platform: Cx.perf_monitor — per-frame ring (240) of paint-to-paint gap +
per-channel CPU us. Built-in channels: event dispatch (outermost, minus
app-attributed time), script exec, GC, pass encode, nextDrawable wait.
Apps register custom channels: cx.perf_monitor.channel("physics", rgb).
Off until enabled; hooks in event dispatch, macos repaint, metal draw_pass.
widgets: PerfGraph — corner-pinned live panel (DrawVector strips): frame-gap
bars colored against 120/60Hz budgets with guide lines, stacked per-channel
CPU, legend with averages. Self-positions bottom-right (DrawVector geometry
+ deferred turtle alignment don't mix — no aligning parent).
gamemaker: PerfGraph hovers the game pane (F3 toggles), engine feeds script
+ physics channels (incl. hot-reload evals); engine text overlay moved to
F4; per-phase engine window kept for ag perf / AIGAME_PERF=1; new 'ag perf'
harness verb + template guidance (template CLAUDE.md force-added: runtime
resource, blanket CLAUDE.md gitignore had kept it untracked).
Measured on my-game-5: engine frame CPU ~0.3ms; the hiccup is frame pacing —
the 8ms NSTimer paint clock beats against the 120Hz display, the drawable
pool drifts full and nextDrawable blocks the main thread in a ~25-frame
sawtooth (avg 2-3.4ms, spikes 20-30ms). The graph shows it as red ramps.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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