fix(session): preserve title on first-turn branches

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

@@ -7506,7 +7506,10 @@ export class AgentSession {
 			await this.#advisors.drainAndDetachRecorders();
 			try {
 				if (!selectedEntry.parentId) {
+					const title = this.sessionManager.getSessionName();
+					const titleSource = this.sessionManager.titleSource;
 					await this.sessionManager.newSession({ parentSession: previousSessionFile });
+					if (title) await this.sessionManager.setSessionName(title, titleSource);
 				} else {
 					this.sessionManager.createBranchedSession(selectedEntry.parentId);
 				}

packages/coding-agent/test/agent-session-branching.test.ts

@@ -181,6 +181,29 @@ function historicalImagePrompt(text: string): UserMessage {
 	};
 }
 
+describe("AgentSession branch title metadata", () => {
+	it("preserves an explicit title when branching before the first prompt", async () => {
+		const ctx = await createTestSession({ inMemory: true });
+		try {
+			const entryId = ctx.sessionManager.appendMessage({
+				role: "user",
+				content: "hello",
+				timestamp: Date.now(),
+			});
+			await ctx.sessionManager.setSessionName("new-ds", "user");
+
+			await ctx.session.branch(entryId);
+
+			expect(ctx.sessionManager.getSessionName()).toBe("new-ds");
+			expect(ctx.sessionManager.titleSource).toBe("user");
+			expect(await ctx.sessionManager.setSessionName("automatic", "auto")).toBe(false);
+			expect(ctx.sessionManager.getSessionName()).toBe("new-ds");
+		} finally {
+			await ctx.cleanup();
+		}
+	});
+});
+
 describe("AgentSession historical image prompts", () => {
 	it("returns the selected images when branching from a user prompt", async () => {
 		const ctx = await createTestSession({ inMemory: true });

packages/coding-agent/test/session-manager/tree-traversal.test.ts

@@ -461,6 +461,9 @@ describe("createBranchedSession", () => {
 		session.createBranchedSession(leafId);
 
 		expect(session.getSessionName()).toBe("new-ds");
+		expect(session.titleSource).toBe("user");
+		expect(await session.setSessionName("automatic", "auto")).toBe(false);
+		expect(session.getSessionName()).toBe("new-ds");
 	});
 
 	it("extracts correct path from branched tree", () => {