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+# ARCHITECTURE.md — **StellaOps.Feedser**
+
+> **Goal**: Build a sovereign-ready, self-hostable **feed-merge service** that ingests authoritative vulnerability sources, normalizes and de-duplicates them into **MongoDB**, and exports **JSON** and **Trivy-compatible DB** artifacts.
+> **Form factor**: Long-running **Web Service** with **REST APIs** (health, status, control) and an embedded **internal cron scheduler**. Controllable by StellaOps.Cli (# stella db ...)
+> **No signing inside Feedser** (signing is a separate pipeline step).
+> **Runtime SDK baseline**: .NET 10 Preview 7 (SDK 10.0.100-preview.7.25380.108) targeting `net10.0`, aligned with the deployed api.stella-ops.org service.
+> **Four explicit stages**:
+>
+> 1. **Source Download** → raw documents.
+> 2. **Parse & Normalize** → schema-validated DTOs enriched with canonical identifiers.
+> 3. **Merge & Deduplicate** → precedence-aware canonical records persisted to MongoDB.
+> 4. **Export** → JSON or TrivyDB (full or delta), then (externally) sign/publish.
+
+---
+
+## 1) Naming & Solution Layout
+
+**Source connectors** namespace prefix: `StellaOps.Feedser.Source.*`
+**Exporters**:
+
+* `StellaOps.Feedser.Exporter.Json`
+* `StellaOps.Feedser.Exporter.TrivyDb`
+
+**Projects** (`/src`):
+
+```
+StellaOps.Feedser.WebService/        # ASP.NET Core (Minimal API, net10.0 preview) WebService + embedded scheduler
+StellaOps.Feedser.Core/              # Domain models, pipelines, merge/dedupe engine, jobs orchestration
+StellaOps.Feedser.Models/            # Canonical POCOs, JSON Schemas, enums
+StellaOps.Feedser.Storage.Mongo/     # Mongo repositories, GridFS access, indexes, resume "flags"
+StellaOps.Feedser.Source.Common/     # HTTP clients, rate-limiters, schema validators, parsers utils
+StellaOps.Feedser.Source.Cve/
+StellaOps.Feedser.Source.Nvd/
+StellaOps.Feedser.Source.Ghsa/
+StellaOps.Feedser.Source.Osv/
+StellaOps.Feedser.Source.Jvn/
+StellaOps.Feedser.Source.CertCc/
+StellaOps.Feedser.Source.Kev/
+StellaOps.Feedser.Source.Kisa/
+StellaOps.Feedser.Source.CertIn/
+StellaOps.Feedser.Source.CertFr/
+StellaOps.Feedser.Source.CertBund/
+StellaOps.Feedser.Source.Acsc/
+StellaOps.Feedser.Source.Cccs/
+StellaOps.Feedser.Source.Ru.Bdu/     # HTML→schema with LLM fallback (gated)
+StellaOps.Feedser.Source.Ru.Nkcki/   # PDF/HTML bulletins → structured
+StellaOps.Feedser.Source.Vndr.Msrc/
+StellaOps.Feedser.Source.Vndr.Cisco/
+StellaOps.Feedser.Source.Vndr.Oracle/
+StellaOps.Feedser.Source.Vndr.Adobe/   # APSB ingest; emits vendor RangePrimitives with adobe.track/platform/priority telemetry + fixed-status provenance.
+StellaOps.Feedser.Source.Vndr.Apple/
+StellaOps.Feedser.Source.Vndr.Chromium/
+StellaOps.Feedser.Source.Vndr.Vmware/
+StellaOps.Feedser.Source.Distro.RedHat/
+StellaOps.Feedser.Source.Distro.Debian/    # Fetches DSA list + detail HTML, emits EVR RangePrimitives with per-release provenance and telemetry.
+StellaOps.Feedser.Source.Distro.Ubuntu/   # Ubuntu Security Notices connector (JSON index → EVR ranges with ubuntu.pocket telemetry).
+StellaOps.Feedser.Source.Distro.Suse/     # CSAF fetch pipeline emitting NEVRA RangePrimitives with suse.status vendor telemetry.
