docs: schema library wiring audit

Records that the SharedSchema resolver is fully consumed at deploy, runtime and in
the UI value-entry forms, but has no authoring path: SchemaBuilder is the only
schema editor on all four surfaces and offers no library-reference option, so the
page creates entries nothing can point at. SchemaBuilder also collapses a $ref it
is shown to {"type":"string"} — currently unreachable, since no ref exists and
there is no UI or CLI to make one, but a trap for the first one authored.

Includes live usage counts (zero entries, zero refs, both environments) and the
resulting recommendation: leave dormant with a trigger, rather than finish or
delete it now.

schemalib.md

@@ -0,0 +1,209 @@
+# Schema Library (`SharedSchema`) — wiring audit
+
+**Date:** 2026-08-11
+**Question:** the Schema Library admin page doesn't seem wired to anything.
+**Verdict:** the *read* path is complete and careful; the *write* path doesn't exist. One of
+the three gaps is active silent data loss, not just a missing feature.
+
+---
+
+## 1. What IS wired
+
+The `{"$ref":"lib:Name"}` resolver has four real consumers, plus guarded CRUD:
+
+| Consumer | Location | Role |
+|---|---|---|
+| Deploy-time flattening | `DeploymentManager/FlatteningPipeline.cs:150` | Pre-loads the library once into a name→JSON map; an unresolved ref fails the deploy |
+| Template validation | `TemplateEngine/Validation/ValidationService.cs:91,149` | Dangling / cyclic / over-depth ref validation |
+| Inbound API runtime | `InboundAPI/SchemaRefResolver.cs` → `ParameterValidator.cs:35`, `ReturnValueValidator.cs:41` | Resolves refs when validating live request/response bodies; gated on `InboundApiSchema.MightContainRef` so ref-free methods pay nothing |
+| Central UI value entry | `CentralUI/Components/Shared/ParameterValueForm.razor:166` via `ISchemaLibraryQueryService` | Inlines referenced schemas so value-entry forms render the real shape |
+
+Supporting cast, all present and correct:
+
+- Entity `Commons/Entities/Schemas/SharedSchema.cs`, repo `ISharedSchemaRepository`,
+  EF mapping `SharedSchemaConfiguration`, registration in `ConfigurationDatabase/ServiceCollectionExtensions.cs:63`.
+- CRUD dispatched through `ManagementActor` (`ManagementActor.cs:2818-2884`) — the guard-running
+  path, never a direct repo write from the UI.
+- Nav entry `NavMenu.razor:35`, page `Pages/Design/SchemaLibrary.razor`, tests
+  `SchemaLibraryPageTests.cs` / `SchemaLibraryHandlerTests.cs`.
+
+So the library is genuinely consumed at deploy time, at runtime, and in one UI surface.
+
+---
+
+## 2. Gap 1 — no UI can produce a `lib:` reference
+
+`SchemaBuilder` is the **only** schema editor on every authoring surface:
+
+- `Pages/Design/ApiMethodForm.razor:84,90` (parameters + return)
+- `Pages/Design/SharedScriptForm.razor:71,76`
+- `Pages/Design/TemplateScriptDialog.razor:141,146`
+- `Pages/Design/SchemaLibrary.razor:46` — the library page itself
+
+Its type picker is `SchemaBuilderModel.PrimitiveTypes` (`SchemaBuilderModel.cs:37-38`):
+
+```csharp
+{ "string", "integer", "number", "boolean", "object", "array" }
+```
+
+No library-reference option, at root or property level. There is also **no raw-JSON escape hatch
+for schemas** — the Monaco editor on those forms edits the C# script body, and
+`ParameterValueForm`'s raw mode edits *values*, not the schema.
+
+**Consequence:** the Schema Library page creates entries that nothing else in the UI can point at.
+The only authoring routes for a ref are a direct DB edit or a bundle import.
