Chat was polling every 5s, which felt sluggish with two users online.
Switched to Server-Sent Events for push delivery. Polling now runs as
a 30s heartbeat just to catch anything missed during reconnect windows.
NATS is still bundled in docker-compose but no Rust code talks to it
yet — that lands in v0.2 for cross-instance fanout. The migration is
"swap the in-process broker for nats.publish/subscribe against
kez.chat.inbox.<handle>"; SSE subscribers don't notice.
Server (kez-chat-server):
• New broker module: per-recipient tokio::sync::broadcast channels,
in-process pub/sub. 64-slot buffer per channel; lagging subscribers
drop on the floor and resync via the polling heartbeat. 4 unit
tests cover subscribe/publish, multi-subscriber fanout, per-handle
isolation, no-op on no-subscribers.
• POST /v1/messages now publishes to broker after persisting → any
open SSE stream for the recipient gets the envelope immediately.
• New GET /v1/inbox/:handle/stream — SSE endpoint, ?auth=<ts>:<sig>
query param (EventSource can't set headers). Signed message is
distinct from the polling header ("GET\n/v1/inbox/<h>/stream\n<ts>"
vs "GET\n/v1/inbox/<h>\nsince=<n>\n<ts>") so a captured poll sig
can't be replayed as a stream sig and vice versa.
• 15s SSE keep-alive ping so Cloudflare/NAT/load balancers don't
drop idle connections.
• 3 new stream-auth unit tests, including the cross-endpoint replay
rejection. 19 unit + 20 integration tests all green.
• New deps: tokio-stream (sync feature for BroadcastStream),
futures (for the Stream trait the Sse handler returns).
Browser (kez-chat/web):
• streamInbox() in lib/messages.ts: long-lived EventSource,
auto-reconnects on error with fresh auth (tears down on `error`,
re-opens after 3s — EventSource's native retry uses the stale URL).
Exposes onMessage + onStatus callbacks.
• Messages.svelte: opens SSE on mount, decrypts pushed envelopes
inline via the new shared ingest() helper. Polling dropped from
5s → 30s heartbeat.
• Sidebar footer shows live status:
● live (green)
● reconnecting… (amber)
○ connecting… (gray)
Verified live: /v1/inbox/<registered>/stream?auth=bad returns 401,
no-auth returns 400. Asset index-C1ogRtUG.js serving.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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