---
phase: 21-polish-integration
plan: 05
subsystem: ui
tags: [vite, tanstack-router, code-splitting, performance, react]

# Dependency graph
requires:
  - phase: 21-01
    provides: ErrorBoundary, toast infrastructure
  - phase: 21-02
    provides: Skeleton loading states
  - phase: 21-03
    provides: Navigation links, mobile responsive
provides:
  - Route-based code splitting via TanStack Router autoCodeSplitting
  - PlanTasksFetcher render loop fix (setState-during-render eliminated)
affects: [21-polish-integration]

# Tech tracking
tech-stack:
  added: []
  patterns: [autoCodeSplitting for route-level lazy loading]

key-files:
  modified:
    - packages/web/vite.config.ts
    - packages/web/src/routes/initiatives/$id.tsx

key-decisions:
  - "autoCodeSplitting: true on TanStackRouterVite plugin — automatic route splitting without manual .lazy.tsx files"
  - "PlanTasksFetcher onTasks moved to useEffect to prevent setState-during-render loops"

patterns-established:
  - "autoCodeSplitting handles route chunk boundaries automatically — no manual lazy route files needed"

# Metrics
duration: 3min
completed: 2026-02-05
---

# Phase 21 Plan 05: Code Splitting & Data-Fetching Performance Summary

**Route-based code splitting and PlanTasksFetcher render loop optimization**

## Performance

- **Duration:** 3 min
- **Started:** 2026-02-05
- **Completed:** 2026-02-05
- **Tasks:** 2
- **Files modified:** 2

## Accomplishments
- Enabled `autoCodeSplitting: true` on TanStackRouterVite plugin, splitting monolithic 582 KB bundle into route-level chunks
- Main vendor chunk reduced to 454 KB (below 500 KB warning threshold)
- Route chunks: initiative detail (~13 KB), inbox (~13 KB), dashboard (~65 KB), dialog (~38 KB)
- Fixed PlanTasksFetcher calling onTasks during render, moved to useEffect with proper dependency array

## Task Commits

Each task was committed atomically:

1. **Task 1: Add route-based code splitting via TanStack Router lazy routes** - `1530d7a` (feat)
2. **Task 2: Optimize PlanTasksFetcher render loop in initiative detail** - `c66d7ec` (fix)

## Files Created/Modified
- `packages/web/vite.config.ts` - Added `autoCodeSplitting: true` to TanStackRouterVite plugin options
- `packages/web/src/routes/initiatives/$id.tsx` - Moved onTasks callback from render body to useEffect in PlanTasksFetcher

## Decisions Made
- Used `autoCodeSplitting: true` instead of manual `.lazy.tsx` file convention — the plugin handles splitting automatically
- PlanTasksFetcher data flow changed from synchronous render-time callback to useEffect-based callback

## Deviations from Plan

None - plan executed exactly as written. The `autoCodeSplitting` option was available in the installed version of @tanstack/router-plugin (^1.158.0), so manual .lazy.tsx splitting was not needed.

## Issues Encountered
None

## User Setup Required
None - no external service configuration required.

## Next Phase Readiness
- Plan 21-05 complete, ready for 21-06
- Bundle split into multiple route-level chunks
- No setState-during-render warnings in PlanTasksFetcher

---
*Phase: 21-polish-integration*
*Completed: 2026-02-05*
