fix(coding-agent): unify compaction UI events closes #2617

packages/coding-agent/test/trigger-compact-extension.test.ts

@@ -0,0 +1,56 @@
+import { describe, expect, test, vi } from "vitest";
+import triggerCompactExtension from "../examples/extensions/trigger-compact.js";
+import type { ExtensionAPI, ExtensionCommandContext, ExtensionContext } from "../src/core/extensions/index.js";
+
+function createContext(tokens: number | null, compact = vi.fn()): ExtensionContext {
+	return {
+		hasUI: false,
+		ui: {} as ExtensionContext["ui"],
+		cwd: process.cwd(),
+		sessionManager: {} as ExtensionContext["sessionManager"],
+		modelRegistry: {} as ExtensionContext["modelRegistry"],
+		model: undefined,
+		isIdle: () => true,
+		abort: vi.fn(),
+		hasPendingMessages: () => false,
+		shutdown: vi.fn(),
+		getContextUsage: () => ({ tokens, contextWindow: 200_000, percent: tokens === null ? null : tokens / 2000 }),
+		compact,
+		getSystemPrompt: () => "",
+	};
+}
+
+describe("trigger-compact example extension", () => {
+	test("only auto-compacts when context usage crosses the threshold", () => {
+		let turnEndHandler:
+			| ((event: { type: "turn_end" }, ctx: ExtensionContext | ExtensionCommandContext) => void)
+			| undefined;
+
+		const api = {
+			on: (event: string, handler: (event: { type: "turn_end" }, ctx: ExtensionContext) => void) => {
+				if (event === "turn_end") {
+					turnEndHandler = handler;
+				}
+			},
+			registerCommand: vi.fn(),
+		} as unknown as ExtensionAPI;
+
+		triggerCompactExtension(api);
+		expect(turnEndHandler).toBeDefined();
+
+		const compact = vi.fn();
+		const event = { type: "turn_end" } as const;
+
+		turnEndHandler?.(event, createContext(110_000, compact));
+		expect(compact).not.toHaveBeenCalled();
+
+		turnEndHandler?.(event, createContext(120_000, compact));
+		expect(compact).not.toHaveBeenCalled();
+
+		turnEndHandler?.(event, createContext(95_000, compact));
+		expect(compact).not.toHaveBeenCalled();
+
+		turnEndHandler?.(event, createContext(105_000, compact));
+		expect(compact).toHaveBeenCalledTimes(1);
+	});
+});