Event System & State Management: Tracking Issue

Overview

This is the tracking issue for the Event System & State Management initiative — the largest architectural refactor for v1.0, touching event processing, state synchronization, and the developer-facing API.

Canonical roadmap: Reflex Framework Roadmap § 1

Goals

• Introduce EventContext as the foundational execution primitive (owns state lock, manages backend event queue, tracks mutability scope)
• Move the event queue to the backend, eliminating frontend round-trips for chained events
• Redesign EventHandler with a global registry, awaitable semantics, and partial-arg call convention
• Replace JSONPatch with Replicache-based state synchronization (optimistic UI, offline support, conflict resolution)
• Extract dirty/accessed var tracking into a standalone mixin independent of rx.State
• Make rx.Field a first-class descriptor enabling composable arbitrary states without rx.State inheritance
• Expose event handlers as HTTP endpoints with auto-generated OpenAPI spec for agent/MCP integration
• Add full-stack OpenTelemetry instrumentation

Sub-Issues

Core Event Processing

• ENG-9028 — EventContext & Backend Event Queue ⚠️ BLOCKING (no GitHub issue yet)
• ENG-9162 ENG-9162
• ENG-9163 ENG-9163
• ENG-9164 ENG-9164
• ENG-6436 — Event Loop Blocking Detection (no GitHub issue yet)

Endpoints & Observability

• ENG-9165 ENG-9165
• ENG-9029 — Event Handler HTTP Endpoints (no GitHub issue yet)
• ENG-9166 ENG-9166

State & Field System

• ENG-9167 ENG-9167
• ENG-6223 — rx.Field as First-Class Descriptor (no GitHub issue yet)
• ENG-9169 ENG-9169
• ENG-9170 ENG-9170
• ENG-9198 ENG-9198

Other

• ENG-9168 ENG-9168
• ENG-9127 ENG-9127
• ENG-9171 ENG-9171
• ENG-9172 ENG-9172

Dependencies

The EventContext is the most critical piece and blocks most other work in this section:

• Sync executor needs a context to propagate into threads
• HTTP endpoints needs a context per POST request
• Var tracking mixin enforces mutation via active EventContext
• Field setters and observers execute/queue within a context
• Replicache processes mutations within an EventContext