Prototype uncertain passages inline before the first build (LIVE_SPIKES)

apps/connector/src/image-file.test.ts

@@ -0,0 +1,114 @@
+import { afterEach, beforeEach, expect, test } from "bun:test";
+import { mkdir, mkdtemp, rm, symlink, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { Client } from "@modelcontextprotocol/sdk/client/index.js";
+import { InMemoryTransport } from "@modelcontextprotocol/sdk/inMemory.js";
+
+import { imageFileArguments, MAX_IMAGE_FILE_BYTES } from "./image-file";
+import { implementationBridge } from "./implementation";
+
+type BridgeApi = Parameters<typeof implementationBridge>[0];
+
+const PNG = new Uint8Array([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 1, 2, 3]);
+
+let base: string;
+let root: string;
+beforeEach(async () => {
+	base = await mkdtemp(join(tmpdir(), "chopin-image-"));
+	root = join(base, "worktree");
+	await mkdir(join(root, "shots"), { recursive: true });
+});
+afterEach(() => rm(base, { recursive: true, force: true }));
+
+test("reads an image inside the worktree as upload arguments", async () => {
+	await writeFile(join(root, "shots", "a.png"), PNG);
+	expect(await imageFileArguments(root, "shots/a.png")).toEqual({
+		data: Buffer.from(PNG).toString("base64"),
+		mimeType: "image/png",
+	});
+	expect((await imageFileArguments(root, join(root, "shots", "a.png"))).mimeType).toBe(
+		"image/png",
+	);
+});
+
+test("refuses paths outside the worktree, including through a symlink", async () => {
+	await writeFile(join(base, "outside.png"), PNG);
+	await symlink(join(base, "outside.png"), join(root, "link.png"));
+	await expect(imageFileArguments(root, "../outside.png")).rejects.toThrow("inside this run");
+	await expect(imageFileArguments(root, join(base, "outside.png"))).rejects.toThrow(
+		"inside this run",
+	);
+	await expect(imageFileArguments(root, "link.png")).rejects.toThrow("inside this run");
+	await expect(imageFileArguments(root, "missing.png")).rejects.toThrow("No file");
+});
+
+test("refuses non-images and images over 1 MiB with a smaller-screenshot hint", async () => {
+	await writeFile(join(root, "notes.txt"), "hello");
+	await expect(imageFileArguments(root, "notes.txt")).rejects.toThrow("PNG, JPEG or WebP");
+	let large = new Uint8Array(MAX_IMAGE_FILE_BYTES + 1);
+	large.set(PNG);
+	await writeFile(join(root, "large.png"), large);
+	await expect(imageFileArguments(root, "large.png")).rejects.toThrow("1280x800");
+});
+
+test("the spike bridge serves upload_image_file by forwarding the file's bytes", async () => {
+	await writeFile(join(root, "shot.png"), PNG);
+	let invoked: Array<{ name: string; args: Record<string, unknown> }> = [];
+	let api = {
+		tools: async () => ({
+			tools: [{
+				name: "upload_investigation_image",
+				inputSchema: { type: "object" as const },
+			}],
+		}),
+		invoke: async (name: string, args: Record<string, unknown> = {}) => {
+			invoked.push({ name, args });
+			return { content: [{ type: "text", text: JSON.stringify({ path: "/images/x.png" }) }] };
+		},
+	};
+	let server = await implementationBridge(api as unknown as BridgeApi, root);
+	let [client, transport] = InMemoryTransport.createLinkedPair();
+	await server.connect(transport);
+	let mcp = new Client({ name: "test", version: "1" });
+	await mcp.connect(client);
+	try {
+		let names = (await mcp.listTools()).tools.map(tool => tool.name);
+		expect(names).toEqual(["upload_investigation_image", "upload_image_file"]);
+		let result = await mcp.callTool({ name: "upload_image_file", arguments: { path: "shot.png" } });
+		expect(result.isError).toBeFalsy();
+		expect(invoked).toEqual([{
+			name: "upload_investigation_image",
+			args: { data: Buffer.from(PNG).toString("base64"), mimeType: "image/png" },
+		}]);
+		let refused = await mcp.callTool({
+			name: "upload_image_file",
+			arguments: { path: "../escape.png" },
+		});
+		expect(refused.isError).toBe(true);
+		expect(invoked).toHaveLength(1);
+	} finally {
+		await mcp.close();
+		await server.close();
+	}
+});
+
+test("bridges without a worktree or image upload offer no local tool", async () => {
+	let api = {
+		tools: async () => ({
+			tools: [{ name: "read_rebuild", inputSchema: { type: "object" as const } }],
+		}),
+		invoke: async () => ({ content: [] }),
+	};
+	let server = await implementationBridge(api as unknown as BridgeApi, root);
+	let [client, transport] = InMemoryTransport.createLinkedPair();
+	await server.connect(transport);
+	let mcp = new Client({ name: "test", version: "1" });
+	await mcp.connect(client);
+	try {
+		expect((await mcp.listTools()).tools.map(tool => tool.name)).toEqual(["read_rebuild"]);
+	} finally {
+		await mcp.close();
+		await server.close();
+	}
+});

