# ScadaBridge Deep Architecture Review — Overall Report (Round 2)

**Date:** 2026-07-12 (round 2; round 1 dated 2026-07-08)
**Scope:** Full system — all 27 components, docker/deploy topology, tests, and design docs, at HEAD `8c888f13`
**Method:** 8 parallel domain re-reviews. Each re-read its round-1 report and fix plan (PLAN-01…08, all complete — 191/192 tasks merged by 2026-07-10), then **verified every round-1 finding's disposition against current source** (trusting code, not plan claims), then swept the ~268 commits since the pre-initiative baseline `b910f5eb` — the fix-plan code itself plus the two post-initiative features nobody had reviewed (aggregated live alarm stream, KPI hourly rollups) — for **new** findings. Dimensions: stability, performance, conventions, underdeveloped areas; all findings carry `file:line` citations in the domain reports.

## Report Index

| # | Report | Domain | Round-2 verdict (one line) |
|---|--------|--------|----------------------------|
| 01 | [Cluster, Host & Failover](01-cluster-host-failover.md) | ClusterInfrastructure, Host, HealthMonitoring, docker/Traefik/deploy | Round 1's Critical (SBR never enabled) fixed and behaviorally proven; active-node model coherently unified — but the never-run failover drill kills the one node keep-oldest can't survive, and seed-order blocks the recovery loop when central-b is the survivor. |
| 02 | [Communication & Store-and-Forward](02-communication-store-and-forward.md) | ClusterClient, gRPC streaming, S&F engine, live alarm stream | Round 1's Critical and all three Highs genuinely fixed and test-backed; the new live alarm stream is solid — but the new anti-entropy peer resync was built on the wrong active-node predicate and an undeliverable-size Akka message: 1 new Critical + 1 new High, both confined to that feature. |
| 03 | [Site Runtime & DCL](03-site-runtime-dcl.md) | SiteRuntime, DataConnectionLayer, SiteEventLogging | All three round-1 risk concentrations (adapter reconnect, script containment, deployment honesty) genuinely fixed — 26/28 verified; one Medium residual on the MxGateway reconnect fault path. |
| 04 | [Data & Audit Backbone](04-data-audit-backbone.md) | ConfigurationDatabase, AuditLog, NotificationOutbox, SiteCallAudit, KpiHistory | All round-1 time bombs genuinely defused and verified; the one new material risk is the brand-new KPI rollup **backfill**, which re-introduces at startup the exact unbounded year-scale single-pass shape the plan eliminated everywhere else. |
| 05 | [Templates, Deployment & Transport](05-templates-deployment-transport.md) | TemplateEngine, DeploymentManager, Transport, ScriptAnalysis | All 26 actionable round-1 findings — including the Critical inheritance-edge loss and the whole silent-data-loss family — fixed in code with zero regressions; residue is 1 Medium perf leftover and 5 Lows. |
| 06 | [Edge Integrations](06-edge-integrations.md) | InboundAPI, ExternalSystemGateway, NotificationService, DelmiaNotifier | All round-1 risk genuinely fixed and source-verified (20/25 fixed, 0 regressions); new residual risk is 1 Medium + 4 Low — the Medium being the script-artifact invalidation bus publishing to zero subscribers. |
| 07 | [UI, Management & Security](07-ui-management-security.md) | CentralUI, ManagementService, CLI, Security | Both round-1 Criticals dead, 17/24 fully fixed, 0 regressions; remaining new findings are Medium-and-below — mostly security seams the fixes themselves exposed (proxy-blind throttle keying, unthrottled hub bind, unscoped secured writes). |
| 08 | [Conventions, Tests & Underdeveloped](08-conventions-tests-underdeveloped.md) | Cross-cutting | Every actionable round-1 finding genuinely fixed and conventions held through 268 commits of churn; new residue is small and mostly hygiene — except a live production API key sitting in an untracked working-tree file. |

