# KNOWLEDGE — tombstones & landmines

Carried across the 2026-09-04 knowledge bankruptcy from the working Express
predecessor. Filter applied: an item was kept only if it (a) cannot be
re-derived from code or a live query, AND (b) is expensive or harmful to
re-learn. Everything else was deliberately left behind to be re-derived from
ground truth. Every entry is dated; re-verify on first POC contact. Add new
entries the same way — dated and falsifiable.

## SAP S/4HANA (tenant `my429480`, Public Cloud, API-only)

- [2026-09-04, verified by predecessor in live use] **BOM items must be POSTed
  sequentially** after the header POST. Parallel item POSTs fail SAP's
  consistency check.
- [2026-09-04, same] **`AvailabilityCheckType` is not exposed in the Product
  API V4** — requires the V2 `API_PRODUCT_SRV` fallback for that one field.
- [2026-09-04, same] **BOM read works only on the v1 service**;
  `API_BILL_OF_MATERIAL_SRV;v=0002` rejects guid key lookups. Writes go to
  `;v=0002`.
- [2026-09-04, same] OData V2 date format is `/Date(ms)/`; the "end of time"
  value (9999-12-31) is `/Date(253402214400000)/`.
- [2026-09-04, same] **Idempotency pattern that works: SAP is the ledger.** The
  Arena ECO number is stamped into `ReasonForChangeText`; no local sync-state
  database is needed or wanted.
- [2026-09-10, predecessor code read] **BOM header create must use
  `EngineeringChangeDocForEdit`** — `EngineeringChangeDocument` is
  `sap:creatable=false` and silently dropped. ECM BOM items must carry
  `HeaderChangeDocument` = the header's change number or SAP answers "Input
  parameters are initial". (arena-plm.js:785-846)
- [2026-09-10, same] **`A_ChangeMasterObjTypeAssgmt` POST requires
  `IsActiveForChangeNumber: true`** — without it SAP returns 201 and silently
  discards the row. (arena-plm.js:914-924)
- [2026-09-10, same] **ProductDescription updates: PATCH by full key**
  (`Product=…,Language='EN'`); PATCH via the nav property returns HTTP 501;
  fall back to POST on 404/405. (arena-plm.js:1411-1414)
- [2026-09-10, same] `ProcurementType` can only be written together with
  `MRPType` in the same `ProductPlantSupplyPlanning` PATCH.
  (arena-plm.js:1623-1640)

## Arena PLM API (`api.arenasolutions.com/v1`)

- [2026-09-04, same] Session auth: `POST /login` → `arenaSessionId`, ~25-minute
  TTL. Concurrent logins race — serialize login behind a promise lock and
  re-login automatically on 401.
- [2026-09-10, predecessor code read] **WORKING-revision overlay is
  load-bearing**: the seven SAP classification attributes (SAP Product Type,
  SAP Plant, …) are writable only on the WORKING revision (Arena error 3224),
  while `/items?number=` resolves the EFFECTIVE revision — merge those
  attributes from WORKING over EFFECTIVE, and treat overlay failure as fatal
  (the predecessor's best-effort overlay silently turned valid items into
  NO_PRODUCT_TYPE errors). (arena-plm.js:508-552)
- [2026-09-10, same] `/items/{guid}/changes` does not exist (404) — derive the
  ECO from `/items/{guid}/revisions`, first EFFECTIVE revision with
  `change.number`. (arena-plm.js:1799-1806)
- [2026-09-10, same] The `/changes` feed has **no working server-side date
  filter** — delta detection must filter client-side (the predecessor pages
  the whole feed, O(history)). The outbound-integration queue
  (`/outboundintegrations/{guid}/events`, `reconciled` flag as a cursor held
  by Arena) is the clean delta mechanism. (arena-plm.js:1117-1263)

## Toolchain (worker)

- [2026-09-10, npm registry] **TypeScript `latest` is the 7.x native-compiler
  major** (no stable 6.x; only `6.0.0-beta`). typescript-eslint 8.70.0
  declares peer `typescript >=4.8.4 <6.1.0`, silently forcing the 5.9.x line —
  the worker pins `~5.9.3`. Falsifiable: recheck
  `npm view typescript-eslint peerDependencies` before any TS bump.
- [2026-09-10, npm registry] **`@types/node` `latest` dist-tag points at
  22.x** while 24.x/26.x lines exist — an unpinned install silently targets
  Node 22 types. Pin the major (`^24`) to match the runtime.

