UNF - Filesystem Flight Recorder for AI Agents

TL;DR

TL;DR: UNF is a local, open-source filesystem watcher that records every file change in real time, letting you rewind any file to any second — useful when an AI agent wipes your workspace between context compaction windows.

What Is UNF?

UNF (stylised UNF*) is a filesystem flight recorder. It runs continuously in the background, watching your project directory for every file change, and stores a point-in-time snapshot you can restore from at any moment.

The problem it solves: when an AI coding agent rewrites files during a session, those changes live only in the agent’s context. Once the context compacts or the session resets, the agent forgets what it touched. If it then makes a conflicting edit, your original code is gone.

UNF sits below that workflow. It records the filesystem state at second-level granularity regardless of what tool made the change — Git, an editor, a script, or an AI agent.

The product page describes it directly:

Every file change, recorded in real time. Rewind any file to any second. No commits required.

UNF is open source under MIT / Apache-2.0.

How It Works

UNF has three moving parts:

01 WATCH — Uses FSEvents on macOS and inotify on Linux to monitor the filesystem. It respects .gitignore, skips binary files, and applies a 3-second smart debounce to avoid recording every keystroke. Resource usage is claimed at under 1% CPU and under 100MB RAM during active recording.

02 STORE — Snapshots are stored locally using BLAKE3 content hashing inside a SQLite database with ACID guarantees. Content-addressed storage means identical files are stored only once. All data stays local.

03 REWIND — Any file can be restored to its state at a specific point in time, by second. Manual pruning with unf prune reclaims disk space.

Practical Workflow

Start watching a project:

unf watch

Review a session after an agent has been active:

unf recap --since 3h

Inspect what a file looked like 30 minutes ago:

unf diff --at 30m path/to/file

Restore a file to its state 30 minutes ago:

unf restore --at 30m path/to/file

The unf diff output shows a standard unified diff, so you can read exactly what changed before deciding whether to restore.

Installation

macOS (Homebrew):

brew install --cask cyrusradfar/unf/unfudged

macOS + Linux (Homebrew CLI):

brew install cyrusradfar/unf/unf

Linux (Debian/Ubuntu):

curl -fsSLO https://downloads.unfudged.io/releases/latest/unf_amd64.deb
sudo dpkg -i unf_amd64.deb

From source (requires Rust 1.80+):

git clone https://github.com/cyrusradfar/homebrew-unf.git
cd homebrew-unf
cargo build --release
cp target/release/unf /usr/local/bin/

Limitations

UNF is a filesystem recorder, not a version control system. It does not track branches, manage commits, or sync across machines. If you need collaborative history, Git remains the right tool. UNF fills the gap for in-progress, uncommitted work that Git cannot capture.

The current version stores snapshots locally. There is no cloud sync or multi-device support.

FAQ

Q: Does this work on Windows? A: Currently no. UNF uses FSEvents on macOS and inotify on Linux. Windows is not supported at this time.

Q: How much disk space does it use? A: It depends on your project size and change frequency. Use unf prune to manually clean up old snapshots and reclaim space.

Q: Does it interfere with editors or AI coding agents? A: No. UNF only watches the filesystem — it does not instrument or interact with running processes. It respects .gitignore and skips binary files.

Q: Is the source code available? A: The project is open source. The Homebrew tap at github.com/cyrusradfar/homebrew-unf hosts the installation tooling. License is MIT / Apache-2.0.

Conclusion

UNF solves a specific, painful problem that surfaces whenever developers work with AI coding agents in long sessions: loss of uncommitted state when the agent’s context resets. It is lightweight, local-only, and requires no infrastructure beyond installing a binary.

If you regularly work with AI agents that modify code across sessions — or if you have ever lost hours of work because “the agent said it had the right version” — UNF is worth a look.

Source and install instructions are at unfudged.io.

Source and Accuracy Notes

• Project page: unfudged.io
• License: MIT / Apache-2.0 (stated on project page)
• HN launch thread: news.ycombinator.com/item?id=44190017 — 137 points
• Source last checked: 2026-08-16