fix: session logs loading state

[joeyorlando]

What changed

• Added an explicit loading row to /llm/logs/session/[sessionId] while the session interactions query is pending.
• Added a focused frontend test covering both pending and completed-empty interaction states.

Why

Long-running session log requests previously defaulted the pending query result to an empty array, so the page could briefly show "No interactions found for this session" before logs finished loading.

[claude]

Claude finished @joeyorlando's task in 4m 41s —— View job

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PR Review: fix: session log loading state

• Read CLAUDE.md for repo guidelines
• Read changed files
• Verify useInteractions hook contract (isLoading exists, data?.data ?? [] flow)
• Check sibling logs pages for loading patterns
• Post review feedback

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Summary

Small, targeted fix that correctly addresses the "No interactions found for this session" flash on /llm/logs/session/[sessionId]. The change reads isLoading from useInteractions and renders an explicit loading row before the empty‑state branch. The new test covers the two key states (loading vs. empty‑after‑load). Follows the repo guideline of preferring useQuery with explicit loading states (CLAUDE.md, "Frontend" section).

The change is minimal, scoped, and aligned with the rest of the codebase. I'd ship this. A few small observations below.

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Observations

1. isLoading vs. isFetching on pagination — minor

useQuery's isLoading is isPending && isFetching, i.e. true only when there is no cached data yet. That's exactly the behavior you want for the first navigation to a session — fixes the flash. However, when the user clicks Next/Previous on the pagination control, the previous page's data stays in the cache for that query key, and the new offset triggers a fresh request where isLoading is false and isFetching is true. The old page rows will remain visible until the new ones land (TanStack default behavior, no keepPreviousData/placeholderData), with no in-table indicator that the next page is loading.

That is arguably an improvement over a flash, but if the goal is "show a loading row whenever the table is fetching session logs", consider isFetching instead of (or in addition to) isLoading. As written, the fix is correct for the bug described in the PR body — just flagging the pagination case as a follow-up consideration.

2. Sibling page uses a different loading affordance

platform/frontend/src/app/llm/logs/[id]/page.client.tsx:63-64 renders <LoadingSpinner /> (from @/components/loading) for its pending state. This PR introduces an inline table row with a Loader2 spinner from lucide. Both are valid; the inline row is actually nicer here because it preserves the page header, summary card, and table chrome while loading. Just noting the inconsistency in case there's a desire to standardize via LoadingSpinner/a shared <TableLoadingRow> later.

3. Hard-coded colSpan={6}

page.client.tsx:278 and page.client.tsx:290 both use colSpan={6}, matching the six <TableHead> columns above. Pre-existing pattern (the empty-state row already does this), so not a blocker — but it's the kind of thing that silently breaks when columns change. A const COLUMN_COUNT = 6; near the top, or counting TableHead children, would be nice if you ever touch this file again.

4. vi.mock("react", …) is heavy-handed

page.client.test.tsx:20-26 mocks the entire react module to stub use() so useSessionId resolves synchronously. This works, but it's the only place in the frontend tests doing this (per grep -l 'vi.mock("react"' frontend/src). Two lighter alternatives:

• Use the Suspense wrapper that production uses: render via <Suspense fallback={null}> and await screen.findByText(...) — React.use() will unwrap the resolved promise on the next tick. The test already uses findBy*, so it would just work.
• Don't mock react at all and instead rely on await Promise.resolve() flushing — paramsPromise is already a resolved promise, and React.use supports thenables.

Mocking core React is the kind of thing that can interact badly with future React/Testing Library upgrades (e.g., concurrent rendering helpers). Worth avoiding if a Suspense wrapper works.

Fix this →

5. Type coverage of mocked hook return values

The as unknown as ReturnType<typeof useInteractions> casts (test lines 32, 37, 45, 69) silently allow shape drift between the real hook and the mock. Not a blocker for a focused state test, but a small function mockUseInteractions(overrides: Partial<ReturnType<typeof useInteractions>>): ReturnType<typeof useInteractions> helper would catch future breakage if the hook starts returning additional fields the component depends on.

6. Test naming nit

"shows the empty state after session interactions finish loading empty" reads slightly awkwardly. Consider "shows the empty state when the session has no interactions".

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Verdict

LGTM — a clean bug fix with a focused test. The notes above are all non-blocking polish/follow-ups. The pagination behavior (point 1) is the only one I'd actually consider tightening before merge, depending on how often users page through a session's logs in practice.
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