fix(fs): cap file list and timeout untracked scan to prevent session init OOM

Large repos (100k+ files, unignored __pycache__ / venvs) caused git ls-files
--others to hang for minutes and allocate hundreds of MB in the workspace-server
process. The resulting GC pressure starved the concurrent session initializationResult()
promise, reliably hitting the 30s timeout when adding a large project.

Two-part fix in FsService.listRepoFiles:
- Abort git ls-files --others after 8 s via AbortController; fall back to []
- Cap combined tracked + untracked array at 50,000 entries before building
  the directory tree (avoids ~200MB+ allocation for very large repos)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TpGjPYBD4pgZpsAHjozzsN

Author: ricardo-leiva

packages/workspace-server/src/services/fs/service.test.ts

@@ -5,20 +5,26 @@ import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 vi.mock("@posthog/git/queries", () => ({
   getChangedFiles: vi.fn(async () => new Set<string>()),
-  listAllFiles: vi.fn(async () => []),
+  listFiles: vi.fn(async () => []),
+  listUntrackedFiles: vi.fn(async () => []),
 }));
 
-import { getChangedFiles, listAllFiles } from "@posthog/git/queries";
+import {
+  getChangedFiles,
+  listFiles,
+  listUntrackedFiles,
+} from "@posthog/git/queries";
 import { FsService } from "./service";
 
 describe("FsService.listRepoFiles", () => {
   it("derives directory entries alongside files", async () => {
     vi.mocked(getChangedFiles).mockResolvedValue(new Set());
-    vi.mocked(listAllFiles).mockResolvedValue([
+    vi.mocked(listFiles).mockResolvedValue([
       "a.ts",
       "src/b.ts",
       "src/sub/c.ts",
     ]);
+    vi.mocked(listUntrackedFiles).mockResolvedValue([]);
 
     const service = new FsService();
     const entries = await service.listRepoFiles("/repo");
@@ -34,11 +40,12 @@ describe("FsService.listRepoFiles", () => {
 
   it("filters directories and files by query substring", async () => {
     vi.mocked(getChangedFiles).mockResolvedValue(new Set());
-    vi.mocked(listAllFiles).mockResolvedValue([
+    vi.mocked(listFiles).mockResolvedValue([
       "a.ts",
       "src/b.ts",
       "src/sub/c.ts",
     ]);
+    vi.mocked(listUntrackedFiles).mockResolvedValue([]);
 
     const service = new FsService();
     const entries = await service.listRepoFiles("/repo", "sub");
@@ -48,6 +55,29 @@ describe("FsService.listRepoFiles", () => {
       { path: "src/sub/c.ts", kind: "file" },
     ]);
   });
+
+  it("caps file list at MAX_REPO_FILES when repo is very large", async () => {
+    vi.mocked(getChangedFiles).mockResolvedValue(new Set());
+    const bigList = Array.from({ length: 60_000 }, (_, i) => `file${i}.ts`);
+    vi.mocked(listFiles).mockResolvedValue(bigList);
+    vi.mocked(listUntrackedFiles).mockResolvedValue([]);
+
+    const service = new FsService();
+    const entries = await service.listRepoFiles("/repo");
+
+    expect(entries.length).toBeLessThanOrEqual(50_000);
+  });
+
+  it("omits untracked files when git ls-files --others is aborted", async () => {
+    vi.mocked(getChangedFiles).mockResolvedValue(new Set());
+    vi.mocked(listFiles).mockResolvedValue(["tracked.ts"]);
+    vi.mocked(listUntrackedFiles).mockRejectedValue(new Error("AbortError"));
+
+    const service = new FsService();
+    const entries = await service.listRepoFiles("/repo");
+
+    expect(entries.some((e) => e.path === "tracked.ts")).toBe(true);
+  });
 });
 
 describe("FsService repo file IO", () => {

packages/workspace-server/src/services/fs/service.ts

@@ -1,13 +1,23 @@
 import fs from "node:fs/promises";
 import path from "node:path";
-import { getChangedFiles, listAllFiles } from "@posthog/git/queries";
+import {
+  getChangedFiles,
+  listFiles,
+  listUntrackedFiles,
+} from "@posthog/git/queries";
 import { injectable } from "inversify";
 import type { BoundedReadResult, DirectoryEntry, FileEntry } from "./schemas";
 
 @injectable()
 export class FsService {
   private static readonly CACHE_TTL = 30000;
   private static readonly READ_REPO_FILES_CONCURRENCY = 24;
+  // Large repos (100k+ files) cause GC pressure that starves the session-init
+  // event loop. Cap the combined tracked + untracked list to bound allocation.
+  private static readonly MAX_REPO_FILES = 50_000;
+  // Abort git ls-files --others if it takes too long (unignored venvs, caches,
+  // or staticfiles directories can make it scan millions of entries).
+  private static readonly UNTRACKED_TIMEOUT_MS = 8_000;
   private cache = new Map<string, { files: FileEntry[]; timestamp: number }>();
 
   async listDirectory(dirPath: string): Promise<DirectoryEntry[]> {
@@ -43,7 +53,7 @@ export class FsService {
       const changedFiles = await getChangedFiles(repoPath);
 
       if (query?.trim()) {
-        const allFiles = await listAllFiles(repoPath);
+        const allFiles = await this.fetchAllFiles(repoPath);
         const directories = this.deriveDirectories(allFiles);
         const lowerQuery = query.toLowerCase();
         const matchingDirs = directories.filter((d) =>
@@ -64,7 +74,7 @@ export class FsService {
         return limit ? cached.files.slice(0, limit) : cached.files;
       }
 
-      const files = await listAllFiles(repoPath);
+      const files = await this.fetchAllFiles(repoPath);
       const directories = this.deriveDirectories(files);
       const entries = [
         ...this.toDirectoryEntries(directories),
@@ -221,6 +231,29 @@ export class FsService {
     }));
   }
 
+  private async fetchAllFiles(repoPath: string): Promise<string[]> {
+    const controller = new AbortController();
+    const timer = setTimeout(
+      () => controller.abort(),
+      FsService.UNTRACKED_TIMEOUT_MS,
+    );
+    try {
+      const [tracked, untracked] = await Promise.all([
+        listFiles(repoPath),
+        listUntrackedFiles(repoPath, { abortSignal: controller.signal }).catch(
+          () => [],
+        ),
+      ]);
+      const combined = tracked.concat(untracked);
+      if (combined.length > FsService.MAX_REPO_FILES) {
+        combined.length = FsService.MAX_REPO_FILES;
+      }
+      return combined;
+    } finally {
+      clearTimeout(timer);
+    }
+  }
+
   private deriveDirectories(files: string[]): string[] {
     const dirs = new Set<string>();
     for (const file of files) {