# Implementation Plan: 116 — Baseline Drift Engine (Final Architecture)

**Branch**: `116-baseline-drift-engine` | **Date**: 2026-03-01 | **Spec**: `specs/116-baseline-drift-engine/spec.md`
**Input**: Feature specification from `specs/116-baseline-drift-engine/spec.md`

## Summary

Align the existing baseline capture/compare pipeline to Spec 116 by (1) defining an explicit meta-fidelity hash contract, (2) enforcing the “coverage guard” based on the latest inventory sync run, and (3) switching baseline-compare findings to snapshot-scoped stable identities (recurrence keys) while preserving existing baseline-profile grouping for UI/stats and auto-close semantics.

## Technical Context

**Language/Version**: PHP 8.4
**Primary Dependencies**: Laravel 12, Filament v5, Livewire v4
**Storage**: PostgreSQL (via Sail)
**Testing**: Pest v4 (PHPUnit 12)
**Target Platform**: Docker (Laravel Sail)
**Project Type**: Web application (Laravel)
**Performance Goals**: Compare jobs must remain bounded by scope size; avoid N+1 queries when loading snapshot + current inventory
**Constraints**:
- Ops-UX: OperationRun lifecycle + 3-surface feedback (toast queued-only, progress in widget/run detail, terminal DB notification exactly-once)
- Summary counts numeric-only and keys restricted to `OperationSummaryKeys`
- Tenant/workspace isolation + RBAC deny-as-not-found rules
**Scale/Scope**: Tenant inventories may be large; baseline compare must be efficient on `(tenant_id, policy_type)` filtering

## Constitution Check

*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*

- Inventory-first: PASS — compare uses Inventory as last observed state; baselines are immutable snapshots.
- Read/write separation: PASS — this feature is read-only analysis; no Graph writes.
- Graph contract path: PASS — inventory sync already uses `GraphClientInterface`; baseline compare itself is DB-only at render time.
- Deterministic capabilities: PASS — baseline capability checks use existing registries/policies; no new ad-hoc strings.
- Workspace + tenant isolation: PASS — baseline profiles are workspace-owned; runs/findings are tenant-owned; authorization remains deny-as-not-found for non-members.
- Run observability (OperationRun): PASS — capture/compare already use OperationRun + queued jobs.
- Ops-UX 3-surface feedback: PASS — existing pages use canonical queued toast presenter.
- Ops-UX lifecycle: PASS — transitions must remain inside `OperationRunService`.
- Ops-UX summary counts: PASS — only numeric summary counts using canonical keys.
- Filament UI contract: PASS — only small scope-picker adjustments; no new pages beyond what exists.
- Filament UX-001 layout: PASS — Baseline Profile Create/Edit will be updated to a Main/Aside layout as part of the scope-picker work.

## Project Structure

### Documentation (this feature)

```text
specs/116-baseline-drift-engine/
├── plan.md
├── research.md
├── data-model.md
├── quickstart.md
├── contracts/
│   └── openapi.yaml
└── checklists/
    └── requirements.md
```

### Source Code (repository root)

```text
app/
├── Filament/
│   ├── Pages/                # Baseline compare landing + run detail links (existing)
│   ├── Resources/            # BaselineProfileResource (existing)
│   └── Widgets/              # Baseline compare widgets (existing)
├── Jobs/
│   ├── CaptureBaselineSnapshotJob.php
│   └── CompareBaselineToTenantJob.php
├── Models/
│   ├── BaselineProfile.php
│   ├── BaselineSnapshot.php
│   ├── BaselineSnapshotItem.php
│   ├── Finding.php
│   ├── InventoryItem.php
│   └── OperationRun.php
├── Services/
│   ├── Baselines/
│   │   ├── BaselineCaptureService.php
│   │   ├── BaselineCompareService.php
│   │   ├── BaselineAutoCloseService.php
│   │   └── BaselineSnapshotIdentity.php
│   ├── Drift/
│   │   ├── DriftFindingGenerator.php
│   │   └── DriftHasher.php
│   ├── Inventory/
│   │   └── InventorySyncService.php
│   └── OperationRunService.php
└── Support/
    ├── Baselines/BaselineCompareStats.php
    └── OpsUx/OperationSummaryKeys.php

tests/
└── Feature/
    └── Baselines/
        ├── BaselineCompareFindingsTest.php
        ├── BaselineComparePreconditionsTest.php
        ├── BaselineCompareStatsTest.php
        └── BaselineOperabilityAutoCloseTest.php
```

**Structure Decision**: Web application (Laravel 12) — all work stays in existing `app/` services/jobs/models and `tests/Feature`.

