diff --git a/src/domain/sourceToBundleComparison.ts b/src/domain/sourceToBundleComparison.ts
index df6965c0f..64155fccd 100644
--- a/src/domain/sourceToBundleComparison.ts
+++ b/src/domain/sourceToBundleComparison.ts
@@ -163,7 +163,7 @@ const compareMappings = (
     omittedCandidateReferences += omittedCandidates;
     const classification = classifyMapping(
       retainedCandidates,
-      omittedEvaluations === 0,
+      omittedCandidates === 0,
       projection.absenceComplete,
     );
     const semantic = {
diff --git a/src/domain/webCaptureDiff.ts b/src/domain/webCaptureDiff.ts
index e3810b061..ca267d88c 100644
--- a/src/domain/webCaptureDiff.ts
+++ b/src/domain/webCaptureDiff.ts
@@ -39,6 +39,13 @@ const dimensionSchema = z.object({
   omitted_changes: z.number().int().min(0),
   reason: z.string().nullable(),
 });
+const legacyUnknownDimension = {
+  status: "unknown" as const,
+  total_changes: 0,
+  changes: [],
+  omitted_changes: 0,
+  reason: "Dimension was not recorded by this version 1 capture diff.",
+};
 
 /** Completeness-aware changes across stable browser evidence dimensions. */
 export const webCaptureDiffSchema = z.object({
@@ -53,8 +60,8 @@ export const webCaptureDiffSchema = z.object({
     network: dimensionSchema,
     metadata: dimensionSchema,
     webmcp: dimensionSchema,
-    accessibility: dimensionSchema,
-    storage: dimensionSchema,
+    accessibility: dimensionSchema.default(legacyUnknownDimension),
+    storage: dimensionSchema.default(legacyUnknownDimension),
   }),
   limitations: z.array(z.string()),
 });
diff --git a/tests/sourceToBundleComparison.test.ts b/tests/sourceToBundleComparison.test.ts
index 5a0a25485..12840a26d 100644
--- a/tests/sourceToBundleComparison.test.ts
+++ b/tests/sourceToBundleComparison.test.ts
@@ -116,6 +116,23 @@ describe("historical source to bundle comparison", () => {
     expect(result.coverage.status).toBe("partial");
   });
 
+  it("keeps exact mappings unknown when candidate output is truncated", () => {
+    const result = compareSourceToBundle({
+      reference: historicalGraph("complete"),
+      application: {
+        evidenceId: EVIDENCE_ID,
+        rootArtifactSha256: HASH.artifact,
+        graph: applicationGraph("complete"),
+      },
+      limits: { ...limits(), max_candidate_nodes: 1 },
+    });
+
+    expect(item(result, "src/duplicated.ts").status).toBe("unknown");
+    expect(
+      item(result, "src/duplicated.ts").omitted_candidates,
+    ).toBeGreaterThan(0);
+  });
+
   it("reports the candidate frontier instead of deciding past a limit", () => {
     const result = compareSourceToBundle({
       reference: historicalGraph("complete", ["src/split.ts"]),
diff --git a/tests/webCaptureDiff.test.ts b/tests/webCaptureDiff.test.ts
index d3b110ae7..37f7c9a48 100644
--- a/tests/webCaptureDiff.test.ts
+++ b/tests/webCaptureDiff.test.ts
@@ -5,6 +5,7 @@ import { inspectWebPageInputSchema } from "../src/domain/browserObservation.js";
 import {
   compareWebCaptures,
   compareWebCapturesInputSchema,
+  webCaptureDiffSchema,
 } from "../src/domain/webCaptureDiff.js";
 import {
   startFakeCdpBrowser,
@@ -59,6 +60,17 @@ describe("web capture diff", () => {
       status: "unknown",
       total_changes: 0,
     });
+    const {
+      accessibility: _accessibility,
+      storage: _storage,
+      ...legacy
+    } = result.dimensions;
+    const parsedLegacy = webCaptureDiffSchema.parse({
+      ...result,
+      dimensions: legacy,
+    });
+    expect(parsedLegacy.dimensions.accessibility.status).toBe("unknown");
+    expect(parsedLegacy.dimensions.storage.status).toBe("unknown");
   });
 
   it("does not claim unchanged when a relevant section is incomplete", async () => {