diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 33ed9b010..4596a3dea 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -8,6 +8,7 @@
 
 ### Fixed
 
+- Fixed extension `pi.setSessionName()` updates to refresh the interactive terminal title immediately ([#3686](https://github.com/badlogic/pi-mono/issues/3686))
 - Fixed `/tree` cancellation via `session_before_tree` leaving the session stuck in compaction state ([#3688](https://github.com/badlogic/pi-mono/issues/3688))
 - Fixed Escape interrupt handling when extensions hide the built-in working loader row ([#3674](https://github.com/badlogic/pi-mono/issues/3674))
 - Fixed coding-agent test expectations for current default models and missing-auth guidance.
diff --git a/packages/coding-agent/src/core/agent-session.ts b/packages/coding-agent/src/core/agent-session.ts
index 9f9c4e6ed..7a26deb44 100644
--- a/packages/coding-agent/src/core/agent-session.ts
+++ b/packages/coding-agent/src/core/agent-session.ts
@@ -119,6 +119,7 @@ export type AgentSessionEvent =
 			followUp: readonly string[];
 	  }
 	| { type: "compaction_start"; reason: "manual" | "threshold" | "overflow" }
+	| { type: "session_info_changed"; name: string | undefined }
 	| {
 			type: "compaction_end";
 			reason: "manual" | "threshold" | "overflow";
@@ -2166,7 +2167,7 @@ export class AgentSession {
 					this.sessionManager.appendCustomEntry(customType, data);
 				},
 				setSessionName: (name) => {
-					this.sessionManager.appendSessionInfo(name);
+					this.setSessionName(name);
 				},
 				getSessionName: () => {
 					return this.sessionManager.getSessionName();
@@ -2648,6 +2649,7 @@ export class AgentSession {
 	 */
 	setSessionName(name: string): void {
 		this.sessionManager.appendSessionInfo(name);
+		this._emit({ type: "session_info_changed", name: this.sessionManager.getSessionName() });
 	}
 
 	// =========================================================================
diff --git a/packages/coding-agent/src/modes/interactive/interactive-mode.ts b/packages/coding-agent/src/modes/interactive/interactive-mode.ts
index f5c755f77..2436c7dc1 100644
--- a/packages/coding-agent/src/modes/interactive/interactive-mode.ts
+++ b/packages/coding-agent/src/modes/interactive/interactive-mode.ts
@@ -2698,6 +2698,12 @@ export class InteractiveMode {
 				this.ui.requestRender();
 				break;
 
+			case "session_info_changed":
+				this.updateTerminalTitle();
+				this.footer.invalidate();
+				this.ui.requestRender();
+				break;
+
 			case "message_start":
 				if (event.message.role === "custom") {
 					this.addMessageToChat(event.message);
@@ -5039,8 +5045,7 @@ export class InteractiveMode {
 			return;
 		}
 
-		this.sessionManager.appendSessionInfo(name);
-		this.updateTerminalTitle();
+		this.session.setSessionName(name);
 		this.chatContainer.addChild(new Spacer(1));
 		this.chatContainer.addChild(new Text(theme.fg("dim", `Session name set: ${name}`), 1, 0));
 		this.ui.requestRender();
diff --git a/packages/coding-agent/test/suite/regressions/3686-session-name-event.test.ts b/packages/coding-agent/test/suite/regressions/3686-session-name-event.test.ts
new file mode 100644
index 000000000..3614c09cc
--- /dev/null
+++ b/packages/coding-agent/test/suite/regressions/3686-session-name-event.test.ts
@@ -0,0 +1,40 @@
+import { afterEach, describe, expect, it } from "vitest";
+import type { ExtensionAPI } from "../../../src/index.js";
+import { createHarness, type Harness } from "../harness.js";
+
+describe("regression #3686: session name changes emit an event", () => {
+	const harnesses: Harness[] = [];
+
+	afterEach(() => {
+		while (harnesses.length > 0) {
+			harnesses.pop()?.cleanup();
+		}
+	});
+
+	it("emits session_info_changed when AgentSession.setSessionName is called", async () => {
+		const harness = await createHarness();
+		harnesses.push(harness);
+
+		harness.session.setSessionName("hello world");
+
+		expect(harness.sessionManager.getSessionName()).toBe("hello world");
+		expect(harness.eventsOfType("session_info_changed").map((event) => event.name)).toEqual(["hello world"]);
+	});
+
+	it("emits session_info_changed when an extension calls pi.setSessionName", async () => {
+		let api: ExtensionAPI | undefined;
+		const harness = await createHarness({
+			extensionFactories: [
+				(pi) => {
+					api = pi;
+				},
+			],
+		});
+		harnesses.push(harness);
+
+		api?.setSessionName("from extension");
+
+		expect(harness.sessionManager.getSessionName()).toBe("from extension");
+		expect(harness.eventsOfType("session_info_changed").map((event) => event.name)).toEqual(["from extension"]);
+	});
+});