shutdownTimeout is silently ignored on iOS (key/unit mismatch with cocoa shutdownTimeInterval) #6748

Summary

The documented shutdownTimeout option is honored on Android but has no effect on iOS. The native cocoa SDK always uses its default 2s shutdown flush interval regardless of what the user sets.

Root cause

The JS layer forwards options to native by key name (wrapper.ts → RNSentry.initNativeSdk(filteredOptions)), and shutdownTimeout passes through unchanged. On native:

• Android — RNSentryStart.java maps shutdownTimeout → setShutdownTimeoutMillis(...). ✅ Works (both are milliseconds).
• iOS — cocoa's dictionary parser (SentryOptionsInternal) only reads the key shutdownTimeInterval (an NSTimeInterval, i.e. seconds). It has no shutdownTimeout key, and RNSentryStart.m does no explicit handling. So the value is dropped and the native default (2s) is always used.

Two mismatches, not one:

1. Key name: RN sends shutdownTimeout; cocoa reads shutdownTimeInterval.
2. Unit: RN's shutdownTimeout is milliseconds (per its JSDoc and Android's ...Millis); cocoa's shutdownTimeInterval is seconds. A rename alone would be a 1000× error — the value must be divided by 1000.

Evidence

• packages/core/src/js/options.ts — shutdownTimeout?: number documented as "milliseconds … default 2 seconds".
• packages/core/src/js/wrapper.ts — shutdownTimeout is not filtered out, so it's forwarded verbatim.
• packages/core/ios/RNSentryStart.m — no shutdown* handling.
• cocoa SentryOptionsInternal — parses only shutdownTimeInterval (seconds).

Expected

Setting shutdownTimeout affects the native iOS shutdown flush interval, matching Android behavior.

Proposed fix

In RNSentryStart.m (createOptionsWithDictionary), read shutdownTimeout (ms) and set sentryOptions.shutdownTimeInterval = value / 1000.0. Add test coverage on both platforms.

Environment

Affects all RN SDK versions on the current native binding; verified against bundled cocoa 9.29.0.