Panic due to InvalidURI exception in JavaScript module on nytimes.com

[prefrontalsys]

Description

The LightPanda browser panics and crashes with a "reached unreachable code" error when attempting to load
https://www.nytimes.com. The crash appears to be triggered by an InvalidURI exception within the browser's
JavaScript engine while parsing a script from static01.nyt.com.

Impact

The panic causes the lightpanda process to hang indefinitely.

• When run from the command line, the shell hangs and requires a ^C (Ctrl+C) to terminate the process and
  return to the prompt.
• When run as a subprocess by the Magg MCP proxy server, the lp browser crash causes the Magg server to also
  hang. A ^C in the Magg terminal is required, which then terminates both the Magg server and the hung
  lightpanda process.

Steps to Reproduce

1. Launch the LightPanda browser from the command line:
   • lightpanda https://www.nytimes.com
2. The browser process will crash and the terminal will hang.

Expected Behavior

The page should either load successfully or fail gracefully without crashing or hanging the browser process.

Actual Behavior

The browser process panics and hangs, requiring a manual ^C to terminate.

System Information

• Operating System: macOS 26.0.1 (Tahoe)
• Architecture: aarch64 (Apple Silicon, MacBook Air M4)

Crash Log

1 $time=6040384 $scope=console $level=warn $msg=warn args="; 1: limitedAds is not set, defaulting
  to false"
2 $time=6040385 $scope=console $level=warn $msg=warn args="; 1: userinfo data unavailable"
3 $time=6040561 $scope=js $level=warn $msg="compile resolved module" specifier=./identify-user-NlI
  stack=null src=null line=0 exception=InvalidURI
4 $time=6040561 $scope=user_script $level=warn $msg="eval script"
  url=https://static01.nyt.com/video-static/betamax/player-2G-OVVMI.js err=unknown cacheable=true
5 thread 124698 panic: reached unreachable code
6 ???:?:?: 0x102405f2b in _browser.js.Context.resolveModuleCallback (???)
7 ???:?:?: 0x101090c73 in _locale_charset (???)
8 ???:?:?: 0x10105d09f in _locale_charset (???)
9 ???:?:?: 0x100b6e3d7 in _locale_charset (???)

10 ???:?:?: 0x100af51df in _locale_charset (???)
11 ???:?:?: 0x1024040ef in _browser.js.Context.module__anon_120176 (???)
12 ???:?:?: 0x1023bce6b in _browser.js.Context.dynamicModuleSourceCallback (???)
13 ???:?:?: 0x1023bc6b3 in _browser.ScriptManager.AsyncModule.doneCallback (???)
14 ???:?:?: 0x102390edb in _http.Client.processMessages (???)
15 ???:?:?: 0x102393bc7 in _http.Client.perform (???)
16 ???:?:?: 0x1023aa7c3 in _http.Client.tick (???)
17 ???:?:?: 0x10240508f in _browser.js.Context.resolveModuleCallback (???)
18 ???:?:?: 0x101090c73 in _locale_charset (???)
19 ???:?:?: 0x10105d09f in _locale_charset (???)
20 ???:?:?: 0x100b6e3d7 in _locale_charset (???)
21 ???:?:?: 0x100af51df in _locale_charset (???)
22 ???:?:?: 0x1023ca527 in _browser.ScriptManager.Script.eval (???)
23 ???:?:?: 0x10254954b in _browser.ScriptManager.evaluate (???)
24 ???:?:?: 0x1023cf13f in _browser.ScriptManager.doneCallback (???)
25 ???:?:?: 0x102390edb in _http.Client.processMessages (???)
26 ???:?:?: 0x102393bc7 in _http.Client.perform (???)
27 ???:?:?: 0x1023aa7c3 in _http.Client.tick (???)
28 ???:?:?: 0x1023d631b in _browser.page.Page.wait (???)
29 ???:?:?: 0x10239ffbb in _main.run (???)
30 ???:?:?: 0x1023a6357 in _main (???)
31 ???:?:?: 0x18ba41d53 in ??? (???)
32 ???:?:?: 0x0 in ??? (???)
33 zsh: abort lightpanda https://www.nytimes.com

This issue was originally discovered while using the LightPanda browser via the gomcp server, but has been
confirmed to be reproducible via the command line directly. The crash is severe enough to terminate the browser
process, causing any controlling process (like an MCP server) to lose its connection.