## Round-1 Finding Disposition (verified against source, not plan claims)

| Report | Tracked | Fixed (verified) | Partial | Deferred/accepted | Not fixed | Regressed |
|--------|--------:|-----------------:|--------:|------------------:|----------:|----------:|
| 01 Cluster/Host/Failover | 28 | 18 | 3 | 6 | 1¹ | 0 |
| 02 Communication/S&F | 26 | 22 | 2 | 2 | 0 | 0 |
| 03 Site Runtime/DCL | 28 | 26 | 0 | 2 | 0 | 0 |
| 04 Data/Audit Backbone | 26 | 19 | 0 | 7² | 0 | 0 |
| 05 Templates/Deploy/Transport | 32 | 26 | 1 | 5 | 0 | 0 |
| 06 Edge Integrations | 25 | 20 | 2 | 3 | 0 | 0 |
| 07 UI/Management/Security | 24 | 17 | 6 | 1³ | 0 | 0 |
| 08 Conventions/Tests | 30 | 20 | 3 | 7 | 0 | 0 |
| **Total** | **~219** | **168** | **17** | **~33** | **1** | **0** |

¹ U5 (NodeName in the wonder-app-vd03 overlay) — deferred out-of-band with an owner, but see new finding 01-N2.
² Includes 1 won't-fix (S10). ³ UA7 was a false premise (No longer applicable).

**Headline: zero regressions, zero false "fixed" claims found.** Every disposition was re-derived from current source with `file:line` evidence. Several fixes exceeded their tickets (content-based inbound handler invalidation, two-signal deploy join, trigger-body trust coverage); PLAN-05's reflection round-trip guard structurally forecloses the entire DTO-drift class that caused round 1's Transport Critical.

## New-Findings Severity Tally (round 2 only)

| Report | Critical | High | Medium | Low |
|--------|---------:|-----:|-------:|----:|
| 01 Cluster/Host/Failover | 0 | 1 | 1 | 4 |
| 02 Communication/S&F | 1 | 1 | 2 | 5 |
| 03 Site Runtime/DCL | 0 | 0 | 1 | 5 |
| 04 Data/Audit Backbone | 0 | 1 | 3 | 3 |
| 05 Templates/Deploy/Transport | 0 | 0 | 1 | 5 |
| 06 Edge Integrations | 0 | 0 | 1 | 4 |
| 07 UI/Management/Security | 0 | 0 | 4 | 5 |
| 08 Conventions/Tests | 0 | 1 | 2 | 5 |
| **Total** | **1** | **4** | **15** | **36** |

Round 1 closed with 7 Critical / 50 High / 85 Medium / 68 Low. Round 2 opens with 1 / 4 / 15 / 36 — an ~80% reduction at every severity, and the residue is concentrated almost entirely in **code written after round 1**, not in anything round 1 flagged.

## Overall Verdict

The arch-review initiative worked: the fix plans delivered what they claimed, verified in source, with zero regressions. The system's round-1 risk profile — the failover crack, the Transport silent data loss, the data-layer time bombs, the cache-coherence family, the security projection leaks — is genuinely closed.

The round-2 risk profile is different in kind: **the new findings live almost exclusively in the newest code** — the anti-entropy resync (built by PLAN-02 itself), the KPI rollup backfill and the live alarm stream (both shipped post-initiative, 2026-07-10), and operational seams the fixes exposed. This is the expected shape for a healthy hardening cycle: the reviewed-and-fixed code held; the code that had never been reviewed is where the defects are.

**Bottom line: the codebase graduated from "production-grade engineering, not production-proven HA" to "one new feature (peer resync) must not ship as-is, one secret must be rotated today, and the failover drill still needs to actually be run."**

## The Findings That Matter Most (fix before anything else)

**C1 (new). The S&F anti-entropy resync can wipe the delivering node's live buffer.** The delivery gate uses oldest-Up (`SelfIsPrimary`) but the resync authority check uses leader+Up (lowest address). After a routine rolling restart of the lower-address site node the two predicates diverge persistently: the *delivering* node requests a resync from the stale rejoined leader and `ReplaceAllAsync`-wipes its own live buffer — silently losing every notification/cached call buffered during the outage and resurrecting delivered rows as duplicates. *(Report 02 N1; `SiteReplicationActor.cs:190-198` vs `AkkaHostedService.cs:881`)*

