Dev Diary #3

Systems touched:

• life.os, my personal dashboard

• tech.interview.practice, an interview coaching tool

Principles explored:

• Privacy-preserving logging and audit trails

• Voice-first interaction design and silence detection

• Graceful degradation in real-time speech systems

• Prompt engineering for domain-specific AI coaching

• Client-side state synchronization without hydration mismatches

Today was split between two very different kinds of work: infrastructure for introspection, and UX refinement for real-time interaction.

In life.os, I've been building out the developer diary system — the very thing I'm writing in now. The work involved rethinking how commits get collected, redacted, and shaped into reflective prose. The core tension here is transparency without exposure: I want genuine records of what I built, but certain details (API endpoints, database schemas, user names) have no business being permanently logged. I refactored the redaction pipeline to be content-aware rather than just path-based. Instead of surgically removing lines, I'm now filtering at a semantic level — checking whether a message references confidential patterns before it ever gets written. This feels more honest than pretending the work didn't happen; it just acknowledges that not every technical choice belongs in a public diary.

In tech.interview.practice, the work was almost entirely about voice interaction. I replaced a text-based mentor with a voice coach ("Sam"), which fundamentally changed how the system needs to behave. Voice introduces latency, ambiguity, and the need for real-time feedback that text doesn't require. I spent time tuning the voice activity detection (VAD) threshold — the moment when silence becomes "you're done talking." Too eager, and it cuts users off mid-thought. Too conservative, and the system feels sluggish. I also discovered that when the code editor is open, VAD should pause entirely; otherwise, keyboard clicks and typing noises trigger false positives.

The other layer was prompt engineering. I realized Alex (the coach) was reading code aloud unnecessarily, wasting tokens and confusing users. Now I explicitly tell the coach to reference lines by number instead. This meant prepending line numbers to the code sent to the API — a small change with outsized impact on the interaction model.

I also fixed 25 audit issues across security, accessibility, and reliability. Most were straightforward (updating dependencies, adding ARIA labels), but a few revealed deeper problems: hydration mismatches in useEffect hooks, Monaco editor cursor jumping on updates. These aren't glamorous bugs, but they're the friction points that erode trust in interactive tools.