fix: Android app crashing on hot-restart in debug mode

[buenaflor]

📜 Description

• After a Flutter hot restart, the old Dart isolate is torn down and its Dart port becomes invalid.
• Android still holds Java/Kotlin callback objects (the recorder’s callbacks) and executes them later on the main thread.
• Those callbacks are Java proxies created via jni that forward into Dart through the now-dead port.
  When the proxy invokes into JNI, libflutter.so dereferences invalid isolate state and crashes (SIGSEGV), often showing PortProxyBuilder.invoke in the stack.

Simple solution

• Wrap every recorder callback with a small guard that checks a generation number.
• Bump that generation when the Flutter engine detaches and before wiring a new recorder.
• Each wrapper captures the generation at creation; if it doesn’t match the current one, it returns immediately and never crosses JNI.
• Close the previous ReplayIntegration during restart so it stops posting work.

💡 Motivation and Context

Fixes crashing on hot-restart on Android

💚 How did you test it?

Manual test

• Check it did not crash after hot restarting
• Check replays are still sent after hot restarting

📝 Checklist

• I reviewed submitted code
• I added tests to verify changes
• No new PII added or SDK only sends newly added PII if sendDefaultPii is enabled
• I updated the docs if needed
• All tests passing
• No breaking changes

🔮 Next steps

[github-actions]

🚨 Detected changes in high risk code 🚨

High-risk code has higher potential to break the SDK and may be hard to test. To prevent severe bugs, apply the rollout process for releasing such changes and be extra careful when changing and reviewing these files:

• packages/flutter/android/src/main/kotlin/io/sentry/flutter/SentryFlutterPlugin.kt

[github-actions]

Android Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	367.51 ms	360.53 ms	-6.98 ms
Size	13.93 MiB	15.18 MiB	1.25 MiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
d3fb366	391.49 ms	385.85 ms	-5.64 ms
a10aff4	488.19 ms	515.02 ms	26.83 ms
6bcdc99	440.23 ms	435.77 ms	-4.46 ms
cdf371b	367.64 ms	377.02 ms	9.38 ms
93b7728	475.28 ms	489.13 ms	13.86 ms
2d34233	470.54 ms	558.90 ms	88.36 ms
7cfee3b	498.78 ms	516.98 ms	18.20 ms
0fb45d0	482.79 ms	554.02 ms	71.23 ms
0fb3800	465.64 ms	536.77 ms	71.13 ms
bfabaf2	408.04 ms	444.38 ms	36.34 ms

App size

Revision	Plain	With Sentry	Diff
d3fb366	13.93 MiB	15.06 MiB	1.13 MiB
a10aff4	13.93 MiB	15.06 MiB	1.13 MiB
6bcdc99	13.93 MiB	15.00 MiB	1.06 MiB
cdf371b	13.93 MiB	15.18 MiB	1.25 MiB
93b7728	6.54 MiB	7.69 MiB	1.15 MiB
2d34233	6.54 MiB	7.55 MiB	1.01 MiB
7cfee3b	6.54 MiB	7.70 MiB	1.17 MiB
0fb45d0	6.54 MiB	7.70 MiB	1.17 MiB
0fb3800	6.54 MiB	7.69 MiB	1.15 MiB
bfabaf2	13.93 MiB	15.06 MiB	1.13 MiB

Previous results on branch: fix/stale-callbacks-crash-on-restart

Startup times

Revision	Plain	With Sentry	Diff
5c9c1da	364.65 ms	359.74 ms	-4.91 ms
df23ec7	423.21 ms	435.02 ms	11.81 ms
1858cb4	479.06 ms	479.72 ms	0.66 ms

App size

Revision	Plain	With Sentry	Diff
5c9c1da	13.93 MiB	15.18 MiB	1.25 MiB
df23ec7	13.93 MiB	15.18 MiB	1.25 MiB
1858cb4	13.93 MiB	15.18 MiB	1.25 MiB

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.33%. Comparing base (cdf371b) to head (331bcc2).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3358      +/-   ##
==========================================
+ Coverage   88.47%   90.33%   +1.86%     
==========================================
  Files         291       95     -196     
  Lines        9917     3198    -6719     
==========================================
- Hits         8774     2889    -5885     
+ Misses       1143      309     -834     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[github-actions]

iOS Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1251.94 ms	1243.50 ms	-8.44 ms
Size	5.53 MiB	6.02 MiB	501.22 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
3615e19	1225.02 ms	1234.57 ms	9.55 ms
393f8ec	1256.45 ms	1259.60 ms	3.16 ms
0929dbf	1275.89 ms	1282.22 ms	6.33 ms
e45c0e1	1269.08 ms	1278.83 ms	9.75 ms
2b5e090	1257.04 ms	1258.07 ms	1.02 ms
8541716	1270.18 ms	1271.80 ms	1.62 ms
9b99523	1256.06 ms	1270.33 ms	14.27 ms
396cb30	1265.06 ms	1265.73 ms	0.67 ms
c8596a6	1234.11 ms	1241.19 ms	7.08 ms
cdf371b	1246.24 ms	1251.10 ms	4.86 ms

App size

Revision	Plain	With Sentry	Diff
3615e19	7.86 MiB	9.44 MiB	1.58 MiB
393f8ec	5.53 MiB	6.01 MiB	488.10 KiB
0929dbf	7.86 MiB	9.54 MiB	1.69 MiB
e45c0e1	7.86 MiB	9.44 MiB	1.58 MiB
2b5e090	5.53 MiB	6.00 MiB	485.10 KiB
8541716	5.53 MiB	6.00 MiB	479.96 KiB
9b99523	7.86 MiB	9.44 MiB	1.58 MiB
396cb30	5.53 MiB	6.01 MiB	488.17 KiB
c8596a6	7.86 MiB	9.44 MiB	1.58 MiB
cdf371b	5.53 MiB	6.02 MiB	501.23 KiB

Previous results on branch: fix/stale-callbacks-crash-on-restart

Startup times

Revision	Plain	With Sentry	Diff
df23ec7	1254.21 ms	1249.83 ms	-4.37 ms
5c9c1da	1261.27 ms	1263.67 ms	2.40 ms
1858cb4	1253.71 ms	1250.65 ms	-3.06 ms

App size

Revision	Plain	With Sentry	Diff
df23ec7	5.53 MiB	6.02 MiB	502.14 KiB
5c9c1da	5.53 MiB	6.02 MiB	502.15 KiB
1858cb4	5.53 MiB	6.02 MiB	502.14 KiB