---
title: File index tracking
editUrl: https://github.com/Cratis/Arc.TypeScript/edit/main/Documentation/proxy-generation/file-index-tracking.md
description: How the proxy generator marks the files it owns, keeps barrels and unchanged files stable, removes stale output, and protects hand-written files.
---


You run the generator on every build, and it shares a folder with code people wrote by hand. It must replace what it owns, remove what no longer exists, and never touch anything else. It does that by marking every file it writes.

## Ownership headers

Every generated file (and, with separate output, generated barrel) starts with a header naming its source, generation time, and a content hash:

```typescript
// @generated by Cratis. Source: Tasks.Registration.RegisterTask. Time: 2026-09-24T20:35:55.3970000Z. Hash: FDB6670D1623B9F818509BA14942A78DF19A6EDEA92F42D7DD2D75CDB7D04895
```

Never edit a file with this header; the next run replaces it.

## What a run changes

| File | Behavior |
| --- | --- |
| An owned file whose content did not change | Kept byte for byte, with its timestamp |
| An owned file whose content changed | Replaced |
| An owned file for an artifact that no longer exists | Removed, unless `--skip-output-deletion` |
| A hand-written file | Never overwritten or deleted |
| A hand-written `index.ts` barrel in separate output | Never replaced; when stale owned files are deleted, only its exports of those files are removed. Directory and package re-exports stay |
| A hand-written `index.ts` in the artifacts tree | Untouched in co-located mode; no barrels are written there |

Co-located output skips barrels automatically. With separate output, `--skip-index-generation` stops the generator from writing them.

## Output folder safety

The output root must exist. The generator resolves symbolic links in its ancestors, such as `/tmp` on macOS, to their real path, and refuses symbolic links *inside* the output.

## Related

- [Configuration](/arc/backend/typescript/proxy-generation/configuration/)
- [Low-level manifest](/arc/backend/typescript/proxy-generation/low-level-manifest/), which writes files with different rules