# Export Center Mirror Bundles

Mirror bundles package StellaOps evidence, policy overlays, and indexes for air-gapped or bandwidth-constrained environments. They are produced by the `mirror:full` and `mirror:delta` profiles described in Epic 10 (Export Center) and implemented across Sprints 35-37 (`EXPORT-SVC-35-004`, `EXPORT-SVC-37-001`, `EXPORT-SVC-37-002`). This guide details bundle layouts, delta mechanics, encryption workflow, import procedures, and operational best practices.

> Export Center workers are being wired while this document is written. Treat the content as the target contract for adapter development and update specifics as the implementation lands.

## 1. Bundle overview

| Profile | Contents | Typical use cases | Distribution |
|---------|----------|-------------------|--------------|
| `mirror:full` | Complete snapshot of raw evidence, normalized records, indexes, policy snapshots, provenance, signatures. | Initial seeding of an air-gapped mirror, disaster recovery drills. | Download bundle, optional OCI artifact. |
| `mirror:delta` | Changes since a specified base export: added/updated/removed advisories, VEX statements, SBOMs, indexes, manifests. | Incremental updates, bandwidth reduction, nightly refreshes. | Download bundle, optional OCI artifact. |

Both profiles respect AOC boundaries: raw ingestion data remains untouched, and policy outputs live under their own directory with explicit provenance.

## 2. Filesystem layout

Directory structure inside the extracted bundle:

```
mirror/
  manifest.yaml
  export.json
  provenance.json
  README.md
  indexes/
    advisories.index.json
    vex.index.json
    sbom.index.json
    findings.index.json
  data/
    raw/
      advisories/*.jsonl.zst
      vex/*.jsonl.zst
      sboms/<subject>/sbom.json
    normalized/
      advisories/*.jsonl.zst
      vex/*.jsonl.zst
    policy/
      snapshot.json
      evaluations.jsonl.zst
    consensus/
      vex_consensus.jsonl.zst
  signatures/
    export.sig
    manifest.sig
```

`manifest.yaml` summarises profile metadata, selectors, counts, sizes, and SHA-256 digests. `export.json` and `provenance.json` mirror the JSON profile manifests and are signed using the configured KMS key.

Example `manifest.yaml`:

```yaml
profile: mirror:full
runId: run-20251029-01
tenant: acme
selectors:
  products:
    - registry.example.com/app:*
  timeWindow:
    from: 2025-10-01T00:00:00Z
    to: 2025-10-29T00:00:00Z
counts:
  advisories: 15234
  vex: 3045
  sboms: 872
  policyEvaluations: 19876
artifacts:
  - path: data/raw/advisories/a0.jsonl.zst
    sha256: 9f4b...
    bytes: 7340021
encryption:
  mode: age
  strict: false
  recipients:
    - age1tenantkey...
```

## 3. Delta mechanics

Delta bundles reference a previous full or delta run via `baseExportId` and `baseManifestDigest`. They contain:

```
delta/
  changed/
    data/raw/advisories/*.jsonl.zst
    ...
  removed/
    advisories.jsonl        # list of advisory IDs removed
    vex.jsonl
    sboms.jsonl
  manifest.diff.json        # summary of counts, hashes, base export metadata
```

- **Base lookup:** The worker verifies that the base export is reachable (download path or OCI reference). If missing, the run fails with `ERR_EXPORT_BASE_MISSING`.
- **Change detection:** Uses deterministic hashing of normalized records to compute additions/updates. Indexes are regenerated only for affected subjects.
- **Application order:** Consumers apply deltas sequentially. A `resetBaseline=true` flag instructs them to drop cached state and apply the bundle as a full refresh.

