fix(sessions): keep conversation pinned to bottom incl. footer

[adamleithp]

Problem

The conversation list wasn't sticking to the bottom — the footer (context-usage chart) sat below the fold, the scroll-to-bottom button flickered, and during streaming the view drifted off the latest content.

Root cause: the footer was rendered as a fake virtual row with a constant key. tanstack's followOnAppend only fires when the last virtual key changes on append (virtual-core didEdgeKeysChange), so a perpetual constant-keyed last item silently disabled it. A hand-rolled [items] effect papered over appends but never covered the footer's own height changes (generating→done, compacting), stranding it below the DOM bottom. anchorTo:"end" also pinned to the virtual end (last message), excluding the non-virtual footer + pb-16 cushion.

Fix — make it tanstack-native

• Take the footer out of the virtual count; reserve its measured height as paddingEnd so virtual-end == DOM-end.
• anchorTo:"end" now handles in-place token growth, followOnAppend handles appends, and isAtEnd/scrollToEnd line up with the footer bottom — all native.
• The one thing tanstack can't see (the footer is not a virtual item) is its own resize → covered by a ResizeObserver → paddingEnd + a single re-pin effect.
• Scroll-to-bottom button gets reporting hysteresis so the append → measure-taller → re-pin cycle doesn't flicker it, plus a far-drift (>400px) escape hatch so follow can't get silently stuck. Button visibility is pure UI state; tanstack still drives all scrolling.

RawLogsView (the other consumer) passes no footer → paddingEnd=0, behaviour unchanged.

Test plan

• Open a session — lands at the footer (true bottom), no button.
• Stream a turn — view tracks tokens, button stays hidden.
• Let the turn finish (footer swaps to "Generated in…") — stays pinned.
• Scroll up — button appears; click — settles at footer; new content follows again.

🤖 Generated with Claude Code

[stamphog]

Review agent failed after 3 attempts — needs human review.

[greptile-apps]

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
apps/code/src/renderer/features/sessions/components/VirtualizedList.tsx:32-34
The far-drift threshold of `400` is the only magic number not extracted into a named constant alongside `AT_BOTTOM_THRESHOLD`, `ESTIMATED_ROW_SIZE`, and `OVERSCAN`. Naming it makes the intent explicit and keeps all tuning knobs in one place.

```suggestion
const AT_BOTTOM_THRESHOLD = 50;
const ESTIMATED_ROW_SIZE = 80;
const OVERSCAN = 6;
const FAR_DRIFT_THRESHOLD = 400;
```

### Issue 2 of 2
apps/code/src/renderer/features/sessions/components/VirtualizedList.tsx:186-188
Use the new named constant here so the threshold value is defined in exactly one place.

```suggestion
    const farFromEnd = el
      ? el.scrollHeight - el.clientHeight - scrollTop > FAR_DRIFT_THRESHOLD
      : false;
```

_{Reviews (1): Last reviewed commit: "fix(sessions): keep conversation pinned ..." | Re-trigger Greptile}

[greptile-apps]

The far-drift threshold of 400 is the only magic number not extracted into a named constant alongside AT_BOTTOM_THRESHOLD, ESTIMATED_ROW_SIZE, and OVERSCAN. Naming it makes the intent explicit and keeps all tuning knobs in one place.

Suggested change

	const AT_BOTTOM_THRESHOLD = 50;
	const ESTIMATED_ROW_SIZE = 80;
	const OVERSCAN = 6;
	const AT_BOTTOM_THRESHOLD = 50;
	const ESTIMATED_ROW_SIZE = 80;
	const OVERSCAN = 6;
	const FAR_DRIFT_THRESHOLD = 400;

Prompt To Fix With AI

This is a comment left during a code review.
Path: apps/code/src/renderer/features/sessions/components/VirtualizedList.tsx
Line: 32-34

Comment:
The far-drift threshold of `400` is the only magic number not extracted into a named constant alongside `AT_BOTTOM_THRESHOLD`, `ESTIMATED_ROW_SIZE`, and `OVERSCAN`. Naming it makes the intent explicit and keeps all tuning knobs in one place.

```suggestion
const AT_BOTTOM_THRESHOLD = 50;
const ESTIMATED_ROW_SIZE = 80;
const OVERSCAN = 6;
const FAR_DRIFT_THRESHOLD = 400;
```

How can I resolve this? If you propose a fix, please make it concise.

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

[greptile-apps]

Use the new named constant here so the threshold value is defined in exactly one place.

Suggested change

	const farFromEnd = el
	? el.scrollHeight - el.clientHeight - scrollTop > 400
	: false;
	const farFromEnd = el
	? el.scrollHeight - el.clientHeight - scrollTop > FAR_DRIFT_THRESHOLD
	: false;

Prompt To Fix With AI

This is a comment left during a code review.
Path: apps/code/src/renderer/features/sessions/components/VirtualizedList.tsx
Line: 186-188

Comment:
Use the new named constant here so the threshold value is defined in exactly one place.

```suggestion
    const farFromEnd = el
      ? el.scrollHeight - el.clientHeight - scrollTop > FAR_DRIFT_THRESHOLD
      : false;
```

How can I resolve this? If you propose a fix, please make it concise.

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!