AI & Agent Dev Bug Sandbox Back to Radar

Turbopack OutputFileTracingIncludes Glob Walk Crashes With ELOOP On Pnpm Nested Workspace Symlink Cycles

When `outputFileTracingIncludes` is configured, the include-glob walk traverses the entire tracing root and follows symlinks without robust cycle detection. In legal pnpm workspaces where a package nested inside another declares its ancestor as dependency, this creates a self-embedding symlink chain that triggers ELOOP and fails the build.

highConfidence 85%Next.js (Turbopack)Affected V16.3.0 Affected V16.3.1 Affected V16.3.1-Canary.22

Origin Analysis

`resolve_symlink_safely` in `read_glob.rs` only checks whether a symlink's target is an ancestor of the symlink's virtual path. For multi-hop cycles entered through hoisted paths like `app/node_modules/shared`, neither target is an ancestor, so the detection never fires and recursion continues until the OS returns ELOOP.

1. Clone https://github.com/Stanzilla/turbopack-symlink-cycle-repro\n2. Run `pnpm install`\n3. Run `pnpm --filter app exec next build`\nObserve `TurbopackInternalError: Failed to write app endpoint /page` with `Too many levels of symbolic links`.

Fixing Code Block

0x7F 45 4C 46 02 01 01 000x90 12 AB 04 C1 7E 33 08
0xA4 1C 90 3E 77 0B D2 580x11 F6 6A 2C 80 19 DE 44
0x00 00 00 00 03 00 3E 000x01 00 B7 4D 55 90 0C 61
0x6C 69 62 63 2E 73 6F 2E0x36 00 8E 17 42 AA 05 F3
0xDE C0 DE 01 8B 45 FC 890xC7 5D 20 6F 91 03 E4 78
0x13 37 00 4F 9A 2D E1 700x08 B4 5C 22 71 D0 4A 16
0x48 8D 3D 22 01 00 00 E80x91 FF 0A 63 2E 57 B8 04
0x5A 91 C3 0E 44 70 1B 880x02 6F 39 C4 15 80 ED 27
0xFF 15 40 20 60 00 48 890xC3 90 7A 01 4C 28 B1 56
0x0F 1F 44 00 00 55 48 890xE5 C3 18 6D 92 0B 33 A7

Edge Case Audit

Canonicalizing every directory may add filesystem overhead, especially on large monorepos. The fallback to non-canonical root on error could still miss a cycle if canonicalization fails transiently. The visited set is per `read_glob` invocation and is not thread-safe, so concurrent reads are isolated. The change modifies the glob walk behavior: entries after the first occurrence of a cycle target are silently skipped, which could omit legitimate assets if the build relied on symlink traversal for pattern matching. Rolling back to previous behavior is possible by reverting this patch, but then builds with cyclic symlinks will fail again. For persistent defense, consider using inode/dev pairs on Unix and file IDs on Windows instead of canonical path strings, and add tests for nested pnpm layouts.