fix(event-buffer): re-compact the event with preserveUserFileBase64: false

[icecrasher321]

Summary

When preserveUserFileBase64 is on and the event still exceeds the threshold, re-compact the event with preserveUserFileBase64: false. This drops inline base64 (clients can lazily fetch it via sim.files.readBase64) while keeping file metadata and the rest of the event intact, so the stream keeps flowing.

Type of Change

• Bug fix

Testing

Tested manually

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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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		May 13, 2026 4:11am

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PR Summary

Medium Risk
Changes execution event compaction behavior when preserveUserFileBase64 is enabled, which can affect SSE/replay payload contents and client expectations in streaming scenarios. Logic is localized but touches a critical path for event delivery under size limits.

Overview
Prevents SSE/replay execution events from failing the LARGE_VALUE_THRESHOLD_BYTES cap when preserveUserFileBase64 is requested by re-compacting oversized payloads with preserveUserFileBase64: false, stripping inline base64 while keeping existing LargeValueRefs intact.

Adds a warning log when this fallback triggers, and still throws if the event remains too large after the second compaction.

^{Reviewed by Cursor Bugbot for commit f0d2431. Configure here.}

[greptile-apps]

Greptile Summary

This PR adds a two-pass compaction fallback in compactEventForBuffer: when preserveUserFileBase64 is enabled and the first-pass result still exceeds LARGE_VALUE_THRESHOLD_BYTES, it re-compacts the already-compacted payload with preserveUserFileBase64: false, stripping inline base64 while preserving existing LargeValueRef objects and all other metadata.

• Fallback recompaction: The second compactExecutionPayload call targets compactedData (not event.data), so LargeValueRef objects from the first pass pass through unchanged via the isLargeValueRef early-return — no duplicate storage objects are created.
• Observability: A logger.warn with execution ID, event type, and byte counts is emitted whenever the fallback path fires.
• Error path preserved: If stripping base64 still leaves the payload over the threshold, the existing throw fires, keeping the hard failure contract intact.

Confidence Score: 5/5

Safe to merge — the fallback path is well-scoped, correctly avoids duplicate storage writes, and preserves the hard-failure contract for payloads that remain oversized after base64 stripping.

The change is a focused, defensive fallback that only activates when preserveUserFileBase64 is explicitly set and the compacted payload is still over the size cap. Recompacting the already-compacted result rather than raw event.data is the correct approach, and the existing isLargeValueRef early-return in compactValue guarantees no duplicate storage objects. The final error-throw path remains intact.

No files require special attention.

Important Files Changed

Filename	Overview
apps/sim/lib/execution/event-buffer.ts	Adds a two-pass size-reduction fallback: strips UserFile base64 inline when the first compaction pass still exceeds the threshold; correctly recompacts compactedData (not raw event.data) and adds logger.warn for observability.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[compactEventForBuffer] --> B{event has data?}
    B -- No --> C[return event unchanged]
    B -- Yes --> D[compactExecutionPayload\npass 1: preserveUserFileBase64=ctx.value]
    D --> E[trimFinalBlockLogsForEventData]
    E --> F[getJsonSize]
    F --> G{preserveUserFileBase64 &&\nsize > THRESHOLD?}
    G -- No --> H{size > THRESHOLD?}
    G -- Yes --> I[compactExecutionPayload\npass 2: preserveUserFileBase64=false\nInput: already-compacted data]
    I --> J[trimFinalBlockLogsForEventData]
    J --> K[getJsonSize]
    K --> L[logger.warn with byte counts]
    L --> H
    H -- No --> M[return event with compacted data]
    H -- Yes --> N[throw Error: still too large]

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[icecrasher321]

@greptile

[icecrasher321]

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^{Reviewed by Cursor Bugbot for commit f0d2431. Configure here.}