## Landmines

- [2026-09-15] **abapGit is not a prerequisite for SAP's ADT for VS Code.** The
  `sapse.adt-vscode` extension talks ADT/HTTP to the tenant and ships no git or
  abapGit commands (extension 1.1.2 `package.json`/readme, verified 2026-09-15).
  The "abapGit must be set up in the ABAP system" idea comes from the community
  extension `murbani.vscode-abap-remote-fs` (installed on this host), whose
  abapGit commands need the open-source `ZABAPGIT` report in the backend — which
  cannot be installed in a Public Cloud tenant. In ABAP Cloud, abapGit exists
  only as SAP's supported fork behind the **Eclipse** ADT plug-in
  (`https://eclipse.abapgit.org/updatesite/`, "abapGit Repositories" view); no
  VS Code variant exists [source: sap-docs sap-help loio
  2002380aeda84875a5fae4adc66b3fdb; /btp-cloud-platform/30-development/
  import-content-from-abapgit-repository-into-the-abap-environment-0b0d894;
  https://github.com/abapGit/ADT_Frontend, verified 2026-09-15]. It imports
  released object types only, from an internet-reachable repository (no Cloud
  Connector), into a chosen package/transport.

- [2026-09-15] **ADT MCP `x-ui-service` generator quirks (my431353, ADT VS
  Code 1.1.2):** every field needs `semanticType` (else "Builtin type of
  field is invalid"); it prepends its own `Z` to your prefix and appends
  `000` even with an empty suffix (`Z` + `ARENA_CHANGE_APPROVAL` →
  `ZZUI_ARENA_CHANGE_APPRVL000_O4`), names SRVD and SRVB identically, and
  the schema's `required` lists a non-existent `businessEntity` key — omit
  it. `get_schema` session ids are single-use. It returns only the SRVB URI;
  other object URIs follow `abap:/repotree-v1/<dest>/System Library/ZLOCAL/<pkg>/…`
  with extensions `.tabl.json`, `.ddls.acds`, `.bdef.json`, `.ddlx.acds`,
  `.dcls.acds`, `.clas.abap`, `.srvd.acds`, `.srvb.json`, `.ront.json`,
  `.nont.json`. `create_object` for SRVD needs `"sourceType":"S"`; BDEF and
  SRVB creation validate the referenced object's ACTIVE version, so create
  and activate DDLS/SRVD sources first. ATC via MCP rejects RONT/NONT.