+StellaOps.Feedser.Source.Ics.Cisa/
+StellaOps.Feedser.Source.Ics.Kaspersky/
+StellaOps.Feedser.Normalization/     # Canonical mappers, validators, version-range normalization
+StellaOps.Feedser.Merge/             # Identity graph, precedence, deterministic merge
+StellaOps.Feedser.Exporter.Json/
+StellaOps.Feedser.Exporter.TrivyDb/
+StellaOps.Feedser.<Component>.Tests/  # Component-scoped unit/integration suites (Core, Storage.Mongo, Source.*, Exporter.*, WebService, etc.)
+```
+
+---
+
+## 2) Runtime Shape
+
+**Process**: single service (`StellaOps.Feedser.WebService`)
+
+* `Program.cs`: top-level entry using **Generic Host**, **DI**, **Options** binding from `appsettings.json` + environment + optional `feedser.yaml`.
+* Built-in **scheduler** (cron-like) + **job manager** with **distributed locks** in Mongo to prevent overlaps, enforce timeouts, allow cancel/kill.
+* **REST APIs** for health/readiness/progress/trigger/kill/status.
+
+**Key NuGet concepts** (indicative): `MongoDB.Driver`, `Polly` (retry/backoff), `System.Threading.Channels`, `Microsoft.Extensions.Http`, `Microsoft.Extensions.Hosting`, `Serilog`, `OpenTelemetry`.
+
+---
+
+## 3) Data Storage — **MongoDB** (single source of truth)
+
+**Database**: `feedser`
+**Write concern**: `majority` for merge/export state, `acknowledged` for raw docs.
+**Collections** (with “flags”/resume points):
+
+* `source`
+  * `_id`, `name`, `type`, `baseUrl`, `auth`, `notes`.
+* `source_state`
+  * Keys: `sourceName` (unique), `enabled`, `cursor`, `lastSuccess`, `failCount`, `backoffUntil`, `paceOverrides`, `paused`.
+  * Drives incremental fetch/parse/map resume and operator pause/pace controls.
+* `document`
+  * `_id`, `sourceName`, `uri`, `fetchedAt`, `sha256`, `contentType`, `status`, `metadata`, `gridFsId`, `etag`, `lastModified`.
+  * Index `{sourceName:1, uri:1}` unique; optional TTL for superseded versions.
+* `dto`
+  * `_id`, `sourceName`, `documentId`, `schemaVer`, `payload` (BSON), `validatedAt`.
+  * Index `{sourceName:1, documentId:1}`.
+* `advisory`
+  * `_id`, `advisoryKey`, `title`, `summary`, `lang`, `published`, `modified`, `severity`, `exploitKnown`.
+  * Unique `{advisoryKey:1}` plus indexes on `modified` and `published`.
+* `alias`
+  * `advisoryId`, `scheme`, `value` with index `{scheme:1, value:1}`.
+* `affected`
+  * `advisoryId`, `platform`, `name`, `versionRange`, `cpe`, `purl`, `fixedBy`, `introducedVersion`.
+  * Index `{platform:1, name:1}`, `{advisoryId:1}`.
+* `reference`
+  * `advisoryId`, `url`, `kind`, `sourceTag` (e.g., advisory/patch/kb).
+* Flags collections: `kev_flag`, `ru_flags`, `jp_flags`, `psirt_flags` keyed by `advisoryId`.
+* `merge_event`
+  * `_id`, `advisoryKey`, `beforeHash`, `afterHash`, `mergedAt`, `inputs` (document ids).
+* `export_state`
+  * `_id` (`json`/`trivydb`), `baseExportId`, `baseDigest`, `lastFullDigest`, `lastDeltaDigest`, `exportCursor`, `targetRepo`, `exporterVersion`.
+* `locks`
+  * `_id` (`jobKey`), `holder`, `acquiredAt`, `heartbeatAt`, `leaseMs`, `ttlAt` (TTL index cleans dead locks).
+* `jobs`
+  * `_id`, `type`, `args`, `state`, `startedAt`, `endedAt`, `error`, `owner`, `heartbeatAt`, `timeoutMs`.
