---
id: T02
parent: S02
milestone: M006
provides: []
requires: []
affects: []
key_files: ["frontend/src/api/public-client.ts", "frontend/src/pages/AdminPipeline.tsx", "frontend/src/App.css"]
key_decisions: ["Placed segmented toggle between event count and refresh button in the header row for natural scan order"]
patterns_established: []
drill_down_paths: []
observability_surfaces: []
duration: ""
verification_result: "Frontend build passed with zero TypeScript errors. Browser verification confirmed Head shows oldest events first (ascending timestamps), Tail shows newest first (descending). Token counts visible on all event rows and video summary. Pager functional in both modes. Slice-level curl checks: order=asc returns ascending timestamps, order=invalid returns HTTP 400."
completed_at: 2026-03-30T11:15:10.303Z
blocker_discovered: false
---

# T02: Added Head/Tail segmented toggle to EventLog with order param wiring — Head shows oldest-first (asc), Tail shows newest-first (desc), switching resets pagination

> Added Head/Tail segmented toggle to EventLog with order param wiring — Head shows oldest-first (asc), Tail shows newest-first (desc), switching resets pagination

## What Happened
---
id: T02
parent: S02
milestone: M006
key_files:
  - frontend/src/api/public-client.ts
  - frontend/src/pages/AdminPipeline.tsx
  - frontend/src/App.css
key_decisions:
  - Placed segmented toggle between event count and refresh button in the header row for natural scan order
duration: ""
verification_result: passed
completed_at: 2026-03-30T11:15:10.304Z
blocker_discovered: false
---

# T02: Added Head/Tail segmented toggle to EventLog with order param wiring — Head shows oldest-first (asc), Tail shows newest-first (desc), switching resets pagination

**Added Head/Tail segmented toggle to EventLog with order param wiring — Head shows oldest-first (asc), Tail shows newest-first (desc), switching resets pagination**

## What Happened

Added `order` param to `fetchPipelineEvents` in the API client. In the EventLog component, added `viewMode` state with Head/Tail toggle buttons wired to pass `order=asc` or `order=desc`. Switching mode resets offset to 0. Added compact segmented-button CSS using existing CSS custom properties. Built and deployed to ub01 — verified both modes work correctly with ascending/descending event ordering, token counts remain visible, and the pager still functions.

## Verification

Frontend build passed with zero TypeScript errors. Browser verification confirmed Head shows oldest events first (ascending timestamps), Tail shows newest first (descending). Token counts visible on all event rows and video summary. Pager functional in both modes. Slice-level curl checks: order=asc returns ascending timestamps, order=invalid returns HTTP 400.

## Verification Evidence

| # | Command | Exit Code | Verdict | Duration |
|---|---------|-----------|---------|----------|
| 1 | `cd frontend && npm run build` | 0 | ✅ pass | 4200ms |
| 2 | `curl -sf 'http://ub01:8096/api/v1/admin/pipeline/events/{vid}?order=asc&limit=3'` | 0 | ✅ pass | 800ms |
| 3 | `curl -s -w '%{http_code}' 'http://ub01:8096/api/v1/admin/pipeline/events/{vid}?order=invalid'` | 0 | ✅ pass (400) | 500ms |


## Deviations

None.

## Known Issues

None.

## Files Created/Modified

- `frontend/src/api/public-client.ts`
- `frontend/src/pages/AdminPipeline.tsx`
- `frontend/src/App.css`


## Deviations
None.

## Known Issues
None.
