[WIP] feat: Open report with linked/unread report actions in the middle of the chat

[chrispader]

@quinthar

Explanation of Change

Updates the initial chat rendering logic so that the initial/unread report action is displayed in the middle of the chat rather then at the bottom.

The centered rendering is acting by the following approach:

• When the linked report action height is smaller than the list height, we center the whole message in the chat
• When the linked report action height is bigger than the list height, we instead center the top edge of the report action, so the "unread marker" line for unread messages is visible alongside earlier message

Fixed Issues

$ #88502
PROPOSAL:

Tests

• Verify that no errors appear in the JS console

Big screen (list height > report action height)

1. Open the app
2. Navigate to a report with an action badge (red "Fix", "Submit", etc.)
3. Make sure the linked report action is initially rendered in the middle of the chat (you can see messages before and after that report action

Small screen (list height < report action height)

1. Open the app
2. Navigate to a report with an action badge (red "Fix", "Submit", etc.)
3. Make sure the upper edge of linked report action is initially rendered in the middle of the chat (you can see the "unread marker" line and messages before the linked report action)

Offline tests

None needed.

QA Steps

• Verify that no errors appear in the JS console

Same as in Tests.

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I followed proper code patterns (see Reviewing the code)
  • I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick)
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  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
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Screenshots/Videos

Android: Native

iOS: Native

Simulator.Screen.Recording.-.iPhone.17.Pro.-.2026-05-19.at.16.53.46.mov

MacOS: Chrome / Safari

Screen.Recording.2026-05-19.at.16.51.52.mov

[chrispader]

This is working relatively well already, though there are some bugs that i still need to fix. Before, it was already possible to open the report with the bottom edge of the linked item in the vertical middle of the chat.

The tricky part is to instead render the top edge of the linked item (where we show the "unread message" line) in the middle, since we need to render the item and re-adjust the scroll position. Since we cannot estimate the message heights, this involves some tricky logic.

Screen.Recording.2026-05-12.at.21.58.28.mov

[chrispader]

There are some bugs that i need to fix, like the report reloading when the message is marked unread. Also, i have to test whether the measurement of the linked item and re-adjusting the scroll position adds a significant delay to the initial render of the chat.

[melvin-bot]

@aimane-chnaif Please copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

[chatgpt-codex-connector]

💡 Codex Review

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[chatgpt-codex-connector]

Memoize measured-scroll callbacks before using as deps

useLayoutEffect depends on resetMeasuredScroll/skipMeasuredScroll, but those callbacks are recreated on every render by useMeasuredLinkedRowScroll. That makes this effect run every render, and each run queues setSessionSnapshot(nextSession) with a fresh object, which can cause a render loop and repeatedly reset initial viewport state (isInitialViewportLoading/measured scroll) instead of letting the initial positioning settle.

Useful? React with 👍 / 👎.

[chatgpt-codex-connector]

Add fallback when initial viewport mount count is under-estimated

This gate requires mountedIndices.size >= requiredMountedItems, where requiredMountedItems is inferred from an average row height. For chats with very tall actions near the anchor, FlashList may mount fewer cells than that estimate, so isInitialViewportCovered never returns true and the full-screen initial skeleton can remain indefinitely. Unlike measured scroll, there is no timeout fallback for this loading gate.

Useful? React with 👍 / 👎.

[aimane-chnaif]

Please fix conflict and failing tests

[aimane-chnaif]

Is this still WIP? If ready for review, remove it from title.

[MelvinBot]

Code Review

This is a well-structured approach to centering linked/unread report actions. The hook decomposition (useCenteredInitialScrollKeyList → useMeasuredLinkedRowScroll) is clean, and the skeleton overlay strategy avoids visual jank. A few issues to address before merging:

---

High Priority

1. Unstable function references cause effects to re-fire every render

resetMeasuredScroll and skipMeasuredScroll in useMeasuredLinkedRowScroll.ts are plain functions recreated every render, but they're listed as deps of the useLayoutEffect in useCenteredInitialScrollKeyList.ts:138. This causes the core initialization effect to thrash on every render — clearing mountedViewportIndicesRef, resetting state, and re-publishing session snapshots.

Since they only close over runtimeRef (stable), wrap them in useCallback with empty deps:

const skipMeasuredScroll = useCallback(() => {
    const runtime = runtimeRef.current;
    runtime.shouldSkipScroll = true;
    resetMeasuredScrollRuntime(runtime);
}, []);

Same for resetMeasuredScroll.

2. tryApplyMeasuredAnchorScroll is unstable in useEffect deps

tryApplyMeasuredAnchorScroll (useMeasuredLinkedRowScroll.ts:46) is a plain arrow function listed as a dep of useEffect at line 202. This causes the pagination realignment effect to re-run on every render, which can trigger spurious scroll resets (runtime.hasCommittedScroll = false) and re-scrolls.

Either wrap in useCallback or call through a ref inside the effect.

---

Medium Priority

3. handleInitialViewportItemMounted is unstable, passed as a prop

This function (useCenteredInitialScrollKeyList.ts:170) is passed as onInitialViewportItemMounted to ReportActionsListInitialViewportCell, where it becomes a dep of useEffect in InitialViewportItemMountObserver (line 13). Every parent re-render fires that effect for all mounted viewport items. The hasInitialViewportLoadedRef guard prevents incorrect behavior but not the wasted work. Wrap in useCallback.

4. Test coverage is thin

Only 3 test cases cover the happy path and unread-marker-only change. Missing:

• Retry logic when scrollToIndex throws
• The 3-second fallback timer
• Pagination realignment (visibleActionCount changes after initial mount)
• listHeight change after viewport loaded

---

Low Priority / Observations

5. Linear scan duplication — findInitialScrollIndex and tryApplyMeasuredAnchorScroll both do Array.findIndex by key. The actionIndexMap in ReportActionsList.tsx:722 already builds a Map<string, number> — consider sharing it to avoid redundant O(n) scans on long chats.

6. Follow-up rAF edge case — If resetMeasuredScrollRuntime is called between frames, followUpFrameIds is replaced with [], but already-scheduled callbacks still fire. The shouldSkipScroll guard covers skipMeasuredScroll, but resetMeasuredScroll sets shouldSkipScroll = false, so a reset followed by an old callback could attempt a scroll with stale closures. Very unlikely in practice (~50ms window) but worth noting.

---

Items 1-2 are the main blockers — the unstable function references mean the initialization and pagination effects fire far more often than intended. The rest are improvements worth considering.

[chrispader]

Closing as this feature would introduce a major initial list render delay. This is something that LegendList solves, so maybe we can pick this back up in the future!