fix: file @ autocomplete performance using fd

- Replace slow synchronous directory walking with fd for fuzzy file search
- Auto-download fd to ~/.pi/agent/tools/ if not found in PATH
- Performance improved from ~900ms to ~10ms per keystroke on large repos
- Remove minimatch dependency from tui package
- Graceful degradation if fd unavailable (empty results)

Fixes #69

packages/coding-agent/CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Fixed
 
 - **Prompt Restoration on API Key Error**: When submitting a message fails due to missing API key, the prompt is now restored to the editor instead of being lost. ([#77](https://github.com/badlogic/pi-mono/issues/77))
+- **File `@` Autocomplete Performance**: Fixed severe UI jank when using `@` for file attachment in large repositories. The file picker now uses `fd` (a fast file finder) instead of synchronous directory walking with minimatch. On a 55k file repo, search time dropped from ~900ms to ~10ms per keystroke. If `fd` is not installed, it will be automatically downloaded to `~/.pi/agent/tools/` on first use. ([#69](https://github.com/badlogic/pi-mono/issues/69))
 
 ## [0.10.2] - 2025-11-27
 

packages/coding-agent/src/main.ts

@@ -12,6 +12,7 @@ import { SessionManager } from "./session-manager.js";
 import { SettingsManager } from "./settings-manager.js";
 import { initTheme } from "./theme/theme.js";
 import { codingTools } from "./tools/index.js";
+import { ensureTool } from "./tools-manager.js";
 import { SessionSelectorComponent } from "./tui/session-selector.js";
 import { TuiRenderer } from "./tui/tui-renderer.js";
 
@@ -612,6 +613,7 @@ async function runInteractiveMode(
 	initialMessages: string[] = [],
 	initialMessage?: string,
 	initialAttachments?: Attachment[],
+	fdPath: string | null = null,
 ): Promise<void> {
 	const renderer = new TuiRenderer(
 		agent,
@@ -621,6 +623,7 @@ async function runInteractiveMode(
 		changelogMarkdown,
 		newVersion,
 		scopedModels,
+		fdPath,
 	);
 
 	// Initialize TUI (subscribes to agent events internally)
@@ -1133,6 +1136,9 @@ export async function main(args: string[]) {
 			console.log(chalk.dim(`Model scope: ${modelList} ${chalk.gray("(Ctrl+P to cycle)")}`));
 		}
 
+		// Ensure fd tool is available for file autocomplete
+		const fdPath = await ensureTool("fd");
+
 		// Interactive mode - use TUI (may have initial messages from CLI args)
 		await runInteractiveMode(
 			agent,
@@ -1146,6 +1152,7 @@ export async function main(args: string[]) {
 			parsed.messages,
 			initialMessage,
 			initialAttachments,
+			fdPath,
 		);
 	} else {
 		// Non-interactive mode (--print flag or --mode flag)

