fix(extension): detect browser error pages earlier

- Add shared browser error URL detection for Chrome, Edge, Brave, and Firefox-style about:error pages.
- Short-circuit read-only DOM and HTML commands with safe fallbacks when tabs are already on browser error pages.
- Fail navigation waits, DOM waits, polling, and URL watches with clearer error-page messages.
- Bump package and extension version to 0.9.8 and extend regression coverage for cross-browser error-page handling.

extension/manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "browser-cli",
-  "version": "0.9.6",
+  "version": "0.9.8",
   "description": "Control your browser from the terminal via browser-cli",
   "permissions": [
     "tabs",

extension/src/commands/dom.ts

@@ -1,5 +1,5 @@
 // @ts-nocheck
-import { executeScript, getActiveTab, isErrorPageScriptError, isScriptableUrl } from '../core';
+import { executeScript, getActiveTab, isBrowserErrorUrl, isErrorPageScriptError, isScriptableUrl } from '../core';
 import { contentDispatch } from './injected';
 
 function fallbackForErrorPageDomOp(funcName, tab) {
@@ -31,6 +31,10 @@ function fallbackForErrorPageDomOp(funcName, tab) {
 export async function domOp(funcName, args = {}) {
   const tab = args?.tabId ? await chrome.tabs.get(args.tabId) : await getActiveTab();
   const tabUrl = tab.url || tab.pendingUrl || "";
+  if (isBrowserErrorUrl(tabUrl)) {
+    const fallback = fallbackForErrorPageDomOp(funcName, tab);
+    if (fallback !== undefined) return fallback;
+  }
   if (!isScriptableUrl(tabUrl)) {
     throw new Error(`Cannot run DOM commands on ${tabUrl} — navigate to a regular web page first`);
   }
@@ -53,7 +57,7 @@ export async function domOp(funcName, args = {}) {
 export async function domEval({ code, tabId } = {}) {
   const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
   const tabUrl = tab.url || tab.pendingUrl || "";
-  if (!isScriptableUrl(tabUrl)) {
+  if (!isScriptableUrl(tabUrl) || isBrowserErrorUrl(tabUrl)) {
     throw new Error(`Cannot run DOM commands on ${tabUrl} — navigate to a regular web page first`);
   }
   const results = await executeScript({
@@ -68,6 +72,10 @@ export async function domEval({ code, tabId } = {}) {
 export async function domWaitFor({ selector, timeout = 10000, visible = false, hidden = false, tabId } = {}) {
   const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
   const tabUrl = tab.url || tab.pendingUrl || "";
+  if (isBrowserErrorUrl(tabUrl)) {
+    if (hidden) return { selector, found: false };
+    throw new Error(`Cannot wait for DOM on browser error page ${tabUrl}`);
+  }
   if (!isScriptableUrl(tabUrl)) {
     throw new Error(`Cannot run DOM commands on ${tabUrl} — navigate to a regular web page first`);
   }
@@ -101,6 +109,9 @@ export async function domWaitFor({ selector, timeout = 10000, visible = false, h
 export async function domPoll({ selector, pattern, attr, timeout = 30000, interval = 500, tabId } = {}) {
   const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
   const tabUrl = tab.url || tab.pendingUrl || "";
+  if (isBrowserErrorUrl(tabUrl)) {
+    throw new Error(`Cannot poll DOM on browser error page ${tabUrl}`);
+  }
   if (!isScriptableUrl(tabUrl)) {
     throw new Error(`Cannot run DOM commands on ${tabUrl} — navigate to a regular web page first`);
   }

extension/src/commands/navigation.ts

@@ -1,5 +1,5 @@
 // @ts-nocheck
-import { getActiveTab, getAliases, resolveGroupId, tabInfo } from '../core';
+import { getActiveTab, getAliases, isBrowserErrorUrl, resolveGroupId, tabInfo } from '../core';
 export async function navOpen({ url, background, window: windowName, windowId: explicitWindowId, group: groupNameOrId }) {
   let windowId;
   if (explicitWindowId != null) {
@@ -77,6 +77,10 @@ export async function navWait({ tabId, timeout = 30000, readyState = "complete"
   const interval = 200;
   while (Date.now() < deadline) {
     const t = await chrome.tabs.get(tab.id);
+    const currentUrl = t.url || t.pendingUrl || "";
+    if (isBrowserErrorUrl(currentUrl)) {
+      throw new Error(`Tab ${tab.id} is showing an error page while waiting for load (${currentUrl})`);
+    }
     if (readyState === "complete" ? t.status === "complete" : t.status !== "loading") {
       return tabInfo(t);
     }

