diff --git a/infra/deploy-runner/nodedc-b2-vps-deploy b/infra/deploy-runner/nodedc-b2-vps-deploy
index 91d8641..afa79f3 100755
--- a/infra/deploy-runner/nodedc-b2-vps-deploy
+++ b/infra/deploy-runner/nodedc-b2-vps-deploy
@@ -197,6 +197,25 @@ PHASE_FILE_SHA256 = {
     },
 }
 
+# Exact immutable baselines from terminally accepted predecessor artifacts.
+# This is intentionally keyed by both patch id and artifact digest so a later
+# artifact cannot inherit compatibility from a merely similar deployment.
+ACCEPTED_PREDECESSOR_FILE_SHA256 = {
+    "foundation": {
+        (
+            "device-edge-vps-foundation-20260806-003",
+            "1be852f144e9f0fea32af70bebd07a2607b6a1818825094bd4c1b4062064716a",
+        ): {
+            "vps/config/00-nodedc-b2-vps.conf":
+                "cc94d0579f85d0af9746b9ce760bc72980f4a22fb59027e1f5f9c7bf3aaebd64",
+            "vps/config/nftables-foundation.conf":
+                "4d44f902d8d98d1aa8506fca9d9582e700f6424def2b1d667ab2cd5a5ee84934",
+            "deployment/device-edge-vps-foundation-v1.json":
+                "317c98b42520fff3238275908482de7aa611b4ee41c6b1f8062abd2730ab072a",
+        },
+    },
+}
+
 
 class DeployError(RuntimeError):
     pass
@@ -455,8 +474,24 @@ def assert_management_key():
         die("verified Mac management key is missing")
 
 
+def phase_file_sha256(phase: str):
+    expected = dict(PHASE_FILE_SHA256[phase])
+    accepted = [
+        record
+        for record in journal_records(APPLIED_JOURNAL)
+        if record.get("phase") == phase and record.get("status") == "ok"
+    ]
+    if len(accepted) == 1:
+        record = accepted[0]
+        identity = (record.get("patch"), record.get("sha256"))
+        expected.update(
+            ACCEPTED_PREDECESSOR_FILE_SHA256.get(phase, {}).get(identity, {})
+        )
+    return expected
+
+
 def source_file_state(phase: str):
-    expected = PHASE_FILE_SHA256[phase]
+    expected = phase_file_sha256(phase)
     actual = {}
     for relative, digest in expected.items():
         path = LIVE_ROOT / relative
diff --git a/infra/deploy-runner/test_device_edge_vps_artifact.py b/infra/deploy-runner/test_device_edge_vps_artifact.py
index 93c91dc..db399d4 100644
--- a/infra/deploy-runner/test_device_edge_vps_artifact.py
+++ b/infra/deploy-runner/test_device_edge_vps_artifact.py
@@ -261,6 +261,50 @@ class DeviceEdgeVpsArtifactTest(unittest.TestCase):
             self.assertIn("command_transport=disabled", rendered)
             self.assertIn("gelios=untouched", rendered)
 
+    def test_source_baseline_is_pinned_to_the_exact_accepted_predecessor(self):
+        with tempfile.TemporaryDirectory(prefix="nodedc-vps-baseline-") as directory:
+            journal = Path(directory) / "applied.jsonl"
+            old_journal = RUNNER.APPLIED_JOURNAL
+            RUNNER.APPLIED_JOURNAL = journal
+            try:
+                journal.write_text(json.dumps({
+                    "patch": "device-edge-vps-foundation-20260806-003",
+                    "phase": "foundation",
+                    "sha256": (
+                        "1be852f144e9f0fea32af70bebd07a2607b6a1818825094bd4c1b4062064716a"
+                    ),
+                    "status": "ok",
+                }) + "\n", encoding="utf-8")
+                expected = RUNNER.phase_file_sha256("foundation")
+                self.assertEqual(
+                    expected["vps/config/00-nodedc-b2-vps.conf"],
+                    "cc94d0579f85d0af9746b9ce760bc72980f4a22fb59027e1f5f9c7bf3aaebd64",
+                )
+                self.assertEqual(
+                    expected["vps/config/nftables-foundation.conf"],
+                    "4d44f902d8d98d1aa8506fca9d9582e700f6424def2b1d667ab2cd5a5ee84934",
+                )
+                self.assertEqual(
+                    expected["deployment/device-edge-vps-foundation-v1.json"],
+                    "317c98b42520fff3238275908482de7aa611b4ee41c6b1f8062abd2730ab072a",
+                )
+
+                journal.write_text(json.dumps({
+                    "patch": "device-edge-vps-foundation-20260806-003",
+                    "phase": "foundation",
+                    "sha256": "0" * 64,
+                    "status": "ok",
+                }) + "\n", encoding="utf-8")
+                unexpected = RUNNER.phase_file_sha256("foundation")
+                self.assertEqual(
+                    unexpected["vps/config/00-nodedc-b2-vps.conf"],
+                    RUNNER.PHASE_FILE_SHA256[
+                        "foundation"
+                    ]["vps/config/00-nodedc-b2-vps.conf"],
+                )
+            finally:
+                RUNNER.APPLIED_JOURNAL = old_journal
+
     def test_units_and_firewalls_keep_the_required_boundaries(self):
         source_root = SCRIPT_DIR.parent.parent / "device-plane"
         foundation = (source_root / "vps/config/nftables-foundation.conf").read_text()