packages/coding-agent/src/tools-manager.ts

@@ -0,0 +1,188 @@
+import chalk from "chalk";
+import { spawnSync } from "child_process";
+import { chmodSync, createWriteStream, existsSync, mkdirSync, renameSync, rmSync } from "fs";
+import { arch, homedir, platform } from "os";
+import { join } from "path";
+import { Readable } from "stream";
+import { finished } from "stream/promises";
+
+const TOOLS_DIR = join(homedir(), ".pi", "agent", "tools");
+
+interface ToolConfig {
+	name: string;
+	repo: string; // GitHub repo (e.g., "sharkdp/fd")
+	binaryName: string; // Name of the binary inside the archive
+	getAssetName: (version: string, plat: string, architecture: string) => string | null;
+}
+
+const TOOLS: Record<string, ToolConfig> = {
+	fd: {
+		name: "fd",
+		repo: "sharkdp/fd",
+		binaryName: "fd",
+		getAssetName: (version, plat, architecture) => {
+			if (plat === "darwin") {
+				const archStr = architecture === "arm64" ? "aarch64" : "x86_64";
+				return `fd-v${version}-${archStr}-apple-darwin.tar.gz`;
+			} else if (plat === "linux") {
+				const archStr = architecture === "arm64" ? "aarch64" : "x86_64";
+				return `fd-v${version}-${archStr}-unknown-linux-gnu.tar.gz`;
+			} else if (plat === "win32") {
+				const archStr = architecture === "arm64" ? "aarch64" : "x86_64";
+				return `fd-v${version}-${archStr}-pc-windows-msvc.zip`;
+			}
+			return null;
+		},
+	},
+};
+
+// Check if a command exists in PATH by trying to run it
+function commandExists(cmd: string): boolean {
+	try {
+		spawnSync(cmd, ["--version"], { stdio: "pipe" });
+		return true;
+	} catch {
+		return false;
+	}
+}
+
+// Get the path to a tool (system-wide or in our tools dir)
+export function getToolPath(tool: "fd"): string | null {
+	const config = TOOLS[tool];
+	if (!config) return null;
+
+	// Check our tools directory first
+	const localPath = join(TOOLS_DIR, config.binaryName + (platform() === "win32" ? ".exe" : ""));
+	if (existsSync(localPath)) {
+		return localPath;
+	}
+
+	// Check system PATH - if found, just return the command name (it's in PATH)
+	if (commandExists(config.binaryName)) {
+		return config.binaryName;
+	}
+
+	return null;
+}
+
+// Fetch latest release version from GitHub
+async function getLatestVersion(repo: string): Promise<string> {
+	const response = await fetch(`https://api.github.com/repos/${repo}/releases/latest`, {
+		headers: { "User-Agent": "pi-coding-agent" },
+	});
+
+	if (!response.ok) {
+		throw new Error(`GitHub API error: ${response.status}`);
+	}
+
+	const data = await response.json();
+	return data.tag_name.replace(/^v/, "");
+}
+
+// Download a file from URL
+async function downloadFile(url: string, dest: string): Promise<void> {
+	const response = await fetch(url);
+
+	if (!response.ok) {
+		throw new Error(`Failed to download: ${response.status}`);
+	}
+
+	if (!response.body) {
+		throw new Error("No response body");
+	}
+
+	const fileStream = createWriteStream(dest);
+	await finished(Readable.fromWeb(response.body as any).pipe(fileStream));
+}
+
+// Download and install a tool
+async function downloadTool(tool: "fd"): Promise<string> {
+	const config = TOOLS[tool];
+	if (!config) throw new Error(`Unknown tool: ${tool}`);
+
+	const plat = platform();
+	const architecture = arch();
+
+	// Get latest version
+	const version = await getLatestVersion(config.repo);
+
+	// Get asset name for this platform
+	const assetName = config.getAssetName(version, plat, architecture);
+	if (!assetName) {
+		throw new Error(`Unsupported platform: ${plat}/${architecture}`);
+	}
+
+	// Create tools directory
+	mkdirSync(TOOLS_DIR, { recursive: true });
+
+	const downloadUrl = `https://github.com/${config.repo}/releases/download/v${version}/${assetName}`;
+	const archivePath = join(TOOLS_DIR, assetName);
+	const binaryExt = plat === "win32" ? ".exe" : "";
+	const binaryPath = join(TOOLS_DIR, config.binaryName + binaryExt);
+
+	// Download
+	await downloadFile(downloadUrl, archivePath);
+
+	// Extract
+	const extractDir = join(TOOLS_DIR, "extract_tmp");
+	mkdirSync(extractDir, { recursive: true });
+
+	try {
+		if (assetName.endsWith(".tar.gz")) {
+			spawnSync("tar", ["xzf", archivePath, "-C", extractDir], { stdio: "pipe" });
+		} else if (assetName.endsWith(".zip")) {
+			spawnSync("unzip", ["-o", archivePath, "-d", extractDir], { stdio: "pipe" });
+		}
+
+		// Find the binary in extracted files
+		const extractedDir = join(extractDir, assetName.replace(/\.(tar\.gz|zip)$/, ""));
+		const extractedBinary = join(extractedDir, config.binaryName + binaryExt);
+
+		if (existsSync(extractedBinary)) {
+			renameSync(extractedBinary, binaryPath);
+		} else {
+			throw new Error(`Binary not found in archive: ${extractedBinary}`);
+		}
+
+		// Make executable (Unix only)
+		if (plat !== "win32") {
+			chmodSync(binaryPath, 0o755);
+		}
+	} finally {
+		// Cleanup
+		rmSync(archivePath, { force: true });
+		rmSync(extractDir, { recursive: true, force: true });
+	}
+
+	return binaryPath;
+}
+
+// Ensure a tool is available, downloading if necessary
+// Returns the path to the tool, or null if unavailable
+export async function ensureTool(tool: "fd", silent: boolean = false): Promise<string | null> {
+	const existingPath = getToolPath(tool);
+	if (existingPath) {
+		return existingPath;
+	}
+
+	const config = TOOLS[tool];
+	if (!config) return null;
+
+	// Tool not found - download it
+	if (!silent) {
+		console.log(chalk.dim(`${config.name} not found. Downloading...`));
+	}
+
+	try {
+		const path = await downloadTool(tool);
+		if (!silent) {
+			console.log(chalk.dim(`${config.name} installed to ${path}`));
+		}
+		return path;
+	} catch (e) {
+		if (!silent) {
+			console.log(chalk.yellow(`Failed to download ${config.name}: ${e instanceof Error ? e.message : e}`));
+		}
+		return null;
+	}
+}

packages/coding-agent/src/tui/tui-renderer.ts

@@ -105,6 +105,7 @@ export class TuiRenderer {
 		changelogMarkdown: string | null = null,
 		newVersion: string | null = null,
 		scopedModels: Array<{ model: Model<any>; thinkingLevel: ThinkingLevel }> = [],
+		fdPath: string | null = null,
 	) {
 		this.agent = agent;
 		this.sessionManager = sessionManager;
@@ -194,6 +195,7 @@ export class TuiRenderer {
 				clearCommand,
 			],
 			process.cwd(),
+			fdPath,
 		);
 		this.editor.setAutocompleteProvider(autocompleteProvider);
 	}