---
phase: 06.3
plan: "04"
subsystem: diagnostics
tags: [client, prediction, reconciliation, telemetry]
requires:
  - phase: "06.2"
    provides: "Initial reconciler window.__rebno diagnostic fields"
provides:
  - "window.__rebno lastReconcileVx/Vy, local position, divergence distance, and predicted position fields"
  - "Idle-state D-58 and motion D-57 diagnostic target for plans 06.3-14 and 06.3-15"
affects: [phase-06.3, D-52, D-57, D-58, PredictionReconciler]
tech-stack:
  added: []
  patterns: ["Unconditional staging-visible window.__rebno diagnostic publish"]
key-files:
  created: []
  modified:
    - apps/client/src/prediction/reconciler.ts
key-decisions:
  - "Extended both existing reconciler telemetry blocks rather than adding a new diagnostic branch."
patterns-established:
  - "Reconciler diagnostics should include server velocity, pre-correction local position, divergence distance, and post-replay predicted position."
requirements-completed:
  - REQ-SRV-14
  - REQ-CLI-08
duration: 8 min
completed: 2026-05-14
---

# Phase 06.3 Plan 04: D-52/D-57/D-58 Reconciler Diagnostics Summary

**Reconciler telemetry now exposes the idle-state and motion fields needed to verify D-57/D-58 fixes.**

## Performance

- **Duration:** 8 min
- **Completed:** 2026-05-14
- **Tasks:** 2
- **Files modified:** 1

## Accomplishments

- Added `lastReconcileVx` and `lastReconcileVy` to both reconciler telemetry paths.
- Added `lastReconcileLocalX`, `lastReconcileLocalY`, and `lastReconcileDist` so operators can compare pre-correction local state against server divergence.
- Added `lastReconcilePredictedX` and `lastReconcilePredictedY` so 06.3-14/06.3-15 can verify convergence after replay.
- Kept the writes unconditional with no DEV gate so the fields are visible on staging.

## Task Commits

1. **Task 1/2: Reconciler diagnostic extension** - `7a84785` (`spike(06.3-04)`)

## Files Created/Modified

- `apps/client/src/prediction/reconciler.ts` - Extended the `divergence-threshold` and `lerp-correction` `window.__rebno` writes.

## Decisions Made

- Used the existing `snap.vx`, `snap.vy`, `cur.x`, `cur.y`, `predicted.x`, `predicted.y`, and `dist` locals already available at both telemetry sites.

## Deviations from Plan

None.

## Verification

- `pnpm --filter @rebno/client test --run` - PASS, 26 test files passed, 190 tests passed, 4 todo.
- Acceptance grep confirmed both telemetry blocks include all seven new fields.

## Next Phase Readiness

Ready for `06.3-14` D-57 tween correction and `06.3-15` D-58 idle convergence. Operators can now read `window.__rebno.lastReconcileVx`, `lastReconcileVy`, and `lastReconcileDist` at idle to confirm whether zero-velocity snapshots still diverge.

---
*Phase: 06.3*
*Completed: 2026-05-14*