- [2026-09-16] **An expired VS Code ADT logon shows up in the ADT MCP only as
  "Your user was logged off."** `abap_list_destinations` still lists the
  destination and `get_object_type_details` still returns field metadata,
  so neither proves a live session. **ADT for VS Code logs on to S/4HANA
  Cloud with a reentrance ticket and a localhost redirect:** it opens
  `https://<tenant>/sap/bc/adt/core/http/reentranceticket?redirect-url=http://localhost:<port>/adt/redirect`,
  and after SSO the tenant redirects to
  `http://localhost:<port>/adt/redirect?…&reentrance-ticket=<ticket>`
  (observed 2026-09-16). The ticket in that URL is a live logon credential:
  never paste it into chats, logs or files. The same mechanism is the
  plausible browser-free login path for `abap-adt-mcp` (OQ-9). **Tested
  2026-09-18: it does not work.** With a freshly captured reentrance
  ticket, `https://my431353.s4hana.cloud.sap/sap/bc/adt/core/discovery`
  and an ABAP class source URL answered HTTP 200 with the same 3094-byte
  SAML redirect page (`SAMLRequest`, `saml2`) for all of: `Cookie:
  MYSAPSSO2=<ticket>`, header `MYSAPSSO2: <ticket>`, and no credential at
  all, with and without `?sap-client=080`. A reentrance ticket is
  therefore neither a logon-ticket cookie nor an assertion-ticket header
  here; ADT exchanges it some other way. Do not spend more on
  `abap-adt-mcp`'s `sso2` mode without first capturing what the extension
  actually sends. `abap_creation-run_validation` is the
  cheapest read-only liveness check (it answers "… validation failed: Your
  user was logged off."). Fix it by logging on to the destination again in
  VS Code; the MCP port and token stay the same unless VS Code reloads
  (live 2026-09-16, ~1.5 h after the last successful call).
- [2026-09-16] **Ask the ADT MCP for name limits and package existence; do
  not guess them.** `abap_creation-get_object_type_details` returns each
  type's create fields and `maxLength`: `TABL/DT` 16, while `DDLS/DF`,
  `SRVD/SRV`, `SRVB/SVB` and `BDEF/BDO` allow 30 (the generator's `APPRVL`
  truncation came from that 30 limit). `abap_creation-run_validation` is a
  read-only way to check that a package exists: a missing package answers
  "Package '<name>' does not exist" [source: adt-mcp on 0M7DEJI, verified
  2026-09-16]. The Claude Code session does not expose the adt-mcp tools
  unless the server was up at session start. A JSON-RPC probe over
  `http://127.0.0.1:2236/mcp` with the `.mcp.json` bearer token works for
  read-only checks in the meantime.

