aws-samples · dougperkes · Jul 17, 2026
diff --git a/sam-dotnet-responsestreaming-bedrock/.gitignore b/sam-dotnet-responsestreaming-bedrock/.gitignore
@@ -0,0 +1,16 @@
+## .NET
+bin/
+obj/
+*.user
+*.suo
+*.userosscache
+*.sln.docstates
+
+## SAM
+.aws-sam/
+samconfig.toml
+
+## IDE
+.idea/
+.vs/
+*.swp
diff --git a/sam-dotnet-responsestreaming-bedrock/README.md b/sam-dotnet-responsestreaming-bedrock/README.md
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+# AWS Lambda Response Streaming with Amazon Bedrock — Story Generator (.NET)
+
+This sample demonstrates **Lambda Response Streaming through Amazon API Gateway** combined with **Amazon Bedrock** (Claude Sonnet) for .NET. A Lambda function invokes Claude Sonnet via the Bedrock `ConverseStream` API and streams the generated story token-by-token back to the client through API Gateway response streaming.
+
+## Architecture
+
+```
+┌──────────────┐       ┌──────────────────┐       ┌────────────────────┐       ┌─────────────┐
+│   Client     │       │   API Gateway    │       │   Lambda Function  │       │   Amazon    │
+│  (curl)      │──GET─▶│   REST API       │──────▶│   (Response        │──────▶│   Bedrock   │
+│              │◀─stream│  ResponseTransfer │◀stream│    Streaming)      │◀stream│  (Claude)   │
+│              │       │  Mode: STREAM    │       │                    │       │             │
+└──────────────┘       └──────────────────┘       └────────────────────┘       └─────────────┘
+```
+
+## What It Demonstrates
+
+- **End-to-end streaming** — Bedrock streams tokens → Lambda pipes them through → API Gateway streams to client. The user sees the story appear word-by-word.
+- **API Gateway response streaming** — Uses `ResponseTransferMode: STREAM` with the `/response-streaming-invocations` Lambda endpoint.
+- **Bedrock ConverseStream API** — Uses the AWS SDK's `ConverseStreamAsync` to get streaming responses from Claude Sonnet.
+- **Customizable story generation** — Users can specify genre, setting, and theme via query parameters.
+- **Minimal latency** — First tokens appear within seconds, no waiting for the full generation to complete.
+
+## Project Structure
+
+```
+├── template.yaml              # SAM template (API Gateway REST API + Lambda + Bedrock IAM)
+├── events/
+│   └── generate-story.json    # Sample API Gateway proxy event
+└── src/
+    ├── Program.cs             # Streaming handler (Bedrock → Lambda → API Gateway → Client)
+    └── StoryStreaming.csproj
+```
+
+---
+
+## Prerequisites
+
+- [.NET 10 SDK](https://dotnet.microsoft.com/download/dotnet/10.0)
+- [AWS SAM CLI](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/install-sam-cli.html)
+- AWS account with credentials configured (`aws configure`)
+- **Amazon Bedrock model access** — Enable access to Claude Sonnet in the [Bedrock console](https://console.aws.amazon.com/bedrock/home#/modelaccess)
+
+---
+
+## Build & Deploy
+
+### Build
+
+```bash
+sam build
+```
+
+### Deploy
+
+```bash
+sam deploy --guided
+```
+
+Follow the prompts to configure stack name, region, and confirm IAM role creation. On subsequent deploys:
+
+```bash
+sam deploy
+```
+
+---
+
+## Testing
+
+### 1. Get the API endpoint
+
+```bash
+API_URL=$(aws cloudformation describe-stacks \
+    --stack-name sam-dotnet-responsestreaming-bedrock \
+    --query "Stacks[0].Outputs[?OutputKey=='ApiEndpoint'].OutputValue" \
+    --output text)
+```
+
+### 2. Generate a story with defaults
+
+```bash
+curl --no-buffer "$API_URL"
+```
+
+You'll see the story appear word-by-word in real-time as Claude generates it.