apps/connector/src/image-file.ts

@@ -0,0 +1,44 @@
+import { readFile, realpath } from "node:fs/promises";
+import { isAbsolute, relative, resolve } from "node:path";
+
+/** Chopin hosts images of at most 1 MiB. */
+export const MAX_IMAGE_FILE_BYTES = 1024 * 1024;
+
+const TOO_LARGE =
+	"Take a smaller screenshot (a 1280x800 viewport PNG of the running prototype) and upload that.";
+
+function mimeType(bytes: Uint8Array): string | undefined {
+	let ascii = (start: number, end: number) => String.fromCharCode(...bytes.subarray(start, end));
+	if (bytes[0] === 0x89 && ascii(1, 4) === "PNG") return "image/png";
+	if (bytes[0] === 0xff && bytes[1] === 0xd8 && bytes[2] === 0xff) return "image/jpeg";
+	if (ascii(0, 4) === "RIFF" && ascii(8, 12) === "WEBP") return "image/webp";
+}
+
+/**
+ * Read a PNG, JPEG or WebP inside the run's worktree as upload_investigation_image arguments, so
+ * the agent passes a path instead of emitting the image's base64 as tokens.
+ */
+export async function imageFileArguments(
+	root: string,
+	path: string,
+): Promise<{ data: string; mimeType: string }> {
+	let base = await realpath(root);
+	let target: string;
+	try {
+		target = await realpath(resolve(base, path));
+	} catch {
+		throw new Error(`No file at ${path} in this worktree.`);
+	}
+	let inside = relative(base, target);
+	if (!inside || inside.startsWith("..") || isAbsolute(inside)) {
+		throw new Error("Upload only image files inside this run's worktree.");
+	}
+	let bytes = new Uint8Array(await readFile(target));
+	let type = mimeType(bytes);
+	if (!type) throw new Error("Upload a PNG, JPEG or WebP image.");
+	if (bytes.byteLength > MAX_IMAGE_FILE_BYTES) {
+		let size = Math.ceil(bytes.byteLength / 1024);
+		throw new Error(`${path} is ${size} KiB; images are limited to 1 MiB. ${TOO_LARGE}`);
+	}
+	return { data: Buffer.from(bytes).toString("base64"), mimeType: type };
+}

apps/connector/src/implementation.ts

@@ -1,21 +1,78 @@
 import { Server } from "@modelcontextprotocol/sdk/server/index.js";
 import { CallToolRequestSchema, ListToolsRequestSchema } from "@modelcontextprotocol/sdk/types.js";
+import { imageFileArguments } from "./image-file";
 import type { remote } from "./mcp";
 