- [2026-09-16] **In the VS Code ADT workspace, the `.json` file in an object
  folder is header metadata, never the source.** A table folder holds
  `zchangeapproval.tabl.json` (formatVersion, description, originalLanguage,
  `abapLanguageVersion`) and `zchangeapproval.tabl.ddic` (the Dictionary DDL
  source). Paste into `.ddic`, and activate through the `.tabl.ddic` URI
  (live, "Activation successful."). For objects created with
  `create_object`, the returned `filePath` names the source file: DDLS
  `.ddls.acds`, DCLS `.dcls.acds`, BDEF **`.bdef.abdl`** [source: adt-mcp
  abap_creation-create_object / abap_activate_objects on 0M7DEJI, verified
  2026-09-16]. The `.tabl.json` / `.bdef.json` activation URIs recorded on
  2026-09-15 were generator objects; trust the returned `filePath` over
  that table. BDEF activation through `.bdef.abdl` is proven (U6, live).
- [2026-09-16] **A managed `strict ( 2 )` BDEF activates before its
  behavior pool class exists** (`ZR_CHANGEAPPROVAL`, "Activation
  successful.", with no class `ZBP_R_CHANGEAPPROVAL` yet) [source: adt-mcp
  abap_activate_objects on 0M7DEJI, verified 2026-09-16]. Once the class
  exists, activate BDEF and class together. `abap_activate_objects` returns
  only "Activation successful." with no warnings on success. On failure it
  lists messages with line and column but no severity (U13 SRVD,
  2026-09-16), so read severity in the editor. Service definitions
  report "Comments are not supported and will be deleted on save" for a
  leading block comment, and **that message blocks activation**: the same SRVD failed with a
  19-line `/* */` header and activated without it (live 2026-09-16; the
  DCLS, DDLX and BDEF headers did not block). The language allows comments
  [source: abap-docs /abap-docs-cloud/ABENCDS_GENERAL_SYNTAX_RULES,
  verified 2026-09-16], so this is the tooling. Keep SRVD sources free of
  comments. `abap_atc_get_result` returned only totals for a run with 43
  infos (UI leg), but per-object `findings[]` (priority, check class,
  message id and title, quick-fix flags) for a run with a priority-3
  warning (worker leg). Expect details for warnings and errors at least
  (both runs live 2026-09-16). A projection BDEF over a view with
  `@AccessControl.authorizationCheck: #CHECK` raises SLIN W607 (+BDL 549)
  "should be replaced with #MANDATORY" (priority 3; it does not block
  activation). An OData V4 **Web API** binding reports
  `bindingCategory: "1"` (UI: `"0"`) in `fetch_services`.
- [2026-09-16] **OData V4 identity on a RAP UI service: the binding name is
  only the URL's first segment.** For definition `ZUI_ARENA_CHANGE_APPROVAL`
  and binding `ZUI_ARENA_CHANGE_APPR_O4`, the live `$metadata` uses
  namespace `com.sap.gateway.srvd.zui_arena_change_approval.v0001`, from the
  **service definition**, and entity type `ChangeApprovalType`, with a
  `Type` suffix and no underscore (live 2026-09-16,
  `docs/v2/zui_arena_change_appr_o4.metadata.xml`). The earlier assumption
  that the namespace carries the binding name and a `_Type` suffix was
  wrong. RAP also emits `__OperationControl` with
  `Core.OperationAvailable Path="_it/__OperationControl/<action>"` for
  `features : instance` actions, `SAP__Messages`, `Nullable="false"` on
  non-key elements, and `cast( case … as abap_boolean preserving type )`
  surfaces as `Edm.Boolean` (INT1 literals as `Edm.Byte`, `utclong` as
  `Edm.DateTimeOffset Precision="7"`). Copying `$metadata` from Chrome's
  XML tree view decodes `&amp;` to `&`; use `view-source:` or re-escape.
- [2026-09-16] **Live RAP `$metadata` works verbatim as Fiori mock metadata**
  (`@sap-ux/fe-mockserver-core` 1.7.15 serves it and accepts `$select` on
  `__OperationControl/approve`). Mock rows must then carry
  `__OperationControl`, or the enablement paths resolve to nothing. The
  app's ESLint config checks only TS/JS, so run `npx @ui5/linter` for UI5.
  The fiori-mcp `list_functionality` for `app/` offers only
  add/delete page and controller extension, so dataSource and annotation
  edits are made directly. The cached `@ui5/manifest` 1.89.0 schema
  rejects the generator's manifest `_version: "2.11.0"`; that is not a
  defect in the app.
- [2026-09-16] **A published custom UI service answers on the UI host, not the
  `-api` host, for a business user.** `fetch_service_information` reports
  the service URL on `my431353-api.s4hana.cloud.sap` (with
  `sap-client=080`), but a browser business-user call there is refused as
  "Forbidden / blocked by UCON". The same path on
  `my431353.s4hana.cloud.sap` returns `$metadata` for the developer user,
  before any IAM app exists (live 2026-09-16). The `-api` host is the
  communication-user entry point (communication arrangement), so the
  worker's A2X service goes there through a custom communication scenario
  (V-2), never the UI service. After publishing, ADT for VS Code reports
  "<binding> published locally".
- [2026-09-16] **In ADT for VS Code, publishing a service binding is a code
  lens, not a button or a palette command.** Open the binding's `.srvb.json`
  source and click the **Publish** code lens; Unpublish and Preview… work the
  same way [source: sap-docs sap-help loio dd6f5de63e7245a7abe7e39389841596
  "ABAP RAP Tools", verified 2026-09-16]. The extension (1.1.2) contributes
  no publish command, and the SAP ADT MCP has no publish tool. `create_object` for a class returns only the global
  `.clas.abap` path, no local-types (CCIMP) path.
- [2026-09-16] **`abap-adt-mcp` 2.1.0 auto-detects a browser for SSO only on
  macOS.** `detectBrowser()` checks `SAP_BROWSER_PATH` and then three
  `/Applications/…` paths; otherwise it throws "No Chrome/Edge/Brave found
  for SSO login" (`dist/lib/browserLogin.js:38-50`, read 2026-09-16). On
  this Linux host the server env must carry
  `SAP_BROWSER_PATH=/usr/bin/google-chrome` along with the desktop display
  variables. Login harvests the HttpOnly `MYSAPSSO2`/`SAP_SESSIONID` cookies
  over the Chrome DevTools Protocol (`puppeteer-core`). `listSystems` needs
  no SAP call and is the safe first probe of its policy. **Its SSO does not
  work from a remote shell:** there is no localhost redirect (SAML returns
  to the tenant), and the sign-in must be typed into the server-side Chrome
  window (`headless: false`, profile
  `~/.abap-adt-mcp/sso/<host>`, `--remote-debugging-port=0`, 300 s timeout).
  Over multi-hop SSH neither the desktop nor a DevTools relay is reachable in
  practice. Do the first sign-in at the server's desktop; with "stay signed
  in" later logins should complete unattended (unverified, 2026-09-16).
- [2026-09-16] **Create fields for the remaining RAP types (`get_object_type_details`
  on 0M7DEJI):** `CLAS/OC`: packageName, name (≤30), description, optional
  superclass, interfaces. `DCLS/DL`: packageName, name (≤30), description,
  optional `protectedEntity`. `DDLX/EX`: packageName, name (≤**40**),
  description, optional `extendedEntity` [source: adt-mcp
  abap_creation-get_object_type_details on 0M7DEJI, verified 2026-09-16].
  Pass `protectedEntity` / `extendedEntity` so the editor starts from the
  right skeleton. DCLS creation does **not** require the protected entity to
  be active. `ZC_CHANGEAPPROVAL_A2X` access control validated and was
  created while its DDLS was still empty and never activated (unlike
  BDEF/SRVB creation). `SRVB/SVB` `bindingType` values are exactly `OData
  V2 - UI`, `OData V2 - Web API`, `OData V4 - UI`, `OData V4 - Web API`,
  whatever label the release notes use [source: adt-mcp
  abap_creation-run_validation / create_object /
  get_object_type_details on 0M7DEJI, verified 2026-09-16].
- [2026-09-16] **Service binding names: SAP Help says 26 characters, the
  ADT MCP allows 30.** The 26-character limit appears on the ABAP Cloud,
  SAP Cloud Platform and ABAP Platform 2021 "Creating Service Binding"
  pages [source: sap-docs sap-help loio 4bad0d7280b742a68dd2d42b1441f09a,
  verified 2026-09-16]. `get_object_type_details` reports 30 for
  `SRVB/SVB`, and the `x-ui-service` generator itself emits 29–30-character
  bindings, which activated unpublished on `my431353` on 2026-09-15.
  Whether publishing accepts more than 26 is unknown. Stay at 26 or fewer
  rather than find out after a whole BO leg. The generator does not keep to
  the documented limit, which is one more reason not to use it for names
  that ship.
- [2026-09-16] **In an OData V4 binding URL
  `/sap/opu/odata4/sap/<binding>/srvd/sap/<alias>/0001/`, the second
  segment is the binding's service name (alias), not necessarily the
  service definition name. It can be renamed only while the binding is
  unpublished** [source: sap-docs community-14433266 "How to rename an
  OData V4 service?", verified 2026-09-16]. Check it before publishing.
- [2026-09-16] **CDS CASE results take the longest branch type, and untyped
  integer literals are typed INT1..INT8 by value** [source: abap-docs
  /abap-docs-cloud/ABENCDS_CASE_EXPRESSION_V2, ABENCDS_UNTYPED_LITERAL_V2,
  verified 2026-09-16]. A text CASE over status codes becomes CHAR(n) of
  the longest literal, and a 0–5 criticality becomes INT1. Cast
  explicitly when the OData type matters.
- [2026-09-16] **The `ui5-mcp-server` linter cannot see this repo.** The
  server is reached over SSE on `mcp.alexzaw.dev`, and `run_ui5_linter` on
  `app/` fails with `ENOENT: realpath '/home/alexz/…/arena-plm/app'`
  (live 2026-09-16). Its doc/API tools work; its file-based tools
  (linter, manifest validation, project info) do not. For real UI5 code
  changes, lint locally (`npx @ui5/linter` inside `app/`) or run the
  server where the files are.
- [2026-09-16] **The Fiori mock server does not simulate bound actions.**
  Without a per-entity `webapp/localService/mainService/data/<Entity>.js`
  exporting `executeAction`, `@sap-ux/fe-mockserver-core` 1.7.15 returns
  the action data unchanged
  (`node_modules/@sap-ux/fe-mockserver-core/dist/mockdata/fileBasedMockData.js:547-549`,
  read locally 2026-09-16). Status transitions can be shown only against
  the live RAP service, or with a hand-written mock handler.
- [2026-09-16] **Cast the whole CASE to a data element, never each
  branch.** "If a data element is specified for `dtype`, the result …
  inherits the semantic properties of the data element. An exception to
  this is the use of the `CAST` expression within a case distinction."
  Write `cast( case … end as abap_boolean preserving type )`.
  `PRESERVING TYPE` requires an exact match of built-in type and length
  [source: abap-docs /abap-docs-cloud/ABENCDS_CAST_EXPRESSION_V2, verified
  2026-09-16]. To guarantee that length, use typed literals in the branches
  (`abap.char'X'`, `abap.char' '` are CHAR(1)): an untyped character
  literal's length is only "at least as large as the actual length of the
  literal" [source: abap-docs /abap-docs-cloud/ABENCDS_TYPED_LITERAL_V2,
  ABENCDS_UNTYPED_LITERAL_V2, verified 2026-09-16]. `ABAP_BOOLEAN` is CHAR 1
  [source: abap-docs /abap-docs-standard/ABENDATAOBJECTS_TRUE_VALUE_GUIDL,
  verified 2026-09-16]. The same caveat means a CASE over untyped status
  literals is not provably CHAR(n) of the longest literal.
- [2026-09-16] **`sap-released-objects` has no `SRVB` object type for
  public_cloud**, the same gap as `DDLS` (use `CDS_STOB` for views). Binding
  release questions cannot be answered from that server.

