feat(coding-agent): add fork position and duplicate session option (#3431)

packages/coding-agent/test/extensions-runner.test.ts

@@ -695,6 +695,30 @@ describe("ExtensionRunner", () => {
 		});
 	});
 
+	describe("command context", () => {
+		it("passes fork options through to the bound handler", async () => {
+			const runtime = createExtensionRuntime();
+			const runner = new ExtensionRunner([], runtime, tempDir, sessionManager, modelRegistry);
+			const fork = vi.fn(async () => ({ cancelled: false }));
+
+			runner.bindCommandContext({
+				waitForIdle: async () => {},
+				newSession: async () => ({ cancelled: false }),
+				fork,
+				navigateTree: async () => ({ cancelled: false }),
+				switchSession: async () => ({ cancelled: false }),
+				reload: async () => {},
+			});
+
+			const commandContext = runner.createCommandContext();
+			await commandContext.fork("entry-1");
+			expect(fork).toHaveBeenCalledWith("entry-1", undefined);
+
+			await commandContext.fork("entry-2", { position: "at" });
+			expect(fork).toHaveBeenLastCalledWith("entry-2", { position: "at" });
+		});
+	});
+
 	describe("hasHandlers", () => {
 		it("returns true when handlers exist for event type", async () => {
 			const extCode = `