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Avoid bun memory leak bug from TransformStream#4255

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Avoid bun memory leak bug from TransformStream#4255
TheodoreSpeaks wants to merge 3 commits intostagingfrom
fix/memory-leak

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@TheodoreSpeaks TheodoreSpeaks commented Apr 22, 2026 •
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Summary

Bun has a bug in TransformStream: oven-sh/bun#28035 causing high memory consumption due to no backpressure signal. We use this in

Type of Change

  • Bug fix
  • New feature
  • Breaking change
  • Documentation
  • Other: ___________

Testing

  • Validated that streaming responses still work fine with an agent block in a workflow locally.

Checklist

  • Code follows project style guidelines
  • Self-reviewed my changes
  • Tests added/updated and passing
  • No new warnings introduced
  • I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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vercel Bot commented Apr 22, 2026 •
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TheodoreSpeaks commented Apr 22, 2026

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cursor Bot commented Apr 22, 2026 •
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PR Summary

Medium Risk
Touches core streaming execution plumbing and how agent responses are persisted, so regressions could break SSE streaming or produce missing/incorrect block outputs; scope is limited to streaming paths with added safeguards.

Overview
Avoids Bun TransformStream memory issues by changing how streaming block outputs are consumed and persisted.

BlockExecutor.handleStreamingExecution no longer tee()s the source stream; it now reads via a single getReader(), forwards bytes to the client stream, assembles full text after drain, and skips output/memory persistence if the source wasn’t fully drained.

Agent streaming memory persistence is moved from memoryService.wrapStreamForPersistence() (removed) to a new optional StreamingExecution.onFullContent callback, which is invoked after the stream drains to append the assistant message to memory.

Reviewed by Cursor Bugbot for commit bf2f9af. Bugbot is set up for automated code reviews on this repo. Configure here.

cursor[bot]
cursor Bot reviewed Apr 22, 2026
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Comment thread apps/sim/executor/execution/block-executor.ts
@TheodoreSpeaks @claude
fix(executor): skip content persistence when stream consumer exits early
c29447a 
Previously, if the onStream consumer caught an internal error without
re-throwing, the block-executor would treat the shortened accumulator
as the complete response, persist a truncated string to memory via
appendToMemory, and set it as executionOutput.content.

Track whether the source ReadableStream actually closed (done=true) in
the pull handler. If onStream returns before the source drains, skip
content persistence and log a warning — the old tee()-based flow was
immune to this because the executor branch drained independently of
the client branch.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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TheodoreSpeaks commented Apr 24, 2026

@BugBot review

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cursor Bot reviewed Apr 24, 2026
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✅ Bugbot reviewed your changes and found no new issues!

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Reviewed by Cursor Bugbot for commit bf2f9af. Configure here.

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