Variable Aggregator Only Aggregates One Variable

[tianshiqingge]

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1. Is this request related to a challenge you're experiencing? Tell me about your story.

Problem Description
I'm experiencing an issue with the Variable Aggregator in Dify where it only aggregates one variable instead of multiple variables as expected.

Current Situation
Input Node: Webhook Trigger
Expected Behavior: The aggregator should collect all configured variables
Actual Behavior: Only the first variable is being aggregated
Detailed Information
The webhook trigger outputs a complete JSON object containing multiple variables:

json
{
"alert_subject": "CPU usage consistently exceeds 95%",
"alert_message": "CPU usage consistently exceeds 95%",
"alert_severity": "High",
"alert_host": "test-server-01",
"trigger_id": "121",
"event_id": "123",
"timestamp": "2026-04-12T03:24:10.283Z",
"source": "zabbix-7.4"
}
However, after passing through the Variable Aggregator, only the first variable appears:

json
{
"alert_subject": "CPU usage consistently exceeds 95%"
}
Expected Result
The Variable Aggregator should aggregate all configured variables into a single output object, not just the first one.

Request for Help
Could anyone help me understand what might be causing this issue? Is this a configuration problem or potentially a bug in the Variable Aggregator component?

Any suggestions or alternative approaches would be greatly appreciated!

2. Additional context or comments

No response

[dosubot[bot]]

This is actually expected behavior, not a bug — the Variable Aggregator node is somewhat misleadingly named. It functions as a fallback selector that picks the first non-null variable from its inputs, rather than merging all variables together [1]. Internally, it loops through the configured variables and breaks after finding the first non-null one, which is why you only see alert_subject.

For your webhook use case, the recommended approach is to skip the Variable Aggregator entirely and instead use one of these alternatives:

1. Pass webhook variables directly to downstream nodes — most nodes (like LLM nodes) can accept multiple input variables in their prompts without needing aggregation.

2. Use a Template node to combine the fields into a single formatted variable:

   Subject: {{ webhook.alert_subject }}
   Message: {{ webhook.alert_message }}
   Severity: {{ webhook.alert_severity }}
   Host: {{ webhook.alert_host }}

3. Use a Code node for more flexible merging logic [2]:

   return {"result": {"alert_subject": arg1, "alert_message": arg2, ...}}

There is also a newer aggregate_all option (introduced in PR #22200) that collects all inputs into a list rather than just the first one [3], but for combining webhook fields specifically, a Template or Code node is the most straightforward solution.

To reply, just mention @dosu.

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