+
+**GridFS buckets**: `fs.documents` for raw large payloads; referenced by `document.gridFsId`.
+
+---
+
+## 4) Job & Scheduler Model
+
+* Scheduler stores cron expressions per source/exporter in config; persists next-run pointers in Mongo.
+* Jobs acquire locks (`locks` collection) to ensure singleton execution per source/exporter.
+* Supports manual triggers via API endpoints (`POST /jobs/{type}`) and pause/resume toggles per source.
+
+---
+
+## 5) Connector Contracts
+
+Connectors implement:
+
+```csharp
+public interface IFeedConnector {
+    string SourceName { get; }
+    Task FetchAsync(IServiceProvider sp, CancellationToken ct);
+    Task ParseAsync(IServiceProvider sp, CancellationToken ct);
+    Task MapAsync(IServiceProvider sp, CancellationToken ct);
+}
+```
+
+* Fetch populates `document` rows respecting rate limits, conditional GET, and `source_state.cursor`.
+* Parse validates schema (JSON Schema, XSD) and writes sanitized DTO payloads.
+* Map produces canonical advisory rows + provenance entries; must be idempotent.
+* Base helpers in `StellaOps.Feedser.Source.Common` provide HTTP clients, retry policies, and watermark utilities.
+
+---
+
+## 6) Merge & Normalization
+
+* Canonical model stored in `StellaOps.Feedser.Models` with serialization contracts used by storage/export layers.
+* `StellaOps.Feedser.Normalization` handles NEVRA/EVR/PURL range parsing, CVSS normalization, localization.
+* `StellaOps.Feedser.Merge` builds alias graphs keyed by CVE first, then falls back to vendor/regional IDs.
+* Precedence rules: PSIRT/OVAL overrides generic ranges; KEV only toggles exploitation; regional feeds enrich severity but don’t override vendor truth.
+* Determinism enforced via canonical JSON hashing logged in `merge_event`.
+
+---
+
+## 7) Exporters
+
+* JSON exporter mirrors `aquasecurity/vuln-list` layout with deterministic ordering and reproducible timestamps.
+* Trivy DB exporter shells out to `trivy-db build`, produces Bolt archives, and reuses unchanged blobs from the last full baseline when running in delta mode. The exporter annotates `metadata.json` with `mode`, `baseExportId`, `baseManifestDigest`, `resetBaseline`, and `delta.changedFiles[]`/`delta.removedPaths[]`, and honours `publishFull` / `publishDelta` (ORAS) plus `includeFull` / `includeDelta` (offline bundle) toggles.
+* `StellaOps.Feedser.Storage.Mongo` provides cursors for delta exports based on `export_state.exportCursor` and the persisted per-file manifest (`export_state.files`).
+* Export jobs produce OCI tarballs (layer media type `application/vnd.aquasec.trivy.db.layer.v1.tar+gzip`) and optionally push via ORAS; `metadata.json` accompanies each layout so mirrors can decide between full refreshes and deltas.
+
+---
+
+## 8) Observability
+
+* Serilog structured logging with enrichment fields (`source`, `uri`, `stage`, `durationMs`).
+* OpenTelemetry traces around fetch/parse/map/export; metrics for rate limit hits, schema failures, dedupe ratios, package size. Connector HTTP metrics are emitted via the shared `feedser.source.http.*` instruments tagged with `feedser.source=<connector>` so per-source dashboards slice on that label instead of bespoke metric names.
+* Prometheus scraping endpoint served by WebService.
+
+---
+
+## 9) Security Considerations
+
+* Offline-first: connectors only reach allowlisted hosts.
+* BDU LLM fallback gated by config flag; logs audit trail with confidence score.
+* No secrets written to logs; secrets loaded via environment or mounted files.
+* Signing handled outside Feedser pipeline.
+
+---
+
+## 10) Deployment Notes
+
+* Default storage MongoDB; for air-gapped, bundle Mongo image + seeded data backup.
+* Horizontal scale achieved via multiple web service instances sharing Mongo locks.
+* Provide `feedser.yaml` template describing sources, rate limits, and export settings.