Local First Architecture

---
name: local-first-architecture
description: "Use when executing, coordinating, planning, or reviewing local first architecture agent workflows, cognitive loops, and architecture standards."
version: 6.0.0
last-updated: 2026-09-29
skills:
  - react-specialist
  - nextjs-react-expert
  - baseline-ui
tools: Read, Grep, Glob, Bash, Edit, Write
scripts-binding:
  - .agent/scripts/lint_runner.js
  - .agent/scripts/verify_all.js
---

# Local-First Architecture — Instant UI & Sync Engines

## Mandatory Pre-Flight Context Inspection
Before reading, generating, or refactoring code in the `local-first-architecture` domain, inspect these 5 critical parameters:
1. **System Boundaries & Dependencies**: Verify that all required dependencies exist in target package manifests and environment paths.
2. **Runtime Context & Platform Invariants**: Confirm target platform constraints (Node.js, Browser, Mobile OS, Edge runtime) before applying APIs.
3. **Execution Guardrails**: Identify potential side-effects, state mutations, and unhandled asynchronous exceptions.
4. **Validation & Type Contracts**: Validate input data schemas and strict type constraints across all module interfaces.
5. **Observability & Proof of Execution**: Ensure execution produces tangible verification signals (terminal output, tests, metrics).


## Activation Boundaries
- **Activate when:** Use when executing, coordinating, planning, or reviewing local first architecture agent workflows, cognitive loops, and architecture standards.
- **DO NOT activate when:** The task falls outside the `local-first-architecture` domain or is managed by a different dedicated specialist agent.


## 🔁 Multi-Pass Execution Protocol

| Pass | Phase | Core Action | Adaptive Depth |
|:---|:---|:---|:---|
| **Pass 1** | **Understand** | Deconstruct the user's explicit objective, implicit requirements, and platform constraints. | Fast / Standard / Deep |
| **Pass 2** | **Plan** | Decompose task into smallest logical steps; map dependencies, affected files, and tool calls. | Standard / Deep |
| **Pass 3** | **Execute** | Implement solution with production-grade craft, zero placeholders, and strict typing. | All Modes |
| **Pass 4** | **Verify** | Run linters, unit tests, or compiler checks to validate structural correctness. | All Modes |
| **Pass 5** | **Attack & Falsify** | Perform adversarial search for edge-case failures, counterexamples, race conditions, and traps. | Standard / Deep |
| **Pass 6** | **Harden** | Eliminate discovered friction, optimize performance, and harden error boundaries. | Standard / Deep |
| **Pass 7** | **Quality Gate** | Enforce Verification-Before-Completion (VBC) with concrete terminal proof before finalizing. | All Modes |


---

## 🛠️ Technical Architecture & Reference Recipes

## 2026 Local-First Architecture & Sync Invariants

1. **OPFS (Origin Private File System) for WASM SQLite**:
   Always prefer OPFS sync access handles for SQLite in web workers. It delivers native near-SSD read/write speeds that dwarf standard IndexedDB overhead.
2. **Idempotency Key Protocol**:
   Every local mutation must generate an `idempotencyKey` (UUID v7). The server stores processed keys for 24h, discarding replays during network flushes.
3. **Delta Sync over Full Sync**:
   Never download entire tables. Use incremental sync cursors (`last_synced_version_id`) and stream compact binary deltas via WebSockets or SSE.

## Hallucination Traps (Read First)

- ❌ Blocking UI render on a remote fetch in a local-first app → ✅ Render local cache immediately; reconcile in background
- ❌ Mutating server state without an idempotency key → ✅ Flushed network retries will duplicate records
- ❌ Putting heavy SQLite WASM operations on the browser main thread → ✅ Always run local DB queries inside a Dedicated Web Worker
- ❌ Storing unindexed large blobs inside IndexedDB → ✅ Store blobs in OPFS; keep metadata in local SQLite/IndexedDB

---

## 4 Pillars of Local-First Architecture

### 1. Read & Write Local First

- **Zero Network Latency**: UI queries (`select * from tasks`) run synchronously or near-instantaneously against in-memory or IndexedDB caches.
- Mutations update the local cache immediately (_optimistic write_), appending a mutation log item to an outbound sync queue.

### 2. Outbound Mutation Queue & Idempotency

- Store mutation logs in a persistent local queue (`IndexedDB` / `SQLite`).
- Assign every client mutation a unique UUID (`idempotencyKey`).
- When network connection is restored, flush queue items sequentially with automatic retry on 5xx failures.

### 3. Conflict Resolution (CRDTs & LWW)

- **Last-Write-Wins (LWW)**: Timestamp + Client ID ordering for simple fields.
- **CRDTs (Yjs / Automerge)**: Conflict-free Replicated Data Types for collaborative text editing and array state.

### 4. Background Delta Streaming

- Receive database updates via WebSockets or Server-Sent Events (SSE) as thin binary deltas (`sync_version > client_version`), applying changes to local storage without re-fetching full datasets.

## 🚨 Edge-Case & Failure Mode Matrix

| Scenario | Risk | Production Mitigation |
|:---|:---|:---|
| **Empty or Null Inputs** | Unhandled exception or unexpected rendering collapse | Enforce fallback guards, optional chaining, and explicit empty state handlers |
| **Network Timeout / Latency** | Hanging operations or duplicate side-effects | Implement bounded abort controllers, exponential backoff, and idempotency keys |
| **Concurrency / Race Conditions** | Stale state overwrite or inconsistent data mutations | Use atomic transactions, mutex locking, or cancel-on-resubmit controls |
| **Invalid Schema / Malformed Payload** | Downstream runtime errors or security injection | Validate boundary payloads with Zod/Pydantic schemas prior to execution |
| **Resource / Memory Saturation** | OOM errors, frame drops, or memory leaks | Clean up listeners, cancel active timers, and enforce pagination/virtualization |


## 🏛️ Tribunal Verification & Guardrails

**Active Reviewers:** `orchestrator` · `agent-organizer` · `logic-reviewer`
**Slash Command:** `/review` or `/tribunal-full`

### 🔬 Evidence Standard (Tri-State Verification)
Every finding, audit statement, or completion claim must classify its factual certainty:
- **`[OBSERVED]`**: Directly confirmed in the codebase or verified via executed terminal command.
- **`[INFERRED]`**: Logically deduced from code patterns, architectural data flow, or schema relations.
- **`[UNVERIFIED]`**: Speculative hypothesis or runtime possibility requiring active testing or measurement.

### ✅ Pre-Flight Self-Audit Checklist
```
✅ Did I deconstruct the root objective before proposing architecture?
✅ Did I identify dependencies, bottlenecks, and parallelizable sub-tasks?
✅ Did I avoid over-engineering and select the simplest effective pattern?
✅ Did I verify assumptions with concrete file reads instead of speculation?
✅ Did I establish measurable verification criteria before completion?
```

### 🛑 Verification-Before-Completion (VBC) Protocol
**CRITICAL:** You must follow a strict "evidence-based closeout" state machine.
- ❌ **Forbidden:** Declaring a task complete because the output "looks correct."
- ✅ **Required:** You are explicitly forbidden from finalizing any task without providing **concrete evidence** (terminal output, passing test suites, compiler success, or equivalent operational proof) that your output works as intended.