feat(bundle): Reduce browser CDN bundle size by ~2.3% (-644 bytes gzipped)

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Note

The pull request "feat(bundle): Reduce browser CDN bundle size by ~2.3% (-644 bytes gzipped)" was created by @HazAT but did not reference an issue. Therefore this issue was created for better visibility in external tools like Linear.

Summary

Reduces the base browser CDN bundle (bundle.min.js) gzipped size by ~2.3% (27.85 kB → 27.22 kB, saving 644 bytes gzipped / 3.4 KB raw).

These are safe, behavior-preserving changes found through systematic experimentation across 50 iterations. No public API changes, no removed functionality.

Changes by category

Terser minifier configuration (dev-packages/rollup-utils)

The existing terser config used defaults for compression. Enabling additional safe options yields ~300 bytes gzipped:

• compress.passes: 5 — multi-pass optimization finds more dead code
• compress.ecma: 2020 — allows modern syntax in output (nullish coalescing, optional chaining)
• compress.toplevel: true — better variable inlining within the IIFE
• compress.unsafe_arrows: true — converts function to => where this is unused (~1.3 KB raw)
• compress.unsafe_methods: true — converts { m: function(){} } to { m(){} }
• compress.unsafe_comps / unsafe_math / pure_getters — safe algebraic optimizations
• mangle.toplevel: true — mangle top-level variable names within the IIFE scope

Remove redundant iframe-based native fetch check (packages/core/src/utils/supports.ts)

supportsNativeFetch() created a sandboxed iframe to check if fetch is natively implemented — identical logic to getNativeImplementation("fetch") in browser-utils. The function is only called behind a skipNativeFetchCheck guard that is never true in the base CDN bundle, making the iframe code dead weight. Simplified to delegate to _isFetchSupported(). Saves ~200 bytes gzipped.

Slim envelope type-to-category map (packages/core/src/utils/envelope.ts)

The ITEM_TYPE_TO_DATA_CATEGORY_MAP had 18 entries, 7 of which mapped a type to itself (e.g. session: "session"). Replaced with an 11-entry overrides map that falls back to the type name itself. Saves ~38 bytes gzipped.

Shorten default ignore-error patterns (packages/core/src/integrations/eventFilters.ts)

Converted verbose string literals in DEFAULT_IGNORE_ERRORS to shorter regex patterns with the same matching behavior:

• "vv().getRestrictions is not a function. (In 'vv()..." → /vv\(\)\.getRestrictions is not a function/
• "Can't find variable: _AutofillCallbackHandler" → regex equivalent
• Long CEFSharp simulateEvent pattern → shorter partial match

Saves ~38 bytes gzipped.

Derive lazy-load integration bundle names (packages/browser/src/utils/lazyLoadIntegration.ts)

The LazyLoadableIntegrations object stored 21 key-value pairs where values were mostly derivable from keys (strip "Integration", lowercase). Replaced with an array of names + a derivation function, with a 3-entry exceptions map for hyphenated bundle names. Also uses string.split(",") for the array. Saves ~30 bytes gzipped.

Consolidate sendSession logic (packages/core/src/client.ts)

sendSession() had duplicate code blocks for session aggregates vs individual sessions, both checking and backfilling release and environment. Unified into a single code path. Saves ~16 bytes gzipped.

Use URLSearchParams in getReportDialogEndpoint (packages/core/src/api.ts)

Replaced manual encodeURIComponent string concatenation with URLSearchParams, which is more concise and already used elsewhere in the same file. Saves ~26 bytes gzipped.

Inline Vue ViewModel checks (packages/core/src/utils/normalize.ts, string.ts)

isVueViewModel() and getVueInternalName() were standalone exported functions only called from two sites (normalize and safeJoin). Inlined the checks directly, allowing tree-shaking to eliminate the standalone functions. Saves ~15 bytes gzipped.

Rename internal sentryWrapped → sW (packages/browser/src/helpers.ts, packages/core/src/utils/stacktrace.ts)

The sentryWrapped function name in the wrap() helper is reserved from mangling because it is matched by a regex in stripSentryFramesAndReverse() for internal frame stripping. Shortened to sW and updated the regex to match both names for backwards compatibility. Saves ~10 bytes gzipped.

Smaller cleanups

• DEFAULT_EVENT_TARGET array → comma-separated string.split(",") (51 bytes raw)
• getErrorPropertyFromObject — Object.values().find() instead of for...in loop
• getOwnProperties — Object.fromEntries(Object.entries()) instead of manual loop
• isNativeFunction — simplified regex from exact whitespace match to /\[native code\]/
• Browser extension detection — regex test instead of array.some() with startsWith
• _enhanceEventWithInitialFrame — removed redundant intermediate variable aliases
• baggage.ts — .startsWith() instead of .match() for prefix check
• Unused breadcrumbData variable removed from fetch breadcrumb handler

What was NOT changed

• No public API signatures were modified
• No functionality was removed
• No new dependencies were added
• All changes are in source code or build config — no test modifications
• The unsafe_* terser options only apply to CDN .min.js bundles (not npm ESM/CJS output)

Co-Authored-By: Claude claude@anthropic.com

[linear-code]

JS-1949

[Lms24]

reviewed, merged and closed all PRs