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;
   }
 

modules/agents/pi/patches/pi-flex-spacer.patch

@@ -32,7 +32,7 @@ diff --git a/packages/coding-agent/src/core/settings-manager.ts b/packages/codin
 diff --git a/packages/coding-agent/src/modes/interactive/interactive-mode.ts b/packages/coding-agent/src/modes/interactive/interactive-mode.ts
 --- a/packages/coding-agent/src/modes/interactive/interactive-mode.ts	2026-08-01 18:41:36.963495957 -0400
 +++ b/packages/coding-agent/src/modes/interactive/interactive-mode.ts	2026-08-01 18:43:04.876341236 -0400
-@@ -210,6 +210,45 @@
+@@ -210,6 +210,47 @@
  	return code !== undefined && DEAD_TERMINAL_ERROR_CODES.has(code);
  }
  
@@ -56,7 +56,9 @@ diff --git a/packages/coding-agent/src/modes/interactive/interactive-mode.ts b/p
 +	private renderGroup(children: Component[], width: number): string[] {
 +		const lines: string[] = [];
 +		for (const child of children) {
-+			lines.push(...child.render(width));
++			for (const line of child.render(width)) {
++				lines.push(line);
++			}
 +		}
 +		return lines;
 +	}
@@ -78,7 +80,7 @@ diff --git a/packages/coding-agent/src/modes/interactive/interactive-mode.ts b/p
  const ANTHROPIC_SUBSCRIPTION_AUTH_WARNING =
  	"Anthropic subscription auth is active. Third-party harness usage draws from extra usage and is billed per token, not your Claude plan limits. Manage extra usage at https://claude.ai/settings/usage. Disable this warning in /settings.";
  
-@@ -335,6 +374,7 @@
+@@ -335,6 +376,7 @@
  	private fdPath: string | undefined;
  	private editorContainer: Container;
  	private footer: FooterComponent;
@@ -86,7 +88,7 @@ diff --git a/packages/coding-agent/src/modes/interactive/interactive-mode.ts b/p
  	private footerDataProvider: FooterDataProvider;
  	// Stored so the same manager can be injected into custom editors, selectors, and extension UI.
  	private keybindings: KeybindingsManager;
-@@ -477,7 +517,9 @@
+@@ -477,7 +519,9 @@
  		this.editorContainer = new Container();
  		this.editorContainer.addChild(this.editor as Component);
  		this.footerDataProvider = new FooterDataProvider(this.sessionManager.getCwd());
@@ -96,7 +98,7 @@ diff --git a/packages/coding-agent/src/modes/interactive/interactive-mode.ts b/p
  		this.footer.setAutoCompactEnabled(this.session.autoCompactionEnabled);
  
  		// Load hide thinking block setting
-@@ -704,19 +746,25 @@
+@@ -704,19 +748,25 @@
  			console.log(theme.fg("dim", `Model scope: ${modelList}${cycleHint}`));
  		}
  
@@ -134,7 +136,7 @@ diff --git a/packages/coding-agent/src/modes/interactive/interactive-mode.ts b/p
  		this.ui.setFocus(this.editor);
  
  		this.setupKeyHandlers();
-@@ -2033,25 +2081,25 @@
+@@ -2033,25 +2083,25 @@
  			| ((tui: TUI, thm: Theme, footerData: ReadonlyFooterDataProvider) => Component & { dispose?(): void })
  			| undefined,
  	): void {