mara on #448: "firefox disconnects bc of too many tabs. needs bg
service worker". picked SharedWorker over full Service Worker:
smaller change, addresses the actual problem (shared connection
across tabs), no offline-cache scope creep.
architecture
per-tab `new EventSource('/dashboard/stream')` replaced with a
SharedWorker-backed facade. one SharedWorker instance per origin
holds ONE upstream EventSource and fans every server-sent event
out to every connected tab via MessagePort. N hyperhive tabs now
share ONE backend connection, immune to Firefox's per-tab SSE
throttling under many-open-tabs pressure.
wire protocol (port.postMessage):
tab → worker
{ kind: 'subscribe', url: '/dashboard/stream' }
{ kind: 'unsubscribe', url: '/dashboard/stream' }
worker → tab
{ kind: 'open', url }
{ kind: 'message', url, data: '<raw SSE data>' }
{ kind: 'error', url }
subscription tracking is per (port, url). a late subscriber that
joins after the upstream is already OPEN gets a synthetic 'open'
event so its onStreamOpen handler still runs (triggers the
snapshot re-sync that recovers events lost during the join gap).
unsubscribing the last port for a URL closes the upstream
EventSource so we don't leak idle streams.
files
- frontend/packages/dashboard/src/stream-worker.js: new — the
worker. multi-URL multiplexing via Map<url, {es, ports}>.
- frontend/packages/dashboard/src/common.js: new exported helper
openStream(url) — returns an EventSource-shaped facade backed
by the SharedWorker. graceful fallback to direct EventSource
when SharedWorker is unavailable.
- frontend/packages/dashboard/src/app.js: replaces the inline
new EventSource('/dashboard/stream') with openStream.
- frontend/packages/dashboard/src/flow.js: passes
streamFactory: openStream to termCreate so the broker
terminal's SSE goes through the worker too.
- frontend/packages/shared/src/terminal.js: accepts an optional
streamFactory(url) option. default unchanged — non-dashboard
consumers (per-agent UI) keep using direct EventSource.
- frontend/packages/dashboard/build.mjs: new esbuild entry for
stream-worker.js → dist/static/stream-worker.js (separate
bundle because SharedWorker scripts run in a different global
scope and can't be inlined into app.js).
scope kept tight
- per-agent UI's /events/stream stays on direct EventSource. the
agent UI's tab count per agent is typically 1; SharedWorker
helps when you have N tabs hitting the SAME stream and the
per-agent stream URLs differ. if mara wants the agent UI to
share its workers too it's a separate small PR.
- no offline-cache, no push notifications — those need full
Service Worker; explicit non-goal here per the design Q.
validation
- npm run build --workspace=@hive/dashboard clean.
- stream-worker.js bundle: 1.8 kb.
- app.js: 154 kb → 158 kb. flow.js: 29.9 kb → 32 kb.
- browser smoke test isn't possible from inside iris's container;
the EventSource-shaped facade preserves the exact onmessage /
onopen / onerror surface the existing IIFE consumers use.
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