main transition-colors hover:bg-sidebar disabled:opacity-40"
+        >
+          {t("previous")}
+        </button>
+        <button
+          onClick={() => setOffset((c) => c + A2A_PAGE_SIZE)}
+          disabled={offset + A2A_PAGE_SIZE >= data.total || loading}
+          className="rounded-lg border border-border px-3 py-2 text-sm font-medium text-text-main transition-colors hover:bg-sidebar disabled:opacity-40"
+        >
+          {t("next")}
+        </button>
+      </div>
+    </div>
+  );
+}

src/app/(dashboard)/dashboard/audit/McpAuditTab.tsx

@@ -23,6 +23,13 @@ type McpAuditResponse = {
   offset: number;
 };
 
+type McpAuditStats = {
+  totalCalls: number;
+  successRate: number;
+  avgDurationMs: number;
+  topTools: Array<{ tool: string; count: number }>;
+};
+
 const MCP_PAGE_SIZE = 25;
 
 export default function McpAuditTab() {
@@ -33,11 +40,25 @@ export default function McpAuditTab() {
     limit: MCP_PAGE_SIZE,
     offset: 0,
   });
+  const [stats, setStats] = useState<McpAuditStats | null>(null);
   const [loading, setLoading] = useState(true);
   const [toolFilter, setToolFilter] = useState("");
   const [successFilter, setSuccessFilter] = useState<"all" | "true" | "false">("all");
   const [offset, setOffset] = useState(0);
 
+  const fetchStats = useCallback(async () => {
+    try {
+      const res = await fetch("/api/mcp/audit/stats");
+      if (res.ok) setStats((await res.json()) as McpAuditStats);
+    } catch {
+      // non-fatal
+    }
+  }, []);
+
+  useEffect(() => {
+    void fetchStats();
+  }, [fetchStats]);
+
   const fetchAudit = useCallback(async () => {
     setLoading(true);
     try {
@@ -80,7 +101,10 @@ export default function McpAuditTab() {
             </p>
           </div>
           <button
-            onClick={() => void fetchAudit()}
+            onClick={() => {
+              void fetchAudit();
+              void fetchStats();
+            }}
             disabled={loading}
             className="inline-flex items-center gap-2 rounded-lg border border-border px-3 py-2 text-sm font-medium text-text-main transition-colors hover:bg-sidebar disabled:opacity-40"
           >
@@ -94,6 +118,54 @@ export default function McpAuditTab() {
         </div>
       </Card>
 
+      {stats && (
+        <div className="grid grid-cols-2 gap-3 md:grid-cols-4">
+          {[
+            {
+              label: "Calls (24h)",
+              value: stats.totalCalls.toLocaleString(),
+              icon: "terminal",
+            },
+            {
+              label: "Success rate",
+              value: `${Math.round(stats.successRate * 100)}%`,
+              icon: "check_circle",
+              highlight: stats.successRate >= 0.9,
+            },
+            {
+              label: "Avg duration",
+              value: `${Math.round(stats.avgDurationMs)}ms`,
+              icon: "timer",
+            },
+            {
+              label: "Top tool",
+              value: stats.topTools[0]?.tool ?? "—",
+              icon: "star",
+            },
+          ].map((item) => (
+            <Card key={item.label} className="px-4 py-3">
+              <div className="flex items-center gap-2 mb-1">
+                <span
+                  className="material-symbols-outlined text-[14px]"
+                  style={{ color: "var(--color-text-muted)" }}
+                >
+                  {item.icon}
+                </span>
+                <span className="text-xs text-text-muted uppercase tracking-wider">
+                  {item.label}
+                </span>
+              </div>
+              <p
+                className="text-lg font-semibold truncate"
+                style={{ color: item.highlight ? "rgb(34,197,94)" : "var(--color-text)" }}
+              >
+                {item.value}
+              </p>
+            </Card>
+          ))}
+        </div>
+      )}
+
       <Card className="p-4">
         <div className="grid gap-3 md:grid-cols-3">
           <label className="space-y-1">