- [2026-09-15] **Developer business catalogs: `SAP_A4C_BC_*` is the Public
  Cloud / BTP ABAP family; `SAP_A4_BC_*` is on-premise / Private Cloud.** On
  `my431353` the developer role carries the A4C catalogs (e.g.
  `SAP_A4C_BC_DEV_OBJ_DIS_PC`, `SAP_A4C_BC_DEV_UID_PC` [source: sap-docs
  sap-help loio f4881a9b9141430dba1c6a76e7f456dc, verified 2026-09-15]); the
  `SAP_A4_BC_DEV_UID_PC` name in the fiori-tools-samples README is the wrong
  family for this tenant. Split stated by the tenant owner 2026-09-15; no SAP
  Help page in the loadout spells it out — do not "fix" a role toward A4.
- [2026-09-15] **Write probes on the dev tenant: `$TMP` and `ZLOCAL` both
  fail, for different reasons.** `$TMP` is a classic package, so creating
  there checks the Standard ABAP language version and a cloud-development
  role is denied with "not authorized to make changes (S_ABPLNGVS)"; `ZLOCAL`
  is a structure package ("cannot contain development objects"). Objects go
  in a sub-package of `ZLOCAL` (prototyping, no workbench request for
  sub-packages created from release 2508) or of `ZCUSTOM_DEVELOPMENT`
  (transport layer YDEV, importable into test/prod); ZLOCAL→ZCUSTOM
  reassignment is allowed, the reverse is not; `ZLOCAL` plays the `$TMP` role
  in Public Cloud [source: sap-docs sap-help loio
  a0d80f14fcb74cb1ac8fb6f3d9ad48cc (2608), verified 2026-09-15]. Refusals
  verified live via ADT MCP, 2026-09-15.

