kandev/docs/plans/plugin-backed-canvases/task-05-live-event-transport.md

id, title, status, wave, depends_on, plan, requirements, acceptance_criteria, system_design

id	title	status	wave	depends_on	plan	requirements	acceptance_criteria	system_design
05-live-event-transport	Live event transport	completed	5	04-browser-data-state	plan.md	REQ-PLUGINS-ISOLATED-WEB-APPS-006 REQ-PLUGINS-ISOLATED-WEB-APPS-009	AC-PLUGINS-ISOLATED-WEB-APPS-006.1 AC-PLUGINS-ISOLATED-WEB-APPS-006.2 AC-PLUGINS-ISOLATED-WEB-APPS-006.3 AC-PLUGINS-ISOLATED-WEB-APPS-006.4 AC-PLUGINS-ISOLATED-WEB-APPS-006.5 AC-PLUGINS-ISOLATED-WEB-APPS-006.6 AC-PLUGINS-ISOLATED-WEB-APPS-009.1 AC-PLUGINS-ISOLATED-WEB-APPS-009.2 AC-PLUGINS-ISOLATED-WEB-APPS-009.3	../../specs/plugins/system-design/isolated-web-app-contributions.md

Task 05: Live event transport

Summary

Add bounded Server-Sent Events for authorized public Kandev events. Define connection ownership, replay, heartbeat, cancellation, and resync behavior.

In scope

• Add the capability-path SSE endpoint and event-scope filters.
• Add process generation and monotonic event identifiers.
• Add 15-second heartbeats and immediate response flushing.
• Add per-user and per-instance connection admission.
• Add bounded time and event-count replay.
• Add gap and restart resync signals.
• Add disconnect cleanup, leak tests, metrics, and safe logs.

Out of scope

• Canvas metadata events, source publishing, and host user interface.

Acceptance

• Reconnect replays one complete range or sends runtime.resync_required.
• Current scope and grants filter every event, including replayed events.
• Disconnect releases subscriptions and counters without a timeout sleep.

Verification

cd apps/backend && go test ./internal/plugins/webapp/... ./internal/events/... ./internal/plugins/...

Files likely touched

• apps/backend/internal/plugins/webapp/events.go
• apps/backend/internal/plugins/webapp/events_test.go
• apps/backend/internal/events/**
• apps/backend/internal/backendapp/**

Dependencies

• Task 04 provides authorized data shapes and runtime context.

Risks

• Replay can expose data after an instance loses access.
• Missing request cancellation can leak subscriptions and counters.
• Proxy buffering can hide heartbeats and delay disconnect detection.

Parallelism

sequential

Inputs

• Live event, request authorization, observability, and recovery sections.
• Current event bus lifecycle and goroutine ownership patterns.

Results

Completed on 2026-08-28. Added the bounded per-instance SSE hub with process generations, monotonic cursors, replay and resync signals, heartbeat flushing, per-user and per-instance stream limits, slow-consumer handling, and context cancellation cleanup. The plugin service projects scoped Kandev bus events into the hub and rechecks capability authority while filtering delivery. Focused web-app and plugin tests pass.