# 01 — Remove the original decision trace end to end

**Gitea:** [#76](https://gitea.nessar.fr/nessar/vac-optimizer/issues/76)

## What to build

Calculations no longer record, retain or deliver an original decision trace. Users receive the displayed plan, its stable explanation and remaining-balance reasons, and can still analyze an alternative date for a displayed placement. The advanced trace explorer, historical calendar replay and historical attempt lists disappear completely.

This is one cohesive contract replacement across the planner, calculation service, workers and UI. Use a scoped integration branch containing the existing #70–#75 implementation work; #75's final verification must not be treated as a prerequisite for removing tracing. The shared functional integration verification gate is #77 — Verify integrated planning after trace removal. Benchmark performance acceptance and any required optimization are owned by #78; performance is no longer a completion gate for #75.

## Acceptance criteria

- [ ] Delete trace capture, materialization, candidate-history retention, replay, historical eligibility and caches or evidence pools used exclusively for tracing. Remove observational work while preserving search breadth, allocation previews, rule priority and incumbent selection.
- [ ] Replace trace contracts directly and update all callers in the same change. Remove trace promises, callbacks, public types, streaming messages, status indexes, acknowledgements and backpressure queues across real-worker, browser-fallback and server-side calculation paths. Do not retain debug toggles, compatibility adapters, empty trace results or replacement history.
- [ ] Preserve immutable calculation, valid-incumbent and final-state snapshots needed by retained behavior. Rename retained state contracts independently of tracing; do not delete cancellation or explanation data because it currently has a trace-related name.
- [ ] Retain stable plan explanations, including placement entitlement and rule provenance, objective contributions and the first decisive objective, time-off periods, remaining balances and concrete non-placement reasons. Preserve invalid-input and conflict explanations and incomplete-calculation behavior.
- [ ] Keep alternative-date analysis for a displayed placement using the captured calculation configuration, the same entitlement, leave type and provenance, and fixed unrelated placements. Remove analysis based on historical decisions; hypothetical analysis never mutates the displayed plan.
- [ ] Remove the advanced trace panel, replay controls, historical calendar overlays and candidate statuses. Remove remaining-balance historical attempt lists, pagination and loading state while retaining classification, validity, earned-entitlement source and truthful displayed-plan reasons. Leave no dead controls or trace-unavailable messages.
- [ ] Preserve explicit cancellation before and after a valid incumbent, best-valid-partial-plan recovery, heartbeat monitoring, stale-response rejection and the existing technical-budget contract. Interrupted calculations do not imply an obligation conflict. Explanation delivery failures do not discard an available outcome, and planning workers do not wait for trace acknowledgements after required delivery.
- [ ] Preserve completed placements, balances, objective values, joint obligation satisfaction, earned-entitlement chronology, deterministic tie-breaking, user-controlled priorities and empty-active-rule behavior. Do not reset saved entitlements, declarations or rule configurations or change the existing migration.
- [ ] Update component styles and translations across supported languages, preserving keyboard access and accessibility for retained explanations, calendar interactions and date analysis.
- [ ] Adapt existing planner, service, worker, explanation, cancellation, calendar and remaining-balance tests. Delete tests exclusively for tracing while retaining assertions for supported behavior in mixed tests. Update benchmark callers, output and assertions to remove obsolete trace requirements without reducing scenarios or changing performance gates.
- [ ] Supersede trace-specific requirements in the domain vocabulary and explanation/cancellation ADRs, and update benchmark documentation. Preserve the remaining planning contracts and document that the original decision trace and historical analysis are removed.

No new dependency, replacement telemetry, optimization-quality change, allocation-preview reduction or benchmark deadline relaxation is part of this ticket. No separate prefactor is required: retained explanation and hypothetical-analysis behavior already exists.

## Blocked by

None — can start immediately.