OpenChamber provides UI runtimes (web/desktop/VS Code) for interacting with an OpenCode server (local auto-start or remote URL). UI uses HTTP + SSE via `@opencode-ai/sdk`.
- External server support: Set `OPENCODE_HOST` (full base URL, e.g. `http://hostname:4096`) or `OPENCODE_PORT`, plus `OPENCODE_SKIP_START=true`, to connect to existing OpenCode instance
This skill contains all color tokens, semantic logic, decision tree, and usage patterns. All UI colors must use theme tokens - never hardcoded values or Tailwind color classes.
These rules exist because violating them has caused measurable regressions (render cascades, memory bloat, UI jank). They apply to all UI and sync layer work.
### Shared-store render discipline
- **Treat common stores as render fanout boundaries.** An unnecessary reference change in shared state can re-render large parts of the app.
- **Do not put high-frequency state in broadly consumed stores.** Fast-changing state should live in narrow stores with narrow subscribers.
- **Update only the fields that changed.** Preserve references for untouched state branches.
- **Prefer leaf selectors over container selectors.** Subscribe to the smallest stable value that satisfies the component.
- **Isolate hot consumers.** If a value changes often and only a few components need it, move it to a narrower store or consume it in a memoized child.
### Zustand referential equality
Zustand skips re-renders when a selector returns the same reference (`Object.is`). Every new object/array reference triggers a re-render in every subscriber.
- **Never spread all state fields in an update.** Only create new references for fields that actually changed. A `message.part.delta` event should not clone `session`, `permission`, etc.
- **Select leaf values, not containers.** `useStore((s) => s.permission[sessionID])` is correct. `useStore((s) => s.permission)` subscribes to every permission change across all sessions.
- **Preserve references when merging.** If prepending older messages, keep existing message object references. Only add truly new items. Return the original array if nothing was added.
### Store splitting
A single store with N properties means every subscriber re-evaluates on every state change. Split stores by change frequency and subscriber set.
- **Group state by how often it changes.** Streaming state (updated 60/sec) must not live with user preferences (updated on click).
- **Group state by who reads it.** If only 2 components need a value, it belongs in a store that only those 2 subscribe to.
- **Cross-store reads use `.getState()`.** Actions in one store that need another store call `useOtherStore.getState()` — imperative, no subscription.
- **Never add unrelated state to an existing store** just because it's convenient. Create a new store.
### Event pipeline and SSE
- **Gate expensive operations on the hot path.** During streaming, `message.part.delta` and `message.part.updated` fire ~60/sec. Any `findIndex`, `filter`, or iteration added to these handlers multiplies across every event. Gate behind a cheap boolean check first (e.g., check `next[0]` before scanning the array).
- **Skip no-op updates.** If an incoming event doesn't change the state (same role, same finish, same timestamps), return `false` from the reducer to avoid creating new references.
- **Coalesce by key.** Same-entity events (e.g., repeated `session.status` for the same session) should replace earlier ones in the queue, not accumulate.
- **Preserve event ordering semantics.** Reducers and queues must not let stale deltas or out-of-order events corrupt the latest state.
- **Do not widen live-activity fallbacks.** A fallback for delayed status should inspect only the current trailing entity, not arbitrary historical records.
### Polling payload fidelity
- **Do not let lightweight polling erase rich fields.** If light mode omits fields (e.g., `diffStats`), preserve previous rich data until a heavy follow-up fetch lands.
- **Use two-phase polling.** Run cheap change detection first; only run heavy status fetches for directories that actually changed.
### Optimistic updates
- **Use the shadow Map pattern.** Insert optimistic data into the store for instant UI, AND register it in a separate tracking Map. Cleanup happens deterministically via `mergeOptimisticPage` on the next data fetch — not via heuristics in the event reducer.
- **Pass client-generated IDs to the server.** Use the same ID format as the server (hex-encoded timestamps). Pass `messageID` to `promptAsync` so the server echoes back the same ID. This prevents duplicates and enables in-place replacement.
- **Rollback on error.** Remove the optimistic entry from both the store and the shadow Map.
- **Stabilize bridge callbacks.** When wiring hook callbacks into module-level refs, use stable ref wrappers so effects do not loop on changing function identities.
### Session/input consistency
- **Capture send config at queue time.** Queue items must include provider/model/agent/variant snapshot; do not re-resolve from mutable live state at send time.
- **Keep server-selected attachments sendable.** Preserve server-backed file selections in queue/submit flows and convert them to proper `file://` URLs before sending.
### Bootstrap resilience
- **Treat startup 502/503 as transient.** Retry bootstrap/session-list flows with bounded retries/intervals, especially in VS Code where API readiness can lag bridge startup.
- **Use polling recovery when failures are swallowed.** If an async loader resolves without throwing on failure, recover with interval retries gated by loaded-state checks.
### Scroll and DOM
- **Never use `await waitForFrames()` for scroll preservation.** Frames of visible scroll jump are unacceptable. Use `useLayoutEffect` to adjust scroll synchronously after React commits DOM — before the browser paints.
- **Capture scroll state before the state change, restore in layout effect.** The pattern: save `scrollHeight`/`scrollTop` into a ref before triggering the update, consume it in `useLayoutEffect` on the rendered output.
### Component isolation
- **Extract high-frequency hook consumers into separate components.** If a hook re-evaluates 60/sec (e.g., streaming status), wrap its consumer in a `React.memo` child component so the parent doesn't re-render.
- **Use custom `React.memo` comparators for message rows.** Compare render-relevant fields (role, finish, parts count, part IDs) — not object references.
### Caching and memory
- **Cap in-memory caches with both count and byte limits.** Entry count alone doesn't prevent memory bloat from large files. Use dual-constraint LRU (e.g., 40 entries OR 20MB).
- **Set store session limits to match loaded data.** If bootstrap loads N sessions, set `limit >= N`. Otherwise the next SSE event triggers trimming that silently removes sessions.
- **Invalidate caches on mutations.** File content cache must clear entries on write, delete, rename. Prefetch cache must clear on session eviction.
- **Use TTLs to prevent redundant fetches.** If a session was fetched <15s ago, skip re-fetching — SSE events keep it current.
### Directory context
- **Never cache directory strings in closures.** Directory can change at any time (worktree switch). Read it dynamically from `opencodeClient.getDirectory()` at call time.
- **Pass directory hints when the source of truth isn't available yet.** Newly created sessions aren't in the sync store until SSE delivers them. Pass the known directory as a parameter instead of relying on lookup.