**H1 (new). The resync snapshot is undeliverable at exactly the scale it exists for.** Up to 10,000 full rows travel as ONE Akka remoting message with no `maximum-frame-size` override (default 128 KB) — silently dropped for any realistic backlog. *(Report 02 N2; `SiteReplicationActor.cs:40,407-410,460`)*

**H2 (new). A live production Inbound API key sits in untracked `test.txt` at the repo root** (`sbk_eb5acc…` for `wonder-app-vd03.zmr.zimmer.com:8085`) — one `git add -A` from history. Rotate the key and delete the file **today**. *(Report 08 NF1; `test.txt:3`)*

**H3 (new). The failover drill codifies a recovery the topology cannot deliver.** `failover-drill.sh` kills the ACTIVE(=oldest) central node — the one crash keep-oldest cannot survive (registered deferred decision) — and the restart recovery loop cannot converge when central-b is the survivor because both nodes list central-a first in `SeedNodes` (Akka's first-seed rule blocks a non-first seed from self-bootstrapping). The README admits the drill was never run live yet promises ~25s failover; the ~25s envelope also remains the last unmeasured headline design claim (the perf harness's skip precondition — the two-node rig — landed 2026-07-08). *(Reports 01 N1, 08 NF2)*

**H4 (new). The KPI rollup backfill re-introduces the unbounded single-pass shape at startup.** The one-shot backfill folds the full 90-day retention window in one tracked `ToListAsync` (potentially tens of millions of rows) + one giant `SaveChanges`, re-runs on **every** singleton failover, and blocks periodic folds while it runs. *(Report 04 R1; `KpiHistoryRecorderActor.cs:510-511`, `KpiHistoryRepository.cs:104-167`)*

## Cross-Cutting Themes (round 2)

### Theme 1 — The oldest-vs-leader predicate split is still alive, and it just caused the new Critical
PLAN-01 unified "active node" on oldest-member semantics, but the helper was never swapped into `SiteCommunicationActor`/`SiteReplicationActor` (a known partial), and the new resync feature then keyed its authority check on the *leader* predicate — producing C1. One shared `IsActiveNode` predicate, used by every gate, would close this class permanently. *(Reports 01, 02)*

### Theme 2 — Post-initiative features carry the new risk
The aggregated live alarm stream and KPI rollups shipped after the review baseline with no adversarial review: the rollup backfill (H4), rate-unit discontinuity at the raw/rollup routing boundary (~60× magnitude jump) and a bucketer re-fold error on rate metrics, per-delta full-snapshot copies + per-circuit fan-out with no coalescing in the live alarm cache, sticky `IsLive` grafting frozen snapshots after aggregator death, and a stale-site poll race on the Alarm Summary page. None are Critical individually; together they say **new features need the round-1 treatment before they accumulate.** *(Reports 02, 04, 07)*

### Theme 3 — The script-artifact invalidation bus publishes into the void
The PLAN-05→06 handoff never completed: `BundleImporter` publishes `ScriptArtifactsChanged`, but zero `Subscribe` call sites exist repo-wide — the Host comment claiming the Inbound API consumer "wired in plan 06" is factually wrong. Correctness currently self-heals via the revision-checked handler cache, so this is a Medium not a Critical — but the contract everyone believes exists, doesn't. Wire the consumer or delete the claim. *(Reports 06 N1, 05 N3)*

### Theme 4 — The eager-options-validation convention has a tail
PLAN-08 validated 12 components, but knobs added *by the fix plans themselves* missed the sweep: `TagSubscribeRetryIntervalMs` (0 hot-loops), `StuckScriptGraceMs` (negative throws), `MaxConcurrentImportSessions` (0 permanently blocks imports), 6 AuditLog sub-options, and Host's `NodeOptions` (empty NodeName silently NULLs audit `SourceNode`). One follow-up batch closes it. *(Reports 03 N3, 05 N6, 08 NF4)*

