fix(session): isolate event listener failures in agent fan-out

Both `AgentSession.#emit` (session/agent-session.ts) and `Agent.#emit`
(packages/agent/src/agent.ts) iterated listeners with no error isolation.
A synchronous throw in any subscriber aborted the for-loop, so later
subscribers (TUI rendering, ACP bridge, task executor progress,
hindsight) silently missed events. Many listeners — see
`modes/controllers/event-controller.ts:141` and
`modes/controllers/input-controller.ts:576` — are registered as
`async (event) => { await this.handleEvent(event); }`; the returned
Promise was dropped, so any rejection became an unhandled rejection.

Wrap each listener invocation in try/catch and attach a `.catch` to any
returned thenable. Errors are logged via `logger.warn` (already imported
in agent-session.ts) and `console.error` (agent.ts has no logger
dependency, keep it that way).

Test: new `test/session/emit-listener-isolation.test.ts` registers two
listeners on both classes; first listener throws (or returns a rejecting
Promise); asserts the second listener still receives the event AND no
`unhandledRejection` fires. 4 cases (sync+async × Agent+AgentSession).
All fail on current main; all pass with the fix.

packages/agent/src/agent.ts

@@ -1074,7 +1074,16 @@ export class Agent {
 
 	#emit(e: AgentEvent) {
 		for (const listener of this.#listeners) {
-			listener(e);
+			try {
+				const result = listener(e) as unknown;
+				if (result && typeof (result as Promise<unknown>).then === "function") {
+					(result as Promise<unknown>).catch(err => {
+						console.error("Agent listener rejected:", err instanceof Error ? err.message : err);
+					});
+				}
+			} catch (err) {
+				console.error("Agent listener threw:", err instanceof Error ? err.message : err);
+			}
 		}
 	}
 

packages/coding-agent/src/session/agent-session.ts

@@ -1307,10 +1307,25 @@ export class AgentSession {
 
 	/** Emit an event to all listeners */
 	#emit(event: AgentSessionEvent): void {
-		// Copy array before iteration to avoid mutation during iteration
+		// Copy array before iteration to avoid mutation during iteration.
 		const listeners = [...this.#eventListeners];
 		for (const l of listeners) {
-			l(event);
+			try {
+				const result = l(event);
+				// Listener may be an async function whose returned Promise we don't await;
+				// attach a catch so a rejection does not become an unhandled rejection.
+				if (result && typeof (result as Promise<unknown>).then === "function") {
+					(result as Promise<unknown>).catch(err => {
+						logger.warn("AgentSession listener rejected", {
+							error: err instanceof Error ? err.message : String(err),
+						});
+					});
+				}
+			} catch (err) {
+				logger.warn("AgentSession listener threw", {
+					error: err instanceof Error ? err.message : String(err),
+				});
+			}
 		}
 	}
 

