feat(anr): Profile main thread when ANR and report ANR profiles to Sentry

[markushi]

📜 Description

Adds ANR (Application Not Responding) profiling integration that profiles the main thread when an ANR is detected and reports the captured profiles to Sentry.

Key Changes:

• New AnrProfilingIntegration to capture profiles during ANR events
• AnrV2Integration now takes care of matching and capturing the profile on the next start
• If the captured ANR event only contains system frames, a static fingerprint will get set, effectively changing the grouping behavior to group all noisy ANRs into a single issue

💡 Motivation and Context

This feature enables better ANR diagnostics by capturing profiling data at the time of ANR detection, allowing developers to identify performance bottlenecks and problematic code paths causing application hangs.

Example event: https://sentry-sdks.sentry.io/issues/7229210096/events/4598ff6fcc0f402d8ecca615005e7f64/

💚 How did you test it?

• Added tests

📝 Checklist

• I added GH Issue ID & Linear ID
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

[github-actions]

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	309.15 ms	359.27 ms	50.12 ms
Size	1.58 MiB	2.29 MiB	727.03 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
b6cfb57	372.92 ms	507.77 ms	134.85 ms
ce0a49e	532.00 ms	609.96 ms	77.96 ms
e59e22a	374.68 ms	442.14 ms	67.46 ms
fc5ccaf	256.80 ms	322.36 ms	65.56 ms
d15471f	294.13 ms	399.49 ms	105.36 ms
d15471f	303.49 ms	439.08 ms	135.59 ms
abfcc92	337.38 ms	427.39 ms	90.00 ms
ee35ac3	346.83 ms	435.48 ms	88.65 ms
d15471f	322.58 ms	396.08 ms	73.50 ms
f634d01	359.58 ms	433.88 ms	74.30 ms

App size

Revision	Plain	With Sentry	Diff
b6cfb57	1.58 MiB	2.28 MiB	718.80 KiB
ce0a49e	1.58 MiB	2.10 MiB	532.94 KiB
e59e22a	1.58 MiB	2.20 MiB	635.34 KiB
fc5ccaf	1.58 MiB	2.13 MiB	557.54 KiB
d15471f	1.58 MiB	2.13 MiB	559.54 KiB
d15471f	1.58 MiB	2.13 MiB	559.54 KiB
abfcc92	1.58 MiB	2.13 MiB	557.31 KiB
ee35ac3	1.58 MiB	2.13 MiB	558.77 KiB
d15471f	1.58 MiB	2.13 MiB	559.54 KiB
f634d01	1.58 MiB	2.10 MiB	533.40 KiB

Previous results on branch: markushi/feat/anr-profiling

Startup times

Revision	Plain	With Sentry	Diff
00299fd	359.87 ms	424.85 ms	64.98 ms
4c0ffee	314.94 ms	377.79 ms	62.86 ms
ddbbe91	289.51 ms	359.74 ms	70.23 ms
2cee1ab	318.29 ms	361.00 ms	42.71 ms
eb02e45	362.67 ms	431.71 ms	69.04 ms
fca8df8	326.79 ms	379.69 ms	52.90 ms
fa76e86	274.32 ms	349.63 ms	75.31 ms
eb7143a	347.66 ms	408.54 ms	60.88 ms
83a9ec4	333.84 ms	390.30 ms	56.47 ms
c10e603	367.92 ms	393.50 ms	25.58 ms

App size

Revision	Plain	With Sentry	Diff
00299fd	1.58 MiB	2.29 MiB	723.50 KiB
4c0ffee	1.58 MiB	2.29 MiB	723.67 KiB
ddbbe91	1.58 MiB	2.29 MiB	724.15 KiB
2cee1ab	1.58 MiB	2.29 MiB	723.68 KiB
eb02e45	1.58 MiB	2.29 MiB	725.26 KiB
fca8df8	1.58 MiB	2.29 MiB	723.68 KiB
fa76e86	1.58 MiB	2.29 MiB	724.06 KiB
eb7143a	1.58 MiB	2.29 MiB	724.12 KiB
83a9ec4	1.58 MiB	2.29 MiB	723.99 KiB
c10e603	1.58 MiB	2.29 MiB	723.72 KiB

[markushi]

@sentry review

[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

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[romtsn]

Great work already! I believe there are some things to address but I can check once more after that

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with Cloud Agents, enable Autofix in the Cursor dashboard.}

[cursor]

toStream closes caller-owned stream then flushes it

Low Severity

The toStream converter wraps sink in a DataOutputStream try-with-resources, which closes both dos and the underlying sink when the block exits. The sink.flush() call afterward operates on an already-closed stream. This works only because the actual sink from FileObjectQueue is a ByteArrayOutputStream where close() is a no-op, but the pattern violates stream ownership conventions and the post-close flush is dead code.

 

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

hasOnlySystemFrames returns true with no frames present

Medium Severity

hasOnlySystemFrames returns true when exceptions have no stacktrace or empty frames, not just when all frames are system frames. When the main thread is absent from the ANR thread dump, setAnrExceptions creates a dummy exception with a null stacktrace. The loop in hasOnlySystemFrames skips exceptions with null stacktraces and never finds any non-system frame, so it returns true. This causes setDefaultAnrFingerprint to apply the "system-frames-only-anr" fingerprint, grouping these no-information ANRs with ANRs that genuinely contain only system frames — two different categories that likely warrant separate investigation.

Additional Locations (1)

• sentry-android-core/src/main/java/io/sentry/android/core/ApplicationExitInfoEventProcessor.java#L736-L746

 

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with Cloud Agents, enable autofix in the Cursor dashboard.}

[cursor]

Redundant method call bypasses local null-checked variable

Low Severity

The local variable thread is assigned from anr.getThread() on line 142 and null-checked on line 144, but the else branch on line 147 calls anr.getThread() again instead of using the already-validated thread variable. The thread local variable was created specifically to handle the null case, so the else branch can safely pass thread directly to the constructor.

Additional Locations (1)

• sentry-android-core/src/main/java/io/sentry/android/core/AnrIntegration.java#L141-L142