[karlseguin]

Potentially fixed by #1123 but a note for anyone looking into this: I was only able to reproduce the issue when using an US ip address.

[krichprollsch]

I have a crash with my FR IP

INFO  http : request complete . . . . . . . . . . . . . . . . [+14.217s]
      source = xhr
      url = https://als-svc.nytimes.com/als?uri=https%3A%2F%2Fwww.nytimes.com%2Fpages%2Findex.html&typ=hp&prop=mnyt&plat=mweb
      status = 200

thread 611012 panic: switch on corrupt value
/home/pierre/wrk/browser/src/browser/ScriptManager.zig:334:17: 0x348dcf0 in waitForModule (lightpanda)
        switch (sync.state) {
                ^
/home/pierre/wrk/browser/src/browser/js/Context.zig:1212:63: 0x348e7a6 in _resolveModuleCallback (lightpanda)
    var fetch_result = try self.script_manager.?.waitForModule(normalized_specifier);
                                                              ^
/home/pierre/wrk/browser/src/browser/js/Context.zig:1110:39: 0x33ac060 in resolveModuleCallback (lightpanda)
    return self._resolveModuleCallback(referrer, specifier) catch |err| {
                                      ^
../../../src/src/objects/source-text-module.cc:367:14: 0x4481b95 in PrepareInstantiate (../../../src/src/objects/source-text-module.cc)
../../../src/src/objects/module.cc:246:12: 0x49be88c in PrepareInstantiate (../../../src/src/objects/module.cc)
../../../src/src/objects/module.cc:214:8: 0x49be24b in Instantiate (../../../src/src/objects/module.cc)
../../../src/src/api/api.cc:2248:8: 0x3cb248e in InstantiateModule (../../../src/src/api/api.cc)
../../../src/binding.cpp:640:33: 0x3b88da3 in ??? (../../../src/binding.cpp)
/home/pierre/.cache/zig/p/v8-0.0.0-xddH63bVAwBSEobaUok9J0er1FqsvEujCDDVy6ItqKQ5/src/v8.zig:1953:40: 0x33aa66a in instantiate (lightpanda)
        c.v8__Module__InstantiateModule(self.handle, ctx.handle, cb, &out);
                                       ^
/home/pierre/wrk/browser/src/browser/js/Context.zig:270:26: 0x3426b94 in module__anon_250063 (lightpanda)
    if (try m.instantiate(v8_context, resolveModuleCallback) == false) {
                         ^
/home/pierre/wrk/browser/src/browser/ScriptManager.zig:726:38: 0x331f2ea in eval (lightpanda)
                    js_context.module(false, content, url, cacheable) catch break :blk false;
                                     ^
/home/pierre/wrk/browser/src/browser/ScriptManager.zig:608:25: 0x3428de7 in doneCallback (lightpanda)
        self.script.eval(manager.page);
                        ^
/home/pierre/wrk/browser/src/browser/ScriptManager.zig:486:24: 0x331fae8 in doneCallback (lightpanda)
    script.doneCallback();
                       ^
/home/pierre/wrk/browser/src/http/Client.zig:469:39: 0x32a8bda in processMessages (lightpanda)
            transfer.req.done_callback(transfer.ctx) catch |err| {
                                      ^
/home/pierre/wrk/browser/src/http/Client.zig:396:33: 0x32a9458 in perform (lightpanda)
    if (try self.processMessages()) {
                                ^
/home/pierre/wrk/browser/src/http/Client.zig:381:25: 0x32a9e7e in makeRequest (lightpanda)
    _ = try self.perform(0);
                        ^
/home/pierre/wrk/browser/src/http/Client.zig:222:32: 0x32a9f65 in process (lightpanda)
        return self.makeRequest(handle, transfer);
                               ^
/home/pierre/wrk/browser/src/http/Client.zig:214:24: 0x32aa0e2 in request (lightpanda)
    return self.process(transfer);
                       ^
/home/pierre/wrk/browser/src/browser/ScriptManager.zig:307:28: 0x33a9ec3 in getModule (lightpanda)
    try self.client.request(.{
                           ^
/home/pierre/wrk/browser/src/browser/js/Context.zig:265:52: 0x34271a1 in module__anon_250063 (lightpanda)
                try self.script_manager.?.getModule(owned_specifier, url);

