fix(node): count event bytes correctly so the size limits are enforced

.changeset/fix-node-event-size-guard.md

@@ -0,0 +1,5 @@
+---
+'@segment/analytics-node': patch
+---
+
+Fix the per-event and batch size limits, which were not enforced. `ContextBatch.calculateSize` used a broken byte-count regex (`split(/%..|i/)`) that counted only `%XX` escapes plus the letter "i" instead of UTF-8 bytes, so a ~39 KB event measured as ~21 bytes and passed the 32 KB per-event guard. Restored the correct byte count so oversized events are rejected before they are sent.

packages/node/src/plugins/segmentio/__tests__/context-batch.test.ts

@@ -0,0 +1,29 @@
+import { ContextBatch } from '../context-batch'
+import { NodeEventFactory } from '../../../app/event-factory'
+import { Context } from '../../../app/context'
+
+const eventFactory = new NodeEventFactory()
+const pending = (context: Context) => ({ resolver: () => undefined, context })
+
+describe('ContextBatch', () => {
+  it('rejects an event that exceeds the 32 KB per-event size limit', () => {
+    // ~40 KB of JSON, well over the 32 KB per-event cap
+    const event = eventFactory.track(
+      'big',
+      { data: 'a'.repeat(40000) },
+      { userId: 'u' }
+    )
+    const batch = new ContextBatch(100)
+    const result = batch.tryAdd(pending(new Context(event)))
+    expect(result.success).toBe(false)
+    if (!result.success) {
+      expect(result.message).toContain('exceeds maximum event size')
+    }
+  })
+
+  it('accepts a normal small event', () => {
+    const event = eventFactory.track('small', { ok: true }, { userId: 'u' })
+    const batch = new ContextBatch(100)
+    expect(batch.tryAdd(pending(new Context(event))).success).toBe(true)
+  })
+})

packages/node/src/plugins/segmentio/context-batch.ts

@@ -53,7 +53,7 @@ export class ContextBatch {
   }
 
   private calculateSize(ctx: Context): number {
-    return encodeURI(JSON.stringify(ctx.event)).split(/%..|i/).length
+    return encodeURI(JSON.stringify(ctx.event)).split(/%..|./).length - 1
   }
 
   getEvents(): SegmentEvent[] {