feat: implement Agent Client Protocol (ACP) for Copilot CLI

cli/package.json

@@ -44,13 +44,14 @@
 		"url": "https://github.com/michaelshimeles/ralphy"
 	},
 	"dependencies": {
-		"commander": "^13.0.0",
-		"yaml": "^2.7.0",
-		"simple-git": "^3.27.0",
+		"@agentclientprotocol/sdk": "^0.13.1",
 		"@octokit/rest": "^21.0.0",
-		"picocolors": "^1.1.0",
+		"commander": "^13.0.0",
 		"nanospinner": "^1.2.0",
 		"node-notifier": "^10.0.1",
+		"picocolors": "^1.1.0",
+		"simple-git": "^3.27.0",
+		"yaml": "^2.7.0",
 		"zod": "^3.24.0"
 	},
 	"devDependencies": {

cli/src/engines/copilot-acp.test.ts

@@ -0,0 +1,99 @@
+import { afterEach, beforeEach, describe, expect, it, mock, spyOn } from "bun:test";
+import { existsSync, mkdirSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { CopilotAcpEngine } from "./copilot-acp.ts";
+import * as baseModule from "./base.ts";
+
+describe("CopilotAcpEngine", () => {
+	let engine: CopilotAcpEngine;
+	const testWorkDir = join(tmpdir(), "copilot-acp-test");
+
+	beforeEach(() => {
+		engine = new CopilotAcpEngine();
+		mkdirSync(testWorkDir, { recursive: true });
+	});
+
+	afterEach(() => {
+		if (existsSync(testWorkDir)) {
+			rmSync(testWorkDir, { recursive: true, force: true });
+		}
+	});
+
+	describe("Basic Properties", () => {
+		it("should have correct name and command", () => {
+			expect(engine.name).toBe("GitHub Copilot");
+			expect(engine.cliCommand).toBe("copilot");
+		});
+	});
+
+	describe("ACP Connection", () => {
+		it("should build prompt content correctly", () => {
+			const promptContent = (engine as any).buildPromptContent("test prompt");
+			expect(promptContent).toEqual([{ type: "text", text: "test prompt" }]);
+		});
+
+		it("should prepend model override as instruction", () => {
+			const promptContent = (engine as any).buildPromptContent("test prompt", {
+				modelOverride: "gpt-4",
+			});
+			expect(promptContent).toHaveLength(2);
+			expect(promptContent[0]).toEqual({ type: "text", text: "[Use model: gpt-4]" });
+			expect(promptContent[1]).toEqual({ type: "text", text: "test prompt" });
+		});
+
+		it("should handle empty prompt", () => {
+			const promptContent = (engine as any).buildPromptContent("");
+			expect(promptContent).toEqual([{ type: "text", text: "" }]);
+		});
+
+		it("should preserve multiline prompts", () => {
+			const multilinePrompt = "Line 1\nLine 2\nLine 3";
+			const promptContent = (engine as any).buildPromptContent(multilinePrompt);
+			expect(promptContent[0].text).toBe(multilinePrompt);
+		});
+	});
+
+	describe("Prompt Content Building", () => {
+		it("should handle various prompt content scenarios", async () => {
+			// Test with model override
+			const withModel = (engine as any).buildPromptContent("test", { modelOverride: "gpt-4" });
+			expect(withModel[0].text).toContain("gpt-4");
+			expect(withModel[1].text).toBe("test");
+
+			// Test without model
+			const withoutModel = (engine as any).buildPromptContent("test");
+			expect(withoutModel).toHaveLength(1);
+			expect(withoutModel[0].text).toBe("test");
+		});
+	});
+
+	describe("Streaming Execution", () => {
+		it("should have executeStreaming method available", () => {
+			expect(engine.executeStreaming).toBeDefined();
+			expect(typeof engine.executeStreaming).toBe("function");
+		});
+	});
+
+	describe("Error Handling", () => {
+		it("should check if copilot command is available", async () => {
+			const isAvailable = await engine.isAvailable();
+			// This will check actual system, but should not throw
+			expect(typeof isAvailable).toBe("boolean");
+		});
+	});
+
+	describe("Integration Properties", () => {
+		it("should have correct engine properties", () => {
+			expect(engine.name).toBe("GitHub Copilot");
+			expect(engine.cliCommand).toBe("copilot");
+		});
+
+		it("should support model override in options", () => {
+			const content = (engine as any).buildPromptContent("test", {
+				modelOverride: "custom-model",
+			});
+			expect(content[0].text).toContain("custom-model");
+		});
+	});
+});