diff --git a/packages/coding-agent/src/modes/interactive/components/session-selector.ts b/packages/coding-agent/src/modes/interactive/components/session-selector.ts
index 74141e5ef..77b5a2bac 100644
--- a/packages/coding-agent/src/modes/interactive/components/session-selector.ts
+++ b/packages/coding-agent/src/modes/interactive/components/session-selector.ts
@@ -190,6 +190,7 @@ class SessionSelectorHeader implements Component {
 interface SessionTreeNode {
 	session: SessionInfo;
 	children: SessionTreeNode[];
+	latestActivity: number;
 }
 
 /** Flattened node for display with tree structure info */
@@ -210,7 +211,7 @@ function buildSessionTree(sessions: SessionInfo[]): SessionTreeNode[] {
 
 	for (const session of sessions) {
 		const sessionPath = canonicalizePath(session.path) ?? session.path;
-		byPath.set(sessionPath, { session, children: [] });
+		byPath.set(sessionPath, { session, children: [], latestActivity: session.modified.getTime() });
 	}
 
 	const roots: SessionTreeNode[] = [];
@@ -227,9 +228,22 @@ function buildSessionTree(sessions: SessionInfo[]): SessionTreeNode[] {
 		}
 	}
 
-	// Sort children and roots by modified date (descending)
+	const updateLatestActivity = (node: SessionTreeNode): number => {
+		let latestActivity = node.session.modified.getTime();
+		for (const child of node.children) {
+			latestActivity = Math.max(latestActivity, updateLatestActivity(child));
+		}
+		node.latestActivity = latestActivity;
+		return latestActivity;
+	};
+
+	for (const root of roots) {
+		updateLatestActivity(root);
+	}
+
+	// Sort children and roots by latest activity in each subtree (descending)
 	const sortNodes = (nodes: SessionTreeNode[]): void => {
-		nodes.sort((a, b) => b.session.modified.getTime() - a.session.modified.getTime());
+		nodes.sort((a, b) => b.latestActivity - a.latestActivity);
 		for (const node of nodes) {
 			sortNodes(node.children);
 		}
diff --git a/packages/coding-agent/test/session-selector-path-delete.test.ts b/packages/coding-agent/test/session-selector-path-delete.test.ts
index 52cae4860..cb702d5e2 100644
--- a/packages/coding-agent/test/session-selector-path-delete.test.ts
+++ b/packages/coding-agent/test/session-selector-path-delete.test.ts
@@ -282,6 +282,45 @@ describe("session selector path/delete interactions", () => {
 		expect(output).toContain("└─ Child");
 	});
 
+	it("sorts threaded sessions by latest activity in their subtree", async () => {
+		const parentOne = makeSession({
+			id: "parent-one",
+			name: "Parent one",
+			modified: new Date("2026-01-02T00:00:00.000Z"),
+		});
+		const parentTwo = makeSession({
+			id: "parent-two",
+			name: "Parent two",
+			modified: new Date("2026-01-01T00:00:00.000Z"),
+		});
+		const childTwo = makeSession({
+			id: "child-two",
+			name: "Child two",
+			parentSessionPath: parentTwo.path,
+			modified: new Date("2026-01-03T00:00:00.000Z"),
+		});
+
+		const selector = new SessionSelectorComponent(
+			async () => [parentOne, parentTwo, childTwo],
+			async () => [],
+			() => {},
+			() => {},
+			() => {},
+			() => {},
+			{ keybindings },
+		);
+		await flushPromises();
+
+		const output = stripAnsi(selector.render(120).join("\n"));
+		const parentTwoIndex = output.indexOf("Parent two");
+		const childTwoIndex = output.indexOf("└─ Child two");
+		const parentOneIndex = output.indexOf("Parent one");
+
+		expect(parentTwoIndex).toBeGreaterThanOrEqual(0);
+		expect(childTwoIndex).toBeGreaterThan(parentTwoIndex);
+		expect(parentOneIndex).toBeGreaterThan(childTwoIndex);
+	});
+
 	it("treats the current session as active across symlink aliases", async () => {
 		const paths = createSymlinkedSessionPaths();
 		tempDirs.push(paths.baseDir);