fix(coding-agent): move temporary extension cache (#5345)

packages/coding-agent/CHANGELOG.md

@@ -11,6 +11,7 @@
 
 ### Fixed
 
+- Fixed temporary extension package installs to use a private `~/.pi/agent/tmp/extensions` directory with `0700` permissions instead of `os.tmpdir()/pi-extensions`.
 - Fixed git package source handling to reject unsafe host/path components and keep managed clone paths inside install roots.
 - Fixed stored XSS in HTML session exports by sanitizing Markdown link and image URLs with a scheme allow-list after stripping control characters.
 - Fixed SDK embedding in bundled Node apps failing with `ENOENT` when `package.json` is not present next to the bundle entrypoint. The package metadata reader now gracefully handles missing `package.json` by using defaults, enabling `createAgentSession()` without requiring package-adjacent files at runtime ([#5226](https://github.com/earendil-works/pi/issues/5226)).

packages/coding-agent/src/core/package-manager.ts

@@ -1,7 +1,7 @@
 import type { ChildProcess, ChildProcessByStdio } from "node:child_process";
 import { createHash } from "node:crypto";
-import { existsSync, mkdirSync, readdirSync, readFileSync, rmSync, statSync, writeFileSync } from "node:fs";
-import { homedir, tmpdir } from "node:os";
+import { chmodSync, existsSync, mkdirSync, readdirSync, readFileSync, rmSync, statSync, writeFileSync } from "node:fs";
+import { homedir } from "node:os";
 
 function getEnv(): NodeJS.ProcessEnv {
 	if (process.platform !== "linux" || Object.keys(process.env).length > 0) {
@@ -206,6 +206,13 @@ function getHomeDir(): string {
 	return process.env.HOME || homedir();
 }
 
+export function getExtensionTempFolder(agentDir: string): string {
+	const tempFolder = join(agentDir, "tmp", "extensions");
+	mkdirSync(tempFolder, { recursive: true, mode: 0o700 });
+	chmodSync(tempFolder, 0o700);
+	return tempFolder;
+}
+
 function prefixIgnorePattern(line: string, prefix: string): string | null {
 	const trimmed = line.trim();
 	if (!trimmed) return null;
@@ -1970,7 +1977,7 @@ export class DefaultPackageManager implements PackageManager {
 	}
 
 	private getTemporaryDir(prefix: string, suffix?: string): string {
-		const root = this.resolveManagedPath(join(tmpdir(), "pi-extensions"), prefix);
+		const root = this.resolveManagedPath(getExtensionTempFolder(this.agentDir), prefix);
 		const hash = createHash("sha256")
 			.update(`${prefix}-${suffix ?? ""}`)
 			.digest("hex")

packages/coding-agent/test/git-update.test.ts

@@ -7,7 +7,6 @@
  */
 
 import { spawnSync } from "node:child_process";
-import { createHash } from "node:crypto";
 import { existsSync, mkdirSync, readFileSync, rmSync, writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
@@ -51,6 +50,20 @@ function getFileContent(repoDir: string, filename: string): string {
 	return readFileSync(join(repoDir, filename), "utf-8");
 }
 
+type GitSourceForTest = {
+	type: "git";
+	repo: string;
+	host: string;
+	path: string;
+	pinned: boolean;
+	ref?: string;
+};
+
+interface PackageManagerPathInternals {
+	parseSource(source: string): GitSourceForTest;
+	getGitInstallPath(source: GitSourceForTest, scope: "temporary"): string;
+}
+
 describe("DefaultPackageManager git update", () => {
 	let tempDir: string;
 	let remoteDir: string; // Simulates the "remote" repository
@@ -376,10 +389,8 @@ describe("DefaultPackageManager git update", () => {
 
