diff --git a/scripts/lib/vitest-local-scheduling.mjs b/scripts/lib/vitest-local-scheduling.mjs
index 12434c3b650..4ef453839a8 100644
--- a/scripts/lib/vitest-local-scheduling.mjs
+++ b/scripts/lib/vitest-local-scheduling.mjs
@@ -1,4 +1,4 @@
-/** @typedef {{ cpuCount?: number, loadAverage1m?: number, totalMemoryBytes?: number }} VitestHostInfo */
+/** @typedef {{ cpuCount?: number, loadAverage1m?: number, totalMemoryBytes?: number, freeMemoryBytes?: number }} VitestHostInfo */
 /** @typedef {{ maxWorkers: number, fileParallelism: boolean, throttledBySystem: boolean }} LocalVitestScheduling */
 
 import os from "node:os";
@@ -30,9 +30,24 @@ export function detectVitestHostInfo() {
       typeof os.availableParallelism === "function" ? os.availableParallelism() : os.cpus().length,
     loadAverage1m: os.loadavg()[0] ?? 0,
     totalMemoryBytes: os.totalmem(),
+    freeMemoryBytes: os.freemem(),
   };
 }
 
+function resolveMemoryPressureWorkerLimit(system) {
+  const freeMemoryGb = (system.freeMemoryBytes ?? 0) / 1024 ** 3;
+  if (!Number.isFinite(freeMemoryGb) || freeMemoryGb <= 0) {
+    return null;
+  }
+  if (freeMemoryGb <= 4) {
+    return 1;
+  }
+  if (freeMemoryGb <= 8) {
+    return 2;
+  }
+  return null;
+}
+
 export function resolveLocalVitestMaxWorkers(
   env = process.env,
   system = detectVitestHostInfo(),
@@ -112,6 +127,16 @@ export function resolveLocalVitestScheduling(
     };
   }
 
+  const memoryPressureLimit = resolveMemoryPressureWorkerLimit(system);
+  if (memoryPressureLimit !== null && inferred > memoryPressureLimit) {
+    const maxWorkers = memoryPressureLimit;
+    return {
+      maxWorkers,
+      fileParallelism: maxWorkers > 1,
+      throttledBySystem: true,
+    };
+  }
+
   if (loadRatio >= 1) {
     const maxWorkers = Math.max(1, Math.floor(inferred / 2));
     return {
@@ -149,6 +174,22 @@ export function shouldUseLargeLocalFullSuiteProfile(
 }
 
 export function resolveLocalFullSuiteProfile(env = process.env, system = detectVitestHostInfo()) {
+  if (!isSystemThrottleDisabled(env)) {
+    const memoryPressureLimit = resolveMemoryPressureWorkerLimit(system);
+    if (memoryPressureLimit === 1) {
+      return {
+        shardParallelism: 1,
+        vitestMaxWorkers: 1,
+      };
+    }
+    if (memoryPressureLimit === 2) {
+      return {
+        shardParallelism: 2,
+        vitestMaxWorkers: 1,
+      };
+    }
+  }
+
   if (shouldUseLargeLocalFullSuiteProfile(env, system)) {
     return {
       shardParallelism: LARGE_LOCAL_FULL_SUITE_PARALLELISM,
diff --git a/test/scripts/vitest-local-scheduling.test.ts b/test/scripts/vitest-local-scheduling.test.ts
index 70de3289a9f..3dacf7ea7be 100644
--- a/test/scripts/vitest-local-scheduling.test.ts
+++ b/test/scripts/vitest-local-scheduling.test.ts
@@ -31,6 +31,7 @@ describe("vitest local full-suite profile", () => {
       cpuCount: 14,
       loadAverage1m: 14,
       totalMemoryBytes: 48 * 1024 ** 3,
+      freeMemoryBytes: 32 * 1024 ** 3,
     };
 
     expect(shouldUseLargeLocalFullSuiteProfile({}, hostInfo)).toBe(false);
@@ -53,4 +54,62 @@ describe("vitest local full-suite profile", () => {
       vitestMaxWorkers: 1,
     });
   });
+
+  it("serializes local full-suite shards under critical memory pressure", () => {
+    const hostInfo = {
+      cpuCount: 10,
+      loadAverage1m: 0,
+      totalMemoryBytes: 24 * 1024 ** 3,
+      freeMemoryBytes: 3 * 1024 ** 3,
+    };
+
+    expect(resolveLocalVitestScheduling({}, hostInfo, "threads")).toEqual({
+      maxWorkers: 1,
+      fileParallelism: false,
+      throttledBySystem: true,
+    });
+    expect(resolveLocalFullSuiteProfile({}, hostInfo)).toEqual({
+      shardParallelism: 1,
+      vitestMaxWorkers: 1,
+    });
+  });
+
+  it("limits local full-suite shards when memory is tight", () => {
+    const hostInfo = {
+      cpuCount: 10,
+      loadAverage1m: 0,
+      totalMemoryBytes: 24 * 1024 ** 3,
+      freeMemoryBytes: 6 * 1024 ** 3,
+    };
+
+    expect(resolveLocalVitestScheduling({}, hostInfo, "threads")).toEqual({
+      maxWorkers: 2,
+      fileParallelism: true,
+      throttledBySystem: true,
+    });
+    expect(resolveLocalFullSuiteProfile({}, hostInfo)).toEqual({
+      shardParallelism: 2,
+      vitestMaxWorkers: 1,
+    });
+  });
+
+  it("lets explicit system throttle opt-out ignore memory pressure", () => {
+    const env = { OPENCLAW_VITEST_DISABLE_SYSTEM_THROTTLE: "1" };
+    const hostInfo = {
+      cpuCount: 10,
+      loadAverage1m: 0,
+      totalMemoryBytes: 24 * 1024 ** 3,
+      freeMemoryBytes: 3 * 1024 ** 3,
+    };
+
+    expect(resolveLocalVitestScheduling(env, hostInfo, "threads")).toEqual({
+      maxWorkers: 4,
+      fileParallelism: true,
+      throttledBySystem: false,
+    });
+    expect(resolveLocalFullSuiteProfile(env, hostInfo)).toEqual({
+      shardParallelism: 4,
+      vitestMaxWorkers: 1,
+    });
+  });
 });