diff --git a/sentry-javascript/18962/.gitignore b/sentry-javascript/18962/.gitignore
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--- /dev/null
+++ b/sentry-javascript/18962/.gitignore
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+node_modules/
+dist/
+.env
diff --git a/sentry-javascript/18962/README.md b/sentry-javascript/18962/README.md
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+# Reproduction for sentry-javascript#18962
+
+**Issue:** https://github.com/getsentry/sentry-javascript/issues/18962
+
+## Description
+
+Sentry's tracing instrumentation (`tracesSampleRate: 1.0`) reportedly breaks OpenAI streaming when using LangChain/LangGraph's `agent.stream()` with `streamMode: ["messages"]`. Instead of receiving incremental chunks, the entire response arrives in one or very few chunks.
+
+## Test Results
+
+**On latest versions (`@sentry/nestjs@10.42.0`, `langchain@1.2.29`), the bug does not reproduce.**
+
+Both endpoints stream correctly with Sentry tracing enabled:
+
+| Endpoint | Sentry | Content Chunks | First Byte | Total |
+|---|---|---|---|---|
+| `/stream-agent` | OFF | ~40 | ~0.7s | ~1.2s |
+| `/stream-agent` | ON | ~46 | ~0.5s | ~1.0s |
+| `/stream-model` | ON | ~41 | ~0.7s | ~1.1s |
+
+The fix was likely included in one of the recent `@sentry/nestjs` releases (possibly PR #19122, released in 10.39.0). The issue was reported on 10.41.0 by @rad20c — pinning to that version may reproduce it.
+
+## Steps to Reproduce
+
+1. Install dependencies:
+   ```bash
+   npm install
+   ```
+
+2. Add your OpenAI API key to `.env`:
+   ```
+   OPENAI_API_KEY=sk-your-key-here
+   ```
+
+3. Run **without** Sentry (baseline):
+   ```bash
+   npm run start:without-sentry
+   ```
+   Then in another terminal:
+   ```bash
+   curl http://localhost:3000/stream-agent
+   ```
+
+4. Stop the server, then run **with** Sentry:
+   ```bash
+   npm run start:with-sentry
+   ```
+   Then:
+   ```bash
+   curl http://localhost:3000/stream-agent
+   ```
+
+5. Compare chunk counts and timing between the two modes. The `/stream-model` endpoint is available for comparison with direct `ChatOpenAI` streaming.
+
+## Environment
+
+- `@sentry/nestjs`: 10.42.0
+- `langchain`: 1.2.29
+- `@langchain/openai`: 1.2.12
+- Node.js: 18+
diff --git a/sentry-javascript/18962/nest-cli.json b/sentry-javascript/18962/nest-cli.json
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--- /dev/null
+++ b/sentry-javascript/18962/nest-cli.json
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+{
+  "$schema": "https://json.schemastore.org/nest-cli",
+  "collection": "@nestjs/schematics",
+  "sourceRoot": "src"
+}
diff --git a/sentry-javascript/18962/package.json b/sentry-javascript/18962/package.json
new file mode 100644
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--- /dev/null
+++ b/sentry-javascript/18962/package.json
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+{
+  "name": "sentry-nestjs-openai-streaming-repro",
+  "version": "1.0.0",
+  "description": "Reproduction for sentry-javascript#18962 - Sentry breaking OpenAI streaming with LangGraph agent",
+  "main": "dist/main.js",
+  "scripts": {
+    "build": "nest build",
+    "start:with-sentry": "ENABLE_SENTRY=true nest start",
+    "start:without-sentry": "ENABLE_SENTRY=false nest start"
+  },
+  "dependencies": {
+    "@langchain/core": "^1.1.30",
+    "@langchain/langgraph": "^1.2.0",
+    "@langchain/openai": "^1.2.12",
+    "@nestjs/common": "^10.0.0",
+    "@nestjs/core": "^10.0.0",
+    "@nestjs/platform-express": "^10.0.0",
+    "@sentry/nestjs": "^10.41.0",
+    "dotenv": "^16.6.1",
+    "langchain": "^1.2.29",
+    "reflect-metadata": "^0.2.0",
+    "rxjs": "^7.8.1"
+  },
+  "devDependencies": {
+    "@nestjs/cli": "^10.0.0",
+    "@types/node": "^22.0.0",
+    "typescript": "^5.0.0"
+  }
+}
diff --git a/sentry-javascript/18962/src/app.module.ts b/sentry-javascript/18962/src/app.module.ts
new file mode 100644
index 0000000..0c80b22
--- /dev/null
+++ b/sentry-javascript/18962/src/app.module.ts
@@ -0,0 +1,9 @@
+import { Module } from "@nestjs/common";
+import { StreamController } from "./stream.controller";
+
+@Module({
+  imports: [],
+  controllers: [StreamController],
+  providers: [],
+})
+export class AppModule {}
diff --git a/sentry-javascript/18962/src/instrument.ts b/sentry-javascript/18962/src/instrument.ts
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+++ b/sentry-javascript/18962/src/instrument.ts
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+import "dotenv/config";
+import * as Sentry from "@sentry/nestjs";
+
+if (process.env.ENABLE_SENTRY === "true") {
+  console.log("Initializing Sentry...");
+
+  Sentry.init({
+    dsn: process.env.SENTRY_DSN || "",
+    environment: "local",
+    // This is the key setting that breaks streaming.