/home/pierre/wrk/browser/src/browser/ScriptManager.zig:726:38: 0x331f2ea in eval (lightpanda)
                    js_context.module(false, content, url, cacheable) catch break :blk false;
                                     ^
/home/pierre/wrk/browser/src/browser/ScriptManager.zig:608:25: 0x3428de7 in doneCallback (lightpanda)
        self.script.eval(manager.page);
                        ^
/home/pierre/wrk/browser/src/browser/ScriptManager.zig:486:24: 0x331fae8 in doneCallback (lightpanda)
    script.doneCallback();
                       ^
/home/pierre/wrk/browser/src/http/Client.zig:469:39: 0x32a8bda in processMessages (lightpanda)
            transfer.req.done_callback(transfer.ctx) catch |err| {
                                      ^
/home/pierre/wrk/browser/src/http/Client.zig:396:33: 0x32a9458 in perform (lightpanda)
    if (try self.processMessages()) {
                                ^
/home/pierre/wrk/browser/src/http/Client.zig:192:24: 0x32c5227 in tick (lightpanda)
    return self.perform(timeout_ms);
                       ^
/home/pierre/wrk/browser/src/browser/page.zig:401:49: 0x34387a3 in _wait (lightpanda)
                        if (try http_client.tick(ms_to_wait) == .extra_socket) {
                                                ^
/home/pierre/wrk/browser/src/browser/page.zig:272:26: 0x33237df in wait (lightpanda)
        return self._wait(wait_ms) catch |err| {
                         ^
/home/pierre/wrk/browser/src/browser/session.zig:158:29: 0x33061b3 in wait (lightpanda)
            return page.wait(wait_ms);
                            ^
/home/pierre/wrk/browser/src/cdp/cdp.zig:122:32: 0x3274a83 in pageWait (lightpanda)
            return session.wait(ms);
                               ^
/home/pierre/wrk/browser/src/server.zig:149:33: 0x327424b in readLoop (lightpanda)
            switch (cdp.pageWait(ms_remaining)) {
                                ^
/home/pierre/wrk/browser/src/server.zig:109:26: 0x3274f0c in run (lightpanda)
            self.readLoop(socket, timeout_ms) catch |err| {
                         ^
/home/pierre/wrk/browser/src/main.zig:150:23: 0x32b13dd in run (lightpanda)
            server.run(address, timeout) catch |err| {
                      ^
/home/pierre/wrk/browser/src/main.zig:45:8: 0x32b3263 in main (lightpanda)
    run(alloc) catch |err| {
       ^
/usr/local/zig-0.15.1/lib/std/start.zig:627:37: 0x32b3a3d in main (lightpanda)
            const result = root.main() catch |err| {
                                    ^
../sysdeps/nptl/libc_start_call_main.h:58:16: 0x71d08402a1c9 in __libc_start_call_main (../sysdeps/x86/libc-start.c)
../csu/libc-start.c:360:3: 0x71d08402a28a in __libc_start_main_impl (../sysdeps/x86/libc-start.c)
???:?:?: 0x2985024 in ??? (???)
???:?:?: 0x0 in ??? (???)
run
└─ run exe lightpanda failure
error: the following command terminated unexpectedly:
./.zig-cache/o/e8894375e11b6907cf0e073ac0d10b47/lightpanda

Build Summary: 3/5 steps succeeded; 1 failed
run transitive failure
└─ run exe lightpanda failure