diff --git a/.github/workflows/acquisition-readiness-scan.yml b/.github/workflows/acquisition-readiness-scan.yml
index 840f33f1c..a825687a5 100644
--- a/.github/workflows/acquisition-readiness-scan.yml
+++ b/.github/workflows/acquisition-readiness-scan.yml
@@ -15,16 +15,33 @@ jobs:
 
     steps:
       - name: checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
 
       - name: setup node
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
         with:
-          node-version: "24"
+          node-version: "24.19.0"
           cache: npm
 
-      - name: install
-        run: npm ci
+      - name: verify package-manager toolchain
+        shell: bash
+        run: |
+          set -euo pipefail
+          test "$(node --version)" = "v24.19.0"
+          test "$(npm --version)" = "11.17.0"
+
+      - name: verify tracked acquisition source before evidence generation
+        shell: bash
+        run: |
+          set -euo pipefail
+          tracked_drift="$(git status --porcelain=v1 --untracked-files=no)"
+          if [ -n "$tracked_drift" ]; then
+            printf '::error::Tracked acquisition source changed before evidence generation:\n%s\n' "$tracked_drift"
+            exit 1
+          fi
+          test "$(git rev-parse HEAD)" = "${{ github.sha }}"
 
       - name: build data-room manifest
         run: npm run acquisition:manifest
@@ -44,8 +61,8 @@ jobs:
 
       - name: upload acquisition artifacts
         if: always()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
         with:
           name: acquisition-readiness-audit
           path: artifacts/acquisition-readiness/**/*
-          if-no-files-found: warn
+          if-no-files-found: error
diff --git a/test/acquisition-readiness-scan-toolchain-integrity.test.ts b/test/acquisition-readiness-scan-toolchain-integrity.test.ts
new file mode 100644
index 000000000..d5453c355
--- /dev/null
+++ b/test/acquisition-readiness-scan-toolchain-integrity.test.ts
@@ -0,0 +1,57 @@
+import { readFileSync } from "node:fs";
+import { describe, expect, it } from "vitest";
+
+const workflow = readFileSync(
+  ".github/workflows/acquisition-readiness-scan.yml",
+  "utf8",
+);
+
+describe("acquisition-readiness workflow supply-chain integrity", () => {
+  it("pins trusted actions and refuses persisted checkout credentials", () => {
+    expect(workflow).toContain(
+      "uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2",
+    );
+    expect(workflow).toContain("persist-credentials: false");
+    expect(workflow).toContain(
+      "uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0",
+    );
+    expect(workflow).toContain(
+      "uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2",
+    );
+    expect(workflow).not.toMatch(
+      /uses:\s+actions\/(?:checkout|setup-node|upload-artifact)@v\d+/,
+    );
+  });
+
+  it("uses exact Node/npm identities without installing dependency code", () => {
+    expect(workflow).toContain('node-version: "24.19.0"');
+    expect(workflow).toContain('test "$(node --version)" = "v24.19.0"');
+    expect(workflow).toContain('test "$(npm --version)" = "11.17.0"');
+    expect(workflow).not.toContain('node-version: "24"');
+    expect(workflow).not.toMatch(/\bnpm\s+(?:ci|install|i)\b/);
+    expect(workflow).not.toContain("      - name: install");
+  });
+
+  it("revalidates tracked buyer-evidence source before evidence generation", () => {
+    const integrityIndex = workflow.indexOf(
+      "      - name: verify tracked acquisition source before evidence generation",
+    );
+    const manifestIndex = workflow.indexOf("      - name: build data-room manifest");
+
+    expect(integrityIndex).toBeGreaterThan(-1);
+    expect(manifestIndex).toBeGreaterThan(integrityIndex);
+
+    const integrityBlock = workflow.slice(integrityIndex, manifestIndex);
+    expect(integrityBlock).toContain("git status --porcelain=v1 --untracked-files=no");
+    expect(integrityBlock).toContain('git rev-parse HEAD');
+    expect(integrityBlock).toContain('github.sha');
+  });
+
+  it("fails closed when retained acquisition evidence is missing", () => {
+    const uploadIndex = workflow.indexOf("      - name: upload acquisition artifacts");
+    expect(uploadIndex).toBeGreaterThan(-1);
+    const uploadBlock = workflow.slice(uploadIndex);
+    expect(uploadBlock).toContain("if-no-files-found: error");
+    expect(uploadBlock).not.toContain("if-no-files-found: warn");
+  });
+});