+    // Removing tracesSampleRate (or setting it to 0) fixes the issue.
+    tracesSampleRate: 1.0,
+  });
+
+  console.log("Sentry initialized with tracesSampleRate: 1.0");
+} else {
+  console.log("Sentry disabled (ENABLE_SENTRY != true)");
+}
diff --git a/sentry-javascript/18962/src/main.ts b/sentry-javascript/18962/src/main.ts
new file mode 100644
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+++ b/sentry-javascript/18962/src/main.ts
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+import "./instrument";
+
+import { NestFactory } from "@nestjs/core";
+import { AppModule } from "./app.module";
+
+async function bootstrap() {
+  const app = await NestFactory.create(AppModule);
+  const port = process.env.PORT || 3000;
+  await app.listen(port);
+  console.log(`Server running at http://localhost:${port}`);
+  console.log(`Test streaming: curl http://localhost:${port}/stream-agent`);
+}
+bootstrap();
diff --git a/sentry-javascript/18962/src/stream.controller.ts b/sentry-javascript/18962/src/stream.controller.ts
new file mode 100644
index 0000000..ceb9a08
--- /dev/null
+++ b/sentry-javascript/18962/src/stream.controller.ts
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+// @ts-nocheck
+import { Controller, Get, Res } from "@nestjs/common";
+import { Response } from "express";
+import { ChatOpenAI } from "@langchain/openai";
+import { createAgent } from "langchain";
+
+@Controller()
+export class StreamController {
+  @Get("/")
+  index() {
+    return {
+      message: "Reproduction for sentry-javascript#18962",
+      issue: "https://github.com/getsentry/sentry-javascript/issues/18962",
+      endpoints: {
+        "/stream-agent":
+          "Test LangGraph agent streaming (reproduces the bug)",
+        "/stream-model":
+          "Test direct ChatOpenAI model streaming (works fine)",
+      },
+      sentryEnabled: process.env.ENABLE_SENTRY === "true",
+    };
+  }
+
+  // This endpoint reproduces the bug.
+  // With Sentry tracing enabled, the stream delivers the full response
+  // in one chunk instead of streaming incrementally.
