Performance Issue: excessive `structuredClone` in `runSubscribersWithMutation`

[daohoangson]

The runSubscribersWithMutation function has a critical performance bottleneck causing long execution time with the potential to hang the browser completely.

Impact

• The example dojo app has 26 active subscribers during streaming
• Message arrays grow from 0 to 42 messages during a 742KB test run with ~200 events
• Current execution time: 810ms

Traffic	Events	Trace

Root Cause

This is in the hot path, called 2× per streaming event (once for onEvent, once for specific event handler), but it:

• Clones per subscriber even if they do not mutate
• Does expensive change detection via JSON.stringify()

Proposed Solution

I have a working fix on my fork with two commits:

• Move cloning from inputs to outputs scoutqa-dot-ai@27b7ab2
• Use reference equality to identify changes scoutqa-dot-ai@bdb380e

Expected Results

• New execution time: ~53ms (15x faster)
• Eliminate serialization bottleneck visible in flame graphs

I'm ready to submit a PR once this approach is validated.

[fhydralisk]

Same issue. Large state causes laggy render when streaming messages.

[daohoangson]

I'm waiting for feedback from the maintainers before opening a PR. I have also cross posted this on Discord for visibility https://discord.com/channels/1379082175625953370/1455463616836010065/1455463616836010065

[NathanTarbert]

Hi @daohoangson, thanks for opening this issue. I will try and get some eyeballs on this for you.

[MikeRyanDev]

Hi @daohoangson, sounds like you've got a good beat on the correct fix here. Please open a PR, and I'll work with you to get it merged! 😃

[daohoangson]

Thanks @NathanTarbert and @MikeRyanDev. I have submitted #899 in an attempt to fix this.

[fhydralisk]

Looking forward to this fix.