Architecture

Runtime paths

Claude Code hook path: bin/open-plan-annotator.mjs -> runtime resolver -> platform runtime package binary -> server/index.ts runtime.
OpenCode path: opencode/index.js -> opencode/bridge.js -> same runtime resolver + runtime package binary.
Shared behavior: both paths produce the same Claude hook payload/response format.

server/runtime/input.ts: stdin parsing, dev-mode plan bootstrap, fallback ~/.claude/plans loading.
server/runtime/preferences.ts: config paths plus preference load/persist logic.
server/runtime/history.ts: per-session history load/write and cleanup.
server/runtime/html.ts: embedded UI string loading with dev fallback.
server/runtime/decision.ts: decision promise control and stdout-safe hook output.
server/index.ts: orchestration only (startup, router wiring, update check, lifecycle).

open-plan-annotator is the canonical npm package.
Platform-specific runtime packages live under packages/runtime-* and each ship one compiled binary.
shared/runtimeResolver.mjs resolves the correct runtime package for the current platform.
Updates are package-managed by the host (OpenCode, Claude Code, or the user's package manager); the runtime never self-updates in place.