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feat(core): Accumulate tokens for gen_ai.invoke_agent spans from child LLM calls #17281

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feat(core): Accumulate tokens for gen_ai.invoke_agent spans from child LLM calls #17281

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feat(core): Accumulate tokens for gen_ai.invoke_agent spans from chil…
RulaKhaled Aug 1, 2025
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fix comment
RulaKhaled Aug 1, 2025
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6 changes: 6 additions & 0 deletions dev-packages/node-integration-tests/suites/tracing/vercelai/test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -432,6 +432,9 @@ describe('Vercel AI integration', () => {
'vercel.ai.settings.maxSteps': 1,
'vercel.ai.streaming': false,
'gen_ai.response.model': 'mock-model-id',
'gen_ai.usage.input_tokens': 15,
'gen_ai.usage.output_tokens': 25,
'gen_ai.usage.total_tokens': 40,
'operation.name': 'ai.generateText',
'sentry.op': 'gen_ai.invoke_agent',
'sentry.origin': 'auto.vercelai.otel',
Expand Down Expand Up @@ -550,6 +553,9 @@ describe('Vercel AI integration', () => {
'vercel.ai.settings.maxSteps': 1,
'vercel.ai.streaming': false,
'gen_ai.response.model': 'mock-model-id',
'gen_ai.usage.input_tokens': 15,
'gen_ai.usage.output_tokens': 25,
'gen_ai.usage.total_tokens': 40,
'operation.name': 'ai.generateText',
'sentry.op': 'gen_ai.invoke_agent',
'sentry.origin': 'auto.vercelai.otel',
Expand Down
48 changes: 48 additions & 0 deletions packages/core/src/utils/vercel-ai.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -62,10 +62,17 @@ function onVercelAiSpanStart(span: Span): void {

function vercelAiEventProcessor(event: Event): Event {
if (event.type === 'transaction' && event.spans) {
// First pass: process all spans normally
for (const span of event.spans) {
// this mutates spans in-place
processEndedVercelAiSpan(span);
}

// Second pass: accumulate tokens for gen_ai.invoke_agent spans
// TODO: Determine how to handle token aggregation for tool call spans.
for (const span of event.spans) {
accumulateTokensFromChildSpans(span, event.spans);
}
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Bug: Token Accumulation Error in Nested Spans

Token accumulation for nested gen_ai.invoke_agent spans is incorrect. The accumulateTokensFromChildSpans function processes spans in arbitrary array order. This means a parent gen_ai.invoke_agent span may aggregate tokens from its children before those children have fully accumulated tokens from their own descendants, resulting in incomplete token totals on the parent.

Locations (1)
Fix in Cursor Fix in Web

}
return event;
}
Expand Down Expand Up @@ -241,6 +248,47 @@ export function addVercelAiProcessors(client: Client): void {
client.addEventProcessor(Object.assign(vercelAiEventProcessor, { id: 'VercelAiEventProcessor' }));
}

/**
* For the gen_ai.invoke_agent span, iterate over child spans and aggregate tokens:
* - Input tokens from client LLM child spans that include `gen_ai.usage.input_tokens` attribute.
* - Output tokens from client LLM child spans that include `gen_ai.usage.output_tokens` attribute.
* - Total tokens from client LLM child spans that include `gen_ai.usage.total_tokens` attribute.
*
* Only immediate children of the `gen_ai.invoke_agent` span need to be considered,
* since aggregation will automatically occur for each parent span.
*/
function accumulateTokensFromChildSpans(spanJSON: SpanJSON, allSpans: SpanJSON[]): void {
if (spanJSON.op !== 'gen_ai.invoke_agent') {
return;
}
const childSpans = allSpans.filter(childSpan => childSpan.parent_span_id === spanJSON.span_id);

let totalInputTokens = 0;
let totalOutputTokens = 0;

for (const childSpan of childSpans) {
const inputTokens = childSpan.data[GEN_AI_USAGE_INPUT_TOKENS_ATTRIBUTE];
const outputTokens = childSpan.data[GEN_AI_USAGE_OUTPUT_TOKENS_ATTRIBUTE];

if (typeof inputTokens === 'number') {
totalInputTokens += inputTokens;
}
if (typeof outputTokens === 'number') {
totalOutputTokens += outputTokens;
}
}

if (totalInputTokens > 0) {
spanJSON.data[GEN_AI_USAGE_INPUT_TOKENS_ATTRIBUTE] = totalInputTokens;
}
if (totalOutputTokens > 0) {
spanJSON.data[GEN_AI_USAGE_OUTPUT_TOKENS_ATTRIBUTE] = totalOutputTokens;
}
if (totalInputTokens > 0 || totalOutputTokens > 0) {
spanJSON.data['gen_ai.usage.total_tokens'] = totalInputTokens + totalOutputTokens;
}
}

function addProviderMetadataToAttributes(attributes: SpanAttributes): void {
const providerMetadata = attributes[AI_RESPONSE_PROVIDER_METADATA_ATTRIBUTE] as string | undefined;
if (providerMetadata) {
Expand Down