[Bug]: Desktop main process SIGTRAPs during preview_open webview attach / debugger.attach #8332

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1. bald-ai commented on Aug 26, 2026

   

   bald-ai

   on Aug 26, 2026

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   This bug happened to me and agent said its not caused by my fork and fixable. So I asked it to post it here, hope it helps. If not delete, I dont care.
2. ibniss commented on Aug 28, 2026

   

   ibniss

   on Aug 28, 2026

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   I hit a similar issue where t3 code crashed while the agent was using the built-in browser tools. Had my agent look into the error dump and found this issue as potentially related. I'm adding the details from my case in case they help narrow down the underlying issue, here's a summary of the investigation by 5.6 Sol:

   I hit what looks like a related preview/CDP lifecycle crash, but with a different native failure mode from the SIGTRAP reported here.

   Environment:

   • T3 Code 0.0.36-nightly.20260828.1208
   • Electron 41.5.0
   • macOS 26.2 (25C56)
   • Apple Silicon, M5
   • App role: Background
   • Process uptime before crash: about 31 minutes

   The crash was:

   Exception Type:    EXC_BAD_ACCESS (SIGSEGV)
   Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000000000010
   Termination Reason: Namespace SIGNAL, Code 11, Segmentation fault: 11
   Triggered by Thread: 0 CrBrowserMain
   

   The raw macOS report attributes the top frame to v8::Object::Set, but that is only the nearest exported symbol in the stripped Electron framework. I resolved the frame offsets against the matching Electron Breakpad symbols.

   The actual top of the stack is:

   content::DevToolsSession::DispatchProtocolNotification(...) + 0x70
   blink::mojom::DevToolsSessionHostStubDispatch::Accept(...)
   mojo::InterfaceEndpointClient::HandleIncomingMessageThunk::Accept(...)
   mojo::MessageDispatcher::Accept(...)
   mojo::InterfaceEndpointClient::HandleIncomingMessage(...)
   IPC::ChannelAssociatedGroupController...
   base::TaskAnnotator::RunTaskImpl(...)
   base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::DoWork()
   

   Electron Framework UUID / Breakpad symbol ID:

   UUID:      4C4C44A2-5555-3144-A1A4-3984082119EF
   Symbol ID: 4C4C44A255553144A1A43984082119EF0
   Top frame image offset: 0x128f1ec
   

   The faulting instructions are:

   ldr x21, [x20, #0x20]
   ...
   ldr x8, [x21]
   ldr x8, [x8, #0x10]   ; crashes reading address 0x10

   At the crash, x21 was non-null, but the first pointer loaded through it was null. Based on the symbolicated function and Chromium's DevToolsSession implementation, this appears to be the virtual call to the DevToolsAgentHostClient while dispatching an incoming protocol notification.

   My interpretation is that a CDP notification remained queued after the associated DevTools client had begun teardown or had been cleared. That would make this a later manifestation of the same preview lifecycle race described in this issue:

   • The reported SIGTRAP appears to happen during debugger.attach().
   • This SIGSEGV happens after attachment, while Chromium is delivering a protocol notification.
   • Both occur in CrBrowserMain with Electron 41.5.0 on macOS 26.2.

   If these share a root cause, checking webContents.isDestroyed() before attaching may not be sufficient by itself. The detach/dispose path may also need a generation guard or ordering that prevents queued CDP notifications from reaching a stale client.

   I can provide the full macOS crash report if useful.

   Apologies if this turns out to be unrelated, happy to move it to a separate issue and remove the comment if so.
3. albertojb commented on Sep 3, 2026

   

   albertojb

   on Sep 3, 2026

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   Linux reproduction of the same SIGTRAP-in-CrBrowserMain / debugger.attach crash.

   Environment:

   • T3 Code desktop v0.0.38 (installed 2026-09-03 ~18:35 EDT, just ~9 min before crash)
   • Electron (stripped, no symbols available)
   • Linux, Omarchy (Arch)
   • Launched with --no-sandbox
   • Crash role: Foreground (not background)
   • Process uptime before crash: < 10 minutes (cold start, not hours)
   • Signal: SIGTRAP (TRAP), si_code SI_KERNEL
   • Crash thread: main thread (TID 109965), CrBrowserMain equivalent
   • ~40 other threads idle in pthread_cond_wait / epoll_wait / g_main_context_iteration (pangoft2, libglib-2.0, libdconfsettings present — Gtk build)

   Timestamp: 2026-09-03 18:44:13 EDT
   Core: coredumpctl PID 109965 (351.2M)
   Backtrace (frame 0 only, stripped): t3code + 0x8d75c91 → t3code + 0x42e1ccd → t3code + 0x4cfcbb9 → t3code + 0x7cb0567 → t3code + 0x5878c2b (no symbols)

   Different trigger from the macOS case (not preview_open of an HTTPS login page while backgrounded). Crash was on a cold start, so the likely cause is the same root issue: debugger.attach / CDP lifecycle without an isDestroyed() or generation gate hitting a Chromium CHECK/ImmediateCrash. Useful to know whether the fix gates apply to the Gtk build too.

   Filed by opencode via static-best-coding.
4. Kabilan108 commented on Oct 6, 2026

   

   Kabilan108

   on Oct 6, 2026

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   Adding a Linux crash report that may be related. I authorized Codex to investigate and post this comment. The native failure appears to be in Chromium navigation-origin validation, so I am not claiming this is the same debugger.attach race as the original report.