## Complexity Tracking

No constitution violations are required for this feature.

## Phase 0 — Outline & Research (DONE)

Outputs:
- `specs/116-baseline-drift-engine/research.md`

Key reconciliations captured:
- Baseline compare finding identity will move to recurrence-key based upsert (snapshot-scoped identity) aligned with the existing `DriftFindingGenerator` pattern.
- Coverage guard requires persisting per-type coverage outcomes into the latest inventory sync run context.
- Scope must include `policy_types` + `foundation_types` with correct empty-default semantics.

## Phase 1 — Design & Contracts (DONE)

Outputs:
- `specs/116-baseline-drift-engine/data-model.md`
- `specs/116-baseline-drift-engine/contracts/openapi.yaml`
- `specs/116-baseline-drift-engine/quickstart.md`

Design highlights:
- Coverage lives in `operation_runs.context` for inventory sync runs (detailed lists), while `summary_counts` remain numeric-only.
- Findings use `recurrence_key` and `fingerprint = recurrence_key` for idempotent upserts.
- Findings remain grouped by `scope_key = baseline_profile:{id}` to preserve existing UI/stats and auto-close behavior.

## Phase 1 — Agent Context Update (REQUIRED)

Run:
- `.specify/scripts/bash/update-agent-context.sh copilot`

## Phase 2 — Implementation Plan

### Step 1 — Baseline scope schema + UI picker

Goal: implement FR-116v1-01 and FR-116v1-02.

Changes:
- Update baseline scope handling (`app/Support/Baselines/BaselineScope.php`) to support:
  - `policy_types: []` meaning “all supported policy types excluding foundations”
  - `foundation_types: []` meaning “none”
- Update `BaselineProfile` form schema (Filament Resource) to show multi-selects for Policy Types and Foundations.
- Document selector-to-config mapping (source of truth for option lists + defaults):

| Selector | Form state path | Options source | Default semantics |
|---|---|---|---|
| Policy Types | `scope_jsonb.policy_types` | `config('tenantpilot.supported_policy_types')` via `App\Support\Inventory\InventoryPolicyTypeMeta::supported()` | Empty ⇒ all supported policy types (**excluding foundations**) |
| Foundations | `scope_jsonb.foundation_types` | `config('tenantpilot.foundation_types')` via `App\Support\Inventory\InventoryPolicyTypeMeta::foundations()` | Empty ⇒ none |

Notes:
- Inventory sync selection uses `App\Services\BackupScheduling\PolicyTypeResolver::supportedPolicyTypes()` for policy types, and `InventorySyncService::foundationTypes()` (derived from `config('tenantpilot.foundation_types')`) when `include_foundations=true`.

Tests:
- Update/add Pest tests around scope expansion defaults (prefer a focused unit-like test if an expansion helper exists).

### Step 2 — Inventory Meta Contract (explicit hash input)

Goal: implement FR-116v1-04, FR-116v1-05, FR-116v1-06, FR-116v1-06a.

Changes:
- Introduce a dedicated contract builder (e.g. `App\Services\Baselines\InventoryMetaContract`) that returns a normalized array for hashing.
  - Contract output must be explicitly versioned (e.g., `meta_contract.version = 1`) so future additions do not retroactively change v1 semantics.
  - Contract signals are best-effort: missing signals are represented as `null` (not omitted) to keep hashing stable across partial inventories.
- Update baseline capture hashing (`BaselineSnapshotIdentity::hashItemContent()` or the capture service) to hash the contract output only.
  - Persist the exact contract payload used for hashing to `baseline_snapshot_items.meta_jsonb.meta_contract` for auditability/reproducibility.
  - Persist observation metadata alongside the hash in `baseline_snapshot_items.meta_jsonb` (at minimum: `fidelity`, `source`, `observed_at`; when available: `observed_operation_run_id`).
- Update baseline compare to compute `current_hash` using the same contract builder.
  - Current-state `observed_at` is derived from persisted inventory evidence (`inventory_items.last_seen_at`) and MUST NOT require per-item external hydration calls during compare.
- Define “latest successful snapshot” (v1) as `baseline_profiles.active_snapshot_id` and ensure compare start is blocked when it is `null` (no “pick newest captured_at” fallback).