+
+---
+
+## 3. Gap 2 — a ref authored outside the UI is silently destroyed on the next save
+
+`ParseSchema` inspects only the `type` property (`SchemaBuilderModel.cs:96-100`). A `$ref` node
+carries no `type`, so the node defaults to `"string"`, and `Serialize` writes that back.
+
+Verified by running the round-trip through `SchemaBuilderModel` directly (throwaway probe, since
+removed):
+
+```
+{"$ref":"lib:Address"}
+  → {"type":"string"}
+
+{"type":"object","properties":{"addr":{"$ref":"lib:Address"},"name":{"type":"string"}},"required":["addr"]}
+  → {"type":"object","properties":{"addr":{"type":"string"},"name":{"type":"string"}},"required":["addr"]}
+```
+
+Both root-level and nested (`SchemaBuilderModel.cs:131-133`) refs collapse.
+
+**Consequence:** open any ApiMethod / SharedScript / TemplateScript whose definition carries a ref,
+change anything at all, save — and the contract is silently widened to a bare string. Deploy still
+passes (the ref is gone, so there is nothing left to dangle) and nothing warns.
+
+**Sharpest edge:** the Schema Library page edits entries with `SchemaBuilder Mode="value"`, so a
+library entry that references *another* library entry — which `ManagementActor.cs:2921` explicitly
+permits — is flattened to `{"type":"string"}` the moment an operator edits it.
+
+**Reachability — correction.** An earlier draft of this report called this "worse than merely
+unfinished: the feature is reachable, and touching it destroys data." That overstates it. The
+corruption requires a `$ref` to exist first, and per §6 **no `$ref` exists anywhere in either
+environment** — and since there is no UI path (§2) and no CLI path (§7) to author one, the only way
+to create one today is a hand-edit of the database. So this is a **trap laid for the first ref**,
+not an active defect. It becomes live the moment §5.2 ships, or the moment someone hand-authors a
+reference.
+
+---
+
+## 4. Gap 3 — library entries don't travel between environments
+
+`SharedSchema` appears **nowhere** in `src/ZB.MOM.WW.ScadaBridge.Transport/`.
+
+Contrast its sibling `SharedScript`, which is a first-class Transport artifact across
+`Serialization/EntityDtos.cs`, `Serialization/EntitySerializer.cs`, `Export/BundleExporter.cs`,
+`Export/ResolvedExport.cs`, `Export/DependencyResolver.cs`, `Import/ArtifactDiff.cs` and
+`Import/BundleImporter.cs`.
+
+**Consequence:** a ref that resolves in dev dangles after import into prod. The import-time script
+trust gate won't catch it — that gate covers script *bodies*, and this is a schema.
+
+---
+
+## 5. Remediation, if the feature is kept
+
+Three separable slices, in dependency order. **Read §6 first** — on current evidence none of these
+is urgent, and the prior question is whether the feature should exist at all.
+
+### 5.1 Close the round-trip trap (small, independent)
+
+Give `SchemaNode` a passthrough for subtrees the model doesn't understand, so an unrecognised node
+(`$ref` included) round-trips **verbatim** instead of collapsing to `{"type":"string"}`. Closes
+Gap 2 outright, needs no new UI, and is a **hard prerequisite for 5.2** — shipping the authoring UI
+without it would make the corruption reachable for the first time.
+
+Test to add alongside: a round-trip guard asserting a `$ref` node survives parse→serialize at both
+root and property level — run it against the current code first and observe it fail, or it proves
+nothing.
+
+### 5.2 Make refs authorable (the actual "wire it up")
+
+Add a library-reference entry to the `SchemaBuilder` type picker, populated from the existing
+`ISchemaLibraryQueryService` (already registered, `CentralUI/ServiceCollectionExtensions.cs:142`).
+Emits `{"$ref":"lib:Name"}`; with 5.1 in place it round-trips. This is what actually connects the
+Schema Library page to the rest of the system.
