Phase F — Post-port product evolution

Improve the Avalonia line without reintroducing WinForms coupling. First ship (A–E) is not the end.

Read evolution tracks to classify a discovered backlog item; do not implement tracks that are absent from the product.

Preconditions

• Avalonia is the active trunk (or dual-running with legacy frozen)
• Layering exists
• Prefer one SDD/spec change per capability

Tracks (select only from repository evidence)

F1. Deferred capability restoration

Restore a deferred behavior in its owning layer with contract and regression evidence. Do not place application rules solely in a ViewModel because that is the easiest entry point.

F2. Boundary or integration replacement

Replace an adapter only after documenting semantics, failure modes, supported environments, resource ownership, and cutover behavior. A fallback is a product decision, not a default.

F3. Additional host or entry point

• Define the host's explicit scope, lifecycle, input binding, result, and failure protocol.
• Reuse application services and composition definitions where their lifetimes are compatible.
• Keep host-specific parsing/transport thin and test application behavior independently.
• Ensure one host does not accidentally start another host's lifetime.

F4. Presentation and operational quality

• Externalize user-facing text when localization is in scope.
• Preserve structured diagnostics and render them at the presentation boundary.
• Add accessibility, observability, and supportability requirements discovered after cutover.

F5. Persisted state evolution

legacy stores -> typed versioned state, when the product persists state
  validated migrators; reject unsupported future versions
  preserve predecessor and last known-good data
  coordinated atomic updates

Define edit/apply/cancel behavior from the product contract. Do not create a new persistence stack for each UI surface.

F6. Extension mechanisms

When the product supports user-extensible or dynamically evaluated behavior, define capabilities, resource budgets, trust boundaries, lifecycle, and diagnostics before implementation.

F7. Workflow discoverability

Make supported actions discoverable, define intentional empty/disabled states, and turn required hidden gestures into accessible command surfaces.

Workflow

1. Spec with clear non-goals and firm decisions (no “may remain…” hedges)
2. Failing tests first with the smallest representative fixtures or scenarios
3. Implement inside existing layers; clean cut when replacing dual models
4. Surface compile/runtime errors to UI and logs
5. Focused + full solution tests (no screenshot-only tasks)
6. Sync long-lived requirements

When the user says not to confirm mid-flight, apply autonomously and report at the end.

Deliverables

• Feature on Avalonia trunk with tests
• No new WinForms statics or UI algorithms in Core
• Composition and every affected host updated if shared services changed

Handoff

Structure/security debt → wfa-harden-decompose Legacy delete → wfa-parity-verify