macOS + REDUCE_EXPORTS: Cap’n Proto misidentifies kj::Exception as unknown non-KJ exception #34723

1. 
   ryanofsky commented at 6:24 pm on March 3, 2026: contributor

   macOS builds with REDUCE_EXPORTS currently cause Cap’n Proto RPC to report:

   0remote exception: unknown non-KJ exception of type: kj::Exception
   

   instead of expected typed exception messages. Tests currently contain a workaround to accept this behavior.

   This issue tracks investigating and fixing the underlying exception type visibility/RTTI problem and removing the workaround.

   Related: #34422 (review)

2. fanquake added the label macOS on Mar 3, 2026
3. fanquake added the label interfaces on Mar 3, 2026

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ryanofsky

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macOS interfaces