Remote mobile: rewrite the feed rendering (mobile-native, and adopt the new ownership-ledger pipeline) #475

Sub-issue of #420 (Remote Mobile Companion). The phone can pair, list sessions, submit prompts, and stream — but the feed rendering is far from done. This tracks a ground-up rework.

Where it stands today (the actual code)

• The phone reuses the DESKTOP Feed component verbatim. src/remote-client/src/ui/SessionView.tsx:3 imports @renderer/features/feed/ui/Feed and renders it, wired via the vite alias table (src/remote-client/vite.config.ts) plus a handful of stubs (stubs/CodeBlock.tsx, SafeInlineCode.tsx, SafeMarkdownLink.tsx, appStateHooks.ts). It feeds the same SessionFeed channels the desktop does (src/main/remote/SessionFeedSource.ts → WebSocketSessionFeed).
• It renders through the LEGACY path only. SessionView passes semanticTurn / semanticHistory / toolUseIndex / toolResultIndex as props — there is no renderItemsOverride / useLedgerFeedItems wiring. So the moment the desktop rendering cutover (the new ownership-ledger pipeline, PR feat(rendering): ownership-ledger rendering pipeline + session recording + soak fixes — integration branch #442) lands, the phone is stranded on the renderer being deleted.
• Styling is desktop-parity, not mobile-native. src/remote-client/src/styles.css is ~174 lines that mostly inherit desktop styles (per PRs fix(remote): client-serving robustness — per-request bundle check, cache headers, self-diagnosing fallback #431/Remote: restart-proof history, richer session picker, desktop style parity #440 "desktop style parity on the phone"). There is almost no mobile-first layout: dense desktop tool rows, marker gutters, collapsed-activity chips, and code blocks were designed for a wide pane with a mouse, not a 390px touch screen.

Why "reuse the desktop Feed" is now the wrong foundation

It was a reasonable bootstrap (ship something fast), but it couples the phone to desktop-shaped rows and, critically, to the legacy renderer that the rewrite is deleting. The desktop feed's density, hover affordances, and fixed-width assumptions don't translate to touch. And the two will diverge hard at cutover.

What "properly done" looks like

1. Adopt the new pipeline, don't fork it. The ownership-ledger pipeline (src/renderer/src/rendering/) is provider-neutral and produces a clean ordered row model (RenderLedger → view bridge). The phone should consume that decision core and render its OWN mobile row components from it — same ownership/ordering guarantees, different presentation. This is exactly the seam the rewrite created (decision core vs. dumb rows). The phone becomes a second "view" over the ledger, like the desktop view bridge.
2. Mobile-native row components. Purpose-built for touch/narrow: readable prompt/assistant bubbles, tap-to-expand tool calls (reuse the plan's JSON/MCP tool-row concepts but sized for the phone), collapsed subagent/Task cards, code blocks with horizontal scroll containers, big tap targets. Not the desktop marker-gutter layout shrunk down.
3. Reuse the session recorder for mobile fixtures. The Session Recording work (Session Recording: continuous debug-gated capture replayable as rendering fixtures #467) records the SessionFeed input stream — the exact stream the phone consumes. A recording replays through the ledger identically for desktop and phone, so the phone's rendering gets the same replay/invariant test net for free, and mobile-specific divergences become fixtures.
4. Handle the mobile-only surfaces properly. Conditions/AskUserQuestion tap-bar (already partially in SessionView), the screen/terminal fallback, connection/restart states, scroll/stick-to-bottom on touch.

Scope / non-goals

• In scope: the feed rendering rewrite for the phone, mobile row components, adopting the ledger decision core, mobile fixtures via recordings.
• Not here: pairing/transport/auth (that's Remote Mobile Companion: control agents from your phone (LAN + optional tunnel) #420 core), which work fine.
• Sequencing: this should land after or alongside the desktop cutover (PR feat(rendering): ownership-ledger rendering pipeline + session recording + soak fixes — integration branch #442) so the phone adopts the ledger rather than chasing the legacy renderer as it's removed.

Pointers

• Phone feed entry: src/remote-client/src/ui/SessionView.tsx, src/remote-client/src/transcript/store.ts
• Server feed: src/main/remote/SessionFeedSource.ts, RemoteController.ts, WebSocketSessionFeed.ts
• The pipeline to adopt: src/renderer/src/rendering/ + docs/rendering/rendering-rewrite-plan-2026-07.md
• Recording/replay for fixtures: docs/rendering/session-recording-plan-2026-07.md (Session Recording: continuous debug-gated capture replayable as rendering fixtures #467)
• Umbrella: Remote Mobile Companion: control agents from your phone (LAN + optional tunnel) #420