perf(core): [SDK Overhead Reduction 7] Lazily allocate Breadcrumb data

[adinauer]

PR Stack (SDK Overhead Reduction)

• perf(core): SDK Overhead Reduction #5499
• perf(core): [SDK Overhead Reduction 1] Skip java.specification.version lookup on Android #5500
• perf(android): [SDK Overhead Reduction 2] Replace reflective OptionsContainer with direct subclass #5501
• perf(android): [SDK Overhead Reduction 3] Reuse SentryExecutorService for DeviceInfoUtil pre-caching #5502
• perf(android): [SDK Overhead Reduction 4] Use default timezone directly #5587
• perf(core): [SDK Overhead Reduction 5] Replace Calendar with Date in DateUtils #5589
• perf(core): [SDK Overhead Reduction 6] Reduce JsonWriter stack allocation #5591
• perf(core): [SDK Overhead Reduction 7] Lazily allocate Breadcrumb data #5598
• perf(core): [SDK Overhead Reduction 8] Reduce context serialization allocations #5599
• perf(core): [SDK Overhead Reduction 9] Lazily allocate reflection serializer state #5600
• perf(core): [SDK Overhead Reduction 10] Lazily create reflection JSON serializer #5601
• perf(core): [SDK Overhead Reduction 11] Replace ISO8601 timestamp handling #5602

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📜 Description

Lazily allocates the Breadcrumb data map instead of creating a ConcurrentHashMap for every breadcrumb.

Plain breadcrumbs that only set message, category, type, or level now keep a shared empty map. The data map is initialized on first setData call with double-checked locking and remains a ConcurrentHashMap after initialization.

💡 Motivation and Context

Most breadcrumbs do not attach data, but each breadcrumb previously allocated an empty ConcurrentHashMap. This reduces allocation overhead for the common plain breadcrumb path while preserving concurrent first-write behavior.

💚 How did you test it?

• ./gradlew :sentry:test --tests io.sentry.BreadcrumbTest
• ./gradlew spotlessApply apiDump

📝 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

#skip-changelog

⚠️ Merge this PR using a merge commit (not squash). Only the collection branch is squash-merged into main.

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.43.1 (1)	release

⚙️ sentry-android Build Distribution Settings

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	352.92 ms	434.28 ms	81.36 ms
Size	0 B	0 B	0 B