[0.77][Needs repro] Unable to launch React Native DevTools in newly upgraded app

[brianaderer]

Description

No info in console. Eventually I get the following error:

Failed to open debugger for com.bevnote.somm725 (iPhone 16 Pro) (React Native Bridgeless [C++ connection]): fetch failed

RN Debugger worked in 0.76.2 before I upgraded. When I try to access it via 'd' in android I get:

INFO Opening Dev Menu...
INFO Launching DevTools...
WARN No compatible apps connected. React Native DevTools can only be used with the Hermes engine.

Steps to reproduce

1. yarn start
2. yarn iOS / yarn android
3. 'j' / 'd'

React Native Version

0.77.0

Output of npx react-native info

System:
  OS: macOS 15.1.1
  CPU: (12) arm64 Apple M2 Max
  Memory: 115.05 MB / 32.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 21.0.0
    path: ~/.nvm/versions/node/v21.0.0/bin/node
  Yarn:
    version: 1.22.22
    path: /usr/local/bin/yarn
  npm:
    version: 10.2.0
    path: ~/.nvm/versions/node/v21.0.0/bin/npm
  Watchman:
    version: 2024.12.02.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.16.2
    path: /Users/brianaderer/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.2
      - iOS 18.2
      - macOS 15.2
      - tvOS 18.2
      - visionOS 2.2
      - watchOS 11.2
  Android SDK:
    API Levels:
      - "34"
      - "35"
    Build Tools:
      - 34.0.0
      - 35.0.0
    System Images:
      - android-35 | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2024.2 AI-242.23339.11.2421.12483815
  Xcode:
    version: 16.2/16C5032a
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.14
    path: /opt/homebrew/opt/openjdk@17/libexec/openjdk.jdk/Contents/Home/bin/javac
  Ruby:
    version: 3.1.2
    path: /Users/brianaderer/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 15.1.3
    wanted: ^15.1.2
  react:
    installed: 18.3.1
    wanted: 18.3.1
  react-native:
    installed: 0.77.0
    wanted: 0.77.0
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Screenshots and Videos

No response

[react-native-bot]

Warning

Missing reproducer: We could not detect a reproducible example in your issue report. Please provide either:

• If your bug is UI related: a Snack
• If your bug is build/upgrade related: a project using our Reproducer Template
• Otherwise send us a Pull Request with the RNTesterPlayground.js edited to reproduce your bug.

[cipolleschi]

@brianaderer thanks for the issue. Let me ask a few clarifying questions:

• Have you tried to press j from the terminal that is running metro? What happens when you try that?
• Are you running your app on a physical device or on a simulator/emulator?
• Does the problem happens for both Android and iOS or is it limited to one platform?

[brianaderer]

Hi Riccardo Thanks yes I do press j. The dev window opens, but I don't get any console logs and cant connect the profiler. I am able to see all the files in the file inspector however. The issue is mostly the same with ios and android, although the messages I get differ slightly, please see above. But the behavior is identical. Brian Aderer senior full-stack developer Python | PHP | React (718) 514 0151 | ***@***.******@***.***> | brianaderer.com<https://brianaderer.com/>

…

________________________________ From: Riccardo Cipolleschi ***@***.***> Sent: Sunday, February 9, 2025 5:58 AM To: facebook/react-native ***@***.***> Cc: Brian Aderer ***@***.***>; Mention ***@***.***> Subject: Re: [facebook/react-native] React Native Dev Tools not working with RN 77 (Issue #49287) @brianaderer<https://github.com/brianaderer> have you tried to press j from the terminal that is running metro? What happens when you try that? Are you running your app on a physical device or on a simulator/emulator? Does the problem happens for both Android and iOS or is it limited to one platform? — Reply to this email directly, view it on GitHub<#49287 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AF5USFGAXOABTG6YZY3S4UL2O4YFFAVCNFSM6AAAAABWX36KPKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDMNBWGE3TKOJQGE>. You are receiving this because you were mentioned.Message ID: ***@***.***>

[brianaderer]

Oh also, I'm using emulators. I didn't try it from physical devices in that config. Also worth noting, I was using the RN debugger in 0.76 and everything worked fine

[shubhamguptadream11]

Hey @brianaderer,

I tested this on a fresh React Native sample app using version 0.77.0, created with:

npx @react-native-community/cli init Reproducer --version 0.77.0

Tested on:

• Android Emulator → React Native DevTools is working fine even console logs are coming.

Attaching a video reference for your review.

Screen.Recording.2025-02-10.at.12.32.45.PM.mov

WARN No compatible apps connected. React Native DevTools can only be used with the Hermes engine.

As per this please check hermesEnabled is true in gradle.properties file.

If you still face this issue. Please provide a valid reproducer.

[huntie]

Hi @brianaderer,

Is this continuing to reproduce? (Please check @shubhamguptadream11's reply above for sanity checking — although seeing React Native Bridgeless [C++ connection] tells me you have a correct modern debugger backend.)

• There's a small chance the failed fetch() is a 404 against a previously cached network address for the device during the development session — in this case, the issue would be transitive and resolved after restarting Metro.
• Have you customised the --host option when running npx @react-native-community/cli start, or via config?
• How about opening the Dev Menu (instructions) — do you see an "Open Debugger" option available?

Since you were previously using the community react-native-debugger project, prior to upgrading, you were depending on a completely different debugging method (Remote JS Debugging, deprecated 2023) — please also check you have a correct version of the template maintained across previous React Native upgrades.

• It may be worth initing a new React Native project on your system to verify you can debug another project on your system.

(Sidenote for maintainers/me: fetch failed is a poor error cause and should be improved.)