diff --git a/src/browser/BrowserScenarioResponseValues.ts b/src/browser/BrowserScenarioResponseValues.ts
index bf7ed27d30..acb69a65de 100644
--- a/src/browser/BrowserScenarioResponseValues.ts
+++ b/src/browser/BrowserScenarioResponseValues.ts
@@ -131,10 +131,11 @@ export const decodedBodyBound = (
   headers: Readonly<Record<string, string>>,
 ): number | undefined => {
   const declared = headers["content-length"]?.trim();
+  // Content-Length allows leading zeros; only significant digits bound precision.
   const bytes =
     received !== undefined && Number.isSafeInteger(received) && received > 0
       ? received
-      : declared !== undefined && /^[1-9]\d{0,14}$/u.test(declared)
+      : declared !== undefined && /^0*[1-9]\d{0,14}$/u.test(declared)
         ? Number(declared)
         : undefined;
   if (bytes === undefined) return undefined;
diff --git a/src/browser/PlaywrightScenarioRequest.test.ts b/src/browser/PlaywrightScenarioRequest.test.ts
index 962b7b840a..aa8f24cf6f 100644
--- a/src/browser/PlaywrightScenarioRequest.test.ts
+++ b/src/browser/PlaywrightScenarioRequest.test.ts
@@ -1699,6 +1699,14 @@ describe("saving from a UI step's response", () => {
     { encoding: "identity", size: 0 },
     { encoding: "gzip", size: 0 },
     { size: 0, length: "0" },
+    { size: 0, length: "0000" },
+    { size: 0, length: "+17" },
+    { size: 0, length: "17.0" },
+    { size: 0, length: "1.7e1" },
+    { size: 0, length: "17, 17" },
+    { size: 0, length: "0001000000000000000" },
+    { size: 0, length: "9007199254740993" },
+    { size: 0, length: "0009007199254740993" },
     { size: -1 },
     { size: Number.NaN },
   ])(
@@ -1831,7 +1839,10 @@ describe("saving from a compressed or cached UI response", () => {
     { encoding: "deflate", size: 32 },
     { encoding: "x-gzip", size: 32 },
     { size: 0, length: "17" },
+    { size: 0, length: "0017" },
+    { size: 0, length: "00000000000000000017" },
     { encoding: "gzip", size: 0, length: "32" },
+    { encoding: "gzip", size: 0, length: "0032" },
   ])(
     "saves from a response whose received size or declared length bounds its decoded size: %j",
     async (bounds) => {
@@ -1852,23 +1863,29 @@ describe("saving from a compressed or cached UI response", () => {
     },
   );
 
-  it("refuses a compressed response that could decode past the limit without reading it", async () => {
-    const parsed = clickSaving("/api/items");
-    const { page, reads } = uiPage([
-      {
-        method: "POST",
-        url: `${ORIGIN}/api/items`,
-        status: 201,
-        body: '{"id":"x"}',
-        encoding: "gzip",
-        size: 12_000,
-      },
-    ]);
-    await expect(
-      perform(page, parsed.actions[0]!, resolved(parsed)),
-    ).rejects.toThrow("could decode past the size limit");
-    expect(reads.count).toBe(0);
-  });
+  it.each([
+    { encoding: "gzip", size: 12_000 },
+    { size: 0, length: "00012000001" },
+    { encoding: "gzip", size: 0, length: "00012000" },
+  ])(
+    "refuses a response that could decode past the limit without reading it: %j",
+    async (bounds) => {
+      const parsed = clickSaving("/api/items");
+      const { page, reads } = uiPage([
+        {
+          method: "POST",
+          url: `${ORIGIN}/api/items`,
+          status: 201,
+          body: '{"id":"x"}',
+          ...bounds,
+        },
+      ]);
+      await expect(
+        perform(page, parsed.actions[0]!, resolved(parsed)),
+      ).rejects.toThrow("could decode past the size limit");
+      expect(reads.count).toBe(0);
+    },
+  );
 });
 
 describe("saved response limits and deadlines", () => {
diff --git a/src/browser/network/PlaywrightScenarioNetwork.test.ts b/src/browser/network/PlaywrightScenarioNetwork.test.ts
index d570e43fe9..fedc66d8bb 100644
--- a/src/browser/network/PlaywrightScenarioNetwork.test.ts
+++ b/src/browser/network/PlaywrightScenarioNetwork.test.ts
@@ -256,35 +256,48 @@ it.each([
   },
 );
 
