# RB-08 MAJOR: PowerAssertion is a non-functional stub on macOS

**Severity:** MAJOR (macOS only)
**Path:** `src-tauri/src/commands/power.rs:41-121`
**Source:** [2026-04-22 code review](../code-review-2026-04-22.md), originally deferred during A.1 #9
**Labels:** release-blocker, major, macos, platform

## Problem

`begin_activity` always returns `Err` on macOS, so `PowerAssertion::begin` converts to `None` and the guard never acquires an `NSProcessInfo beginActivityWithOptions:reason:` assertion. Live recording and LLM cleanup therefore run without App Nap protection on the one platform where it matters.

The stub was deliberate (A.1 #9 acceptance concession — untestable on Linux without a macOS build host). Re-flagged here so it is not forgotten before the first macOS ship.

## Acceptance

- `objc2` + `objc2-foundation` deps added to the kon crate, gated `cfg(target_os = "macos")`.
- `begin_activity` calls `[NSProcessInfo processInfo] beginActivityWithOptions:(NSActivityUserInitiated | NSActivityLatencyCritical) reason:reason]` and retains the returned activity handle.
- `end_activity` calls `endActivity:` on the retained handle.
- Manual-test on a real macOS box: 10-minute background live session completes without throttling; `pmset -g assertions` shows Kon's activity during capture.

## Fix scope

Medium. Dep addition + FFI glue + manual verification. Can be done from Linux with `cargo check --target=aarch64-apple-darwin` for compile validation, but runtime behaviour needs a macOS machine.

## Dependencies

- **Hard blocker:** before first macOS build/ship.