Two test runtimes, two coverage reports, one fragile merge

You have unit tests in Vitest (or Jest). You have E2E tests in Playwright. CI runs both. Coverage works for each, until you try to look at a single number. Then it gets weird. Two runtimes, two coverage outputs Unit tests run in Node, instrumented by V8 or istanbul. Playwright runs your real app in a real browser. Each produces its own coverage data. Stitching them together usually means: nyc merge (or a custom step) combining coverage-final.json files Reconciling source maps between Vitest's tr