packages/coding-agent/test/session/emit-listener-isolation.test.ts

@@ -0,0 +1,144 @@
+// Tests #emit listener isolation in agent.ts (Agent) and agent-session.ts (AgentSession):
+// a throwing or rejecting listener must not prevent later listeners from receiving the event,
+// and an async listener's rejection must not become an unhandled rejection.
+import { afterEach, beforeEach, describe, expect, it } from "bun:test";
+import * as fs from "node:fs";
+import * as os from "node:os";
+import * as path from "node:path";
+import { Agent, type AgentEvent } from "@oh-my-pi/pi-agent-core";
+import { getBundledModel } from "@oh-my-pi/pi-ai";
+import { createMockModel } from "@oh-my-pi/pi-ai/providers/mock";
+import { ModelRegistry } from "@oh-my-pi/pi-coding-agent/config/model-registry";
+import { Settings } from "@oh-my-pi/pi-coding-agent/config/settings";
+import { AgentSession } from "@oh-my-pi/pi-coding-agent/session/agent-session";
+import { AuthStorage } from "@oh-my-pi/pi-coding-agent/session/auth-storage";
+import { SessionManager } from "@oh-my-pi/pi-coding-agent/session/session-manager";
+import { Snowflake } from "@oh-my-pi/pi-utils";
+
+function makeEvent(): AgentEvent {
+	return { type: "tool_execution_start", toolCallId: "probe-1", toolName: "probe" };
+}
+
+describe("#emit listener isolation", () => {
+	describe("Agent.#emit (packages/agent/src/agent.ts)", () => {
+		it("continues to deliver to later listeners when an earlier listener throws synchronously", () => {
+			const agent = new Agent();
+			const calls: string[] = [];
+			agent.subscribe(() => {
+				calls.push("A");
+				throw new Error("listener A boom");
+			});
+			agent.subscribe(() => {
+				calls.push("B");
+			});
+
+			agent.emitExternalEvent(makeEvent());
+
+			expect(calls).toEqual(["A", "B"]);
+		});
+
+		it("does not surface an unhandled rejection when an async listener rejects", async () => {
+			const agent = new Agent();
+			const unhandled: unknown[] = [];
+			const onUnhandled = (reason: unknown) => unhandled.push(reason);
+			process.on("unhandledRejection", onUnhandled);
+			const calls: string[] = [];
+			try {
+				agent.subscribe(async () => {
+					calls.push("A");
+					throw new Error("async A boom");
+				});
+				agent.subscribe(() => {
+					calls.push("B");
+				});
+
+				agent.emitExternalEvent(makeEvent());
+				await Bun.sleep(10);
+
+				expect(calls).toEqual(["A", "B"]);
+				expect(unhandled).toEqual([]);
+			} finally {
+				process.off("unhandledRejection", onUnhandled);
+			}
+		});
+	});
+
+	describe("AgentSession.#emit (packages/coding-agent/src/session/agent-session.ts)", () => {
+		let session: AgentSession;
+		let tempDir: string;
+		let authStorage: AuthStorage | undefined;
+
+		beforeEach(async () => {
+			tempDir = path.join(os.tmpdir(), `pi-emit-iso-${Snowflake.next()}`);
+			fs.mkdirSync(tempDir, { recursive: true });
+			const model = getBundledModel("anthropic", "claude-sonnet-4-5");
+			if (!model) throw new Error("Test model not found");
+			authStorage = await AuthStorage.create(path.join(tempDir, "auth.db"));
+			authStorage.setRuntimeApiKey("anthropic", "test-key");
+			const modelRegistry = new ModelRegistry(authStorage, path.join(tempDir, "models.yml"));
+			const mock = createMockModel({ responses: [{ content: ["ok"] }] });
+			const agent = new Agent({
+				initialState: { model, systemPrompt: ["t"], tools: [], messages: [] },
+				streamFn: mock.stream,
+			});
+			session = new AgentSession({
+				agent,
+				sessionManager: SessionManager.inMemory(),
+				settings: Settings.isolated(),
+				modelRegistry,
+			});
+		});
+
+		afterEach(async () => {
+			await session.dispose();
+			authStorage?.close();
+			authStorage = undefined;
+			if (fs.existsSync(tempDir)) {
+				try {
+					fs.rmSync(tempDir, { recursive: true, force: true });
+				} catch {
+					// Windows may hold sqlite handles briefly after close; best-effort cleanup.
+				}
+			}
+		});
+
+		it("continues to deliver to later listeners when an earlier listener throws synchronously", () => {
+			const calls: string[] = [];
+			session.subscribe(() => {
+				calls.push("A");
+				throw new Error("session listener A boom");
+			});
+			session.subscribe(() => {
+				calls.push("B");
+			});
+
+			session.emitNotice("info", "probe", "test");
+
+			expect(calls).toEqual(["A", "B"]);
+		});
+
+		it("does not surface an unhandled rejection when an async listener rejects", async () => {
+			const unhandled: unknown[] = [];
+			const onUnhandled = (reason: unknown) => unhandled.push(reason);
+			process.on("unhandledRejection", onUnhandled);
+			const calls: string[] = [];
+			try {
+				session.subscribe(async () => {
+					calls.push("A");
+					throw new Error("async session A boom");
+				});
+				session.subscribe(() => {
+					calls.push("B");
+				});
+
+				session.emitNotice("info", "probe", "test");
+				await Bun.sleep(10);
+
+				expect(calls).toEqual(["A", "B"]);
+				expect(unhandled).toEqual([]);
+			} finally {
+				process.off("unhandledRejection", onUnhandled);
+			}
+		});
+	});
+});