From 14d9df31cc8a5954e23d2f1ed0120a0827d63787 Mon Sep 17 00:00:00 2001
From: Local Dev <dev@localhost>
Date: Sun, 4 Oct 2026 01:50:31 +0200
Subject: [PATCH] =?UTF-8?q?fix(theseus/error):=20show=20branded=20error=20?=
 =?UTF-8?q?page=20on=20BCNR=E2=86=92clearnet=20fallback=20failures?=
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flytastic.ru (and any other site where the BCNR lookup NXDOMAINs and
the clearnet fallback fails with a cert / network error) was leaving
the tab blank instead of showing the error page.

Cause — tab.internalNav was overloaded. loadBns's fallbackToWeb sets
internalNav=true before loadURL("https://host/") so will-navigate
doesn't re-route the programmatic nav back through navigateTab. The
did-fail-load handler was using the SAME flag to suppress recursion
on its own loadFile(error.html) call — so a cert error during the
clearnet fallback was silently swallowed.

Narrow the suppression to its real target: skip did-fail-load only
when the failing URL is file:// (our own error.html / home.html
loads). Clearnet HTTPS failures from a programmatic loadURL now
surface the branded error page like any other failed navigation. The
will-navigate guard (its original purpose) is untouched.
---
 main.js | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/main.js b/main.js
index 5b7e1b1c..d8a1a439 100644
--- a/main.js
+++ b/main.js
@@ -4013,13 +4013,18 @@ function createTab(initial, opts = {}) {
   wc.on("did-finish-load", () => { if (!tab.settings && !tab.addonId) webapps.probeTab(tab).then(() => { if (tab.id === activeId) emitTabs(); }).catch(() => {}); });
   // Failed loads: NAME_NOT_RESOLVED, CONNECTION_REFUSED, cert errors, etc.
   // Show the branded error page instead of Chromium's default "This site
-  // can't be reached". Skip subframe errors, our own programmatic loads,
-  // and the couple of Chromium codes that fire on normal user actions
-  // (Stop / superseded nav / extension cancel).
+  // can't be reached". Skip subframe errors and the couple of Chromium
+  // codes that fire on normal user actions (Stop / superseded nav /
+  // extension cancel). Also skip failures of our own file:// loads
+  // (error.html / home.html) to avoid recursion — but DO handle failures
+  // of programmatic loadURL calls to clearnet (BNS fallbackToWeb sets
+  // internalNav to block will-navigate re-entry, not to swallow errors;
+  // without this, a cert-expired or unreachable upstream after a failed
+  // BNS lookup leaves the tab blank).
   wc.on("did-fail-load", (_e, code, desc, validatedURL, isMainFrame) => {
     if (!isMainFrame) return;
-    if (tab.internalNav) return;
     if (ERROR_CODE_IGNORE.has(code)) return;
+    if (typeof validatedURL === "string" && validatedURL.startsWith("file://")) return;
     loadErrorPage(tab, tab.id, { url: validatedURL || tab.url, code, desc });
   });
   // Firefox / Chrome-style bottom-left link preview: fires with the href