fix(staged): pre-compute hasUserAfter to fix O(N²) UI freeze in SessionModal - #617
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… SessionModal
The template had an inline `grouped.findIndex(...)` call inside an
`{#each grouped}` loop, causing O(N²) scanning for long sessions and
freezing the UI. Replace it with a `$derived` boolean array computed
once in O(N) via a reverse pass, giving O(1) lookup per tool group.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
Array.indexOfas the top hotspot (121/2179 samples) in the Staged web app, causing UI freezes on long sessions.grouped.findIndex(...)call inside an{#each grouped}template loop inSessionModal.svelte, resulting in O(N²) scanning.$derivedboolean array (hasUserAfter) that pre-computes in O(N) via a single reverse pass whether a user message exists after each group index, reducing per-group lookup to O(1).Test plan
sendingis true (input submitted but not yet responded to).🤖 Generated with Claude Code