Upstream Mike PR #291 review

[github-actions]

Automated-Upstream-Mike-Sync: true
Upstream-Risk: high

Promising coverage-ratchet capability, but ROSS lacks the required frontend test harness and one upstream seam. Adding the harness would change dependencies and lockfiles, requiring an explicit decision.

Mike PR open-legal-products#291

• Outcome: needs-decision
• Capability: ROSS-native contract tests for frontend API wrappers and model helpers, backed by a measured no-regression coverage ratchet
• Series: frontend-lib-coverage
• Dependencies: Mike PR [Testing 05] test: minimal vitest harness for backend and frontend open-legal-products/mike#228 (minimal Vitest harness), Mike PR [Testing 18] test(frontend): API-client/SSE tests + coverage ratchet open-legal-products/mike#255 (initial frontend API-client tests)
• Prerequisites: Approval to add frontend test dependencies and update lockfiles, Baseline coverage measurement for current ROSS frontend library seams, Focused mapping of upstream cases to ROSS-specific API routes and provider behavior
• Reason: ROSS has mikeApi.ts and modelAvailability.ts seams, but no frontend test scripts, Vitest configuration, or test dependencies; folderDeleteState.ts is absent. Upstream tests and thresholds therefore cannot be adopted reliably without an approved ROSS-native harness and fresh measurements.

Architecture brief

Add an isolated frontend unit-test layer around current ROSS library contracts, using mocked transport boundaries and coverage limited to stable library seams. Establish ratchet floors only from reproducible ROSS measurements, not upstream values.

Implementation plan

• Decide whether Vitest and its coverage provider may be added to frontend devDependencies and lockfiles.
• Create a minimal ROSS-native Vitest configuration and test scripts without changing CI workflows.
• Map current mikeApi.ts endpoints and modelAvailability.ts branches to table-driven contract tests; exclude absent Mike-only seams.
• Run repeated clean coverage measurements and select conservative no-regression floors.
• Validate lint, type-check, unit tests, coverage enforcement, and existing repository baseline tests before adoption.

Required human action

This is a draft state-only architecture record. Review the brief and implementation plan before any code is attempted.