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Fix iteration node streaming bug #6328

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Fix iteration node streaming bug #6328

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6bdc00c
Fix iteration node streaming bug
j-sanaa May 1, 2026
29227dc
Merge branch 'main' into fix-iteration-streaming-bug
j-sanaa May 1, 2026
3591b98
Merge branch 'main' into fix-iteration-streaming-bug
j-sanaa May 6, 2026
781aaf4
Merge branch 'fix-iteration-streaming-bug' of https://github.com/Flow…
j-sanaa May 6, 2026
f38d49e
Fixed gemini comment
j-sanaa May 6, 2026
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15 changes: 10 additions & 5 deletions packages/server/src/utils/buildAgentflow.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1287,7 +1287,6 @@ const executeNode = async ({
flowData: JSON.stringify(iterationFlowData)
}

// Initialize array to collect results from iterations
const iterationResults: string[] = []

// Execute sub-flow for each item in the iteration array
Expand Down Expand Up @@ -1334,9 +1333,16 @@ const executeNode = async ({
productId
})

// Store the result
if (subFlowResult?.text) {
iterationResults.push(subFlowResult.text)
if (subFlowResult) {
iterationResults.push(subFlowResult.text || '')
if (subFlowResult.text) {
// Stream each result as it completes rather than batching at the end.
// Sub-flows run with isRecursive=true, so inner nodes (e.g. DirectReply)
// never reach isLastNode=true and never call streamTokenEvent themselves.
if (isLastNode && sseStreamer) {
sseStreamer.streamTokenEvent(chatId, (i > 0 ? '\n' : '') + subFlowResult.text)
}
}
}
Comment on lines +1336 to 1346
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@gemini-code-assist gemini-code-assist Bot May 1, 2026

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medium

The current streaming logic skips empty results, which creates a discrepancy with the final output generated by iterationResults.join('\n') (which includes empty strings as empty lines).

To maintain consistency between the real-time stream and the final persisted message, consider streaming every result. Using the loop index i instead of successfulCount ensures the newline separator correctly matches the join behavior.

                        if (subFlowResult) {
                            const resultText = subFlowResult.text || ''
                            iterationResults.push(resultText)
                            if (isLastNode && sseStreamer) {
                                // Stream each result (including empty ones) to match the final joined output
                                sseStreamer.streamTokenEvent(chatId, (i > 0 ? '\n' : '') + resultText)
                            }
                        }
References
  1. A suggested change, even if valid, may be deferred if it pertains to logic that is not being modified in the current pull request.

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@j-sanaa j-sanaa May 6, 2026

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@HenryHengZJ @jocelynlin-wd
There are 2 approaches to resolving the streaming bug:

Approach 1 — Errors excluded from content (Ref: 328d652)
Aligns iteration with every other v2 node (errors go to execution log only, not chat content), but
this changes the non-streaming API response and persisted chat history for existing flows.

Approach 2 — Errors included in content, not in stream (Changes made in this PR)
Preserves the pre-fix API response and chat history (errors visible on reload), but what was streamed
live differs from what gets saved — a user watching live sees fewer results than a user reading
history.

Decision: Should iteration errors be part of content (and therefore streamed to keep live and history
consistent), or excluded from content entirely to match all v2 node behavior ?


// Add executed data from sub-flow to main execution data with appropriate iteration context
Expand Down Expand Up @@ -1392,7 +1398,6 @@ const executeNode = async ({
}
}

// Update the output with combined results
results.output = {
...(results.output || {}),
iterationResults,
Expand Down
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