extension/src/commands/tabs.ts

@@ -1,5 +1,5 @@
 // @ts-nocheck
-import { executeScript, getActiveTab, getAliases, isScriptableUrl, resolveTabForDirectAction, tabInfo } from '../core';
+import { executeScript, getActiveTab, getAliases, isBrowserErrorUrl, isErrorPageScriptError, isScriptableUrl, resolveTabForDirectAction, tabInfo } from '../core';
 export async function tabsList() {
   const windows = await chrome.windows.getAll({ populate: true });
   const aliases = await getAliases();
@@ -102,8 +102,12 @@ export async function tabsQuery({ search }) {
 export async function tabsHtml({ tabId }) {
   for (let i = 0; i < 3; i++) {
     const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
-    if (!isScriptableUrl(tab.url || tab.pendingUrl || "")) {
+    const tabUrl = tab.url || tab.pendingUrl || "";
-      throw new Error(`Cannot get HTML of ${tab.url || tab.pendingUrl} — navigate to a regular web page first`);
+    if (isBrowserErrorUrl(tabUrl)) {
+      return "";
+    }
+    if (!isScriptableUrl(tabUrl)) {
+      throw new Error(`Cannot get HTML of ${tabUrl} — navigate to a regular web page first`);
     }
     try {
       const results = await executeScript({
@@ -112,7 +116,8 @@ export async function tabsHtml({ tabId }) {
       });
       return results[0]?.result || "";
     } catch (e) {
-      const transient = e.message && (e.message.includes("Frame with ID") || e.message.includes("No tab with id")) && !e.message.includes("error page");
+      if (isErrorPageScriptError(e)) return "";
+      const transient = e.message && (e.message.includes("Frame with ID") || e.message.includes("No tab with id"));
       if (i < 2 && transient) {
         await new Promise(r => setTimeout(r, 300));
         continue;
@@ -205,7 +210,7 @@ export async function tabsWatchUrl({ pattern, timeout = 30000, tabId } = {}) {
     lastUrl = t.url || t.pendingUrl || "";
     lastStatus = t.status || "unknown";
     if (matches(t.pendingUrl || "") || matches(t.url || "")) return tabInfo(t);
-    if ((t.url || "").startsWith("chrome-error://")) {
+    if (isBrowserErrorUrl(t.url || "")) {
       throw new Error(`Tab ${tab.id} is showing an error page while waiting for URL to match '${pattern}'`);
     }
     await new Promise(r => setTimeout(r, 200));

extension/src/core.ts

@@ -5,9 +5,26 @@ export async function getProfileAlias() {
   return profileAlias || "default";
 }
 
+export function isBrowserErrorUrl(url) {
+  const value = String(url || "").toLowerCase();
+  return value.startsWith("chrome-error://") ||
+         value.startsWith("edge-error://") ||
+         value.startsWith("brave-error://") ||
+         value.startsWith("about:neterror") ||
+         value.startsWith("about:certerror") ||
+         value.startsWith("about:blocked") ||
+         value.startsWith("about:tabcrashed");
+}
+
 export function isErrorPageScriptError(error) {
-  const message = String(error?.message || error || "");
+  const message = String(error?.message || error || "").toLowerCase();
-  return message.includes("error page") || message.includes("chrome-error://chromewebdata");
+  return message.includes("error page") ||
+         message.includes("chrome-error://") ||
+         message.includes("edge-error://") ||
+         message.includes("brave-error://") ||
+         message.includes("about:neterror") ||
+         message.includes("about:certerror") ||
+         message.includes("about:tabcrashed");
 }
 
 export function isTransientScriptError(error) {

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "browser-cli"
-version = "0.9.6"
+version = "0.9.8"
 description = "Control your real running browser from the terminal via a browser extension"
 requires-python = ">=3.10"
 dependencies = [

tests/test_extension_error_page_handling.py

@@ -5,8 +5,13 @@ ROOT = Path(__file__).resolve().parents[1]
 def test_extension_retries_error_page_script_injection_before_failing():
     core = (ROOT / "extension" / "src" / "core.ts").read_text()
 
+    assert "isBrowserErrorUrl" in core
     assert "isErrorPageScriptError" in core
-    assert "chrome-error://chromewebdata" in core
+    assert "chrome-error://" in core
+    assert "edge-error://" in core
+    assert "brave-error://" in core
+    assert "about:neterror" in core
+    assert "about:certerror" in core
     assert "isTransientScriptError(e)" in core
 
 def test_read_only_dom_commands_have_error_page_fallbacks():
@@ -17,12 +22,16 @@ def test_read_only_dom_commands_have_error_page_fallbacks():
     assert "return false;" in dom
     assert 'case "domQuery":' in dom
     assert 'case "extractText":' in dom
+    assert "isBrowserErrorUrl(tabUrl)" in dom
     assert "isErrorPageScriptError(e)" in dom
 
-def test_tabs_watch_url_reports_last_seen_url_on_timeout():
+def test_navigation_and_tabs_report_browser_error_pages():
     tabs = (ROOT / "extension" / "src" / "commands" / "tabs.ts").read_text()
+    navigation = (ROOT / "extension" / "src" / "commands" / "navigation.ts").read_text()
 
     assert "lastUrl" in tabs
     assert "lastStatus" in tabs
     assert "showing an error page" in tabs
     assert "last URL:" in tabs
+    assert "isBrowserErrorUrl" in navigation
+    assert "showing an error page while waiting for load" in navigation

uv.lock

@@ -4,7 +4,7 @@ requires-python = ">=3.10"
 
 [[package]]
 name = "browser-cli"
-version = "0.9.6"
+version = "0.9.8"
 source = { editable = "." }
 dependencies = [
     { name = "click" },