Unreachable code reached, Cannot toggle network tracking

Version

v26.4.0

Platform

Darwin Local-pc 25.5.0 Darwin Kernel Version 25.5.0: Tue Jun  9 22:26:15 PDT 2026; root:xnu-12377.121.10~1/RELEASE_ARM64_T6031 arm64

Subsystem

No response

What steps will reproduce the bug?

Run a script with --inspect-wait=0.0.0.0:9229 --experimental-network-inspection enabled.
The debugger which is attaching is from vscode

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Test",
      "type": "node",
      "request": "attach",
      "port": 9229,
      "restart": true,
      "address": "localhost"
    }
  ]
}

full command

node --inspect-wait=0.0.0.0:9229 --experimental-network-inspection --env-file=.env -r ts-node/register/transpile-only index.ts

How often does it reproduce? Is there a required condition?

Its very flaky and happens out of random.

What is the expected behavior? Why is that the expected behavior?

Nodejs process is crashing due to unexpected condition. Application should boot properly and not crash immediately.

What do you see instead?

Debugger attached.
node:internal/worker/io:250
class ReadableWorkerStdio extends Readable {
                                  ^

TypeError: Class extends value undefined is not a constructor or null
    at node:internal/worker/io:250:35
    at compileForInternalLoader (node:internal/bootstrap/realm:407:7)
    at requireBuiltin (node:internal/bootstrap/realm:438:14)
    at node:internal/worker:48:18
    at compileForInternalLoader (node:internal/bootstrap/realm:407:7)
    at requireBuiltin (node:internal/bootstrap/realm:438:14)
    at node:worker_threads:13:5
    at compileForInternalLoader (node:internal/bootstrap/realm:407:7)
    at requireBuiltin (node:internal/bootstrap/realm:438:14)
    at node:inspector:37:26
    at compileForInternalLoader (node:internal/bootstrap/realm:407:7)
    at requireBuiltin (node:internal/bootstrap/realm:438:14)
    at node:internal/inspector/network_http:20:21
    at compileForInternalLoader (node:internal/bootstrap/realm:407:7)
    at requireBuiltin (node:internal/bootstrap/realm:438:14)
    at enable (node:internal/inspector_network_tracking:4:3)
    at node:internal/streams/readable:1:1
    at compileForInternalLoader (node:internal/bootstrap/realm:407:7)
    at requireBuiltin (node:internal/bootstrap/realm:438:14)
    at node:internal/streams/duplex:39:18
    at compileForInternalLoader (node:internal/bootstrap/realm:407:7)
    at requireBuiltin (node:internal/bootstrap/realm:438:14)
    at node:internal/streams/pipeline:16:16
    at compileForInternalLoader (node:internal/bootstrap/realm:407:7)
    at requireBuiltin (node:internal/bootstrap/realm:438:14)
    at node:internal/streams/compose:7:22
    at compileForInternalLoader (node:internal/bootstrap/realm:407:7)
    at requireBuiltin (node:internal/bootstrap/realm:438:14)
    at node:stream:44:17
    at compileForInternalLoader (node:internal/bootstrap/realm:407:7)
    at requireBuiltin (node:internal/bootstrap/realm:438:14)
    at node:net:45:16
    at compileForInternalLoader (node:internal/bootstrap/realm:407:7)
    at compileForPublicLoader (node:internal/bootstrap/realm:346:10)
    at loadBuiltinModule (node:internal/modules/helpers:128:7)
    at loadBuiltinWithHooks (node:internal/modules/cjs/loader:1301:15)
    at node:internal/modules/cjs/loader:1396:48
    at wrapModuleLoad (node:internal/modules/cjs/loader:260:19)
    at node:internal/modules/cjs/loader:1689:12
    at require (node:internal/modules/helpers:191:16)
    at <REDACTED>index.js:21:13
    at node:internal/modules/cjs/loader:1944:14
    at node:internal/modules/cjs/loader:2084:10
    at node:internal/modules/cjs/loader:1666:32
    at node:internal/modules/cjs/loader:1447:12
    at wrapModuleLoad (node:internal/modules/cjs/loader:260:19)
    at node:internal/modules/cjs/loader:1689:12
    at node:internal/modules/cjs/loader:2245:12
    at loadPreloadModules (node:internal/process/pre_execution:774:5)
    at initializeModuleLoaders (node:internal/process/pre_execution:246:5)
    at prepareExecution (node:internal/process/pre_execution:174:5)
    at prepareMainThreadExecution (node:internal/process/pre_execution:46:10)
    at node:internal/main/run_main_module:15:19

  #  node[29371]: void node::inspector::Agent::ToggleNetworkTracking(Isolate *, Local<Function>) at ../src/inspector_agent.cc:1023
  #  Assertion failed: "Unreachable code reached" ": " "Cannot toggle network tracking, please report this."

