feat(core): Automatically disable truncation when span streaming is enabled in LangGraph integration (#20231)

When span streaming is enabled, the `enableTruncation` option now
defaults
to `false` unless the user has explicitly set it.

Closes: #20225

Author: andreiborza

dev-packages/node-integration-tests/suites/tracing/langgraph/instrument-streaming-with-truncation.mjs

@@ -0,0 +1,16 @@
+import * as Sentry from '@sentry/node';
+import { loggingTransport } from '@sentry-internal/node-integration-tests';
+
+Sentry.init({
+  dsn: 'https://public@dsn.ingest.sentry.io/1337',
+  release: '1.0',
+  tracesSampleRate: 1.0,
+  sendDefaultPii: true,
+  transport: loggingTransport,
+  traceLifecycle: 'stream',
+  integrations: [
+    Sentry.langGraphIntegration({
+      enableTruncation: true,
+    }),
+  ],
+});

dev-packages/node-integration-tests/suites/tracing/langgraph/instrument-streaming.mjs

@@ -0,0 +1,11 @@
+import * as Sentry from '@sentry/node';
+import { loggingTransport } from '@sentry-internal/node-integration-tests';
+
+Sentry.init({
+  dsn: 'https://public@dsn.ingest.sentry.io/1337',
+  release: '1.0',
+  tracesSampleRate: 1.0,
+  sendDefaultPii: true,
+  transport: loggingTransport,
+  traceLifecycle: 'stream',
+});

dev-packages/node-integration-tests/suites/tracing/langgraph/test.ts

@@ -398,4 +398,50 @@ describe('LangGraph integration', () => {
       });
     },
   );
+
+  const streamingLongContent = 'A'.repeat(50_000);
+
+  createEsmAndCjsTests(__dirname, 'scenario-no-truncation.mjs', 'instrument-streaming.mjs', (createRunner, test) => {
+    test('automatically disables truncation when span streaming is enabled', async () => {
+      await createRunner()
+        .expect({
+          span: container => {
+            const spans = container.items;
+
+            const chatSpan = spans.find(s =>
+              s.attributes?.[GEN_AI_INPUT_MESSAGES_ATTRIBUTE]?.value?.includes(streamingLongContent),
+            );
+            expect(chatSpan).toBeDefined();
+          },
+        })
+        .start()
+        .completed();
+    });
+  });
+
+  createEsmAndCjsTests(
+    __dirname,
+    'scenario-no-truncation.mjs',
+    'instrument-streaming-with-truncation.mjs',
+    (createRunner, test) => {
+      test('respects explicit enableTruncation: true even when span streaming is enabled', async () => {
+        await createRunner()
+          .expect({
+            span: container => {
+              const spans = container.items;
+
+              // With explicit enableTruncation: true, truncation keeps only the last message
+              // and drops the long content. The result should NOT contain the full 50k 'A' string.
+              const chatSpan = spans.find(s =>
+                s.attributes?.[GEN_AI_INPUT_MESSAGES_ATTRIBUTE]?.value?.includes('Follow-up question'),
+              );
+              expect(chatSpan).toBeDefined();
+              expect(chatSpan!.attributes[GEN_AI_INPUT_MESSAGES_ATTRIBUTE].value).not.toContain(streamingLongContent);
+            },
+          })
+          .start()
+          .completed();
+      });
+    },
+  );
 });

packages/core/src/tracing/langgraph/index.ts

@@ -17,6 +17,7 @@ import {
   getJsonString,
   getTruncatedJsonString,
   resolveAIRecordingOptions,
+  shouldEnableTruncation,
 } from '../ai/utils';
 import type { LangChainMessage } from '../langchain/types';
 import { normalizeLangChainMessages } from '../langchain/utils';
@@ -150,7 +151,7 @@ function instrumentCompiledGraphInvoke(
                 span.setAttribute(GEN_AI_SYSTEM_INSTRUCTIONS_ATTRIBUTE, systemInstructions);
               }
 
-              const enableTruncation = options.enableTruncation ?? true;
+              const enableTruncation = shouldEnableTruncation(options.enableTruncation);
               const filteredLength = Array.isArray(filteredMessages) ? filteredMessages.length : 0;
               span.setAttributes({
                 [GEN_AI_INPUT_MESSAGES_ATTRIBUTE]: enableTruncation