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.

Generated by 🚫 dangerJS against 5ae3e11

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	304.55 ms	377.88 ms	73.33 ms
Size	1.58 MiB	2.29 MiB	727.01 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
e59e22a	329.74 ms	383.31 ms	53.57 ms
fc5ccaf	270.49 ms	363.90 ms	93.41 ms
d15471f	361.89 ms	378.07 ms	16.18 ms
d15471f	322.58 ms	396.08 ms	73.50 ms
abfcc92	304.04 ms	370.33 ms	66.29 ms
91bb874	310.68 ms	359.24 ms	48.56 ms
ab8a72d	316.24 ms	356.38 ms	40.14 ms
d15471f	286.65 ms	314.68 ms	28.03 ms
6727e14	337.22 ms	373.94 ms	36.71 ms
f064536	329.00 ms	395.62 ms	66.62 ms

App size

Revision	Plain	With Sentry	Diff
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
91bb874	1.58 MiB	2.13 MiB	559.07 KiB
ab8a72d	1.58 MiB	2.12 MiB	551.55 KiB
d15471f	1.58 MiB	2.13 MiB	559.54 KiB
6727e14	1.58 MiB	2.28 MiB	718.64 KiB
f064536	1.58 MiB	2.20 MiB	633.90 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
fa76e86	274.32 ms	349.63 ms	75.31 ms
8c4e7d6	309.15 ms	359.27 ms	50.12 ms
2cee1ab	318.29 ms	361.00 ms	42.71 ms
4c0ffee	314.94 ms	377.79 ms	62.86 ms
31581b9	350.00 ms	420.63 ms	70.63 ms
ddbbe91	289.51 ms	359.74 ms	70.23 ms
c10e603	367.92 ms	393.50 ms	25.58 ms
edecf31	310.80 ms	367.02 ms	56.22 ms
83a9ec4	333.84 ms	390.30 ms	56.47 ms

App size

Revision	Plain	With Sentry	Diff
00299fd	1.58 MiB	2.29 MiB	723.50 KiB
fa76e86	1.58 MiB	2.29 MiB	724.06 KiB
8c4e7d6	1.58 MiB	2.29 MiB	727.03 KiB
2cee1ab	1.58 MiB	2.29 MiB	723.68 KiB
4c0ffee	1.58 MiB	2.29 MiB	723.67 KiB
31581b9	1.58 MiB	2.19 MiB	624.94 KiB
ddbbe91	1.58 MiB	2.29 MiB	724.15 KiB
c10e603	1.58 MiB	2.29 MiB	723.72 KiB
edecf31	1.58 MiB	2.29 MiB	726.95 KiB
83a9ec4	1.58 MiB	2.29 MiB	723.99 KiB

[markushi]

@sentry review

[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.

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[cursor]

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

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[cursor]

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

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[cursor]

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

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[romtsn]

some bugbot comments still left, but to me this looks great, hats off!

[sentry]

Bug: The QueueFile capacity MAX_NUM_STACKTRACES (~121) is smaller than the number of collected stacks MAX_NUM_STACKS (151), causing the oldest stack traces to be silently dropped.
_{Severity: MEDIUM}

Suggested Fix

Unify the constants so that the QueueFile capacity is at least as large as the maximum number of stack traces to be collected. The value for MAX_NUM_STACKTRACES should be derived from the same timeout as MAX_NUM_STACKS to ensure they are consistent.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location:
sentry-android-core/src/main/java/io/sentry/android/core/anr/AnrProfileManager.java#L43-L45

Potential issue: There is a discrepancy between the number of stack traces collected and
the storage capacity for them during ANR profiling. The integration attempts to collect
`MAX_NUM_STACKS` (approximately 151) stack traces. However, the underlying `QueueFile`
is initialized with a smaller capacity of `MAX_NUM_STACKTRACES` (approximately 121).
Because `QueueFile` acts as a circular buffer, once it reaches capacity, it starts
overwriting the oldest entries. This results in the silent loss of the first ~30 stack
traces, which could contain critical information about the root cause of the ANR.

[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]

IOException from checkMainThread permanently kills polling thread

Medium Severity

The checkMainThread method declares throws IOException (from clearStacks() and addStackTrace()), but the inner try-catch in run() only catches InterruptedException. Any IOException propagates to the outer catch (Throwable t) on line 198, which logs a warning and exits the method, permanently terminating the ANR profiling thread. A single transient I/O error (disk full, file locked, etc.) silently and irrecoverably disables ANR profiling for the entire app session.

Additional Locations (1)

• sentry-android-core/src/main/java/io/sentry/android/core/anr/AnrProfilingIntegration.java#L203-L249