-it("reads and redacts marked gzip content its received size bounds", async () => {
-  const { collector, events, secrets } = harness({
-    request_body: false,
-    response_body: true,
-    header_values: false,
-  });
-  const request = new RequestFixture("marked");
-  const body = '{"token":"secret-token"}';
-  request.responseSize = 20;
-  const response = new ResponseFixture(request, body);
-  vi.spyOn(response, "headers").mockReturnValue({
-    "content-type": "application/json",
-    "content-encoding": "gzip",
-  });
-  secrets.responseProtector("login", [
-    { name: "token", json_pointer: "/token", secret: true },
-  ])?.(request);
-  collector.request(request);
-  collector.response(response);
-  collector.finished(request);
-  await collector.finish();
-  const content = events.find(
-    (event) => event.kind === "network-content" && event.phase === "response",
-  );
-  expect(content).toBeDefined();
-  const text = bodyText(content!);
-  expect(text).not.toContain("secret-token");
-  expect(text).toContain("[REDACTED:page:login.token]");
-});
+it.each([
+  { size: 20, headers: { "content-encoding": "gzip" } },
+  { size: 0, headers: { "content-length": "24" } },
+  { size: 0, headers: { "content-length": "0024" } },
+  { size: 0, headers: { "content-length": "00000000000000000024" } },
+  {
+    size: 0,
+    headers: { "content-encoding": "gzip", "content-length": "0024" },
+  },
+])(
+  "reads and redacts marked content within its decoded bound: %j",
+  async (bounds) => {
+    const { collector, events, secrets } = harness({
+      request_body: false,
+      response_body: true,
+      header_values: false,
+    });
+    const request = new RequestFixture("marked");
+    const body = '{"token":"secret-token"}';
+    request.responseSize = bounds.size;
+    const response = new ResponseFixture(request, body);
+    vi.spyOn(response, "headers").mockReturnValue({
+      "content-type": "application/json",
+      ...bounds.headers,
+    });
+    secrets.responseProtector("login", [
+      { name: "token", json_pointer: "/token", secret: true },
+    ])?.(request);
+    collector.request(request);
+    collector.response(response);
+    collector.finished(request);
+    await collector.finish();
+    const content = events.find(
+      (event) => event.kind === "network-content" && event.phase === "response",
+    );
+    expect(content).toBeDefined();
+    const text = bodyText(content!);
+    expect(text).not.toContain("secret-token");
+    expect(text).toContain("[REDACTED:page:login.token]");
+    expect(response.bodyReads).toBe(1);
+  },
+);
 
 it("preserves unselected source spellings while redacting escaped aliases", async () => {
   const { collector, events, secrets } = harness({
@@ -346,22 +359,28 @@ it("associates sensitive fields by request identity while keeping same-URL unmar
   );
 });
 
-it.each(["br", "cache"])(
-  "withholds marked response content when decoded bounds are unknown: %s",
-  async (kind) => {
+it.each([
+  { size: 64, headers: { "content-encoding": "br" } },
+  { size: 0, headers: {} },
+  { size: 0, headers: { "content-length": "0000" } },
+  { size: 0, headers: { "content-length": "24, 24" } },
+  { size: 0, headers: { "content-length": "0009007199254740993" } },
+  { size: 0, headers: { "content-length": "00012000001" } },
+])(
+  "withholds marked response content when decoded bounds are unknown or over budget: %j",
+  async (bounds) => {
     const { collector, events, secrets } = harness();
     const request = new RequestFixture("marked");
-    if (kind === "cache") request.responseSize = 0;
+    request.responseSize = bounds.size;
     const secret = "private-source-token";
     const response = new ResponseFixture(
       request,
       JSON.stringify({ token: secret }),
     );
-    if (kind === "br")
-      vi.spyOn(response, "headers").mockReturnValue({
-        "content-type": "application/json",
-        "content-encoding": "br",
-      });
+    vi.spyOn(response, "headers").mockReturnValue({
+      "content-type": "application/json",
+      ...bounds.headers,
+    });
     secrets.responseProtector("login", [
       { name: "token", json_pointer: "/token", secret: true },
     ])?.(request);