feat(web): nest delegated threads under their parent in the sidebar

[rynfar]

Delegated child threads showed up as unrelated top-level rows in the sidebar. They were often sorted above their parent, so it was hard to tell which agent started which task.

What changed

• Shared helper (@t3tools/client-runtime/state/delegated-threads):
  • Reads the parent from the child id format delegated:<parent>:<16 hex>. Parent ids can contain colons, so it doesn't split on :.
  • Nests each child under a parent in the same list.
  • Keeps a child top-level when its parent isn't in that list, so a thread never disappears.
• Live sidebar (Sidebar.tsx):
  • Grouping runs per section (pinned, active, snoozed, settled). Children render indented under their parent.
  • Pin, snooze and settle are per thread, so when a child and its parent end up in different sections, the child shows as its own row there.
  • Paging ("Show more"), collapsed shelves and drag order use only top-level rows. A child's own order keys are never shown, so a drop never writes them.
  • Jump shortcuts, shift-range select and next/previous thread follow the rendered order, children included.
  • The open thread stays visible when its parent sits behind a collapsed shelf or "Show more".
  • A parent row with children wraps them in its sortable node, so the group moves as one during a drag.
  • The drag listeners and the file-drop target stay on the parent's own row, so pressing or dropping files on a child never acts on the parent.
  • Rows without children render exactly as before.
• Docs: docs/user/agent-delegation.md explains where children appear.

Not covered: the legacy per-project sidebar and the mobile app still list children as ordinary threads. The helper lives in client-runtime so mobile can adopt it later. There is no collapse toggle per parent (a parent has at most eight live children).

Before / after

Isolated dev server with a fixture: a parent with two delegated children, an unrelated thread, and a child whose parent is settled.

Before	After

"Audit lockfile changes" stays top-level in both because its parent is settled.

Verification

• Focused tests:
  • vp test run packages/client-runtime/src/state/delegatedThreads.test.ts: 8 new tests covering id parsing, colon-containing parent ids, malformed ids, environment scoping, orphan fallback, flattening and route containment.
  • Sidebar.logic, Sidebar.drag, Sidebar.motion and Sidebar.pointer tests: 259 passing together with the new file.
• Static checks:
  • vp run -F web typecheck and vp run -F @t3tools/client-runtime typecheck pass, re-run on web after rebasing onto pylon.
  • vp run knip:check passes.
  • Lint shows no new warnings: 24 before and after on Sidebar.tsx.
• Browser, on the isolated dev server:
  • Children render nested.
  • Clicking a child opens the child.
  • Pressing and dragging on a child does not start a drag.
  • Dragging the parent translates the whole group.
  • Dropping the parent into Settled settled it on the server, and its children became top-level active rows.
  • Un-settling it nested them again.

Adversarial review (Fable)

The first pass found no blocking issues but verified three real defects, all fixed in c128af68c1:

1. Wrong drag gap. The gap was measured from a group's height. The layout code now takes groupKeys: group rows no longer set the base row height, and a lifted group keeps its own height. Two new tests fail on the old code.
2. Optimistic hold released early. This happened when a parent was dropped into the section holding its children. resolveSidebarDropTarget now takes the dragged row's children as nestingKeys and removes them from the destination order, so their order keys are never written. Live check: I pinned the parent, then dragged it back into Active. The order stayed stable across 4 seconds of samples, the children re-nested, and their order keys stayed null in SQLite.
3. Settled parent hidden during a drag. This happened when its nested child was the open thread. The route exception now receives the top-level row that holds the open thread.

Also fixed: a grandchild stays top-level (one-level guard, with a test), and an attribute the live sidebar never reads was removed from the nested list.

The re-review of the fixes found no blocking issues and nothing new. One accepted preview inaccuracy: when a group moves between Pinned and Active, the gap is group-sized, and the children split back out on release. Parent rows with children still re-render on each shell update, because the nested lists are rebuilt on every update anyway.

Done by Claude Opus 5 in Claude Code.

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Project	Deployment	Actions	Updated
pylon-marketing	Ready	Preview	Sep 17, 2026 5:54am UTC

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.9 KiB	13.9 KiB	−13 B (−0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.2 KiB	7.2 KiB	+2 B (+0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.7 KiB	6.7 KiB	−15 B (−0.2%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.0 KiB	58.0 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	8	8	0 (0.0%)	21	✅
Claude	Total thread wire	14.1 KiB	14.1 KiB	+15 B (+0.1%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.2 KiB	7.2 KiB	−12 B (−0.2%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.8 KiB	6.9 KiB	+27 B (+0.4%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	59.7 KiB	59.7 KiB	+44 B (+0.1%)	66.4 KiB	✅
Claude	Live turn messages	9	10	+1 (+11.1%)	21	✅

Baseline: 00b2ffc · PR result: c128af6 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 115.7 KiB
• Claude decoded thread snapshot: 116.3 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.