diff --git a/scripts/test-local.mjs b/scripts/test-local.mjs
index 8e058a1..7ee44eb 100644
--- a/scripts/test-local.mjs
+++ b/scripts/test-local.mjs
@@ -1,5 +1,5 @@
 import assert from "node:assert/strict";
-import { readFileSync } from "node:fs";
+import { readFileSync, writeFileSync } from "node:fs";
 import { mkdtemp, rm } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
@@ -331,9 +331,124 @@ async function runWarningTests() {
   }
 }
 
+// Runs `callback` with console.warn captured (and silenced), returning the
+// collected warning messages so tests can assert a warning was surfaced
+// without polluting test output.
+async function withCapturedWarnings(callback) {
+  const messages = [];
+  const originalWarn = console.warn;
+  console.warn = (...args) => messages.push(args.join(" "));
+
+  try {
+    await callback();
+  } finally {
+    console.warn = originalWarn;
+  }
+
+  return messages;
+}
+
+async function runWarningRegistryHardeningTests() {
+  const validWarning = {
+    messageId: "CVE_SCHEMA_DEPRECATION",
+    notificationMessage: "This field will be removed in a future schema version.",
+    notificationDetails: "Use the replacement field before the warning end date.",
+    schemaPath: "#/definitions/example/properties/deprecatedField",
+    dateAdded: "2026-07-01T00:00:00.000Z",
+    dateUpdated: "2026-07-02T00:00:00.000Z",
+    dateStart: "2026-08-01T00:00:00.000Z",
+    dateEnd: "2027-08-01T00:00:00.000Z",
+    priority: 1,
+  };
+
+  const temporaryDirectory = await mkdtemp(join(tmpdir(), "cve-warning-registry-hardening-"));
+  const malformedJsonPath = join(temporaryDirectory, "malformed.json");
+  const wrongShapePath = join(temporaryDirectory, "wrong-shape.json");
+
+  try {
+    // A registry file containing invalid JSON must not throw on construction,
+    // and must surface the problem via console.warn while yielding no warnings.
+    writeFileSync(malformedJsonPath, "{ this is not valid json", "utf8");
+    const malformedWarnings = await withCapturedWarnings(() => {
+      const registry = new WarningRegistry(malformedJsonPath);
+      assert.deepEqual(registry.warnings, []);
+
+      // Diagnostics construction reads the registry; it must not throw either.
+      const diagnostics = Diagnostics.success(new WarningRegistry(malformedJsonPath));
+      assert.deepEqual(diagnostics.warnings, []);
+    });
+    assert.ok(
+      malformedWarnings.some((message) => message.includes(malformedJsonPath)),
+      "expected a console.warn mentioning the malformed registry path",
+    );
+
+    // Valid JSON of the wrong shape is treated the same way: fail soft, no throw,
+    // and the problem is surfaced on stderr.
+    writeFileSync(wrongShapePath, JSON.stringify([{ notAWarning: true }]), "utf8");
+    const wrongShapeWarnings = await withCapturedWarnings(() => {
+      const registry = new WarningRegistry(wrongShapePath);
+      assert.deepEqual(registry.warnings, []);
+    });
+    assert.ok(
+      wrongShapeWarnings.some((message) => message.includes(wrongShapePath)),
+      "expected a console.warn mentioning the wrong-shape registry path",
+    );
+
+    // addWarning must refuse to overwrite an unreadable registry so its contents
+    // are never silently destroyed; the file stays byte-for-byte unchanged. This
+    // holds for both malformed JSON and valid-JSON-of-the-wrong-shape.
+    for (const corruptPath of [malformedJsonPath, wrongShapePath]) {
+      const before = readFileSync(corruptPath, "utf8");
+      await withCapturedWarnings(() => {
+        const registry = new WarningRegistry(corruptPath);
+        assert.throws(() => registry.addWarning(validWarning), /refusing to modify/);
+      });
+      assert.equal(readFileSync(corruptPath, "utf8"), before);
+    }
+
+    // A corruption episode is reported once (deduped), but after a successful
+    // read the dedupe entry is cleared, so a later re-corruption warns again and
+    // is not silently swallowed.
+    const recurringPath = join(temporaryDirectory, "recurring.json");
+
+    writeFileSync(recurringPath, "broken", "utf8");
+    const firstCorruption = await withCapturedWarnings(() => {
+      new WarningRegistry(recurringPath);
+      // A second construction during the same episode must not warn again.
+      new WarningRegistry(recurringPath);
+    });
+    assert.equal(
+      firstCorruption.filter((message) => message.includes(recurringPath)).length,
+      1,
+      "a corruption episode should warn exactly once",
+    );
+
+    // Repair with a valid (empty) registry: reads cleanly, no warning.
+    writeFileSync(recurringPath, "[]", "utf8");
+    const afterRepair = await withCapturedWarnings(() => {
+      const registry = new WarningRegistry(recurringPath);
+      assert.deepEqual(registry.warnings, []);
+    });
+    assert.equal(afterRepair.length, 0, "a valid registry must not warn");
+
+    // Re-corrupt: the new episode must be reported again.
+    writeFileSync(recurringPath, "broken again", "utf8");
+    const secondCorruption = await withCapturedWarnings(() => {
+      new WarningRegistry(recurringPath);
+    });
+    assert.ok(
+      secondCorruption.some((message) => message.includes(recurringPath)),
+      "a new corruption episode after repair must warn again",
+    );
+  } finally {
+    await rm(temporaryDirectory, { recursive: true, force: true });
+  }
+}
+
 runSmokeTests();
 runSchemaValidationIntegrationTests();
 runBusinessRuleIntegrationTests();
 await runWarningTests();
+await runWarningRegistryHardeningTests();
 
