User-visible problem: agent-comms panel opens mid-conversation on long
histories (the same chat-opens-in-middle bug PR #2903 fixed for
my-chat) and silently renders empty state when the history fetch fails
(no retry button, no diagnostic).
Three changes mirror the my-chat patterns from ChatTab:
1. Initial-mount instant scroll.
Adds hasInitialScrollRef + switches the scroll hook from useEffect
to useLayoutEffect. First arrival of messages → scrollIntoView
`instant`; subsequent appends → `smooth` as before. useLayoutEffect
runs before paint so the user never sees the panel jump for one
frame on every append.
2. Error UI with Retry button.
Adds `loadError` state. The history-load .catch now sets the
error message; a new branch in the render renders a red alert
with the failure text and a Retry button that re-invokes
`loadInitial`. Same shape as ChatTab MyChatPanel's `loadError`
handling — both surfaces should fail loud, not silent.
3. Extracted `loadInitial` callback.
The history-load body becomes a useCallback so the retry button
has a stable reference to call. Mirrors ChatTab's loadInitial.
Tests (4 new in AgentCommsPanel.render.test.tsx):
- Loading state renders the loading copy.
- Error state with Retry button renders on rejection; clicking
Retry fires a second api.get.
- Empty state renders when load succeeds with zero rows.
- scrollIntoView is called with behavior=instant on first message
arrival (pins the chat-opens-in-middle prevention).
Verification:
- pnpm test → 1284/1284 pass (1280 prior + 4 new)
- tsc --noEmit → clean
- 92 → 93 test files, no existing test broken
Closes the parity gap raised in chat. The two surfaces now share:
loading copy / error UI / empty-state placeholder / scroll behaviour /
useLayoutEffect timing.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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