-export async function implementationBridge(api: Awaited<ReturnType<typeof remote>>) {
-	let tools = await api.tools();
-	let names = new Set(tools.tools.map(tool => tool.name));
-	let server = new Server({ name: "chopin-implementation", version: "0.1.0" }, {
-		capabilities: { tools: {} },
-	});
-	server.setRequestHandler(ListToolsRequestSchema, () => tools);
-	server.setRequestHandler(CallToolRequestSchema, async request => {
-		if (!names.has(request.params.name)) {
-			return { isError: true, content: [{ type: "text", text: "Tool unavailable for this run." }] };
+/**
+ * Relay a run's server tools. With a worktree `root`, a run that may upload images also gets the
+ * connector-local upload_image_file, which reads the file here and forwards its bytes.
+ */
+export async function implementationBridge(
+	api: Pick<Awaited<ReturnType<typeof remote>>, "tools" | "invoke">,
+	root?: string,
+) {
+	return (await relay(api, root))();
+}
+
+/** List the run's tools once and return a factory for relaying servers, one per transport. */
+export async function relay(
+	api: Pick<Awaited<ReturnType<typeof remote>>, "tools" | "invoke">,
+	root?: string,
+) {
+	let listed = await api.tools();
+	let names = new Set(listed.tools.map(tool => tool.name));
+	let local = !!root && names.has("upload_investigation_image");
+	let tools = local
+		? {
+			...listed,
+			tools: [...listed.tools, {
+				name: "upload_image_file",
+				description:
+					"Upload a PNG, JPEG or WebP screenshot (at most 1 MiB) saved in this worktree and "
+					+ "return its image path for submit_spike_result.",
+				inputSchema: {
+					type: "object" as const,
+					properties: {
+						path: {
+							type: "string",
+							description: "The image file, relative to the worktree root.",
+						},
+					},
+					required: ["path"],
+					additionalProperties: false,
+				},
+			}],
 		}
-		return api.invoke(request.params.name, request.params.arguments ?? {});
-	});
-	return server;
+		: listed;
+	return () => {
+		let server = new Server({ name: "chopin-implementation", version: "0.1.0" }, {
+			capabilities: { tools: {} },
+		});
+		server.setRequestHandler(ListToolsRequestSchema, () => tools);
+		server.setRequestHandler(CallToolRequestSchema, async request => {
+			let args = request.params.arguments ?? {};
+			if (local && request.params.name === "upload_image_file") {
+				try {
+					if (typeof args.path !== "string" || !args.path) throw new Error("Give an image path.");
+					return await api.invoke(
+						"upload_investigation_image",
+						await imageFileArguments(root!, args.path),
+					);
+				} catch (error) {
+					let text = error instanceof Error ? error.message : "Image upload failed.";
+					return { isError: true, content: [{ type: "text", text }] };
+				}
+			}
+			if (!names.has(request.params.name)) {
+				return {
+					isError: true,
+					content: [{ type: "text", text: "Tool unavailable for this run." }],
+				};
+			}
+			return api.invoke(request.params.name, args);
+		});
+		return server;
+	};
 }
 
 export let implementationPrompt = [

apps/connector/src/local-bridge.ts

@@ -0,0 +1,42 @@
+import { randomBytes, timingSafeEqual } from "node:crypto";
+import { WebStandardStreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/webStandardStreamableHttp.js";
+import type { Server } from "@modelcontextprotocol/sdk/server/index.js";
+
+/**
+ * Serve run-scoped MCP tools to a local ACP agent over loopback streamable HTTP. Some agents (Copilot
+ * CLI in ACP mode) reject client-provided stdio servers, so connector-local tools need an HTTP URL.
+ * Each request gets a fresh stateless server; a per-run bearer token keeps other local processes
+ * and pages out.
+ */
+export function serveLocalBridge(open: () => Promise<Server>) {
+	let token = randomBytes(32).toString("base64url");
+	let expected = Buffer.from(`Bearer ${token}`);
+	let http = Bun.serve({
+		hostname: "127.0.0.1",
+		port: 0,
+		idleTimeout: 255,
+		async fetch(request) {
+			let given = Buffer.from(request.headers.get("authorization") ?? "");
+			if (given.length !== expected.length || !timingSafeEqual(given, expected)) {
+				return new Response(null, { status: 401 });
+			}
+			if (new URL(request.url).pathname !== "/mcp") return new Response(null, { status: 404 });
+			let server = await open();
+			let transport = new WebStandardStreamableHTTPServerTransport({
+				sessionIdGenerator: undefined,
+				enableJsonResponse: true,
+			});
+			await server.connect(transport);
+			try {
+				return await transport.handleRequest(request);
+			} finally {
+				void server.close();
+			}
+		},
+	});
+	return {
+		url: `http://127.0.0.1:${http.port}/mcp`,
+		token,
+		close: () => http.stop(true),
+	};
+}

apps/connector/src/main.ts

@@ -25,8 +25,10 @@ async function bridge() {
 		process.env.CHOPIN_BRIDGE_TOKEN!,
 	);
 	let server;
-	if (process.env.CHOPIN_BRIDGE_KIND === "implementation") server = await implementationBridge(api);
-	else {
+	// A spike's tools are the server's run-scoped list, relayed as they are.
+	if (["implementation", "spike"].includes(process.env.CHOPIN_BRIDGE_KIND ?? "")) {
+		server = await implementationBridge(api, process.env.CHOPIN_BRIDGE_ROOT);
+	} else {
 		let context = await api.call("read_experiment") as { input: unknown };
 		server = createBridge(requestSchema.parse(context.input), async result => {
 			await api.call("submit_experiment_result", { result });