----- Native stack trace -----

 1: 0x10affa930 node::Assert(node::AssertionInfo const&) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
 2: 0x109e7d944 node::inspector::Agent::ToggleNetworkTracking(v8::Isolate*, v8::Local<v8::Function>) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
 3: 0x10b064984 node::inspector::Agent::EnableNetworkTracking() (.cold.1) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
 4: 0x109e7d7f0 node::inspector::Agent::EnableNetworkTracking() [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
 5: 0x109e92708 node::inspector::NetworkInspector::Enable() [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
 6: 0x109e932e8 node::inspector::NetworkAgent::enable(std::__1::optional<int>, std::__1::optional<int>) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
 7: 0x109f03d80 node::inspector::protocol::Network::DomainDispatcherImpl::enable(crdtp::Dispatchable const&) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
 8: 0x10a9d86d0 crdtp::UberDispatcher::DispatchResult::Run() [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
 9: 0x10b06455c node::inspector::NodeInspectorClient::dispatchMessageFromFrontend(int, v8_inspector::StringView const&) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
10: 0x109e7fca4 node::inspector::(anonymous namespace)::SameThreadInspectorSession::Dispatch(v8_inspector::StringView const&) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
11: 0x109e8d6e4 node::inspector::(anonymous namespace)::MainThreadSessionState::Dispatch(std::__1::unique_ptr<v8_inspector::StringBuffer, std::__1::default_delete<v8_inspector::StringBuffer>>) [/opt/home
12: 0x109e8d728 void node::inspector::(anonymous namespace)::AnotherThreadObjectReference<node::inspector::(anonymous namespace)::MainThreadSessionState>::Apply<std::__1::unique_ptr<v8_inspector::StringB
13: 0x109e8ca14 node::inspector::MainThreadInterface::DispatchMessages() [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
14: 0x109e8dcd4 node::CallbackQueue<void, node::Environment*>::CallbackImpl<node::inspector::MainThreadInterface::Post(std::__1::unique_ptr<node::inspector::Request, std::__1::default_delete<node::inspec
15: 0x109d2d7e0 node::Environment::RunAndClearInterrupts() [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
16: 0x109d31304 node::Environment::RequestInterruptFromV8()::$_0::__invoke(v8::Isolate*, void*) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
17: 0x10a033c58 v8::internal::Isolate::InvokeApiInterruptCallbacks() [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
18: 0x10a049b64 v8::internal::StackGuard::HandleInterrupts(v8::internal::StackGuard::InterruptLevel) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
19: 0x10a3c2810 v8::internal::Runtime_StackGuard(int, unsigned long*, v8::internal::Isolate*) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
20: 0x10a84ccac Builtins_CEntry_Return1_ArgvOnStack_NoBuiltinExit [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
21: 0x10a7a94c8 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
22: 0x11c780610
23: 0x11c7802b4
24: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
25: 0x11c780610
26: 0x11c7802b4
27: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
28: 0x11c780610
29: 0x11c7802b4
30: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
31: 0x11c780610
32: 0x11c7802b4
33: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
34: 0x11c780610
35: 0x11c7802b4
36: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
37: 0x11c780610
38: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
39: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
40: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
41: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
42: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
43: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
44: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
45: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
46: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
47: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
48: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
49: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
50: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
51: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
52: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
53: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
54: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
55: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
56: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
57: 0x10a7a9424 Builtins_InterpreterEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
58: 0x10a7a6788 Builtins_JSEntryTrampoline [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
59: 0x10a7a6478 Builtins_JSEntry [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
60: 0x10a025090 v8::internal::(anonymous namespace)::Invoke(v8::internal::Isolate*, v8::internal::(anonymous namespace)::InvokeParams const&) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
61: 0x10a024ac8 v8::internal::Execution::Call(v8::internal::Isolate*, v8::internal::DirectHandle<v8::internal::Object>, v8::internal::DirectHandle<v8::internal::Object>, v8::base::Vector<v8::internal::DirectHandle<v8::internal::Object> const>) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
62: 0x10b0943d0 v8::Function::Call(v8::Isolate*, v8::Local<v8::Context>, v8::Local<v8::Value>, int, v8::Local<v8::Value>*) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
63: 0x109d6317c node::builtins::BuiltinLoader::CompileAndCall(v8::Local<v8::Context>, char const*, node::Realm*) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
64: 0x10b02268c node::Realm::ExecuteBootstrapper(char const*) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
65: 0x10afe6d28 node::StartExecution(node::Environment*, char const*) (.cold.1) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
66: 0x109d4e3b8 node::StartExecution(node::Environment*, char const*) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
67: 0x109d4e350 node::StartExecution(node::Environment*, std::__1::function<v8::MaybeLocal<v8::Value> (node::StartExecutionCallbackInfoWithModule const&)>) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
68: 0x109cdd138 node::LoadEnvironment(node::Environment*, std::__1::function<v8::MaybeLocal<v8::Value> (node::StartExecutionCallbackInfoWithModule const&)>, std::__1::function<void (node::Environment*, v8::Local<v8::Value>, v8::Local<v8::Value>)>) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
69: 0x109db009c node::NodeMainInstance::Run(node::ExitCode*, node::Environment*) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
70: 0x109dafe2c node::NodeMainInstance::Run() [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
71: 0x109d50e04 node::Start(int, char**) [/opt/homebrew/Cellar/node/26.4.0/lib/libnode.147.dylib]
72: 0x1894fbe00 start [/usr/lib/dyld]

----- JavaScript stack trace -----

1: node:internal/streams/readable:1:1
2: compileForInternalLoader (node:internal/bootstrap/realm:407:7)
3: requireBuiltin (node:internal/bootstrap/realm:438:14)
4: node:internal/streams/duplex:39:18
5: compileForInternalLoader (node:internal/bootstrap/realm:407:7)
6: requireBuiltin (node:internal/bootstrap/realm:438:14)
7: node:internal/streams/pipeline:16:16
8: compileForInternalLoader (node:internal/bootstrap/realm:407:7)
9: requireBuiltin (node:internal/bootstrap/realm:438:14)
10: node:internal/streams/compose:7:22

Additional information

This i tried with node24 as well and was reproducible.
With --experimental-network-inspection removed this does not happen, so seems like only that is causing issue

REDACTED part

L20 const fs = require('fs');
L21 const net = require('net');
L22 const async_hooks = require('async_hooks');

Run the supplied Node.js command with inspector and network inspection enabled while attaching from VS Code to investigate the flaky startup crash. Then inspect node:inspector_network_tracking and src/inspector_agent.cc:1023, using the ReadableWorkerStdio initialization failure as the observed path; done means the process boots without the assertion when network tracking is enabled.