 console.log("Local tests passed.");
diff --git a/src/registry/warnings.ts b/src/registry/warnings.ts
index 00dee83..15c23c2 100644
--- a/src/registry/warnings.ts
+++ b/src/registry/warnings.ts
@@ -74,10 +74,20 @@ function defaultWarningRegistryPath(): string {
   );
 }
 
+/**
+ * Registry paths already reported as unreadable during the current corruption
+ * episode. Validation constructs a WarningRegistry per Diagnostics result, so
+ * this keeps a corrupt registry from emitting one identical stderr line per
+ * validated record. Entries are cleared on the next successful read, so a later
+ * re-corruption of the same path is reported again.
+ */
+const warnedRegistryPaths = new Set<string>();
+
 /** File-backed registry for non-fatal warning messages. */
 export class WarningRegistry {
   readonly #registryPath: string;
   readonly #warnings: DiagnosticWarning[];
+  readonly #loadError: Error | null;
 
   /**
    * Creates a warning registry.
@@ -88,7 +98,10 @@ export class WarningRegistry {
     this.#registryPath = registryPath instanceof URL
       ? fileURLToPath(registryPath)
       : registryPath;
-    this.#warnings = this.read();
+
+    const { warnings, error } = this.read();
+    this.#warnings = warnings;
+    this.#loadError = error;
   }
 
   /** All warnings currently registered. */
@@ -141,22 +154,55 @@ export class WarningRegistry {
       throw new TypeError('Invalid diagnostic warning');
     }
 
+    if (this.#loadError) {
+      // The existing file could not be parsed. Refuse to append, otherwise
+      // save() would overwrite the unreadable file and destroy its contents.
+      throw new Error(
+        `WarningRegistry: refusing to modify ${this.#registryPath} because it could not be read (${this.#loadError.message}).`,
+      );
+    }
+
     this.#warnings.push({ ...warning });
     this.save();
   }
 
-  private read(): DiagnosticWarning[] {
+  private read(): { warnings: DiagnosticWarning[]; error: Error | null } {
     if (!existsSync(this.#registryPath)) {
-      return [];
+      // A missing file is a valid empty state, not corruption; clear any prior
+      // dedupe entry so a later re-corruption of this path is reported again.
+      warnedRegistryPaths.delete(this.#registryPath);
+      return { warnings: [], error: null };
     }
 
-    const data: unknown = JSON.parse(readFileSync(this.#registryPath, 'utf8'));
-
-    if (!Array.isArray(data) || !data.every(isDiagnosticWarning)) {
-      throw new TypeError(`Invalid warning registry: ${this.#registryPath}`);
+    try {
+      const data: unknown = JSON.parse(readFileSync(this.#registryPath, 'utf8'));
+
+      if (!Array.isArray(data) || !data.every(isDiagnosticWarning)) {
+        throw new TypeError(`Invalid warning registry: ${this.#registryPath}`);
+      }
+
+      // A successful read ends any prior corruption episode for this path.
+      warnedRegistryPaths.delete(this.#registryPath);
+      return { warnings: data.map((warning) => ({ ...warning })), error: null };
+    } catch (error) {
+      // Fail soft: validation constructs a WarningRegistry for every Diagnostics
+      // result, so a malformed registry file must not throw and take down
+      // otherwise-successful validation. Surface the problem on stderr and
+      // continue with no warnings; addWarning still refuses to overwrite the
+      // unreadable file. Warn once per corruption episode per path (the entry is
+      // cleared on the next successful read) to avoid flooding stderr while a
+      // corrupt registry persists.
+      const readError = error instanceof Error ? error : new Error(String(error));
+
+      if (!warnedRegistryPaths.has(this.#registryPath)) {
+        warnedRegistryPaths.add(this.#registryPath);
+        console.warn(
+          `WarningRegistry: could not read ${this.#registryPath} (${readError.message}); continuing with no warnings.`,
+        );
+      }
+
+      return { warnings: [], error: readError };
     }
-
-    return data.map((warning) => ({ ...warning }));
   }
 
   private save(): void {