src/app/(dashboard)/dashboard/audit/a2a/page.tsx

@@ -0,0 +1,7 @@
+"use client";
+
+import A2aAuditTab from "../A2aAuditTab";
+
+export default function AuditA2aPage() {
+  return <A2aAuditTab />;
+}

src/i18n/messages/en.json

@@ -772,6 +772,7 @@
     "logsConsole": "Console",
     "logsActivity": "Activity",
     "auditMcp": "MCP Audit",
+    "auditA2a": "A2A Audit",
     "settingsGeneral": "General",
     "settingsAppearance": "Appearance",
     "settingsAi": "AI Settings",
@@ -890,7 +891,24 @@
     "allResults": "All results",
     "success": "Success",
     "failure": "Failure",
-    "noMcpEvents": "No MCP audit events recorded."
+    "noMcpEvents": "No MCP audit events recorded.",
+    "a2aAudit": "A2A Audit",
+    "a2aAuditDesc": "Task execution audit trail recorded by the A2A server.",
+    "a2aShowingTasks": "Showing {count} of {total} tasks",
+    "a2aSkill": "Skill",
+    "a2aSkillPlaceholder": "Filter by skill name",
+    "a2aState": "State",
+    "a2aAllStates": "All states",
+    "a2aStateSubmitted": "Submitted",
+    "a2aStateWorking": "Working",
+    "a2aStateCompleted": "Completed",
+    "a2aStateFailed": "Failed",
+    "a2aStateCancelled": "Cancelled",
+    "a2aTaskId": "Task ID",
+    "a2aEvents": "Events",
+    "a2aArtifacts": "Artifacts",
+    "a2aNoTasks": "No A2A tasks recorded.",
+    "a2aLoadingTasks": "Loading A2A tasks..."
   },
   "themesPage": {
     "title": "Themes",
@@ -965,6 +983,8 @@
     "logsConsoleDescription": "Application console output and debug logs",
     "logsActivityDescription": "Audit trail of user actions and system events",
     "auditMcpDescription": "MCP tool invocation audit trail and compliance records",
+    "auditA2a": "A2A Audit",
+    "auditA2aDescription": "A2A task execution audit trail, state transitions, and skill invocation records",
     "settingsGeneralDescription": "Storage, database, and general instance configuration",
     "settingsAppearanceDescription": "Theme, branding, and visual customization",
     "settingsAiDescription": "AI behaviors, thinking budgets, vision, and memory settings",

src/shared/constants/sidebarVisibility.ts

@@ -43,6 +43,7 @@ export const HIDEABLE_SIDEBAR_ITEM_IDS = [
   // Monitoring > Audit
   "audit",
   "audit-mcp",
+  "audit-a2a",
   // Dev Tools
   "translator",
   "playground",
@@ -277,6 +278,7 @@ const AUDIT_GROUP: SidebarItemGroup = {
   items: [
     { id: "audit", href: "/dashboard/audit", i18nKey: "auditLog", icon: "policy" },
     { id: "audit-mcp", href: "/dashboard/audit/mcp", i18nKey: "auditMcp", icon: "security" },
+    { id: "audit-a2a", href: "/dashboard/audit/a2a", i18nKey: "auditA2a", icon: "device_hub" },
   ],
 };
 
@@ -296,10 +298,7 @@ const MCP_GROUP: SidebarItemGroup = {
   id: "mcp",
   titleKey: "mcp",
   titleFallback: "MCP Server",
-  items: [
-    { id: "mcp", href: "/dashboard/mcp", i18nKey: "mcp", icon: "hub" },
-    { id: "audit-mcp", href: "/dashboard/audit/mcp", i18nKey: "auditMcp", icon: "security" },
-  ],
+  items: [{ id: "mcp", href: "/dashboard/mcp", i18nKey: "mcp", icon: "hub" }],
 };
 
 const AGENTIC_FEATURES_ITEMS: readonly SidebarSectionChild[] = [