diff --git a/.github/workflows/platform-vitest-main.yaml b/.github/workflows/platform-vitest-main.yaml
index 79ffb5d479b..0eecd0c8b07 100644
--- a/.github/workflows/platform-vitest-main.yaml
+++ b/.github/workflows/platform-vitest-main.yaml
@@ -134,6 +134,11 @@ jobs:
           stat --version | head -n 1
           awk --version | head -n 1
 
+      - name: Install pinned OpenShell
+        env:
+          NEMOCLAW_NON_INTERACTIVE: "1"
+        run: env -u GH_TOKEN -u GITHUB_TOKEN bash scripts/install-openshell.sh
+
       - name: Install dependencies
         run: |
           npm ci --ignore-scripts
diff --git a/src/lib/onboard/gateway-host-runtime.test.ts b/src/lib/onboard/gateway-host-runtime.test.ts
index c7b268fc1ac..5d4fbde19b6 100644
--- a/src/lib/onboard/gateway-host-runtime.test.ts
+++ b/src/lib/onboard/gateway-host-runtime.test.ts
@@ -1,7 +1,7 @@
 // SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-import { afterEach, describe, expect, it, vi } from "vitest";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 import { createGatewayHostRuntime, type GatewayHostRuntimeDeps } from "./gateway-host-runtime";
 import { GATEWAY_MANAGEMENT_ENV_VAR } from "./gateway-management";
@@ -29,6 +29,10 @@ const DECLARATION = {
 
 const ORIGINAL_ENV = { ...process.env };
 
+beforeEach(() => {
+  vi.spyOn(process, "platform", "get").mockReturnValue("linux");
+});
+
 afterEach(() => {
   process.env = { ...ORIGINAL_ENV };
   vi.restoreAllMocks();
diff --git a/test/e2e/docs/README.md b/test/e2e/docs/README.md
index dddbc5ad0f6..dcd631b0bcf 100644
--- a/test/e2e/docs/README.md
+++ b/test/e2e/docs/README.md
@@ -284,9 +284,10 @@ test/e2e/
   reporting and scorecards. The workflow boundary requires every selected job
   shard to upload its evidence artifact.
 - `.github/workflows/platform-vitest-main.yaml` runs the full Vitest suite in
-  four independent shards on each of macOS and WSL. Each macOS shard has a
-  30-minute budget, each WSL shard has a 90-minute budget, and WSL runs its
-  additional root-required contracts on shard 1 only.
+  four independent shards on each of macOS and WSL, with `fail-fast` disabled.
+  Each macOS shard installs the pinned OpenShell formula and has a 30-minute
+  budget. Each WSL shard has a 90-minute budget, and WSL runs its additional
+  root-required contracts on shard 1 only.
   `.github/workflows/e2e-branch-validation.yaml`, `macos-e2e.yaml`,
   `wsl-e2e.yaml`, and `regression-e2e.yaml` call focused E2E targets directly
   for their E2E coverage. Individual repository-hosted targets, including
diff --git a/test/onboard-exit-handler.test.ts b/test/onboard-exit-handler.test.ts
index 0a0478664d4..c067f33edb7 100644
--- a/test/onboard-exit-handler.test.ts
+++ b/test/onboard-exit-handler.test.ts
@@ -21,6 +21,7 @@ type OnboardModule = typeof import("../src/lib/onboard") & {
 const require = createRequire(import.meta.url);
 const onboard = require("../src/lib/onboard.js") as OnboardModule;
 const onboardSession = onboard.onboardSession;
+const ONBOARD_FIXTURE_PATH = ["/usr/bin", "/bin"].join(path.delimiter);
 const originalHome = process.env.HOME;
 const restoreOriginalHome =
   originalHome === undefined
@@ -175,6 +176,7 @@ const { onboard } = require(${onboardPath});
       env: {
         ...process.env,
         HOME: tmpDir,
+        PATH: ONBOARD_FIXTURE_PATH,
         TMPDIR: tmpDir,
         NEMOCLAW_TEST_NO_SLEEP: "1",
       },
@@ -330,6 +332,7 @@ const { onboard } = require(${onboardPath});
       env: {
         ...process.env,
         HOME: tmpDir,
+        PATH: ONBOARD_FIXTURE_PATH,
         TMPDIR: tmpDir,
         NEMOCLAW_TEST_NO_SLEEP: "1",
         NEMOCLAW_OPENSHELL_BIN: openshellPath,
diff --git a/test/platform-vitest-main-workflow.test.ts b/test/platform-vitest-main-workflow.test.ts
index db0550e8572..721e8f234ea 100644
--- a/test/platform-vitest-main-workflow.test.ts
+++ b/test/platform-vitest-main-workflow.test.ts
@@ -34,6 +34,7 @@ describe("platform Vitest main workflow", () => {
     const checkout = step("macos-vitest", "Checkout");
     const setupPython = step("macos-vitest", "Setup Python");
     const install = step("macos-vitest", "Install macOS test dependencies");
+    const installOpenShell = step("macos-vitest", "Install pinned OpenShell");
     const run = install.run ?? "";
 
     expect(job("macos-vitest")["timeout-minutes"]).toBe(30);
@@ -49,6 +50,9 @@ describe("platform Vitest main workflow", () => {
       stepNames.indexOf("Install macOS test dependencies"),
     );
     expect(stepNames.indexOf("Install macOS test dependencies")).toBeLessThan(
+      stepNames.indexOf("Install pinned OpenShell"),
+    );
+    expect(stepNames.indexOf("Install pinned OpenShell")).toBeLessThan(
       stepNames.indexOf("Run full Vitest suite on macOS"),
     );
     expect(setupPython.uses).toBe("actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97");
@@ -66,6 +70,12 @@ describe("platform Vitest main workflow", () => {
     expect(run).toContain("--only-binary=:all:");
     expect(run).toContain("--require-hashes");
     expect(run).toContain(`--requirement ${MACOS_REQUIREMENTS_PATH}`);
+    expect(installOpenShell.env).toMatchObject({
+      NEMOCLAW_NON_INTERACTIVE: "1",
+    });
+    expect(installOpenShell.run).toBe(
+      "env -u GH_TOKEN -u GITHUB_TOKEN bash scripts/install-openshell.sh",
+    );
     expect(step("macos-vitest", "Run full Vitest suite on macOS").run).toContain(
       '--shard="${{ matrix.shard }}/4"',
     );