- [2026-09-14] `sap-released-objects` has no `DDLS` type for public_cloud;
  CDS views are catalogued as `CDS_STOB`. A "not found" for `I_PRODUCT` under
  `DDLS` is a type-key artefact, not a release verdict — query with
  `object_type=CDS_STOB` (verified 2026-09-14).
- [2026-09-14] **A Fiori Elements app generated on hand-written mock metadata
  agrees with itself and hides service-shape mismatches.** ABAP Cloud OData V4
  services emit `Schema Namespace="com.sap.gateway.<srvd|srvd_a2x>.<service-binding-name>.v0001"
  Alias="SAP__self"` — the name in the namespace is the **service binding
  (group)**, which is also the first URL segment; the service definition /
  alias is the second segment (`/api_currencyexchangerate/srvd_a2x/sap/currencyexchangerate/0001`
  → `…srvd_a2x.api_currencyexchangerate.v0001`; `/api_product/srvd_a2x/sap/product/0002`
  [source: sap-docs sap-help loio 5f45f125dfe84c20beb18f5de1512f5a, verified
  2026-09-14]). Shown for released A2X services; for custom UI (`srvd`)
  bindings it is strongly indicated, not proven — V-2 confirms. Also, entity types suffixed `_Type`, un-suffixed entity sets,
  and vocabulary aliases `SAP__common`/`SAP__capabilities`/`SAP__core`
  [source: live tenant my429480 EDMX `~/projects/sap-apps/exchange-rates-cap/srv/external/API_CURRENCYEXCHANGERATE.edmx`
  lines 13–31, 55, 57, 95, verified 2026-09-14]. Front-end annotation targets
  written against any other namespace silently match nothing at runtime (no
  columns, no filters, no actions). Reconcile every `Annotations Target`, the
  `edmx:Reference` include namespace, and every `DataFieldForAction.Action`
  against the live `$metadata` before the first deploy — never trust the mock.

