UI5 2.x and Fiori Elements Readiness: UI5 Linter, Deprecated APIs and Regression-Testing Custom Fiori Apps

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UI5 readiness checklist

• Status: UI5 2.x delivery is on hold (autumn 2026); SAPUI5 stays strategic; best-practice 1.x code needs no migration. Recheck SAP's status before planning.
• Goals: no sync code loading (CSP), no sync data loading, no globals, no deprecated APIs.
• App rules: IAsyncContentCreation, async views/fragments/bundles, never async:false, Manifest Version 2, XML or typed views, this.byId().
• Inventory: owner, technology, SAPUI5 version, usage, linter report, suite status for every custom app; retire what nobody uses.
• Linter: npx ui5lint --details --format json; record ignore patterns; dry-run then --fix; test every fix.
• Triage by rule type: globals are cheap; sync loading, JS views and deprecated libraries are expensive.
• Rebuild as Fiori elements V4 when data-centric and an OData V4 service exists; FPM building blocks for custom parts.
• Tests: Test Starter, QUnit 2, IstanbulJS; OPA5 per commit; wdi5 nightly in CMQ with stable IDs and UI5 waiting.
• Gates: linter report → no new findings after baseline → OPA5 → wdi5 → key user acceptance → CMR regression.
• Report findings by rule type and incidents caused by remediation; close a phase only when every app has its target state.