### Theme 5 — Security seams the fixes exposed
`LoginThrottle` landed everywhere except the DebugStreamHub bind; no `ForwardedHeaders` handling anywhere means behind Traefik the throttle key collapses to `username|proxy-IP` — anyone can lock out `admin` for all operators with 5 bad passwords; and none of the four secured-write handlers enforces site scope, so a site-scoped Operator/Verifier can submit/approve MxGateway device writes fleet-wide — the same class of gap C2 (round 1) just closed, on a higher-consequence path. *(Report 07 N1–N3)*

### Theme 6 — Deferral tracking is fragmenting again
The canonical deferred-work register is substantially accurate (all 10 "Resolved 2026-07-10" claims spot-verified true), but the SBR oldest-crash gap and the wonder-app overlay edits live only in the master tracker, the perf-envelope row's revisit trigger fired unnoticed, an untracked `deferred.md` snapshot has drifted, and the CHANGELOG (last touched 2026-06-02) is now factually wrong. One tracking home, enforced. *(Reports 01 N6, 08 NF3/NF5)*

## What's Genuinely Good (keep doing this)

- **The fix plans held under adversarial re-verification** — 168 findings re-proven fixed from source, zero regressions, zero false claims; several fixes exceeded scope.
- **Structural guards over point fixes**: the reflection round-trip suite (Transport), the frozen 138-command authz matrix + dispatch-coverage pair, contract-lock tests (which surfaced the real Newtonsoft default(T) wire behavior), and the design-invariant DI lock tests.
- **The live alarm cache lifecycle engineering** (ref-counting, linger, version-checked timers, fail-safe viewer cap, self-healing start retry) is exemplary — the defects around it are in the fan-out economics, not the lifecycle.
- **NodeB-failover reconciliation pull clients and the composite keyset cursor** dodge every classic trap (transport-fault-only failover, per-row fault isolation, `DateTime.MinValue` underflow).
- **Conventions survived 268 commits of churn**: UTC discipline, Commons purity, additive contracts, clean reference graph all re-verified.

## Prioritized Recommendations

**P0 — immediately**
1. Rotate the exposed Inbound API key and delete `test.txt`. *(H2)*
2. Fix the resync predicate inversion — one shared oldest-member active-node predicate for delivery gate AND resync authority. *(C1)*
3. Chunk the anti-entropy snapshot (or page it) so it fits Akka remoting frames; add a delivery-confirmation check. *(H1)*

**P1 — before relying on the affected features**
4. Bound the rollup backfill (time-sliced like the purges, `AsNoTracking`, skip-on-failover-if-current) and fix the rate-metric unit discontinuity at the raw/rollup boundary. *(H4, Report 04 R2/R3)*
5. Make the failover drill honest: kill the *younger* node in the scripted drill (document the oldest-crash gap), fix seed-list ordering or document the constraint, then **actually run it** and measure the ~25s envelope with the now-landed two-node rig. *(H3)*
6. Enforce site scope in the four secured-write handlers; throttle the DebugStreamHub bind; add `ForwardedHeaders` handling so throttle keying survives Traefik. *(Theme 5)*
7. Wire the Inbound API subscriber to `IScriptArtifactChangeBus` (or remove the claim from Host and the tracker). *(Theme 3)*

**P2 — hardening batch**
8. Close the options-validation tail (5 spots, Theme 4); guard the MxGateway reconnect generic-catch with `ct.IsCancellationRequested` (Report 03 N1); add failure mapping to the expression-eval `PipeTo`s (03 N2); batch the SiteCalls terminal purge (04 R6); cache Expression-trigger compiles on read-only validation paths (05 N1); coalesce live-alarm deltas (02 N6); fix the Alarm Summary stale-site poll race (07 N4).
9. Consolidate deferral tracking into the canonical register; refresh or delete the CHANGELOG; sweep the doc drift each report catalogues (stale "leader" comments, "off-thread" compile-gate claim, "throttling complete" claim, Host bus comment).

## Reading Order

If you read only three reports this round: **02** (the new Critical, plus the live-alarm stream review), **01** (what the failover story still owes), **04** (the rollup backfill). Report **08** again carries the best overall-health picture, the refreshed test inventory (~30 projects, ~6,300 executed cases), and the deferred-register audit.
