fix(lighthouse): resolve per-run TEMP to absolute — unbreaks all Web Vitals on Windows

packages/parity/src/engine/benchmark.ts

@@ -1447,11 +1447,14 @@ export async function runSideBenchmark(opts: RunSideOptions): Promise<SideBenchm
         id: `${opts.side}-${opts.viewport}-${id}`,
         formFactor: ff,
       });
-    const [home, plp, pdp] = await Promise.all([
-      lh("home", opts.base),
-      lh("plp", targets.category),
-      lh("pdp", targets.product),
-    ]);
+    // Sequential, not Promise.all: Lighthouse measures CPU, so running the three
+    // pages at once both inflates their own numbers and starves Chrome's launch
+    // handshake while Playwright still holds browsers open — which fails all
+    // three attempts with "Unable to connect to Chrome". Same reasoning the
+    // vitals command encodes in its cores/2-capped-2 --lighthouse-concurrency.
+    const home = await lh("home", opts.base);
+    const plp = await lh("plp", targets.category);
+    const pdp = await lh("pdp", targets.product);
     vitals = { home, plp, pdp };
   }
 
@@ -1785,11 +1788,10 @@ export async function runSideBenchmarkContent(
         id: `${opts.side}-${opts.viewport}-${id}`,
         formFactor: ff,
       });
-    const [home, plp, pdp] = await Promise.all([
-      lh("home", opts.base),
-      lh("page1", new URL(opts.contentPaths.pageA, opts.base).toString()),
-      lh("page2", new URL(opts.contentPaths.pageB, opts.base).toString()),
-    ]);
+    // Sequential for the same reason as the commerce path above.
+    const home = await lh("home", opts.base);
+    const plp = await lh("page1", new URL(opts.contentPaths.pageA, opts.base).toString());
+    const pdp = await lh("page2", new URL(opts.contentPaths.pageB, opts.base).toString());
     vitals = { home, plp, pdp };
   }
 

packages/parity/src/engine/lighthouse.ts

@@ -13,7 +13,7 @@
 //     run gets its own writable TEMP.
 import { spawn } from "node:child_process";
 import { mkdirSync, readFileSync } from "node:fs";
-import { join } from "node:path";
+import { join, resolve } from "node:path";
 import type { AgentA11yAudit, LhOpportunity, LhScores } from "../types/schema.ts";
 
 export type { AgentA11yAudit, LhOpportunity, LhScores };
@@ -173,7 +173,12 @@ async function measureLighthouseOnce(
   // dir and can hit EPERM there (Windows AV/ACL flakiness) — give this run its
   // own writable TEMP so chrome-launcher's tmp dir creation lands somewhere
   // uncontended instead of fighting --chrome-flags quoting.
-  const runTemp = join(opts.outDir, `.tmp-${opts.id}-a${attempt}`);
+  // MUST be absolute: this becomes TEMP/TMP for the spawned lighthouse, whose
+  // chrome-launcher feeds os.tmpdir() straight into Chrome's --user-data-dir.
+  // outDir descends from --output, which defaults to the RELATIVE "./parity-output",
+  // and Chrome cannot resolve a relative profile dir — it dies on launch and
+  // chrome-launcher reports the misleading "Unable to connect to Chrome".
+  const runTemp = resolve(opts.outDir, `.tmp-${opts.id}-a${attempt}`);
   mkdirSync(runTemp, { recursive: true });
   const args = [
     "--yes",