Context

Seed desktop today is polling-based with manual TanStack Query invalidation over Connect-RPC to a local Go daemon. The daemon already owns the source-of-truth SQLite database on the same machine; IPC is the boundary, not the network. P2P sync results in the daemon, but the renderer only learns about new data on the next poll tick or manual invalidateQueries().

Observed pain points motivating this work:

Flicker / loading states on navigation. Switching documents shows skeletons even when data is already cached locally, because each panel waits on its own query lifecycle.
P2P sync feels frozen. Discovery and inbound blobs land in the daemon but the UI takes seconds (or a focus event) to reflect them.
State sprawl. Server cache (TanStack), UI state (React + electron-store), document editor state (XState) live in separate reactive systems with ad-hoc bridges. Bugs leak across them.

Riffle solves analogous problems via (a) reactive relational queries, (b) synchronous transactional updates, (c) unifying UI + domain state in one reactive substrate. We adopt the reactive layer ideas only — daemon SQLite stays the source of truth; we do not ship a client-side DB. Web app (@shm/web) out of scope.

Goal

Replace polling + manual invalidation with push-driven, dependency-tracked reactive queries that batch into transactional UI ticks, plus a single reactive store for UI state that participates in the same tick.

Strategy: vertical slices, not horizontal layers

Build the smallest end-to-end loop (event source → bus → reactive graph → one UI surface) for one feature first. Each subsequent slice adds one more fetcher + topic + UI surface. The transport, engine, and UI-state store evolve inside the same vertical pipeline, swapped behind a stable renderer-facing API.

Benefits over horizontal phasing:

Ship visible win after slice 1 (~days, not weeks).
API gets stress-tested on real component before broad migration.
Can be killed cheaply if approach fails — small blast radius.
Each slice is independently mergeable; no big-bang flag.

Target design (end state)

┌────────────────────────────── Go daemon ──────────────────────────────┐
│  SQLite (truth) → commit hooks → internal pubsub                      │
│  Events.Watch streaming RPC                                           │
│  • emits typed events: blob.inserted, doc.changed, sub.updated…       │
│  • topic-tagged (ENTITY:<id>, DIRECTORY:<acct>:<path>, ACCOUNT:<id>)  │
└──────────────────────────────┬────────────────────────────────────────┘
                               │ Connect-RPC server-streaming
                               ▼
┌──────────────────────── Electron main process ────────────────────────┐
│  EventBridge — owns the single daemon stream, fans out to renderers   │
│  TopicPoller (slice-1 fallback) — polls daemon, diffs, emits events   │
│  Both push to renderers over electron-trpc subscription               │
└──────────────────────────────┬────────────────────────────────────────┘
                               │ tRPC observable
                               ▼
┌──────────────────────────── Renderer ─────────────────────────────────┐
│  @shm/reactive                                                        │
│   • graph.ts: Node={key,topics,fetcher,equals?}, dirty, tick scheduler│
│   • event-bus.ts: pipes events → markDirty(topic)                     │
│   • react.tsx: useReactiveQuery(node), useReactiveState(schema)       │
│  UIStateStore (later slice) — extends StateStream, same tick          │
└───────────────────────────────────────────────────────────────────────┘

Stable API contract from day 1: useReactiveQuery(node) and useReactiveState(schema, scope). Everything below can change without touching components.

Key design choices:

Engine deferred. No client SQLite. Slice 1 = "refetch whole result on dirty". Later: swap for IVM (cr-sqlite, materialize-wasm) behind same node API.
Transport swap, not rewrite. Slice 1 uses electron-trpc subscription backed by main-process polling. Later slice swaps event source for Events.Watch Connect streaming RPC; renderer untouched.
Topic-level reactivity, not row-level. Mirrors Riffle's "on-demand layer" (paper §A). Manually declare topics per node; later derive from query shape.
Transactional tick. All dirty nodes triggered by one event resolve before React notification. Mirrors Riffle §3.2 (synchronous transactional updates).
UI state migration is its own slice. Don't conflate with server-state reactivity.

Slice plan

Each slice = one fetcher + one topic + one UI surface. Stop or pivot after any slice if no win.

Slice 1 — Live sidebar directory listing (FIRST)

Why this slice: smallest end-to-end. One RPC (Documents.ListDocuments / ListDirectory). Visible P2P win — synced sibling docs appear without focus. No editor/CRDT involvement.

Components:

frontend/packages/reactive/ (NEW pkg @shm/reactive)
- src/graph.ts (~120 LOC): defineNode({key, topics, fetcher, equals?}), internal Map<key, Node>, markDirty(topic), microtask-batched tick() that re-runs dirty fetchers in topological order and notifies via per-node StateStream.
- src/react.tsx: useReactiveQuery(node) via useSyncExternalStore reusing frontend/packages/shared/src/utils/stream.ts.
- src/event-bus.ts: dispatch(event), onEvent(topic, fn).
- src/index.ts exports.
Main process — frontend/apps/desktop/src/main/topic-poller.ts (NEW)
- Registers topic DIRECTORY:<account>:<path>.
- When ≥1 renderer subscribes, polls grpcClient.documents.listDocuments every ~1s, hashes ID list, emits event on change.
- Stops when 0 subscribers.
Main process — extend frontend/apps/desktop/src/app-api.ts
- Add events router with watch(topics: string[]) returning tRPC Observable<Event> (electron-trpc subscriptions).
Renderer wiring — frontend/apps/desktop/src/app-context.tsx
- At boot, open one trpc.events.watch.subscribe({topics: ['*']}).
- Pipe next into reactive.dispatch(event).
Migrate one component — sidebar directory list (currently uses TanStack useQuery)
- Replace with useReactiveQuery(directoryNode({account, path})).
- Node declares topics: ['DIRECTORY:'+account+':'+path], fetcher = existing Connect call.