- [2026-09-04] The predecessor's `config/procurement-type.json`,
  `catalog-to-planning-strategy.json`, and `arena-category-to-sap.json` were
  loaded but **never read by any code path**, and procurement-type's keys
  (`MTS`/`OTS`) and values (`E`) do not match the Arena field (`1`–`9` Item
  Type) or SAP values (`X`) the code actually used. Do not port these configs
  on trust — re-derive every mapping via POC.
- [2026-09-04] Deployment/exposure target is an OPEN decision (PRD OQ-3). The
  old estate fronts apps through a shared `mcl-apps` approuter with shared
  XSUAA; a CF route mapped to more than one app round-robins and causes ~50%
  intermittent 404s. Whatever is chosen, audit routes after every push.
- [2026-09-04] HANA Cloud compute is the dominant cost lever of the old estate;
  an auto-stop systemd timer (`sap-apps/ops/hana-autostop`) guards it. If this
  package binds HANA, account for the stop/start cycle in the design.
- [2026-09-04] The predecessor kept its approval queue in a SQLite file inside
  the CF droplet — wiped on every restart. Durable persistence is a hard
  requirement of the rebuild (PRD ARN-003), not an optimization.
- [2026-09-10] Predecessor BOM and DOCUMENTS syncs are **non-idempotent**
  (re-approval creates a second MaterialBOM header / duplicate attachments) —
  the rebuild's executors must check existence first (ARN-006).
- [2026-09-10] The predecessor uses **two disagreeing change-master lookup
  keys** (`startswith(ChangeNumberDescription,'ECO:')` in the product link vs
  `ReasonForChangeText eq 'ARENA <eco>'` everywhere else; the 40-char
  truncation can split them). The rebuild uses exactly one key.
- [2026-09-10] Document sync links only Arena files with
  `storageMethodName === 'WEB'` (URL links, no bytes) — blob-stored files are
  silently skipped, and the DOKAR mapping config existed but was ignored
  (`BUS1001006`/`text/url` hardcoded). Decide blob handling explicitly in the
  rebuild.
- [2026-09-04] **If `.github/agents/sap-odata-*.agent.md`, a root `AGENTS.md`
  about "SAP OData Workspace", or `.vscode/mcp.json` pointing at
  `sap-odata-mcp.exe` appear in this repo — delete them.** They are scaffolded
  (evidence points to the `harieprasad.sap-odata-mcp` VS Code extension writing
  its workspace kit on folder open; observed 2026-09-04 14:40, removed same
  day). The referenced MCP binary is a Windows .exe that cannot run on this
  host, so those agents fabricate SAP results — the documented failure the
  founding kit exists to prevent. The root `AGENTS.md` is the dangerous part:
  Claude Code reads it as project instructions. [Update 2026-09-04 15:32] The
  suspect extension was uninstalled from all machines (verified: deregistered
  and marked obsolete on this host; directory purges on next VS Code reload).
  If the bundle STILL reappears after this, the extension hypothesis was wrong
  — hunt the real writer instead of re-deleting silently.