diff --git a/.github/workflows/gitnexus-skill-evolution.yml b/.github/workflows/gitnexus-skill-evolution.yml
index 936b46a92..66e87ad18 100644
--- a/.github/workflows/gitnexus-skill-evolution.yml
+++ b/.github/workflows/gitnexus-skill-evolution.yml
@@ -151,6 +151,17 @@ jobs:
           test "$("${canary_runtime}/node_modules/@anthropic-ai/claude-code-linux-x64/claude" --version)" = \
             '2.1.214 (Claude Code)'
 
+      - name: Install monorepo root dependencies
+        run: |
+          set -euo pipefail
+          # The benchmark's task bindings sandbox-copy node_modules from the
+          # monorepo root as well as gitnexus-shared and gitnexus (see the
+          # sandbox_copy entries in tasks.scenarios.yaml). The two steps below
+          # install the subpackage trees; the root tree needs its own install
+          # or capture_task_dependency_binding aborts at task binding on the
+          # missing root node_modules.
+          npm ci
+
       - name: Build pinned shared runtime
         run: |
           set -euo pipefail
diff --git a/gitnexus/test/unit/skill-evolution-workflow.test.ts b/gitnexus/test/unit/skill-evolution-workflow.test.ts
index 50b93ec02..c2c3240fe 100644
--- a/gitnexus/test/unit/skill-evolution-workflow.test.ts
+++ b/gitnexus/test/unit/skill-evolution-workflow.test.ts
@@ -59,6 +59,20 @@ describe('gitnexus skill-evolution workflow contract', () => {
     expect(provision).toContain('${HOME}/GitNexus');
   });
 
+  it('installs node_modules for the monorepo root, gitnexus-shared, and gitnexus', () => {
+    // The benchmark sandbox-copies node_modules from all three (tasks.scenarios.yaml).
+    // The root tree was absent on the first real run because only the two subpackage
+    // steps ran, so capture_task_dependency_binding aborted at task binding.
+    const rootStep = evolveJob?.steps?.find(
+      ({ name }) => name === 'Install monorepo root dependencies',
+    );
+    expect(rootStep).toBeDefined();
+    expect(rootStep).not.toHaveProperty('working-directory'); // installs at the repo root
+    expect(String(rootStep?.run)).toContain('npm ci');
+    expect(stepRun('Build pinned shared runtime')).toContain('npm ci');
+    expect(stepRun('Install and build pinned GitNexus runtime')).toContain('npm ci');
+  });
+
   it('names the promotion branch with the run attempt for re-run recovery', () => {
     const openPr = stepRun('Open the promotion PR');
     expect(openPr).toContain('${GITHUB_RUN_ID}-${GITHUB_RUN_ATTEMPT}');