diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9eeac161fdf..7106390f08e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -23,6 +23,7 @@ Docs: https://docs.openclaw.ai
 - Hooks/Inbound metadata: include `guildId` and `channelName` in `message_received` metadata for both plugin and internal hook paths. (#26115) Thanks @davidrudduck.
 - Discord/Component auth: evaluate guild component interactions with command-gating authorizers so unauthorized users no longer get `CommandAuthorized: true` on modal/button events. (#26119) Thanks @bmendonca3.
 - Discord/Typing indicator: prevent stuck typing indicators by sealing channel typing keepalive callbacks after idle/cleanup and ensuring Discord dispatch always marks typing idle even if preview-stream cleanup fails. (#26295) Thanks @ngutman.
+- Tests/Low-memory stability: disable Vitest `vmForks` by default on low-memory local hosts (`<64 GiB`), keep low-profile extension lane parallelism at 4 workers, and align cron isolated-agent tests with `setSessionRuntimeModel` usage to avoid deterministic suite failures. (#26324) Thanks @ngutman.
 - Slack/Inbound media fallback: deliver file-only messages even when Slack media downloads fail by adding a filename placeholder fallback, capping fallback names to the shared media-file limit, and normalizing empty filenames to `file` so attachment-only messages are not silently dropped. (#25181) Thanks @justinhuangcode.
 
 ## 2026.2.24
diff --git a/scripts/test-parallel.mjs b/scripts/test-parallel.mjs
index 0ec8d2fdc5f..35afef83c3f 100644
--- a/scripts/test-parallel.mjs
+++ b/scripts/test-parallel.mjs
@@ -88,14 +88,20 @@ const isCI = process.env.CI === "true" || process.env.GITHUB_ACTIONS === "true";
 const isMacOS = process.platform === "darwin" || process.env.RUNNER_OS === "macOS";
 const isWindows = process.platform === "win32" || process.env.RUNNER_OS === "Windows";
 const isWindowsCi = isCI && isWindows;
+const hostCpuCount = os.cpus().length;
+const hostMemoryGiB = Math.floor(os.totalmem() / 1024 ** 3);
+// Keep aggressive local defaults for high-memory workstations (Mac Studio class).
+const highMemLocalHost = !isCI && hostMemoryGiB >= 96;
+const lowMemLocalHost = !isCI && hostMemoryGiB < 64;
 const nodeMajor = Number.parseInt(process.versions.node.split(".")[0] ?? "", 10);
 // vmForks is a big win for transform/import heavy suites, but Node 24 had
-// regressions with Vitest's vm runtime in this repo. Keep it opt-out via
+// regressions with Vitest's vm runtime in this repo, and low-memory local hosts
+// are more likely to hit per-worker V8 heap ceilings. Keep it opt-out via
 // OPENCLAW_TEST_VM_FORKS=0, and let users force-enable with =1.
 const supportsVmForks = Number.isFinite(nodeMajor) ? nodeMajor !== 24 : true;
 const useVmForks =
   process.env.OPENCLAW_TEST_VM_FORKS === "1" ||
-  (process.env.OPENCLAW_TEST_VM_FORKS !== "0" && !isWindows && supportsVmForks);
+  (process.env.OPENCLAW_TEST_VM_FORKS !== "0" && !isWindows && supportsVmForks && !lowMemLocalHost);
 const disableIsolation = process.env.OPENCLAW_TEST_NO_ISOLATE === "1";
 const runs = [
   ...(useVmForks
@@ -176,11 +182,6 @@ const testProfile =
 const overrideWorkers = Number.parseInt(process.env.OPENCLAW_TEST_WORKERS ?? "", 10);
 const resolvedOverride =
   Number.isFinite(overrideWorkers) && overrideWorkers > 0 ? overrideWorkers : null;
-const hostCpuCount = os.cpus().length;
-const hostMemoryGiB = Math.floor(os.totalmem() / 1024 ** 3);
-// Keep aggressive local defaults for high-memory workstations (Mac Studio class).
-const highMemLocalHost = !isCI && hostMemoryGiB >= 96;
-const lowMemLocalHost = !isCI && hostMemoryGiB < 64;
 const parallelGatewayEnabled =
   process.env.OPENCLAW_TEST_PARALLEL_GATEWAY === "1" || (!isCI && highMemLocalHost);
 // Keep gateway serial by default except when explicitly requested or on high-memory local hosts.
@@ -206,7 +207,7 @@ const defaultWorkerBudget =
     ? {
         unit: 2,
         unitIsolated: 1,
-        extensions: 1,
+        extensions: 4,
         gateway: 1,
       }
     : testProfile === "serial"
@@ -236,7 +237,7 @@ const defaultWorkerBudget =
                 // Sub-64 GiB local hosts are prone to OOM with large vmFork runs.
                 unit: 2,
                 unitIsolated: 1,
-                extensions: 1,
+                extensions: 4,
                 gateway: 1,
               }
             : {
@@ -335,9 +336,15 @@ const runOnce = (entry, extraArgs = []) =>
   new Promise((resolve) => {
     const maxWorkers = maxWorkersForRun(entry.name);
     const reporterArgs = buildReporterArgs(entry, extraArgs);
+    // vmForks with a single worker has shown cross-file leakage in extension suites.
+    // Fall back to process forks when we intentionally clamp that lane to one worker.
+    const entryArgs =
+      entry.name === "extensions" && maxWorkers === 1 && entry.args.includes("--pool=vmForks")
+        ? entry.args.map((arg) => (arg === "--pool=vmForks" ? "--pool=forks" : arg))
+        : entry.args;
     const args = maxWorkers
       ? [
-          ...entry.args,
+          ...entryArgs,
           "--maxWorkers",
           String(maxWorkers),
           ...silentArgs,
@@ -345,7 +352,7 @@ const runOnce = (entry, extraArgs = []) =>
           ...windowsCiArgs,
           ...extraArgs,
         ]
-      : [...entry.args, ...silentArgs, ...reporterArgs, ...windowsCiArgs, ...extraArgs];
+      : [...entryArgs, ...silentArgs, ...reporterArgs, ...windowsCiArgs, ...extraArgs];
     const nodeOptions = process.env.NODE_OPTIONS ?? "";
     const nextNodeOptions = WARNING_SUPPRESSION_FLAGS.reduce(
       (acc, flag) => (acc.includes(flag) ? acc : `${acc} ${flag}`.trim()),
diff --git a/src/cron/isolated-agent/run.skill-filter.test.ts b/src/cron/isolated-agent/run.skill-filter.test.ts
index f1f5ac9d693..02d986819d9 100644
--- a/src/cron/isolated-agent/run.skill-filter.test.ts
+++ b/src/cron/isolated-agent/run.skill-filter.test.ts
@@ -112,6 +112,7 @@ vi.mock("../../cli/outbound-send-deps.js", () => ({
 vi.mock("../../config/sessions.js", () => ({
   resolveAgentMainSessionKey: vi.fn().mockReturnValue("main:default"),
   resolveSessionTranscriptPath: vi.fn().mockReturnValue("/tmp/transcript.jsonl"),
+  setSessionRuntimeModel: vi.fn(),
   updateSessionStore: vi.fn().mockResolvedValue(undefined),
 }));