Browsing performance

Define the affected route/interaction and observable completion. Use scripts/react-perf/config.mjs for covered deterministic flows; do not treat passing settings scenarios as proof about an unvisited feed.

Run corepack yarn perf:check --scenario <name> after a relevant React state/effect/subscription/rendering change. Use corepack yarn perf:record --scenario <name> for JSON and native Chrome traces, optionally --url <origin> to reuse a compatible instrumented server. The approved runner manages its isolated browser, resource lock, and owned server; a delegated profiler may use it directly. Keep browser work and heavy checks serialized and leave preexisting servers untouched. Install the pinned browser with yarn perf:install when absent, and run yarn perf:test after React/Bippy/collector upgrades.

Run corepack yarn doctor:check for source diagnostics on the task diff (--base <base> when the default base is unsuitable). Doctor findings guide investigation; its runtime summary is not a complete rerender counter. Runtime counts come from the bounded window.__REACT_PERF__ Bippy collector, and actual subtree render timing comes from React's Profiler.

Read measurement guidance for covered scenarios, collector limits, profiling builds, and the evidence to return. If a new interaction is needed, the task owner can add an authorized scenario; a read-only profiling child reports the missing coverage without changing product code. Manual browser investigations still use playwright-cli through ./scripts/pw-session.sh.

Compare the same flow with equivalent content, viewport, throttle, build mode, and capture settings. Return measured costs and counts with evidence, separating observed symptoms from suspected causes. Cheap expected updates alone do not justify an optimization.