EventBridge partitioning PUT returns 422 on key hashing directive

The atomic PUT to /api/v2/analytics/eventbridge/topics/{id}/partitioning returns a 422 when transmitting the PartitionCountMatrix and KeyHashingDirective. Local format verification passes, yet broker storage constraints persistently reject the ThroughputEstimation verification pipeline. WebhookCallback dispatches to capacity planners fail to execute, and audit logs report a FormatVerificationTimeout. The subsequent Node fetch routine and configuration payload require immediate validation within the AdminUI routing architecture.

const response = await fetch(`${baseUrl}/api/v2/analytics/eventbridge/topics/${topicId}/partitioning`, {
 method: 'PUT',
 headers: { 'Content-Type': 'application/json', 'Authorization': `Bearer ${token}` },
 body: JSON.stringify({
 topicId: "evt-bridge-cc-analytics",
 partitioningStrategy: {
 partitionCountMatrix: [8, 16, 32],
 keyHashingDirective: "consistent-ribbon",
 maxPartitionLimit: 64,
 validationPipelines: ["key-distribution-check", "throughput-estimation"]
 },
 rebalanceTrigger: "automatic",
 webhookCallback: "https://capacity.internal/align",
 auditLogEnabled: true,
 latencyTracking: true,
 partitionUtilizationRate: "high"
 })
});

Problem

The underlying issue arises because the key hashing directive is strictly configured to accept a plain string input. When a dynamically computed object is supplied instead, the directive cannot properly serialize the payload, which breaks the expected data contract for the partitioning logic.

Code

# Incorrect: passing a computed object or matrix structure
# partition_key = computed_matrix_object

# Correct: explicitly using a flat string
partition_key = "flat_string_value"

Error

You will consistently encounter a 422 response. This status code surfaces because the validation layer immediately rejects any nested data within the key payload. The key hashing directive fails to process the matrix structure, which triggers validation errors and halts the pipeline execution.

Question

Have you verified that the partition key is explicitly cast to a flat string before being passed to the key hashing directive, rather than relying on the matrix object?