   Environment and impact

   • T3 Code desktop AppImage 0.0.46-nightly.20261005.2676, verified from the packaged package.json.
   • NixOS 26.11, build 26.11.20261001.c59305b; Linux 6.18.54, x86_64.
   • niri/Wayland. The running renderer and GPU subprocess command lines include --ozone-platform=wayland.
   • Main-process launch argument: --password-store=gnome-libsecret. No --no-sandbox argument in the recorded main-process command line.
   • Exact Electron/Chromium versions have not been independently verified.
   • Crash at 2026-10-05 20:26:33 EDT / 2026-10-06 00:26:33 UTC.
   • Entire desktop main process terminated, rather than only a renderer or a typed preview operation failing. Main PID/TID was 11901.
   • Relaunch at 20:26:52 EDT succeeded in starting another desktop instance. The original backend remained alive and was reparented to systemd --user, matching the separate lifecycle issue [Bug]: Desktop backend outlives a crashed main process and keeps its port, so the relaunch silently moves to another port #13747. No claim about database corruption or data-loss testing.

   Observed sequence, not a deterministic repro

   The app had been running for about 68 minutes, with agent-driven embedded-preview automation active. No deliberate reproduction has been attempted against the daily profile. Window foreground/background state at the instant of the crash was not captured.

   The desktop trace records:

   1. 20:26:16.849 EDT: PreviewManager.navigate fails during navigate.normalizeUrl. The nested cause is PreviewUrlNormalizationError: Invalid preview URL (parse: https:; input length 11) and TypeError: Invalid URL. This is a recorded, handled Effect failure. It is not evidence that this exception directly caused the native crash.
   2. 20:26:16.959–16.992: requireWebContents, ensureControlSession, sendCommand, performAutomationEvaluate, automationEvaluate, and automationStatus complete successfully.
   3. 20:26:31.062–31.364: a periodic update check completes successfully and reports 0.0.46-nightly.20261005.2702 available. There is no captured evidence of update installation.
   4. 20:26:33: the kernel records a main-thread int3 trap and systemd captures a core dump.

   The exact URL/frame that was navigating when the native check failed is not yet known. A failing preview operation about 16 seconds earlier, or a successful update check about 2 seconds earlier, establishes timing, not causation.

   Native evidence

   Sanitized kernel line:

   traps: t3code[11901] trap int3 ip:646d022ace53 sp:7ffdda8c1620 error:0 in t3code[40a6e53,646d015fd000+9efd000]
   

   Systemd reports Signal: 5 (TRAP) and a present core dump, compressed size about 78.8 MiB. Its unwound main-thread frames are stripped; representative executable-relative offsets:

   #0  t3code + 0x40a7e53
   #1  t3code + 0x4f3ec20
   #2  t3code + 0x4e2c333
   #3  t3code + 0x85583cb
   #4  t3code + 0x5163fb0
   #5  t3code + 0x51633ae
   #6  t3code + 0x51ded48
   #7  t3code + 0x50cfa7b
   #8  t3code + 0x50c9e88
   #9  t3code + 0x50ce0da
   

   GDB confirms the trap instruction at executable offset 0x40a7e52, followed by ud2 at 0x40a7e53. Disassembly shows a call at 0x40a7853 to 0x3f29ca0, testing its Boolean result and branching to that trap if false:

   0x40a7853: call 0x3f29ca0
   0x40a7858: test %al,%al
   0x40a785a: je   0x40a7e52
   ...
   0x40a7e52: int3
   0x40a7e53: ud2
   

   The containing function references these diagnostic strings:

   Bug1454273-is_in_main_frame
   Bug1454273-current_origin
   Bug1454273-parent_origin
   Bug1454273-outer_doc_origin
   Bug1454273-embedder_origin
   Bug1454273-initiator_origin
   Bug1454273-initiator_relationship
   

   Those strings and the check structure match Chromium's NavigationRequest::GetOriginForURLLoaderFactoryAfterResponse(), which checks that the target renderer is permitted to commit the chosen origin through ChildProcessSecurityPolicyImpl::CanAccessOrigin(...):
   https://chromium.googlesource.com/chromium/src/+/refs/heads/main/content/browser/renderer_host/navigation_request.cc

   Inference: the crash is consistent with that navigation-origin security CHECK. This is a source/disassembly match, not a fully symbolicated stack against the exact bundled Chromium revision. GDB could not recover a useful full backtrace; the offsets above are from systemd's unwind.

   Other checks and available diagnostics

   • No matching OOM kill or GPU-reset/amdgpu error appeared in the kernel log for the inspected 20-minute window around the crash.
   • The launcher's stdout and stderr go to /dev/null. The existing desktop-main.log was historical, so it did not provide this crash's native CHECK message. Current evidence comes from the core dump, system journal, and desktop.trace.ndjson.
   • Local core and debugger output are retained. The full core is not attached publicly because it can contain credentials, browser session data, and private workspace content. Sanitized symbolication output can be supplied if maintainers specify the matching Electron symbols or another useful diagnostic.

   Is this navigation-origin CHECK best tracked here, or should it be a separate issue? A reliable reproduction and the exact failing origin remain missing.
5. t3dotgg commented on Oct 21, 2026

   

   t3dotgg

   on Oct 21, 2026

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   Note

   🤖 Claude Opus 5.5 responding on behalf of Theo

   Thanks for the report. One part of this is fixed on main in #9068. Please test on the nightly built from main on 2026-10-21, or on the next stable release. One part is still open: later crashes possibly unrelated to the original attach race. If that part still matters to you, please open a new issue for that part only.
6. t3dotgg

   closed this as completedon Oct 21, 2026