+
+### 5.3 Carry `SharedSchema` in Transport bundles (separate, larger)
+
+DTO + serializer + exporter + dependency resolution (walk definition bodies for `lib:` refs so
+referenced entries are pulled into the bundle) + differ + importer. Mirrors the `SharedScript`
+shape throughout. Worth its own pass, and worth deciding whether an unresolved ref on import is a
+blocker row or an advisory warning — the existing name-resolution severity split (template =
+advisory, ApiMethod = hard error) is the precedent.
+
+---
+
+## 6. Is the feature needed at all?
+
+The gaps above describe an unfinished feature. The prior question — asked after the audit — is
+whether it should be finished, and the evidence says not on current usage.
+
+### 6.1 Usage: zero, in both environments
+
+Queried live against `scadabridge-mssql` on 2026-08-11:
+
+| | `ScadaBridgeConfig` (docker rig) | `ScadaBridgeConfig2` (docker-env2) |
+|---|---|---|
+| `SharedSchemas` rows | **0** | **0** |
+| Definitions containing `$ref` | **0** | **0** |
+| `ApiMethods` | 0 | 0 |
+| `TemplateScripts` | 31 | 15 |
+| …of those, carrying *any* parameter definition | 5 | 4 |
+
+Not only has the library never been used — most scripts don't declare a typed parameter shape at
+all, which is the precondition for ever wanting a reusable one.
+
+*(Production `wonder-app-vd03` was deliberately not queried; see §7.)*
+
+### 6.2 Origin: speculative, not requirement-driven
+
+It was not built to satisfy a stated need. The schema-editor design doc lists it under deferred
+future work — reuse of `$ref` across templates *"could be a future template-level schema library"*
+(`docs/plans/2026-05-12-script-schema-editor.md:117-118`). It was built later as M9/T32. The
+`Scope` column is likewise documented as being for *future* namespacing — a speculative field on a
+speculative feature.
+
+### 6.3 The benefit is authoring-time DRY only
+
+Resolution is **inlining, not indirection**: `FlatteningPipeline` and `SchemaRefResolver` expand
+`lib:Name` into the schema body at deploy / validation / runtime. The library therefore adds no
+runtime capability whatsoever — an inline schema does the entire job. Its single benefit is not
+retyping a shared shape at authoring time.
+
+That benefit also carries a cost that *grows with adoption*: there is no reverse index. Editing
+`lib:Address` silently changes every referencing contract at the next deploy, with no
+"what references this?" view and no versioning. Tolerable at 2 references, unpleasant at 20. Any
+decision to finish the feature should budget for an impact-analysis view alongside 5.2.
+
+### 6.4 Options
+
+1. **Delete it.** The resolver plumbing (4 consumers), the page, entity, table, repository,
+   ManagementActor handlers and tests are all carried for zero users. Defensible on the evidence.
+2. **Leave it dormant, fix nothing.** Zero cost today, because per §3 the defect cannot fire
+   without a ref and no ref exists. Revisit when a genuinely repeated payload shape appears.
+3. **Finish it** (5.1 + 5.2 + 5.3, plus an impact-analysis view per 6.3). Justified only by known
+   upcoming work with a repeated non-trivial shape — e.g. one MES order envelope shared across
+   several inbound methods.
+
+**Recommendation: option 2, with a hard trigger.** If a `lib:` ref is ever authored, §5.1 must land
+in the same change or the builder will destroy it. If nothing needs the library within roughly six
+months, take option 1 rather than leaving permanent unexercised surface in the codebase.
+
+---
+
+## 7. Notes
+
+- Nothing in this report was changed. No fix has been applied; the verification probe used in §3
+  was deleted after use.
+- The CLI has no schema-library commands either (`src/ZB.MOM.WW.ScadaBridge.CLI/` has no
+  `SharedSchema` reference), so there is no scriptable authoring path as a workaround. This is why
+  §3's trap is currently unreachable: hand-editing the database is the only way to create a ref.
+- The §6.1 counts are from the two **local docker** environments only. Production
+  (`wonder-app-vd03`) was not queried — that is an operator action, not one to take unasked. If
+  that box carries inbound methods with `$ref` definitions, §3 is live there and the §6.4
+  recommendation changes.