Building
I've lost voice recordings before. App crashes, battery dies, system freezes—poof, gone.
That sinking feeling of "I just spent 10 minutes articulating something important and now it's lost" is devastating.
When I started building Reso, I made a promise: This will never happen.
The Traditional Approach (And Why It Fails)
Most recording apps work like this:
1. Start recording → audio buffered in memory
2. Stop recording → write audio file to disk
3. Return the file path
Problem: If the app crashes between steps 1 and 2, the audio is gone forever.
macOS apps crash. Power cables get yanked. Kernel panics happen (rarely, but they do).
The Solution: Incremental Writes
What if we wrote audio while recording, not after?
Here's how Shadow Recording works:
1. Recording starts → create a timestamped M4A file immediately
2. As audio chunks arrive, append them to the file on disk
3. If the app crashes, the file is already there
Result: Even if Reso explodes mid-sentence, your recording survives.
The Implementation Details
This sounds simple, but M4A is a complex format. You can't just naively append raw audio bytes—the file would be corrupted.
I had to:
1. Use a streaming audio encoder that supports incremental writes
2. Ensure the M4A container is "valid" even if writing stops abruptly
3. Handle file cleanup (old shadow recordings can't pile up forever)
We keep shadow recordings for 7 days. After that, they're auto-deleted. This prevents unbounded storage growth while giving you a safety net.
What I Learned
The best features are the ones people never notice.
Shadow Recording has saved dozens of recordings from crashes. But people don't think "wow, shadow recording is great!" They just think "Reso is reliable."
That's exactly what I wanted.
Reliability isn't sexy. It doesn't make for good demos. But it's the foundation of trust.
When you know your ideas are safe, you use the tool differently—you're willing to capture half-formed thoughts, experiments, mistakes.
That's when a tool stops being a utility and becomes part of your thinking process.