 	describe("temporary git sources", () => {
 		it("should refresh cached temporary git sources when resolving", async () => {
-			const gitHost = "github.com";
-			const gitPath = "test/extension";
-			const hash = createHash("sha256").update(`git-${gitHost}-${gitPath}`).digest("hex").slice(0, 8);
-			const cachedDir = join(tmpdir(), "pi-extensions", `git-${gitHost}`, hash, gitPath);
+			const managerWithPaths = packageManager as unknown as PackageManagerPathInternals;
+			const cachedDir = managerWithPaths.getGitInstallPath(managerWithPaths.parseSource(gitSource), "temporary");
 			const extensionFile = join(cachedDir, "pi-extensions", "session-breakdown.ts");
 
 			rmSync(cachedDir, { recursive: true, force: true });
@@ -423,10 +434,8 @@ describe("DefaultPackageManager git update", () => {
 		});
 
 		it("should not refresh pinned temporary git sources", async () => {
-			const gitHost = "github.com";
-			const gitPath = "test/extension";
-			const hash = createHash("sha256").update(`git-${gitHost}-${gitPath}`).digest("hex").slice(0, 8);
-			const cachedDir = join(tmpdir(), "pi-extensions", `git-${gitHost}`, hash, gitPath);
+			const managerWithPaths = packageManager as unknown as PackageManagerPathInternals;
+			const cachedDir = managerWithPaths.getGitInstallPath(managerWithPaths.parseSource(gitSource), "temporary");
 			const extensionFile = join(cachedDir, "pi-extensions", "session-breakdown.ts");
 
 			rmSync(cachedDir, { recursive: true, force: true });

packages/coding-agent/test/package-manager.test.ts

@@ -1,5 +1,5 @@
 import { EventEmitter } from "node:events";
-import { mkdirSync, rmSync, symlinkSync, writeFileSync } from "node:fs";
+import { mkdirSync, rmSync, statSync, symlinkSync, writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join, relative } from "node:path";
 import { PassThrough } from "node:stream";
@@ -33,6 +33,16 @@ interface PackageManagerInternals {
 		options?: { cwd?: string; timeoutMs?: number; env?: Record<string, string> },
 	): Promise<string>;
 	getLocalGitUpdateTarget(installedPath: string): Promise<{ ref: string; head: string; fetchArgs: string[] }>;
+	parseSource(
+		source: string,
+	):
+		| { type: "npm"; spec: string; name: string; pinned: boolean }
+		| { type: "git"; repo: string; host: string; path: string; pinned: boolean; ref?: string }
+		| { type: "local"; path: string };
+	getNpmInstallPath(
+		source: { type: "npm"; spec: string; name: string; pinned: boolean },
+		scope: "user" | "project" | "temporary",
+	): string;
 	getGitInstallPath(
 		source: { type: "git"; repo: string; host: string; path: string; pinned: boolean; ref?: string },
 		scope: "user" | "project" | "temporary",
@@ -1161,6 +1171,26 @@ Content`,
 		});
 	});
 
+	describe("temporary install paths", () => {
+		it("should place temporary npm packages under the agent temp extension folder", () => {
+			const managerWithInternals = packageManager as unknown as PackageManagerInternals;
+			const source = managerWithInternals.parseSource("npm:left-pad");
+			if (source.type !== "npm") {
+				throw new Error("Expected npm source");
+			}
+
+			const installPath = managerWithInternals.getNpmInstallPath(source, "temporary");
+			const tempRoot = join(agentDir, "tmp", "extensions");
+
+			expect(pathEndsWith(installPath, "node_modules/left-pad")).toBe(true);
+			expect(relative(tempRoot, installPath).startsWith("..")).toBe(false);
+			expect(installPath.startsWith(join(tmpdir(), "pi-extensions"))).toBe(false);
+			if (process.platform !== "win32") {
+				expect(statSync(tempRoot).mode & 0o777).toBe(0o700);
+			}
+		});
+	});
+
 	describe("settings source normalization", () => {
 		it("should store global local packages relative to agent settings base", () => {
 			const pkgDir = join(tempDir, "packages", "local-global-pkg");