diff --git a/src/contracts/javascript/javascriptApplicationWorkflowExamples.ts b/src/contracts/javascript/javascriptApplicationWorkflowExamples.ts
index 948670fb41..7834ee50a6 100644
--- a/src/contracts/javascript/javascriptApplicationWorkflowExamples.ts
+++ b/src/contracts/javascript/javascriptApplicationWorkflowExamples.ts
@@ -1,4 +1,4 @@
-import { jsonObjectSchema } from "../../domain/jsonValue.js";
+import type { JsonValue } from "../../domain/jsonValue.js";
 import { createEvidence } from "../../domain/evidence.js";
 import {
   readRuntimeReconciliationInput,
@@ -73,7 +73,7 @@ export const JAVASCRIPT_APPLICATION_VERSION_COMPARISON_EXAMPLE = {
 };
 
 /** Historical source inventory compared with inline application Evidence. */
-export const SOURCE_TO_BUNDLE_COMPARISON_EXAMPLE = jsonObjectSchema.parse({
+export const SOURCE_TO_BUNDLE_COMPARISON_EXAMPLE = {
   reference: createHistoricalSourceGraph({
     schema: "HistoricalSourceGraph",
     authority: "historical-reference",
@@ -112,4 +112,4 @@ export const SOURCE_TO_BUNDLE_COMPARISON_EXAMPLE = jsonObjectSchema.parse({
     limitations: [],
   }),
   application: JAVASCRIPT_APPLICATION_EVIDENCE_EXAMPLE,
-});
+} satisfies Readonly<Record<string, JsonValue>>;
diff --git a/src/domain/referenceSourceGraph.test.ts b/src/domain/referenceSourceGraph.test.ts
index 7f0576763f..70cdfb8f69 100644
--- a/src/domain/referenceSourceGraph.test.ts
+++ b/src/domain/referenceSourceGraph.test.ts
@@ -131,6 +131,25 @@ describe("historical source graph", () => {
     ).toThrow(/Unicode code point/u);
   });
 
+  it("omits absent local diagnostics and rejects explicitly undefined non-JSON metadata", () => {
+    const input = graphInput();
+    const graph = createHistoricalSourceGraph(input);
+    expect(
+      graph.entries.every(
+        (entry) => !Object.hasOwn(entry, "local_diagnostics"),
+      ),
+    ).toBe(true);
+    expect(() =>
+      createHistoricalSourceGraph({
+        ...input,
+        entries: input.entries.map((entry) => ({
+          ...entry,
+          local_diagnostics: undefined,
+        })),
+      }),
+    ).toThrow();
+  });
+
   it("builds and verifies internal root and manifest commitments", () => {
     const graph = createHistoricalSourceGraph(graphInput());
     const first = createHistoricalSourceManifest(graph);
diff --git a/src/domain/referenceSourceGraph.ts b/src/domain/referenceSourceGraph.ts
index 9ac3163ff3..80a1ce6dbb 100644
--- a/src/domain/referenceSourceGraph.ts
+++ b/src/domain/referenceSourceGraph.ts
@@ -41,7 +41,7 @@ const entryBaseShape = {
   classifications: z.array(classificationSchema).min(1),
   limitations: z.array(boundedTextSchema),
   // Host presentation is retained evidence, separate from relocatable semantics.
-  local_diagnostics: z.array(boundedTextSchema).optional(),
+  local_diagnostics: z.array(boundedTextSchema).exactOptional(),
 };
 
 const sourceFileBaseShape = {