React Native 0.82 – JS Timers & Fetch Freeze After Launching a Non-React AppCompatActivity (Worked Fine in Earlier RN Versions) #54534
Description
Description
Environment
React: 19.1.1
React Native: 0.82.0
Hermes: Enabled
Platform: Android
Architecture: Reproducible on both Old Architecture & New Architecture
🚨 Summary
After upgrading to React Native 0.82.x, the JS Timers Module and Networking Module freeze whenever a non-React AppCompatActivity is launched from the app (e.g., from a 3rd-party native SDK).
This is a regression —
✅ Everything worked perfectly in RN 0.71 – 0.80
❌ The issue appears only after upgrading to RN 0.81 / 0.82
🔍 What Still Works
JS thread is alive
JS Promise microtasks execute
Native → JS events via DeviceEventEmitter work
React UI continues working
Synchronous JS code runs normally
❌ What Stops Working (Regression)
As soon as a non-React AppCompatActivity takes the foreground:
fetch() stops resolving or rejecting
setTimeout() does not execute
requestAnimationFrame() does not execute
NetworkingModule callbacks do not reach JS
TimersModule does not fire
Fetch requests still GO OUT successfully (verified via proxy tools)
Server responds, but JS never receives the response
This only happens after launching the external AppCompatActivity.
✔️ Working Behavior in Older React Native Versions
In React Native 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79 the exact same code and SDK integration works fully.
Fetch resolves normally.
Timers fire normally.
External AppCompatActivity does not impact the JS environment.
Therefore — this is a regression introduced in RN 0.81 or RN 0.82.
Steps to reproduce
Build any React Native app using RN 0.82
Integrate a simple native SDK that launches a plain AppCompatActivity (not ReactActivity)
Emit an event from the SDK → JS
Inside JS event listener:
Promise.resolve().then() → runs
setTimeout(...) → does NOT run
requestAnimationFrame(...) → does NOT run
fetch() → never resolves
Verify using proxy (e.g., Burp Suite):
Fetch does hit the server
Server sends a valid response
JS never receives the response callback
React Native Version
0.82.0
Affected Platforms
Runtime - Android
Output of npx @react-native-community/cli info
npx @react-native-community/cli -v
20.0.1
shubham.garg@GLH0CY1VHGK2 ~ % npx @react-native-community/cli info
error: unknown command 'info'
(Did you mean init?)
Stacktrace or Logs
Actual Behavior (RN 0.82 Regression)
JS thread alive
Events delivered
Timers & fetch stop working
Network request reaches server
Response returns
JS never gets the response
📌 Expected Behavior (Worked in RN ≤ 0.80)
Launching a non-React Android Activity should NOT pause RN’s TimersModule or NetworkingModule
fetch should continue resolving normally
setTimeout, RAF, requestAnimationFrame should continue executing
This is how React Native behaved for many years until RN 0.81+.
🧠 Diagnosis
Evidence indicates:
ReactContext timers + networking modules get suspended when a non-React AppCompatActivity becomes active.
JS microtasks still run → JS engine (Hermes) alive.
NetworkingModule native → JS callback never fires → indicates bridge suspension.
This DID NOT occur in earlier RN versions.
You can check our sample app https://github.com/payu-intrepos/payu-non-seamless-react
MANDATORY Reproducer
https://github.com/ShubhGar/RN-Fetch-issue
Screenshots and Videos
No response