vitest >=5.0.0 changed what `Duration` does. The Duration line of the summary breaks the run down into phases as percentages of tracked time. Silent: code written for older versions still runs, without an error.

const fs = require("fs");
const path = require("path");
const cp = require("child_process");
const dir = "/w/durationpct";
fs.rmSync(dir, { recursive: true, force: true });
fs.mkdirSync(dir, { recursive: true });
fs.writeFileSync(path.join(dir, "sum.test.mjs"), [
  "import { test, expect } from 'vitest'",
  "test('adds', () => { expect(1 + 1).toBe(2) })",
].join("\n") + "\n");
const r = cp.spawnSync(process.execPath, ["/w/node_modules/vitest/vitest.mjs", "run", "--reporter=default"], {
  cwd: dir,
  encoding: "utf8",
  env: { ...process.env, NO_COLOR: "1", CI: "1" },
  timeout: 60000,
});
const out = (r.stdout || "") + (r.stderr || "") + (r.error ? String(r.error) : "");
console.log(out);
const line = out.split(/\r?\n/).find((l) => /^\s*Duration\s+\S+\s+\(.*\)\s*$/.test(l));
if (r.status !== 0 || !line) {
  console.error("ERROR: no Duration summary line with a breakdown (exit " + r.status + ")");
  process.exit(2);
}
const parts = line.slice(line.indexOf("(") + 1, line.lastIndexOf(")")).split(",").map((s) => s.trim());
console.log("breakdown: " + JSON.stringify(parts));
if (parts.length > 0 && parts.every((p) => /^[a-z]+ \d+%$/.test(p))) {
  console.log("PASS: the Duration breakdown is reported as percentages");
  process.exit(0);
}
if (parts.length > 0 && parts.every((p) => /^[a-z]+ \d+(\.\d+)?(ms|s|m)$/.test(p))) {
  console.error("FAIL: the Duration breakdown is reported as times, not percentages");
  process.exit(1);
}
console.error("ERROR: unexpected Duration line: " + line.trim());
process.exit(2);

const fs = require("fs");
const path = require("path");
const cp = require("child_process");
const dir = "/w/durationpct";
fs.rmSync(dir, { recursive: true, force: true });
fs.mkdirSync(dir, { recursive: true });
fs.writeFileSync(path.join(dir, "sum.test.mjs"), [
  "import { test, expect } from 'vitest'",
  "test('adds', () => { expect(1 + 1).toBe(2) })",
].join("\n") + "\n");
const r = cp.spawnSync(process.execPath, ["/w/node_modules/vitest/vitest.mjs", "run", "--reporter=default"], {
  cwd: dir,
  encoding: "utf8",
  env: { ...process.env, NO_COLOR: "1", CI: "1" },
  timeout: 60000,
});
const out = (r.stdout || "") + (r.stderr || "") + (r.error ? String(r.error) : "");
console.log(out);
const line = out.split(/\r?\n/).find((l) => /^\s*Duration\s+\S+\s+\(.*\)\s*$/.test(l));
if (r.status !== 0 || !line) {
  console.error("ERROR: no Duration summary line with a breakdown (exit " + r.status + ")");
  process.exit(2);
}
const parts = line.slice(line.indexOf("(") + 1, line.lastIndexOf(")")).split(",").map((s) => s.trim());
console.log("breakdown: " + JSON.stringify(parts));
if (parts.length > 0 && parts.every((p) => /^[a-z]+ \d+%$/.test(p))) {
  console.log("PASS: the Duration breakdown is reported as percentages");
  process.exit(0);
}
if (parts.length > 0 && parts.every((p) => /^[a-z]+ \d+(\.\d+)?(ms|s|m)$/.test(p))) {
  console.error("FAIL: the Duration breakdown is reported as times, not percentages");
  process.exit(1);
}
console.error("ERROR: unexpected Duration line: " + line.trim());
process.exit(2);