diff --git a/.github/workflows/e2e.yml b/.github/workflows/e2e.yml
index 02efa1bdf28..09bbe6391e7 100644
--- a/.github/workflows/e2e.yml
+++ b/.github/workflows/e2e.yml
@@ -126,7 +126,7 @@ jobs:
       # scripts still need the Linux toolchain even though this shard reuses
       # the prebuilt Electron output.
       - name: Install native build tools
-        run: sudo apt-get update && sudo apt-get install -y build-essential python3
+        run: sudo apt-get update && sudo apt-get install -y build-essential python3 zsh
 
       # Why: Electron on Linux needs an X display even when the app
       # suppresses mainWindow.show() via ORCA_E2E_HEADLESS. xvfb provides a
@@ -202,7 +202,7 @@ jobs:
           ref: ${{ inputs.ref || github.ref }}
 
       - name: Install native build and headless UI tools
-        run: sudo apt-get update && sudo apt-get install -y build-essential python3 xvfb
+        run: sudo apt-get update && sudo apt-get install -y build-essential python3 xvfb zsh
 
       - name: Setup Node.js
         uses: actions/setup-node@v6
@@ -261,7 +261,7 @@ jobs:
           ref: ${{ inputs.ref || github.ref }}
 
       - name: Install native build and headless UI tools
-        run: sudo apt-get update && sudo apt-get install -y build-essential openssh-client python3 xvfb
+        run: sudo apt-get update && sudo apt-get install -y build-essential openssh-client python3 xvfb zsh
 
       - name: Setup Node.js
         uses: actions/setup-node@v6
diff --git a/config/scripts/pr-e2e-gate-contract.test.mjs b/config/scripts/pr-e2e-gate-contract.test.mjs
index 9ee2095e420..74dd9c25d0c 100644
--- a/config/scripts/pr-e2e-gate-contract.test.mjs
+++ b/config/scripts/pr-e2e-gate-contract.test.mjs
@@ -83,6 +83,15 @@ describe('PR E2E gate contract', () => {
     expect(sshDockerRunner).toContain("'electron-headful'")
   })
 
+  it('installs zsh in every Linux lane that can run paired startup readiness', () => {
+    for (const jobName of ['e2e', 'changed-e2e', 'ssh-docker-watcher-isolation']) {
+      const installStep = e2eWorkflow.jobs[jobName].steps.find((step) =>
+        step.name.startsWith('Install native build')
+      )
+      expect(installStep.run, jobName).toMatch(/\bzsh\b/)
+    }
+  })
+
   it('keeps dedicated E2E workflows out of pull request CI', () => {
     const dedicatedWorkflows = [
       'golden-e2e-experiment.yml',