diff --git a/src/browser/CdpCaptureDocuments.baseUrl.test.ts b/src/browser/CdpCaptureDocuments.baseUrl.test.ts
index c2c9378b89..94b04dc65b 100644
--- a/src/browser/CdpCaptureDocuments.baseUrl.test.ts
+++ b/src/browser/CdpCaptureDocuments.baseUrl.test.ts
@@ -100,6 +100,44 @@ describe("DOM metadata document base URLs", () => {
     });
   });
 
+  it.each([
+    "javascript:void(0)",
+    "mailto:someone@example.test",
+    "data:text/plain,hello",
+    "ftp://app.example.test/file",
+  ])("classifies the non-http(s) destination %s as unsupported", (href) => {
+    const result = capture(snapshot(undefined, "assets/", documentUrl, href));
+    expect(result.urls[1]).toMatchObject({
+      url: null,
+      destination_scope: "unsupported",
+    });
+  });
+
+  it("classifies an unparseable destination as unsupported", () => {
+    const result = capture(
+      snapshot(undefined, "assets/", documentUrl, "https://[invalid"),
+    );
+    expect(result.urls[1]).toMatchObject({
+      url: null,
+      destination_scope: "unsupported",
+    });
+  });
+
+  it("classifies a same-origin destination with credentials as approved", () => {
+    const result = capture(
+      snapshot(
+        undefined,
+        "assets/",
+        documentUrl,
+        "https://user:secret@app.example.test/guide",
+      ),
+    );
+    expect(result.urls[1]).toMatchObject({
+      url: `${origin}/guide`,
+      destination_scope: "approved",
+    });
+  });
+
   it("does not authorize a foreign document using its approved base URL", () => {
     const result = capture(
       snapshot(
diff --git a/tests/boundary/browser/webSourceMapFetcher.test.ts b/tests/boundary/browser/webSourceMapFetcher.test.ts
index 7d251b41ad..2ce7903a3c 100644
--- a/tests/boundary/browser/webSourceMapFetcher.test.ts
+++ b/tests/boundary/browser/webSourceMapFetcher.test.ts
@@ -193,6 +193,37 @@ describe("web source-map fetching and validation: fetching maps and following re
     });
   });
 
+  it.each([
+    ["embedded credentials", "https://user:secret@app.example.test/a.map"],
+    ["a different scheme on the same host", "http://app.example.test/a.map"],
+    ["another origin", "https://private.example.test/a.map"],
+    ["a non-http(s) scheme", "ftp://app.example.test/a.map"],
+    ["a file URL", "file:///tmp/a.map"],
+    ["an unparseable URL", "not a url"],
+  ])(
+    "filters a declared fetch URL with %s before any request",
+    async (_description, fetchUrl) => {
+      const calls: string[] = [];
+      const result = await fetchWebSourceMaps(
+        [{ ...request, fetchUrl }],
+        input(),
+        undefined,
+        {
+          fetch: (url) => {
+            calls.push(String(url));
+            return Promise.resolve(new Response("{}", { status: 200 }));
+          },
+        },
+      );
+
+      expect(calls).toEqual([]);
+      expect(result).toMatchObject({
+        status: "unavailable",
+        items: [{ status: "policy_filtered" }],
+      });
+    },
+  );
+
   it("follows an approved redirect chain without an arbitrary hop ceiling", async () => {
     const calls: string[] = [];
     const result = await fetchWebSourceMaps([request], input(), undefined, {