Example `manifest.diff.json` (delta):

```json
{
  "baseExportId": "run-20251025-01",
  "baseManifestDigest": "sha256:aa11...",
  "resetBaseline": false,
  "added": {
    "advisories": 43,
    "vex": 12,
    "sboms": 5
  },
  "changed": {
    "advisories": 18,
    "vex": 7
  },
  "removed": {
    "advisories": 2,
    "vex": 0,
    "sboms": 0
  }
}
```

## 4. Encryption workflow

Mirror bundles support optional encryption of the `data/` subtree:

- **Algorithm:** Age (X25519) or AES-GCM (256-bit) based on profile configuration.
- **Key wrapping:** Keys fetched from Authority-managed KMS through Export Center. Wrapped data keys stored in `provenance.json` under `encryption.recipients[]`.
- **Metadata:** `manifest.yaml` records `encryption.mode`, `recipients`, and `encryptedPaths`.
- **Strict mode:** `strict=true` encrypts everything except `manifest.yaml` and `export.json`. Default (`false`) leaves manifests unencrypted to simplify discovery.
- **Verification:** CLI (`stella export verify`) and Offline Kit scripts perform signature checks prior to decryption.

Operators must distribute recipient keys out of band. Export Center does not transmit private keys.

## 5. Import workflow

### 5.1 Offline Kit

Offline Kit bundles reference the latest full mirror export plus the last `N` deltas. Administrators run:

```
./offline-kit/bin/mirror import /path/to/mirror-20251029-full.tar.zst
./offline-kit/bin/mirror import /path/to/mirror-20251030-delta.tar.zst
```

The tool verifies signatures, applies deltas, and updates the mirror index served by the local gateway.

### 5.2 Custom automation

1. Download bundle (`stella export download`) and verify signatures (`stella export verify`).
2. Extract archive into a staging directory.
3. For encrypted bundles, decrypt using the provided age/AES key.
4. Sync `mirror/data` onto the target mirror store (object storage, NFS, etc.).
5. Republish indexes or reload services that depend on the mirror.

Delta consumers must track `appliedExportIds` to ensure ordering.

Sequence diagram of download/import:

```mermaid
sequenceDiagram
  participant CLI as stella CLI
  participant Mirror as Mirror Store
  participant Verify as Verification Tool
  CLI->>CLI: stella export download run-20251029-01
  CLI->>Verify: stella export verify run-20251029-01
  CLI->>Mirror: mirror import mirror-20251029-full.tar.zst
  CLI->>Mirror: mirror import mirror-20251030-delta.tar.zst
  Mirror-->>CLI: import complete (run-20251030-02)
```

## 6. Operational guidance

- **Retention:** Keep at least one full bundle plus the deltas required for disaster recovery. Configure `ExportCenter:Retention:Mirror` to prune older bundles automatically.
- **Storage footprint:** Full bundles can exceed tens of gigabytes. Plan object storage or NAS capacity accordingly and enable compression (`compression.codec=zstd`).
- **Scheduling:** For high-churn environments, run daily full exports and hourly deltas. Record cadence in `manifest.yaml` (`schedule.cron`).
- **Incident recovery:** To rebuild a mirror:
  1. Apply the most recent full bundle.
  2. Apply deltas in order of `createdAt`.
  3. Re-run integrity checks (`mirror verify <path>`).
- **Audit logging:** Export Center logs `mirror.bundle.created`, `mirror.delta.applied`, and `mirror.encryption.enabled` events. Consume them in the central observability pipeline.

## 7. Troubleshooting

| Symptom | Meaning | Action |
|---------|---------|--------|
| `ERR_EXPORT_BASE_MISSING` | Base export not available | Republish base bundle or rebuild as full export. |
| Delta applies but mirror misses entries | Deltas applied out of order | Rebuild from last full bundle and reapply in sequence. |
| Decryption fails | Recipient key mismatch or corrupted bundle | Confirm key distribution and re-download bundle. |
| Verification errors | Signature mismatch | Do not import; regenerate bundle and investigate signing pipeline. |
| Manifest hash mismatch | Files changed after extraction | Re-extract bundle and re-run verification; check storage tampering. |

## 8. References

- [Export Center Overview](overview.md)
- [Export Center Architecture](architecture.md)
- [Export Center API reference](api.md)
- [Export Center CLI Guide](cli.md)
- [Concelier mirror runbook](../concelier/operations/mirror.md)
- [Aggregation-Only Contract reference](../../ingestion/aggregation-only-contract.md)

> **Imposed rule:** Work of this type or tasks of this type on this component must also be applied everywhere else it should be applied.