# Implementation Questions

**Purpose**: Track questions and ambiguities discovered during plan generation that require follow-up before or during implementation.

---

## Open Questions

### Phase 7: Integrations

| # | Question | Context | Impact | Status |
|---|----------|---------|--------|--------|
| Q12 | What Microsoft 365 tenant/app registration is available for SMTP OAuth2 testing? | Affects Notification Service OAuth2 implementation. | Phase 7. | Deferred — won't be known during development. Implement against Basic Auth first; OAuth2 tested when tenant available. |

---

## Resolved Questions

| # | Question | Resolution | Date |
|---|----------|------------|------|
| Q1 | What .NET version should we target? | .NET 10 LTS (released November 2025, supported through 2028). | 2026-03-16 |
| Q2 | What Akka.NET version? | Latest stable 1.5.x (currently 1.5.62). | 2026-03-16 |
| Q3 | Monorepo or separate repos? | Single monorepo with SLNX solution file (`.slnx`, the new XML-based format default in .NET 10). | 2026-03-16 |
| Q4 | What CI/CD platform? | None for now. No CI/CD pipeline. | 2026-03-16 |
| Q5 | What LDAP server for dev/test? | GLAuth (lightweight LDAP) in Docker. See `infra/glauth/config.toml` and `docs/test_infra/test_infra_ldap.md`. | 2026-03-16 |
| Q6 | What MS SQL version and hosting? | SQL Server 2022 Developer Edition in Docker. See `infra/docker-compose.yml` and `docs/test_infra/test_infra_db.md`. | 2026-03-16 |
| Q7 | JWT signing key storage? | `appsettings.json` (per environment). | 2026-03-16 |
| Q8 | OPC UA server for dev/test? | Azure IoT OPC PLC simulator in Docker. See `infra/opcua/nodes.json` and `docs/test_infra/test_infra_opcua.md`. | 2026-03-16 |
| Q10 | Target site hardware? | Windows Server 2022, 24 GB RAM, 1 TB drive, 16-core Xeon. | 2026-03-16 |
| Q9 | What is the custom protocol? Is there an existing specification or SDK? | LmxProxy — gRPC-based protocol (protobuf-net code-first, port 5050, API key auth). Client SDK: `LmxProxyClient` NuGet package. See docs/requirements/Component-DataConnectionLayer.md for full API mapping and protocol details. | 2026-03-16 |
| Q11 | Are there specific external systems (MES, recipe manager) to integrate with for initial testing? | REST API test server (`infra/restapi/`) provides simulated external endpoints for External System Gateway and Inbound API testing. No real MES/recipe system needed for initial phases. | 2026-03-16 |
| Q15 | Should the Machine Data Database schema be designed in this project, or is it out of scope? | Out of scope — Machine Data Database is a pre-existing database at customer sites. Test infra seeds sample tables/data in `infra/mssql/machinedata_seed.sql`. | 2026-03-16 |
| Q13 | Who is the development team? | Solo developer with extensive Akka.NET experience and full availability. No parallelization constraints — phases are sequential. | 2026-03-16 |
| Q14 | Is there an existing deployment target environment for early pilot testing? | Yes — developer can test directly. No separate pilot environment needed. | 2026-03-16 |
| Q16 | Should `Result<T>` use a OneOf-style library or be hand-rolled? | Hand-rolled to maintain zero-dependency constraint (REQ-COM-7). | 2026-03-16 |
| Q17 | Should entity POCO properties be required (init-only) or settable? | `{ get; set; }` for EF compatibility, with constructor invariants for required fields. | 2026-03-16 |
| Q18 | What `QualityCode` values should the protocol abstraction define? | Good, Bad, Uncertain as the minimal set, with room to extend. | 2026-03-16 |
| Q19 | Should `IDataConnection` be `IAsyncDisposable` for connection cleanup? | Yes — add `IAsyncDisposable` to support proper cleanup in DCL connection actors. | 2026-03-16 |
| Q-P1-1 | Data Protection keys — DB or shared filesystem? | DB storage (EF Core Data Protection key store). More portable than shared filesystem mount. | 2026-03-16 |
| Q-P2-1 | What hashing algorithm for revision hashes? | SHA-256. | 2026-03-16 |
| Q-P2-2 | What serialization format for the deployment package contract? | JSON for debuggability. Can add binary format later if needed. | 2026-03-16 |
| Q-P2-3 | How should script pre-compilation handle references to runtime APIs? | Compile against a stub ScriptApi assembly at central. Site uses real implementation. | 2026-03-16 |
| Q-P2-4 | Semantic validation for CallShared — current library or deployed version? | Validate against current library; re-validate on deploy. | 2026-03-16 |
| Q-P3A-1 | Staggered Instance Actor startup batch size/delay? | Default 20 actors per batch, 100ms delay. Make configurable. Tune during Phase 3B/8. | 2026-03-16 |
| Q-P3A-2 | Single SQLite file or separate files per concern? | Single file with separate tables. Simpler transaction management. | 2026-03-16 |
| Q-P3A-3 | Akka.Persistence or direct SQLite for Deployment Manager singleton? | Direct SQLite. Recovery is full read-all-configs-and-rebuild, not event replay. | 2026-03-16 |
| Q-P3B-1 | Blocking I/O dispatcher config for Script Execution Actors? | Use Akka.NET default blocking-io-dispatcher config. Tune during Phase 8 performance testing. | 2026-03-16 |
| Q-P3B-2 | Should WriteBatchAndWaitAsync be on IDataConnection or protocol-specific? | Add to `IDataConnection` — both OPC UA and LmxProxy can implement it. | 2026-03-16 |
| Q-P3B-3 | Rate of Change alarm evaluation time window? | Configurable window, default per-second rate. Document in alarm definition schema. | 2026-03-16 |
| Q-P3B-4 | Health report sequence number across failover? | Resolved in design — offline detection handles the reset naturally. Central accepts lower seq after site goes offline/online. | 2026-03-16 |
| Q-P3C-1 | S&F retry timers on failover — reset or continue? | Continue from `last_attempt_at` to avoid burst retries. | 2026-03-16 |
| Q-P3C-2 | Max parked messages per remote query? | Paginated, 100 per page, consistent with Site Event Logging pattern. | 2026-03-16 |
| Q-P3C-3 | Per-instance operation lock — in-memory or persisted? | In-memory. Released on failover. Site state query resolves any ambiguity. | 2026-03-16 |
| Q-P4-1 | API key values — auto-generated or user-provided? | Auto-generated with copy-to-clipboard. User can regenerate. | 2026-03-16 |
| Q-P4-2 | Health dashboard refresh interval? | Updates on every report arrival (server push). No UI-side polling. | 2026-03-16 |
| Q-P4-3 | Area deletion — cascade or bottom-up? | Cascade delete child areas if no instances are assigned to any area in the subtree. | 2026-03-16 |