Tests:
- Add a small Pest test for contract normalization stability (ordering, missing fields, nullability) in `tests/Unit/Baselines/InventoryMetaContractTest.php`.
- Update baseline capture/compare tests if they currently assume hashing full `meta_jsonb`.

### Step 3 — Inventory sync coverage recording

Goal: provide coverage for FR-116v1-07.

Changes:
- Extend inventory sync pipeline (in `App\Services\Inventory\InventorySyncService` and/or the job that orchestrates sync) to write a coverage payload into the inventory sync `OperationRun.context`:
  - Per policy type: status (`succeeded|failed|skipped`) and optional `item_count`.
  - Foundations can be included in the same shape if they are part of selection.
- Ensure this is written even when some types fail, so downstream compare can determine uncovered types.

Tests:
- Add/extend tests around inventory sync operation context writing (mocking Graph calls as needed; keep scope minimal).

### Step 4 — Baseline compare coverage guard + outcome semantics

Goal: implement FR-116v1-07 and align to Ops-UX.

Changes:
- In baseline compare job/service:
  - Resolve the latest inventory sync run for the tenant.
  - Compute `covered_policy_types` from sync run context.
  - Compute `uncovered_policy_types = effective_scope.policy_types - covered_policy_types`.
  - Skip emission of *all* finding types for uncovered policy types.
  - Record coverage details into the compare run `context` for auditability.
  - If uncovered types exist, set compare outcome to `partially_succeeded` via `OperationRunService` and set `summary_counts.errors_recorded = count(uncovered_policy_types)`.
  - If effective scope expands to zero types, complete as `partially_succeeded` and set `summary_counts.errors_recorded = 1` so the warning remains visible under numeric-only summary counts.
  - If there is no completed inventory sync run (or coverage proof is missing/unreadable), treat coverage as unproven for all effective-scope types (fail-safe): emit zero findings and complete as `partially_succeeded`.

Tests:
- Add a new Pest test in `tests/Feature/Baselines` asserting:
  - uncovered types cause partial outcome
  - uncovered types produce zero findings (even if snapshot/current data would otherwise create missing/unexpected/different)
  - covered types still produce findings

### Step 5 — Snapshot-scoped stable finding identity

Goal: implement FR-116v1-09 and FR-116v1-10.

Changes:
- Replace hash-evidence-based `fingerprint` generation in baseline compare with a stable recurrence key:
  - Inputs: `tenant_id`, `baseline_snapshot_id`, `policy_type`, `subject_external_id`, `change_type`
- Persist:
  - `findings.recurrence_key = <computed>`
  - `findings.fingerprint = <same computed>`
- Keep `scope_key = baseline_profile:{baselineProfileId}`.
- Ensure retry idempotency: do not increment lifecycle counters more than once per run identity.

Tests:
- Update `tests/Feature/Baselines/BaselineCompareFindingsTest.php`:
  - Ensure fingerprint no longer depends on baseline/current hash.
  - Assert stable identity across re-runs with changed evidence hashes.
- Add coverage for “recapture uses new snapshot id → new finding identity”.

### Step 6 — Auto-close + stats compatibility

Goal: preserve existing operability expectations and keep UI stable.

Changes:
- Ensure `BaselineAutoCloseService` still resolves stale findings after a fully successful compare, even though identities now include snapshot id.
- Confirm `BaselineCompareStats` remains correct for grouping by `scope_key = baseline_profile:{id}`.

Tests:
- Update/keep `tests/Feature/Baselines/BaselineOperabilityAutoCloseTest.php` passing.
- Update `tests/Feature/Baselines/BaselineCompareStatsTest.php` only if scope semantics change.

### Step 7 — Ops UX + auditability

Goal: implement FR-116v1-03 and FR-116v1-11.

Changes:
- Ensure both capture and compare runs write:
  - `effective_scope.*` in run context
  - coverage summary and uncovered lists when partial
  - numeric summary counts using canonical keys only
  - per-change-type finding counts in `operation_runs.context.findings.counts_by_change_type`
  - Treat the `operation_runs` record as the canonical audit trail for this feature slice (do not add parallel “audit summary” persistence for the same data).

Tests:
- Add a regression test that asserts `summary_counts` contains only allowed keys and numeric values (where a helper exists).

## Post-design Constitution Re-check

Expected: PASS (no changes introduce new Graph endpoints or bypass services; OperationRun lifecycle + 3-surface feedback remain intact; RBAC deny-as-not-found semantics preserved).