EventBridge transformation template API returning 202 but validation job hangs on JSONata complexity limits

Problem
Pushing a new EventBridge transformation template via the REST API keeps getting stuck in that async validation queue. The whole setup is supposed to sync transformation status with our external data platform via webhook callbacks. Instead, the pipeline just drops the ball. We don’t get any useful feedback.

We’ve got a Java service on the backend constructing these payloads for the transformation configurator. It’s supposed to catch the completion event, but the Node.js Express middleware just sees a dead callback. Tracking configuration latency and validation success rates for DevOps efficiency is pretty much useless right now since the jobs never finish.

Code

Here’s the request hitting /api/v2/eventbridge/event-transformation-templates:

{
 "name": "voice-event-flattener-v3",
 "description": "Maps raw telephony events to downstream schema",
 "transformation": {
 "expression": "$merge([$.metadata, { 'agent_id': $.routing.agent_id, 'queue_status': $.routing.queue_state, 'error_code': if($.routing.error != null) { $.routing.error.code } else { 0 } })",
 "fieldMappings": [
 { "source": "routing.mediaType", "target": "media_type", "required": true },
 { "source": "routing.wfmData", "target": "wfm_context", "required": false }
 ],
 "outputStructure": {
 "type": "object",
 "maxDepth": 3,
 "strictMode": true
 }
 },
 "validation": {
 "runMockTest": true,
 "mockPayload": { "routing": { "agent_id": "12345", "queue_state": "available" } }
 }
}

Error

The API spits back a 202 Accepted with a job ID. Waiting on that callback times out after 15 minutes. Checked the audit logs endpoint and it shows VALIDATION_FAILED but the error payload is completely empty. Looks like the expression complexity limit is tripping the automatic test execution trigger. Or maybe the output type checking pipeline is choking on the conditional logic inside the JSONata matrix.

Question

How do I structure the JSONata expression or adjust the field mapping directives to bypass that complexity limit without breaking the mock payload evaluation? Also, is there a way to force the syntax verification to return the actual error instead of swallowing it in the async job?

Generating transformation audit logs for governance compliance is straightforward, but the validation step keeps blocking the whole chain. Just need the exact JSONata structure that actually passes the output structure constraints. Or whatever the actual limit is.

HTTP 202 Accepted usually masks a nested conditional block hitting the 500-byte AST limit. The Java builder’s packing too many lookups into a single rule. Strip the recursive references before the async worker chokes. Split it into two smaller templates. The queue clears on its own.

The 202 hang usually happens because the Java builder nests $filter and $map inside a single string variable. The parser doesn’t even finish before hitting the async queue. Try moving the transformation logic into a version-controlled HCL module instead of pushing raw JSON via REST.

resource "genesyscloud_eventbridge_transformation" "main" {
 name = "webhook_payload_v2"
 template = file("${path.module}/jsonata/stage1.jsonata")
}

This keeps the payload under the byte limit and lets the CLI handle the validation hook. Saw a similar thread last month where someone ran into the exact same AST ceiling. The fix was just chaining two smaller templates and letting the platform route them sequentially. Attached is a screenshot of the deployment pipeline showing the split working cleanly across environments. Run genesyscloud eventbridge transformation create locally first to catch the syntax errors. Just drop the nested conditionals.

You might want to try bypassing the Java builder’s inline parser. Here’s a quick breakdown:

• Problem: Async validator chokes on nested lookups inside the JSONata string.
• Code:

const payload = { template: JSON.stringify({ rule: "$map(events)" }) }

• Error: Returns 202 Accepted but the worker stalls on AST depth checks.
• Question: Still waiting on a platform config patch to lift the limit.