---
phase: 12-comparison-view
plan: "01"
subsystem: ui
tags: [react, tailwind, comparison-table, zustand, framer-motion]

# Dependency graph
requires:
  - phase: 11-candidate-ranking
    provides: RankBadge component and sort_order-based candidate ordering
  - phase: 10-schema-foundation-pros-cons-fields
    provides: pros/cons fields on CandidateWithCategory type
provides:
  - ComparisonTable component with sticky label column and horizontal scroll
  - candidateViewMode "compare" value in uiStore
  - Compare toggle in thread detail toolbar (visible when 2+ candidates)
  - Weight/price delta highlighting with best-cell color coding
  - Resolved thread winner column marking (amber tint + trophy)
affects: [future comparison features, thread detail enhancements]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - Declarative ATTRIBUTE_ROWS array pattern for table row rendering (key, label, render, cellClass)
    - useMemo delta computation for best-cell identification in comparison views

key-files:
  created:
    - src/client/components/ComparisonTable.tsx
  modified:
    - src/client/stores/uiStore.ts
    - src/client/routes/threads/$threadId.tsx

key-decisions:
  - "ATTRIBUTE_ROWS declarative array pattern keeps JSX clean and row reordering trivial"
  - "cellClass function pattern in ATTRIBUTE_ROWS allows per-row cell styling without duplicating winner-check logic in every render"
  - "Compare toggle only shown when >= 2 candidates (locked decision from plan)"
  - "Add Candidate button hidden in compare view — compare is for reading, not mutation"
  - "Winner highlight priority: weight/price color wins over amber tint when both apply (more informative)"

patterns-established:
  - "Declarative table row config: ATTRIBUTE_ROWS array with { key, label, render, cellClass } objects"
  - "Sticky left column pattern: sticky left-0 z-10 bg-white on every label cell for scroll bleed prevention"

requirements-completed: [COMP-01, COMP-02, COMP-03, COMP-04]

# Metrics
duration: 2min
completed: 2026-03-17
---

# Phase 12 Plan 01: Comparison View Summary

**Side-by-side candidate comparison table with sticky labels, weight/price delta highlighting, and resolved-thread winner marking via a new "compare" candidateViewMode**

## Performance

- **Duration:** 2 min
- **Started:** 2026-03-17T14:28:12Z
- **Completed:** 2026-03-17T14:30:00Z
- **Tasks:** 2
- **Files modified:** 3

## Accomplishments
- Built ComparisonTable component with 10 attribute rows (Image, Name, Rank, Weight, Price, Status, Link, Notes, Pros, Cons) using declarative ATTRIBUTE_ROWS pattern
- Implemented useMemo delta computation — lightest weight cell highlighted blue-50, cheapest price cell green-50, non-best cells show gray +delta string
- Sticky left column with bg-white prevents content bleed-through on horizontal scroll
- Amber tint + trophy icon on winner column in resolved threads; weight/price color takes priority when winner is also best
- Extended uiStore candidateViewMode to "list" | "grid" | "compare" and wired compare toggle in thread detail toolbar
- Compare toggle only appears when thread has 2+ candidates; Add Candidate button hidden in compare view
- All 135 existing tests pass, no regressions

## Task Commits

Each task was committed atomically:

1. **Task 1: Build ComparisonTable component** - `e442b33` (feat)
2. **Task 2: Wire compare toggle and ComparisonTable into thread detail** - `5b4026d` (feat)

## Files Created/Modified
- `src/client/components/ComparisonTable.tsx` - New comparison table component with all 10 attribute rows, delta computation, sticky labels, and winner highlighting
- `src/client/stores/uiStore.ts` - Extended candidateViewMode union to include "compare"
- `src/client/routes/threads/$threadId.tsx` - Added ComparisonTable import, compare toggle button (columns-3 icon), ComparisonTable rendering branch, and "Add Candidate" hidden in compare view

## Decisions Made
- ATTRIBUTE_ROWS declarative array pattern keeps table JSX clean and row reordering trivial — each row is just { key, label, render, cellClass }
- cellClass function in ATTRIBUTE_ROWS allows per-row cell styling without duplicating winner-check logic in every render function
- Compare toggle only shown for 2+ candidates per locked plan decision
- Add Candidate button hidden in compare view to keep toolbar uncluttered (users switch to list/grid to add)
- When winner IS also the lightest/cheapest, weight/price color (blue/green) takes priority over amber tint — more informative

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered
- Minor formatting differences caught by Biome auto-formatter (indentation depth in conditional JSX) — resolved with `biome check --write`. No logic changes.

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

## Next Phase Readiness
- ComparisonTable is complete and functional; compare mode wired end-to-end in thread detail
- No blockers — ready for any follow-on comparison view enhancements
- All existing tests pass; no backend changes needed

---
*Phase: 12-comparison-view*
*Completed: 2026-03-17*