diff --git a/src/onboarding/adapters/postgres/restore-validation.ts b/src/onboarding/adapters/postgres/restore-validation.ts
index 32bdd24..0fc81f4 100644
--- a/src/onboarding/adapters/postgres/restore-validation.ts
+++ b/src/onboarding/adapters/postgres/restore-validation.ts
@@ -184,6 +184,15 @@ const FUNCTION_BODY_SHA256 = {
 } as const;
 
 const REQUIRED_TRIGGERS = [
+  {
+    minimumMigration: 5,
+    maximumMigration: 7,
+    triggerName: "external_snapshots_immutable",
+    tableName: "external_source_snapshots",
+    functionName: "reject_external_history_mutation",
+    functionBodySha256: FUNCTION_BODY_SHA256.reject_external_history_mutation,
+    events: ["DELETE", "UPDATE"],
+  },
   {
     minimumMigration: 5,
     triggerName: "external_content_immutable",
@@ -444,7 +453,10 @@ export function assessRestoredDatabaseEvidence(
     uniqueTriggers.size === evidence.triggers.length &&
     evidence.triggers.every(({ enabled }) => enabled === "origin") &&
     REQUIRED_TRIGGERS.filter(
-      ({ minimumMigration }) => minimumMigration <= latestMigration,
+      (required) =>
+        required.minimumMigration <= latestMigration &&
+        (!("maximumMigration" in required) ||
+          latestMigration <= required.maximumMigration),
     ).every((required) =>
       evidence.triggers.some(
         (trigger) =>
diff --git a/tests/unit/onboarding/restored-database-validation.test.ts b/tests/unit/onboarding/restored-database-validation.test.ts
index 4d3d3a0..77c1e56 100644
--- a/tests/unit/onboarding/restored-database-validation.test.ts
+++ b/tests/unit/onboarding/restored-database-validation.test.ts
@@ -454,6 +454,60 @@ describe("production restored-database validation", () => {
     });
   });
 
+  it("requires the original snapshot immutability trigger through migration 007", () => {
+    const accountId = randomUUID();
+    const checksums = Array.from({ length: 7 }, (_, index) =>
+      (index + 1).toString(16).padStart(64, "0"),
+    );
+    const migration007Triggers = REQUIRED_TRIGGERS.map((entry) =>
+      entry.triggerName === "external_snapshots_immutable"
+        ? trigger(
+            "external_snapshots_immutable",
+            "external_source_snapshots",
+            "reject_external_history_mutation",
+            ["DELETE", "UPDATE"],
+          )
+        : entry.triggerName === "external_classification_transition_valid"
+          ? {
+              ...entry,
+              functionBodySha256:
+                "7e29bd82153cfd0976b925d2dd6a18879f3c9e16a4c79faf1586fdddb9aad718",
+            }
+          : entry,
+    );
+    const valid = evidence({
+      accountId,
+      checksums,
+      triggers: migration007Triggers,
+    });
+
+    expect(
+      assessRestoredDatabaseEvidence(valid, {
+        expectedMigrations: valid.migrations,
+        installationAccountId: accountId,
+        expectedActiveApiKeys: 2,
+        expectedDatabase: "postgres",
+        expectedState: databaseStateExpectation(valid),
+      }),
+    ).toMatchObject({ latestMigration: "007", ready: true });
+
+    const missing = {
+      ...valid,
+      triggers: valid.triggers.filter(
+        ({ triggerName }) => triggerName !== "external_snapshots_immutable",
+      ),
+    };
+    expect(() =>
+      assessRestoredDatabaseEvidence(missing, {
+        expectedMigrations: missing.migrations,
+        installationAccountId: accountId,
+        expectedActiveApiKeys: 2,
+        expectedDatabase: "postgres",
+        expectedState: databaseStateExpectation(missing),
+      }),
+    ).toThrow(/restore validation/i);
+  });
+
   it("rejects the superseded classification-trigger function body after migration 010", () => {
     const accountId = randomUUID();
     const checksums = Array.from({ length: 10 }, (_, index) =>