perf: enable vitest fs module cache by default

docs/help/testing.md

@@ -82,7 +82,8 @@ Think of the suites as “increasing realism” (and increasing flakiness/cost):
 - Fast-local iteration note:
   - `pnpm test:changed` runs the wrapper with `--changed origin/main`.
   - The base Vitest config marks the wrapper manifests/config files as `forceRerunTriggers` so changed-mode reruns stay correct when scheduler inputs change.
-  - Use `OPENCLAW_VITEST_FS_MODULE_CACHE=1` for repeated local reruns on a stable branch when transform cost dominates.
+  - Vitest's filesystem module cache is now enabled by default for Node-side test reruns.
+  - Opt out with `OPENCLAW_VITEST_FS_MODULE_CACHE=0` or `OPENCLAW_VITEST_FS_MODULE_CACHE=false` if you suspect stale transform cache behavior.
 - Perf-debug note:
   - `pnpm test:perf:imports` enables Vitest import-duration reporting plus import-breakdown output.
   - `pnpm test:perf:imports:changed` scopes the same profiling view to files changed since `origin/main`.

docs/reference/test.md

@@ -39,7 +39,7 @@ For local PR land/gate checks, run:
 If `pnpm test` flakes on a loaded host, rerun once before treating it as a regression, then isolate with `pnpm vitest run <path/to/test>`. For memory-constrained hosts, use:
 
 - `OPENCLAW_TEST_PROFILE=low OPENCLAW_TEST_SERIAL_GATEWAY=1 pnpm test`
-- `OPENCLAW_VITEST_FS_MODULE_CACHE=1 pnpm test:changed`
+- `OPENCLAW_VITEST_FS_MODULE_CACHE=0 pnpm test:changed`
 
 ## Model latency bench (local keys)
 

test/vitest-performance-config.test.ts

@@ -2,8 +2,12 @@ import { describe, expect, it } from "vitest";
 import { loadVitestExperimentalConfig } from "../vitest.performance-config.ts";
 
 describe("loadVitestExperimentalConfig", () => {
-  it("returns an empty object when no perf flags are enabled", () => {
-    expect(loadVitestExperimentalConfig({})).toEqual({});
+  it("enables the filesystem module cache by default", () => {
+    expect(loadVitestExperimentalConfig({})).toEqual({
+      experimental: {
+        fsModuleCache: true,
+      },
+    });
   });
 
   it("enables the filesystem module cache explicitly", () => {
@@ -18,6 +22,14 @@ describe("loadVitestExperimentalConfig", () => {
     });
   });
 
+  it("allows disabling the filesystem module cache explicitly", () => {
+    expect(
+      loadVitestExperimentalConfig({
+        OPENCLAW_VITEST_FS_MODULE_CACHE: "0",
+      }),
+    ).toEqual({});
+  });
+
   it("enables import timing output and import breakdown reporting", () => {
     expect(
       loadVitestExperimentalConfig({
@@ -26,6 +38,7 @@ describe("loadVitestExperimentalConfig", () => {
       }),
     ).toEqual({
       experimental: {
+        fsModuleCache: true,
         importDurations: { print: true },
         printImportBreakdown: true,
       },

vitest.performance-config.ts

@@ -5,6 +5,11 @@ const isEnabled = (value: string | undefined): boolean => {
   return normalized === "1" || normalized === "true";
 };
 
+const isDisabled = (value: string | undefined): boolean => {
+  const normalized = value?.trim().toLowerCase();
+  return normalized === "0" || normalized === "false";
+};
+
 export function loadVitestExperimentalConfig(env: EnvMap = process.env): {
   experimental?: {
     fsModuleCache?: true;
@@ -18,7 +23,7 @@ export function loadVitestExperimentalConfig(env: EnvMap = process.env): {
     printImportBreakdown?: true;
   } = {};
 
-  if (isEnabled(env.OPENCLAW_VITEST_FS_MODULE_CACHE)) {
+  if (!isDisabled(env.OPENCLAW_VITEST_FS_MODULE_CACHE)) {
     experimental.fsModuleCache = true;
   }
   if (isEnabled(env.OPENCLAW_VITEST_IMPORT_DURATIONS)) {