fix(pi): prevent oversized subagent result crashes

modules/agents/pi/extensions/subagents/supervisor.test.ts

@@ -140,6 +140,22 @@ test("activity exposes ordered transcript events while status and list keep only
   assert.doesNotMatch(JSON.stringify(listed), /private transcript body|secret file contents/u);
 });
 
+test("status activity history keeps only the 100 most recent summaries", async () => {
+  const runner = new FakeRunner();
+  const supervisor = new Supervisor(runner, "/tmp");
+  const accepted = await spawnStarted(supervisor);
+
+  for (let index = 0; index < 150; index += 1) {
+    runner.starts[0].events.running(`tick ${index}`);
+  }
+
+  const history = supervisor.status(accepted.id).activityHistory;
+
+  assert.equal(history.length, 100);
+  assert.equal(history[0].summary, "tick 50");
+  assert.equal(history[99].summary, "tick 149");
+});
+
 test("process failure reaches failed with diagnostics", async () => {
   const runner = new FakeRunner();
   const supervisor = new Supervisor(runner, "/tmp");
@@ -303,6 +319,22 @@ test("maxConcurrent preserves queued records", async () => {
   assert.equal(runner.starts.length, 2);
 });
 
+test("clearTerminal returns only removed terminal ids", async () => {
+  const runner = new FakeRunner();
+  const supervisor = new Supervisor(runner, "/tmp");
+  const first = await spawnStarted(supervisor, "one");
+  const second = await spawnStarted(supervisor, "two");
+  const running = await spawnStarted(supervisor, "three");
+
+  runner.starts[0].events.completed("one done", "agent_settled");
+  runner.starts[1].events.completed("two done", "agent_settled");
+
+  assert.deepEqual(supervisor.clearTerminal(), [first.id, second.id]);
+  assert.throws(() => supervisor.status(first.id), /unknown subagent id/);
+  assert.throws(() => supervisor.status(second.id), /unknown subagent id/);
+  assert.equal(supervisor.status(running.id).state, "running");
+});
+
 test("terminal records stay listed past ttl and remain retrievable until cleared", async () => {
   const runner = new FakeRunner();
   const supervisor = new Supervisor(runner, "/tmp", { recentTerminalTtlMs: 5 });

modules/agents/pi/extensions/subagents/supervisor.ts

@@ -44,6 +44,8 @@ const DEFAULT_TIMEOUTS = {
   runMs: 0,
 };
 
+const MAX_ACTIVITY_HISTORY = 100;
+
 export class Supervisor {
   private nextChild = 0;
   private readonly children = new Map<string, RunningChild>();
@@ -90,14 +92,14 @@ export class Supervisor {
     return cloneResult(this.require(id).record);
   }
 
-  clearTerminal(ids?: string[]): SubagentStatus[] {
+  clearTerminal(ids?: string[]): string[] {
     const selectedIds = ids ? [...new Set(ids.map((id) => id.trim()).filter(Boolean))] : undefined;
     if (selectedIds) for (const id of selectedIds) this.require(id);
-    const cleared: SubagentStatus[] = [];
+    const cleared: string[] = [];
     for (const [id, child] of this.children) {
       if (selectedIds && !selectedIds.includes(id)) continue;
       if (!isTerminal(child.record.status.state)) continue;
-      cleared.push(cloneStatus(child.record.status));
+      cleared.push(id);
       this.children.delete(id);
     }
     if (cleared.length > 0) this.emitChange();
@@ -344,6 +346,9 @@ export class Supervisor {
     const summary = summarizeActivity(activity);
     record.status.currentActivity = summary;
     record.status.activityHistory.push(summary);
+    if (record.status.activityHistory.length > MAX_ACTIVITY_HISTORY) {
+      record.status.activityHistory.splice(0, record.status.activityHistory.length - MAX_ACTIVITY_HISTORY);
+    }
     return activity;
   }