diff --git a/.github/workflows/ci-build-artifacts-testbox.yml b/.github/workflows/ci-build-artifacts-testbox.yml
index f01271bde66f..e73594ed12f0 100644
--- a/.github/workflows/ci-build-artifacts-testbox.yml
+++ b/.github/workflows/ci-build-artifacts-testbox.yml
@@ -27,7 +27,7 @@ jobs:
     permissions:
       contents: read
     name: "build-artifacts"
-    runs-on: blacksmith-8vcpu-ubuntu-2404
+    runs-on: blacksmith-16vcpu-ubuntu-2404
     timeout-minutes: 35
     steps:
       - name: Begin Testbox
@@ -156,7 +156,7 @@ jobs:
       - name: Build dist on cache miss
         if: steps.dist-cache.outputs.cache-hit != 'true'
         env:
-          NODE_OPTIONS: --max-old-space-size=12288
+          NODE_OPTIONS: --max-old-space-size=16384
         run: pnpm build:ci-artifacts
 
       - name: Build Control UI on cache miss
diff --git a/docs/ci.md b/docs/ci.md
index 0f07f8209089..e3a95ee530f1 100644
--- a/docs/ci.md
+++ b/docs/ci.md
@@ -138,7 +138,7 @@ gh workflow run full-release-validation.yml --ref main -f ref=<branch-or-sha>
 | `ubuntu-24.04`                  | Manual CI dispatch and non-canonical repository fallbacks, CodeQL JavaScript/actions quality scans, workflow-sanity, labeler, auto-response, docs workflows outside CI, and install-smoke preflight so the Blacksmith matrix can queue earlier                                                          |
 | `blacksmith-4vcpu-ubuntu-2404`  | `preflight`, `security-fast`, lower-weight extension shards, `checks-fast-core` except QA Smoke CI, plugin/channel contract shards, most bundled/lower-weight Linux Node shards, `check-guards`, `check-prod-types`, `check-test-types`, selected `check-additional-*` shards, and `check-dependencies` |
 | `blacksmith-8vcpu-ubuntu-2404`  | Retained heavy Linux Node suites, boundary/extension-heavy `check-additional-*` shards, and `android`                                                                                                                                                                                                   |
-| `blacksmith-16vcpu-ubuntu-2404` | QA Smoke CI, `build-artifacts`, `check-lint` (CPU-sensitive enough that 8 vCPU cost more than they saved); install-smoke Docker builds (32-vCPU queue time cost more than it saved)                                                                                                                     |
+| `blacksmith-16vcpu-ubuntu-2404` | QA Smoke CI, `build-artifacts` in CI and Testbox, `check-lint` (CPU-sensitive enough that 8 vCPU cost more than they saved); install-smoke Docker builds (32-vCPU queue time cost more than it saved)                                                                                                   |
 | `blacksmith-8vcpu-windows-2025` | `checks-windows`                                                                                                                                                                                                                                                                                        |
 | `blacksmith-6vcpu-macos-15`     | `macos-node` on `openclaw/openclaw`; forks fall back to `macos-15`                                                                                                                                                                                                                                      |
 | `blacksmith-12vcpu-macos-26`    | `macos-swift` and `ios-build` on `openclaw/openclaw`; forks fall back to `macos-26`                                                                                                                                                                                                                     |
diff --git a/test/scripts/ci-workflow-guards.test.ts b/test/scripts/ci-workflow-guards.test.ts
index 3cdb730154fe..9c6b511c78ad 100644
--- a/test/scripts/ci-workflow-guards.test.ts
+++ b/test/scripts/ci-workflow-guards.test.ts
@@ -16,6 +16,10 @@ function readCiWorkflow() {
   return parse(readFileSync(".github/workflows/ci.yml", "utf8"));
 }
 
+function readBuildArtifactsTestboxWorkflow() {
+  return parse(readFileSync(".github/workflows/ci-build-artifacts-testbox.yml", "utf8"));
+}
+
 function readWorkflowSanityWorkflow() {
   return parse(readFileSync(".github/workflows/workflow-sanity.yml", "utf8"));
 }
@@ -287,10 +291,19 @@ describe("ci workflow guards", () => {
 
   it("uses bundled Node shards and telemetry-backed runner sizes", () => {
     const workflow = readCiWorkflow();
+    const buildArtifactsTestbox = readBuildArtifactsTestboxWorkflow();
     const source = readFileSync(".github/workflows/ci.yml", "utf8");
 
     expect(source).toContain("createNodeTestShardBundles");
     expect(workflow.jobs["build-artifacts"]["runs-on"]).toContain("blacksmith-16vcpu-ubuntu-2404");
+    expect(buildArtifactsTestbox.jobs["build-artifacts"]["runs-on"]).toBe(
+      "blacksmith-16vcpu-ubuntu-2404",
+    );
+    expect(
+      buildArtifactsTestbox.jobs["build-artifacts"].steps.find(
+        (step: { name?: string }) => step.name === "Build dist on cache miss",
+      ).env.NODE_OPTIONS,
+    ).toBe("--max-old-space-size=16384");
     expect(workflow.jobs["checks-node-core-test-nondist-shard"]["runs-on"]).toContain(
       "blacksmith-4vcpu-ubuntu-2404",
     );