+  @Get("/stream-agent")
+  async streamAgent(@Res() res: Response) {
+    try {
+      const agent = createAgent({
+        model: "openai:gpt-4o-mini",
+        tools: [],
+      });
+
+      res.setHeader("Content-Type", "text/plain; charset=utf-8");
+      res.setHeader("Transfer-Encoding", "chunked");
+
+      console.log("\n[agent.stream] Starting streaming request...");
+      const startTime = Date.now();
+      let chunkCount = 0;
+      let contentChunkCount = 0;
+
+      // @ts-ignore - type instantiation issues with langchain generics
+      const stream = await agent.stream({
+          messages: [
+            {
+              role: "user",
+              content:
+                "Count from 1 to 20, each number on a new line. Be slow and deliberate.",
+            },
+          ],
+        },
+        { streamMode: ["messages"] },
+      );
+
+      for await (const chunk of stream) {
+        chunkCount++;
+        const elapsed = Date.now() - startTime;
+        // chunk is ["messages", AIMessageChunk] or similar tuple
+        const msg = Array.isArray(chunk[1]) ? chunk[1][0] : chunk[1];
+        const content = msg?.kwargs?.content ?? msg?.content ?? "";
+        if (content) {
+          contentChunkCount++;
+          console.log(
+            `  [${elapsed}ms] Chunk ${contentChunkCount}: "${String(content).replace(/\n/g, "\\n")}"`,
+          );
+          res.write(String(content));
+        }
+      }
+
+      const elapsed = Date.now() - startTime;
+      console.log(
+        `\n[agent.stream] Done in ${elapsed}ms, total chunks: ${chunkCount}, content chunks: ${contentChunkCount}`,
+      );
+
+      if (contentChunkCount < 10) {
+        console.log(
+          "WARNING: Very few content chunks received - streaming may be broken!",
+        );
+      }
+
+      res.end(
+        `\n\n--- Stats ---\nTotal chunks: ${chunkCount}\nContent chunks: ${contentChunkCount}\nTime: ${elapsed}ms\nSentry: ${process.env.ENABLE_SENTRY === "true" ? "ENABLED" : "disabled"}\n`,
+      );
+    } catch (error: any) {
+      console.error("Error:", error.message);
+      if (!res.headersSent) {
+        res.status(500).json({ error: error.message });
+      } else {
+        res.end(`\nError: ${error.message}`);
+      }
+    }
+  }
+
+  // This endpoint uses direct model streaming for comparison.
+  // It typically works fine even with Sentry enabled.
+  @Get("/stream-model")
+  async streamModel(@Res() res: Response) {
+    try {
+      const model = new ChatOpenAI({
+        model: "gpt-4o-mini",
+        temperature: 0,
+        streaming: true,
+      });
+
+      res.setHeader("Content-Type", "text/plain; charset=utf-8");
+      res.setHeader("Transfer-Encoding", "chunked");
+
+      console.log("\n[model.stream] Starting streaming request...");
+      const startTime = Date.now();
+      let chunkCount = 0;
+      let contentChunkCount = 0;
+
+      const stream = await model.stream(
+        "Count from 1 to 20, each number on a new line. Be slow and deliberate.",
+      );
+
+      for await (const chunk of stream) {
+        chunkCount++;
+        const elapsed = Date.now() - startTime;
+        const content = chunk.content.toString() || "";
+        if (content) {
+          contentChunkCount++;
+          console.log(
+            `  [${elapsed}ms] Chunk ${contentChunkCount}: "${content.replace(/\n/g, "\\n")}"`,
+          );
+          res.write(content);
+        }
+      }
+
+      const elapsed = Date.now() - startTime;
+      console.log(
+        `\n[model.stream] Done in ${elapsed}ms, total chunks: ${chunkCount}, content chunks: ${contentChunkCount}`,
+      );
+
+      res.end(
+        `\n\n--- Stats ---\nTotal chunks: ${chunkCount}\nContent chunks: ${contentChunkCount}\nTime: ${elapsed}ms\nSentry: ${process.env.ENABLE_SENTRY === "true" ? "ENABLED" : "disabled"}\nMethod: direct model.stream()\n`,
+      );
+    } catch (error: any) {
+      console.error("Error:", error.message);
+      if (!res.headersSent) {
+        res.status(500).json({ error: error.message });
+      } else {
+        res.end(`\nError: ${error.message}`);
+      }
+    }
+  }
+}
diff --git a/sentry-javascript/18962/tsconfig.json b/sentry-javascript/18962/tsconfig.json
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+++ b/sentry-javascript/18962/tsconfig.json
@@ -0,0 +1,21 @@
+{
+  "compilerOptions": {
+    "module": "commonjs",
+    "declaration": true,
+    "removeComments": true,
+    "emitDecoratorMetadata": true,
+    "experimentalDecorators": true,
+    "allowSyntheticDefaultImports": true,
+    "target": "ES2021",
+    "sourceMap": true,
+    "outDir": "./dist",
+    "baseUrl": "./",
+    "incremental": true,
+    "skipLibCheck": true,
+    "strictNullChecks": false,
+    "noImplicitAny": false,
+    "strictBindCallApply": false,
+    "forceConsistentCasingInFileNames": false,
+    "noFallthroughCasesInSwitch": false
+  }
+}