fix(core): Set cache token attributes on spans

The setTokenUsageAttributes function was accepting cache token parameters
but only using them to calculate total tokens. Now it also sets them as
individual span attributes (gen_ai.usage.input_tokens.cache_write and
gen_ai.usage.input_tokens.cached).

Also updates .size-limit.js to use develop branch value.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: codyde

.size-limit.js

@@ -287,7 +287,7 @@ module.exports = [
     import: createImport('init'),
     ignore: [...builtinModules, ...nodePrefixedBuiltinModules],
     gzip: true,
-    limit: '163 KB',
+    limit: '166 KB',
   },
   {
     name: '@sentry/node - without tracing',

packages/core/src/tracing/ai/utils.ts

@@ -4,6 +4,8 @@
 import type { Span } from '../../types-hoist/span';
 import {
   GEN_AI_USAGE_INPUT_TOKENS_ATTRIBUTE,
+  GEN_AI_USAGE_INPUT_TOKENS_CACHE_WRITE_ATTRIBUTE,
+  GEN_AI_USAGE_INPUT_TOKENS_CACHED_ATTRIBUTE,
   GEN_AI_USAGE_OUTPUT_TOKENS_ATTRIBUTE,
   GEN_AI_USAGE_TOTAL_TOKENS_ATTRIBUTE,
 } from './gen-ai-attributes';
@@ -47,15 +49,15 @@ export function buildMethodPath(currentPath: string, prop: string): string {
  * @param span - The span to add attributes to
  * @param promptTokens - The number of prompt tokens
  * @param completionTokens - The number of completion tokens
- * @param cachedInputTokens - The number of cached input tokens
- * @param cachedOutputTokens - The number of cached output tokens
+ * @param cacheWriteTokens - The number of cache creation/write input tokens
+ * @param cacheReadTokens - The number of cache read input tokens
  */
 export function setTokenUsageAttributes(
   span: Span,
   promptTokens?: number,
   completionTokens?: number,
-  cachedInputTokens?: number,
-  cachedOutputTokens?: number,
+  cacheWriteTokens?: number,
+  cacheReadTokens?: number,
 ): void {
   if (promptTokens !== undefined) {
     span.setAttributes({
@@ -67,18 +69,28 @@ export function setTokenUsageAttributes(
       [GEN_AI_USAGE_OUTPUT_TOKENS_ATTRIBUTE]: completionTokens,
     });
   }
+  if (cacheWriteTokens !== undefined) {
+    span.setAttributes({
+      [GEN_AI_USAGE_INPUT_TOKENS_CACHE_WRITE_ATTRIBUTE]: cacheWriteTokens,
+    });
+  }
+  if (cacheReadTokens !== undefined) {
+    span.setAttributes({
+      [GEN_AI_USAGE_INPUT_TOKENS_CACHED_ATTRIBUTE]: cacheReadTokens,
+    });
+  }
   if (
     promptTokens !== undefined ||
     completionTokens !== undefined ||
-    cachedInputTokens !== undefined ||
-    cachedOutputTokens !== undefined
+    cacheWriteTokens !== undefined ||
+    cacheReadTokens !== undefined
   ) {
     /**
      * Total input tokens in a request is the summation of `input_tokens`,
      * `cache_creation_input_tokens`, and `cache_read_input_tokens`.
      */
     const totalTokens =
-      (promptTokens ?? 0) + (completionTokens ?? 0) + (cachedInputTokens ?? 0) + (cachedOutputTokens ?? 0);
+      (promptTokens ?? 0) + (completionTokens ?? 0) + (cacheWriteTokens ?? 0) + (cacheReadTokens ?? 0);
 
     span.setAttributes({
       [GEN_AI_USAGE_TOTAL_TOKENS_ATTRIBUTE]: totalTokens,