perf: add a scenario for switching between and scrolling long agent conversations (#2259)

Adds the agentTabs perf scenario: two 2,100-entry agent conversations switched with Ctrl+Tab and scrolled, with budgets on DOM size, rows skipping rendering off screen, switch latency, scroll jumps and frame pacing.

src/features/agents/index.ts

@@ -45,6 +45,22 @@ export function activate(): () => void {
   sync(useProject.getState().project?.root);
   const disposers = [
     activateSettingsPages(),
+    // The performance harness (`perf/`): long conversations to switch between and scroll.
+    import.meta.env.DEV || import.meta.env.MODE === "perf"
+      ? registerActions([
+          {
+            id: "agents.openSampleConversations",
+            title: "Open Sample Conversations",
+            category: "Agents",
+            hidden: true,
+            run: async ({ arg }) => {
+              const { tasks = 2, turns = 150 } = (arg ?? {}) as { tasks?: number; turns?: number };
+              const { openSampleConversations } = await import("./sampleConversation");
+              openSampleConversations(tasks, turns);
+            },
+          },
+        ])
+      : () => {},
     useProject.subscribe((s, prev) => {
       if (s.project?.root !== prev.project?.root || s.project?.trusted !== prev.project?.trusted) sync(s.project?.root);
     }),

src/features/agents/sampleConversation.ts

@@ -0,0 +1,108 @@
+/**
+ * Agent tasks with long generated conversations, opened as editor tabs: what the
+ * performance harness (`perf/`) switches between and scrolls. Dev and perf builds only.
+ */
+import type { AgentEntry, AgentTask } from "@/bindings";
+import { useProject } from "@/platform/project";
+import { openTask, useAgents } from "./store";
+
+function task(id: string, title: string, cwd: string): AgentTask {
+  return {
+    id,
+    title,
+    provider: "claude",
+    model: null,
+    status: "ready",
+    isolation: "worktree",
+    cwd,
+    branch: null,
+    base: null,
+    baseCommit: null,
+    error: null,
+    createdMs: null,
+    updatedMs: null,
+    config: [],
+    commands: [],
+    usage: null,
+    queue: [],
+  };
+}
+
+/** A turn as agents work: a request, reasoning, a run of tool calls, then a reply with code. */
+function turn(cwd: string, i: number): AgentEntry[] {
+  const file = (k: number) => `${cwd}/src/orders/Order${(i + k) % 40}.kt`;
+  const tools: AgentEntry[] = Array.from({ length: 10 }, (_, k) => {
+    // Tool titles as agents report them (commands and paths, not UI text).
+    const command = k % 3 === 2 ? `Edit ${file(k)}` : k % 3 === 1 ? `Read ${file(k)}` : `grep -rn "order${i}" src`;
+    return {
+      type: "tool",
+      id: `tool-${i}-${k}`,
+      title: command,
+      kind: k % 3 === 2 ? "edit" : k % 3 === 1 ? "read" : "execute",
+      status: "completed",
+      locations: [],
+      output: Array.from(
+        { length: 12 },
+        (_, l) => `${file(l)}:${l * 7 + 3}:  val order${i} = repository.find(id${l})`,
+      ).join("\n"),
+      diffs: k % 3 === 2 ? [{ path: file(k), added: 4 + (k % 5), removed: 2 }] : [],
+    };
+  });
+  // What a user and an agent wrote (conversation content, not UI text).
+  const request = `Turn ${i}: make the order service retry failed payments and cover it with tests`;
+  const reasoning = `The payment client throws on timeouts; retrying belongs in the service (turn ${i}).`;
+  return [
+    {
+      type: "user",
+      text: request,
+      attachments: [],
+      sentMs: null,
+      doneMs: null,
+    },
+    {
+      type: "thought",
+      text: reasoning,
+    },
+    ...tools,
+    {
+      type: "agent",
+      text: [
+        `## Turn ${i}`,
+        "",
+        `Payments now retry **three times** with backoff before the order fails. Changed \`OrderService.kt\` and added tests:`,
+        "",
+        "- `retries` on timeouts, not on declined cards",
+        "- waits 200 ms, then 400 ms, then 800 ms",
+        "- logs each attempt with the order id",
+        "",
+        "```kotlin",
+        `suspend fun pay${i}(order: Order): Receipt =`,
+        "    retry(times = 3, initialDelay = 200.milliseconds) {",
+        "        payments.charge(order.id, order.total)",
+        "    }",
+        "```",
+        "",
+        "| Case | Before | After |",
+        "|---|---|---|",
+        "| Timeout | failed | retried |",
+        "| Declined | failed | failed |",
+      ].join("\n"),
+    },
+  ];
+}
+
+/** Opens `count` tasks of `turns` turns each (14 entries a turn), the last one shown. */
+export function openSampleConversations(count: number, turns: number) {
+  const cwd = useProject.getState().project?.root ?? "/";
+  const entries = Array.from({ length: turns }, (_, i) => turn(cwd, i)).flat();
+  const s = useAgents.getState();
+  const tasks = new Map(s.tasks);
+  const all = new Map(s.entries);
+  const ids = Array.from({ length: count }, (_, n) => `sample-${n + 1}`);
+  ids.forEach((id, n) => {
+    tasks.set(id, task(id, `Sample task ${n + 1}`, cwd));
+    all.set(id, entries);
+  });
+  useAgents.setState({ tasks, entries: all });
+  for (const id of ids) openTask(id);
+}

src/platform/locales/text/zh.json

@@ -2440,6 +2440,7 @@
   "Stop to Edit": "停止以编辑",
   "Stopped after {count} matches": "匹配 {count} 处后停止",
   "Stream Sample Output": "流式输出示例日志",
+  "Open Sample Conversations": "打开示例会话",
   "Strikeout": "删除线",
   "Struct": "结构体",
   "Struct type": "结构体类型",