🖼️ fix: Message Icon Flickering from Context-Triggered Re-renders#12489
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…gating MessageIcon receives full `agent` and `assistant` objects as props from useMessageActions, which recomputes them when AgentsMapContext or AssistantsMapContext update (e.g., react-query refetch on window focus). These context-triggered re-renders bypass MessageRender's React.memo, producing new object references for agent/assistant even when the underlying data is unchanged. The default shallow comparison in MessageIcon's memo then fails, causing unnecessary re-renders that manifest as visible icon flickering. Add arePropsEqual comparator that checks only the fields MessageIcon actually uses (name, avatar filepath, metadata avatar) instead of object identity, so the component correctly bails out when icon-relevant data hasn't changed.
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Pull request overview
This PR addresses UI flicker in chat message icons by preventing unnecessary MessageIcon re-renders that were triggered by agents/assistants context updates (e.g., react-query refetches) even when the icon-relevant data didn’t change.
Changes:
- Adds a custom
React.memoprops comparator forMessageIconthat compares only render-relevant fields (agent/assistant name + avatar fields, plusiconDataby reference). - Extracts a
MessageIconPropstype to share between the component and comparator.
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- Export arePropsEqual so it can be tested in isolation - Add JSDoc documenting which fields are intentionally omitted (id) and why iconData uses reference equality - Replace five trivial useMemo calls (agent?.name ?? '', etc.) with direct computed values — the custom comparator already gates re-renders, so these memos only add closure/dep-array overhead without ever providing cache hits - Remove unused React import
Exercise the custom memo comparator to ensure: - New object references with same display fields are treated as equal - Changed name or avatar filepath triggers re-render - iconData reference change triggers re-render - undefined→defined agent with undefined fields is treated as equal
danny-avila
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iconData is a useMemo'd object from the parent, but comparing by reference still causes unnecessary re-renders when the parent recomputes the memo with identical primitive values. Compare all five fields individually (endpoint, model, iconURL, modelLabel, isCreatedByUser) for consistency with how agent/assistant are handled.
yidianyiko
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Apr 13, 2026
…nny-avila#12489) * perf: add custom memo comparator to MessageIcon for stable re-render gating MessageIcon receives full `agent` and `assistant` objects as props from useMessageActions, which recomputes them when AgentsMapContext or AssistantsMapContext update (e.g., react-query refetch on window focus). These context-triggered re-renders bypass MessageRender's React.memo, producing new object references for agent/assistant even when the underlying data is unchanged. The default shallow comparison in MessageIcon's memo then fails, causing unnecessary re-renders that manifest as visible icon flickering. Add arePropsEqual comparator that checks only the fields MessageIcon actually uses (name, avatar filepath, metadata avatar) instead of object identity, so the component correctly bails out when icon-relevant data hasn't changed. * refactor: export arePropsEqual, drop redundant useMemos, add JSDoc - Export arePropsEqual so it can be tested in isolation - Add JSDoc documenting which fields are intentionally omitted (id) and why iconData uses reference equality - Replace five trivial useMemo calls (agent?.name ?? '', etc.) with direct computed values — the custom comparator already gates re-renders, so these memos only add closure/dep-array overhead without ever providing cache hits - Remove unused React import * test: add unit tests for MessageIcon arePropsEqual comparator Exercise the custom memo comparator to ensure: - New object references with same display fields are treated as equal - Changed name or avatar filepath triggers re-render - iconData reference change triggers re-render - undefined→defined agent with undefined fields is treated as equal * fix: replace nested ternary with if-else for eslint compliance * test: add comment on subtle equality invariant and defined→undefined case * perf: compare iconData by field values instead of reference iconData is a useMemo'd object from the parent, but comparing by reference still causes unnecessary re-renders when the parent recomputes the memo with identical primitive values. Compare all five fields individually (endpoint, model, iconURL, modelLabel, isCreatedByUser) for consistency with how agent/assistant are handled.
jcbartle
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May 11, 2026
…nny-avila#12489) * perf: add custom memo comparator to MessageIcon for stable re-render gating MessageIcon receives full `agent` and `assistant` objects as props from useMessageActions, which recomputes them when AgentsMapContext or AssistantsMapContext update (e.g., react-query refetch on window focus). These context-triggered re-renders bypass MessageRender's React.memo, producing new object references for agent/assistant even when the underlying data is unchanged. The default shallow comparison in MessageIcon's memo then fails, causing unnecessary re-renders that manifest as visible icon flickering. Add arePropsEqual comparator that checks only the fields MessageIcon actually uses (name, avatar filepath, metadata avatar) instead of object identity, so the component correctly bails out when icon-relevant data hasn't changed. * refactor: export arePropsEqual, drop redundant useMemos, add JSDoc - Export arePropsEqual so it can be tested in isolation - Add JSDoc documenting which fields are intentionally omitted (id) and why iconData uses reference equality - Replace five trivial useMemo calls (agent?.name ?? '', etc.) with direct computed values — the custom comparator already gates re-renders, so these memos only add closure/dep-array overhead without ever providing cache hits - Remove unused React import * test: add unit tests for MessageIcon arePropsEqual comparator Exercise the custom memo comparator to ensure: - New object references with same display fields are treated as equal - Changed name or avatar filepath triggers re-render - iconData reference change triggers re-render - undefined→defined agent with undefined fields is treated as equal * fix: replace nested ternary with if-else for eslint compliance * test: add comment on subtle equality invariant and defined→undefined case * perf: compare iconData by field values instead of reference iconData is a useMemo'd object from the parent, but comparing by reference still causes unnecessary re-renders when the parent recomputes the memo with identical primitive values. Compare all five fields individually (endpoint, model, iconURL, modelLabel, isCreatedByUser) for consistency with how agent/assistant are handled.
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Summary
I fixed message icon flickering caused by unnecessary re-renders of
MessageIconwhenAgentsMapContextorAssistantsMapContextupdate. After #12454 introduced aggressive memoization onMessageRender, context-triggered re-renders became the only source of visual updates for non-latest messages — making icon flicker far more noticeable than before.arePropsEqualcomparator toMessageIcon'sReact.memothat compares only the fields the component actually renders (agent.name,agent.avatar.filepath,assistant.name,assistant.metadata.avatar) instead of relying on object reference equality.arePropsEqualand add unit tests covering: same-data new-reference stability, field-change detection, iconData reference semantics, and undefined→defined edge cases.useMemocalls for trivial property accesses (agent?.name ?? '', etc.) with direct computed values — the custom comparator already gates re-renders, so these memos only added closure/dep-array overhead without providing cache hits.agent.id,assistant.id) and whyiconDatauses reference equality.Root cause
useMessageActions(called inside memo'dMessageRender) subscribes touseAgentsMapContext()anduseAssistantsMapContext(). Context subscriptions bypassReact.memo, so when react-query refetches the agents/assistants list (e.g., on window focus),MessageRenderre-renders regardless of its custom comparator. Theagent/assistantuseMemorecomputes with the new map reference, producing a new object identity even when the data is unchanged.MessageIcon's default shallowmemocomparison then fails, triggering a re-render that causes visible icon flickering.This was introduced by #12454 — not as a bug in that PR's logic, but as a newly visible symptom: before that PR,
MessagePartswas unmemoized, so everything re-rendered together and the icon refresh blended in. After aggressive memoization isolated non-latest messages, the context-triggered icon re-render became the only visual change, making the flicker stand out.Change Type
Testing
npx jest -- "Messages/__tests__/MessageIcon"from theclient/directory — all 9 tests pass.Checklist