debugger: wait for target startup by panva · Pull Request #65194 · nodejs/node · GitHub

Important

This ought to deflake parallel/test-debugger-profile and parallel/test-debugger-exceptions.

The inspector can accept a connection before an --inspect-brk target enters its frontend wait. Runtime.runIfWaitingForDebugger can then be handled too early, allowing the target to subsequently block forever.

Wait for NodeRuntime.waitingForDebugger before initializing and releasing launched targets. Race the handshake against disconnects and apply it to both interactive and probe startup.

Refs: #64116
Assisted-by: codex:gpt-5.6-sol

The inspector can accept a connection before an --inspect-brk target enters its frontend wait. Runtime.runIfWaitingForDebugger can then be handled too early, allowing the target to subsequently block forever. Wait for NodeRuntime.waitingForDebugger before initializing and releasing launched targets. Race the handshake against disconnects and apply it to both interactive and probe startup. Refs: nodejs#64116 Assisted-by: codex:gpt-5.6-sol Co-authored-by: Archkon <180910180+Archkon@users.noreply.github.com> Signed-off-by: Archkon <180910180+Archkon@users.noreply.github.com> Signed-off-by: Filip Skokan <panva.ip@gmail.com>

The startup-readiness handshake and its initial integration were adapted from @Archkon's work in #64304. This version narrows and hardens that approach by covering disconnects during the full handshake, preserving probe-mode structured errors, and adding focused failure and cleanup tests.

Codecov Report

❌ Patch coverage is 87.79343% with 26 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.12%. Comparing base (404b0cf) to head (198e386).
⚠️ Report is 111 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/debugger/inspect_helpers.js	87.69%	18 Missing and 6 partials ⚠️
lib/internal/debugger/inspect_probe.js	83.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65194      +/-   ##
==========================================
- Coverage   90.32%   90.12%   -0.21%     
==========================================
  Files         760      752       -8     
  Lines      248525   251780    +3255     
  Branches    46894    47354     +460     
==========================================
+ Hits       224488   226911    +2423     
- Misses      15469    16210     +741     
- Partials     8568     8659      +91

Files with missing lines	Coverage Δ
lib/internal/debugger/inspect_repl.js	91.34% <100.00%> (+0.03%)	⬆️
lib/internal/debugger/inspect_probe.js	83.06% <83.33%> (+1.01%)	⬆️
lib/internal/debugger/inspect_helpers.js	92.50% <87.69%> (-4.91%)	⬇️

... and 151 files with indirect coverage changes

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CI: https://ci.nodejs.org/job/node-test-pull-request/75746/

I ran parallel/test-debugger-exceptions 1,000 times with -j16 on macOS 15:

this PR (821e267): 1,000/1,000 passed
parent commit (404b0cf): 25/1,000 failed, all timing out while waiting for the initial break

The A/B result suggests this likely fixes the flake, and the code looks good to me. My only non-blocking nit is the lack of a probe-mode disconnect test while waitForDebugger() is pending. LGTM.

CI: https://ci.nodejs.org/job/node-test-pull-request/75860/

Thanks for adding the probe disconnect test!
I also ran a broader A/B stress test across the debugger tests on macOS 15, repeating each test 100 times.

this PR (821e267): 7,900/7,900 passed
parent commit (404b0cf): 34/7,800 failed

This suggests that the startup handshake may deflake debugger tests beyond parallel/test-debugger-profile and parallel/test-debugger-exceptions called out in the description.

Additional validation:

stress test for parallel/test-debugger-profile 1,000 times with -j16 on macOS 15:

this PR (821e267): 1,000/1,000 passed
parent commit (404b0cf): 2/1,000 failed, both timing out while waiting for the initial break

Assisted-by: codex:gpt-5.6-sol Signed-off-by: Filip Skokan <panva.ip@gmail.com>

CI: https://ci.nodejs.org/job/node-test-pull-request/75916/

The inspector can accept a connection before an --inspect-brk target enters its frontend wait. Runtime.runIfWaitingForDebugger can then be handled too early, allowing the target to subsequently block forever. Wait for NodeRuntime.waitingForDebugger before initializing and releasing launched targets. Race the handshake against disconnects and apply it to both interactive and probe startup. Refs: #64116 Assisted-by: codex:gpt-5.6-sol Co-authored-by: Archkon <180910180+Archkon@users.noreply.github.com> Signed-off-by: Archkon <180910180+Archkon@users.noreply.github.com> Signed-off-by: Filip Skokan <panva.ip@gmail.com> PR-URL: #65194 Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>

Landed in 2004fbd

The inspector can accept a connection before an --inspect-brk target enters its frontend wait. Runtime.runIfWaitingForDebugger can then be handled too early, allowing the target to subsequently block forever. Wait for NodeRuntime.waitingForDebugger before initializing and releasing launched targets. Race the handshake against disconnects and apply it to both interactive and probe startup. Refs: #64116 Assisted-by: codex:gpt-5.6-sol Co-authored-by: Archkon <180910180+Archkon@users.noreply.github.com> Signed-off-by: Archkon <180910180+Archkon@users.noreply.github.com> Signed-off-by: Filip Skokan <panva.ip@gmail.com> PR-URL: #65194 Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com>

panva requested a review from joyeecheung August 10, 2026 12:17

nodejs-github-bot added debugger Issues and PRs related to the debugger subsystem. needs-ci PRs that need a full CI run. labels Aug 10, 2026

panva force-pushed the debugger-startup-handshake branch from f206372 to 821e267 Compare August 10, 2026 13:25

trivikr added the flaky-test Issues and PRs related to the tests with unstable failures on the CI. label Aug 11, 2026

fixup! debugger: wait for target startup

18ce20f

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inoway46 mentioned this pull request Aug 15, 2026

parallel/test-debugger-run-after-quit-restart is flaky on macOS #64005

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trivikr requested changes Aug 16, 2026

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Comment thread lib/internal/debugger/inspect_helpers.js

fixup! debugger: wait for target startup

198e386

Assisted-by: codex:gpt-5.6-sol Signed-off-by: Filip Skokan <panva.ip@gmail.com>

trivikr approved these changes Aug 16, 2026

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panva added author ready PRs that have at least one approval, no outstanding review comments, and a CI started. request-ci Add this label to start a Jenkins CI on a PR. labels Aug 16, 2026

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jasnell approved these changes Aug 17, 2026

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panva closed this Aug 17, 2026

panva deleted the debugger-startup-handshake branch August 17, 2026 08:09

This was referenced Aug 18, 2026

debugger: wait for initial break render during startup #64189

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test: remove test-debugger-run-after-quit-restart flaky designation #65424

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github-actions Bot mentioned this pull request Aug 25, 2026

2026-08-26, Version 26.8.0 (Current) #65551

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debugger: wait for target startup by panva · Pull Request #65194 · nodejs/node · GitHub

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debugger: wait for target startup - #65194

debugger: wait for target startup#65194panva wants to merge 3 commits intonodejs:mainnodejs/node:mainfrom panva:debugger-startup-handshakepanva/node:debugger-startup-handshakeCopy head branch name to clipboard

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debugger: wait for target startup#65194
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