Verification (slice 1):

Open desktop, log in. From a second daemon (or ./dev script), create new doc under same account/path.
Sidebar should grow within ~1s without click/focus. Compare to baseline polling (10s + focus refetch).
Confirm: no console spam, poller stops when sidebar unmounts.
pnpm --filter @shm/desktop test:unit, pnpm typecheck.

What's intentionally NOT in slice 1:

New proto file. None.
Daemon commit hooks / pubsub. None.
IVM engine. None.
UI state migration. None.
Streaming Connect RPC. None.
Schema mirror, GraphQL, materialized views. None.

Slice 2 — Account profile header

Topic ACCOUNT:<id>. Fetcher = Documents.GetAccount. Same poller pattern. Replaces one more useQuery. Validates topic taxonomy at 2 surfaces.

Slice 3 — Open document body (biggest P2P win)

Topic ENTITY:<id>. Fetcher = Documents.GetDocument. Remote change arrives → doc rerenders without manual reload. First contact with editor surface — confirm XState documentMachine can consume a reactive context value.

Slice 4 — Comments thread

Topic COMMENTS:<entity>. Fetcher = Comments.ListComments. Validates "many small topics under one parent entity" pattern + invalidation fan-out.

Slice 5 — Swap event source to real streaming RPC

Only main-process change. Add proto/events/v1alpha/events.proto with Events.Watch(filter) returns stream Event. Implement Go handler reading from internal pubsub fed by SQLite commit hooks (or by tailing structural_blobs.insert_time). Replace TopicPoller with stream consumer. Renderer untouched.

Slice 6 — UI state into reactive store (transactional consistency)

Move sidebar selection + breadcrumb + nav stack from React state + electron-store into UIStateStore (new). Same tick batches server updates and UI writes. Mirrors Riffle §3.2 — eliminates half-rendered nav (sidebar selected B, main pane still A).

Slice 7+ — Cleanup + optional IVM

Delete refetchIntervals once parity holds.
(Optional) Swap "refetch on dirty" for cr-sqlite / materialize-wasm with incremental views. Requires schema mirror — separate design doc.

Reuse (do not re-invent)

frontend/packages/shared/src/utils/stream.ts — StateStream/EventStream already used (appWindowEvents, darkMode). Build on this; no RxJS / signals lib.
frontend/packages/shared/src/use-stream.ts — existing useSyncExternalStore binding.
frontend/packages/shared/src/models/query-client.ts — TanStack stays for non-migrated surfaces during rollout.
frontend/apps/desktop/src/trpc.ts — existing electron-trpc setup; add subscription router only.
Existing Subscriptions RPC stays — orthogonal (sync intent), not push.

Files (slice 1 only)

NEW:

frontend/packages/reactive/package.json
frontend/packages/reactive/src/{graph,react,event-bus,index}.ts
frontend/apps/desktop/src/main/topic-poller.ts

EDIT:

frontend/apps/desktop/src/app-api.ts — add events.watch subscription.
frontend/apps/desktop/src/app-context.tsx — wire bus on boot.
One sidebar component file (TBD when scanning components) — swap hook.

Boundaries respected

Daemon untouched in slice 1. First proto/Go change lands in slice 5.
vault/ workspace untouched.
Web app (@shm/web) unaffected.
Per frontend/AGENTS.md 95% threshold met via 4 clarifying answers.

Open questions / risks (mostly deferred until they bite)

Backpressure (relevant slice 5+). Daemon may emit thousands of events during sync burst. Coalesce per-topic with debounce in main process before fanning to renderers.
Reconnect / replay (slice 5+). On daemon restart, renderer must resync. Either cursor on stream (mirroring P2P.ListBlobs) or full-refetch-on-reconnect.
UI-thread cost (slice 6+). Riffle §6.4 warns synchronous graph can block paint. Mitigation: keep heavy transforms in component memoization, not in graph fetchers.
Persisted UI state queryability (slice 6+). electron-store blobs aren't queryable. Acceptable for v1.

Verification per slice

Common gates after every slice:

pnpm typecheck
pnpm --filter @shm/reactive test (once tests exist, slice 1 prototype skips)
pnpm --filter @shm/desktop test:unit
Manual: golden path + monitor devtools (no console spam, single tRPC subscription open).

Slice-specific:

Slice 1: P2P-added sidebar doc appears <1.5s, no manual focus. Baseline = current 10s polling.
Slice 3: remote change of open doc reflects in body <1s.
Slice 5: swap to streaming verified by grpcurl plus desktop e2e equivalence with slice-1 polling baseline.
Slice 6: Playwright frame trace confirms sidebar selection + main pane swap in same paint.

How to test slice 1 specifically

pnpm install (new workspace pkg).
pnpm --filter @shm/desktop dev.
Open two daemons (local + second device or local + ./dev synthetic peer). Log into same account.
On the second daemon, create a new doc in the active directory.
Watch the sidebar in the first desktop instance update without clicking or refocusing.
Compare: revert the sidebar component to the old useQuery hook and repeat — confirm the old behavior takes ≥10s or requires window focus.
Devtools network panel: one open tRPC subscription, no rapid HTTP polling for the migrated query.