+
+### 3. Customize the story
+
+```bash
+# Science fiction story
+curl --no-buffer "$API_URL?genre=science+fiction&setting=a+space+station+orbiting+Jupiter&theme=finding+home"
+
+# Mystery story
+curl --no-buffer "$API_URL?genre=mystery&setting=a+foggy+Victorian+London+street&theme=trust+and+betrayal"
+
+# Horror story
+curl --no-buffer "$API_URL?genre=horror&setting=an+abandoned+hospital&theme=facing+your+fears"
+```
+
+### Parameters
+
+| Parameter | Default | Description |
+|-----------|---------|-------------|
+| `genre`   | fantasy | The genre of the story (e.g., science fiction, mystery, horror, romance) |
+| `setting` | a mysterious ancient library | Where the story takes place |
+| `theme`   | the power of curiosity | The central theme or message |
+
+---
+
+## How It Works
+
+### API Gateway → Lambda (Response Streaming)
+
+The API Gateway integration uses `/response-streaming-invocations` to invoke Lambda with streaming:
+
+```yaml
+Integration:
+  Type: AWS_PROXY
+  IntegrationHttpMethod: POST
+  ResponseTransferMode: STREAM
+  Uri: !Sub arn:aws:apigateway:${AWS::Region}:lambda:path/2021-11-15/functions/${StoryFunction.Arn}/response-streaming-invocations
+```
+
+### Lambda → Bedrock (ConverseStream)
+
+The Lambda function calls Bedrock's streaming API and pipes each token to the response stream:
+
+```csharp
+// Set up Lambda response streaming
+using var responseStream = LambdaResponseStreamFactory.CreateHttpStream(prelude);
+using var writer = new StreamWriter(responseStream);
+
+// Call Bedrock with streaming
+var response = await bedrockClient.ConverseStreamAsync(converseRequest);
+
+// Pipe each token from Bedrock → API Gateway → Client
+foreach (var item in response.Stream.AsEnumerable())
+{
+    if (item is ContentBlockDeltaEvent deltaEvent && deltaEvent.Delta?.Text is not null)
+    {
+        await writer.WriteAsync(deltaEvent.Delta.Text);
+        await writer.FlushAsync();  // Sends immediately to the client
+    }
+}
+```
+
+Key points:
+- `ConverseStreamAsync` returns an event stream that yields `ContentBlockDeltaEvent` items as Claude generates tokens.
+- Each `FlushAsync()` pushes the token(s) through API Gateway to the client immediately.
+- The model used is `us.anthropic.claude-sonnet-5` (cross-region inference profile for higher availability).
+- `Temperature: 0.8` and `TopP: 0.9` produce creative, varied stories.
+
+---
+
+## Cleanup
+
+```bash
+sam delete
+```
+
+---
+
+## Useful Commands
+
+| Command | Description |
+|---------|-------------|
+| `sam build` | Build the Lambda function |
+| `sam deploy --guided` | Deploy with interactive prompts |
+| `sam deploy` | Deploy with saved config |
+| `sam logs --tail` | Tail CloudWatch logs |
+| `sam delete` | Tear down the stack |
+| `dotnet build src/` | Build locally without SAM |
+
+---
+
+## References
+
+- [Building responsive APIs with API Gateway response streaming](https://aws.amazon.com/blogs/compute/building-responsive-apis-with-amazon-api-gateway-response-streaming/)
+- [Serverless strategies for streaming LLM responses](https://aws.amazon.com/blogs/compute/serverless-strategies-for-streaming-llm-responses/)
+- [Lambda Response Streaming (.NET SDK PR)](https://github.com/aws/aws-lambda-dotnet/pull/2288)
+- [Amazon Bedrock ConverseStream API](https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_ConverseStream.html)
+- [Claude Sonnet on Bedrock](https://docs.aws.amazon.com/bedrock/latest/userguide/model-card-anthropic-claude-sonnet-5.html)
+- [AWS SAM Developer Guide](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/)
diff --git a/sam-dotnet-responsestreaming-bedrock/events/generate-story.json b/sam-dotnet-responsestreaming-bedrock/events/generate-story.json
@@ -0,0 +1,31 @@
+{
+  "resource": "/story",
+  "path": "/story",
+  "httpMethod": "GET",
+  "headers": {
+    "Accept": "*/*",
+    "Host": "abc123.execute-api.us-east-1.amazonaws.com"
+  },
+  "queryStringParameters": {
+    "genre": "science fiction",
+    "setting": "a space station orbiting Jupiter",
+    "theme": "finding home in unexpected places"
+  },
+  "pathParameters": null,
+  "stageVariables": null,
+  "requestContext": {
+    "resourceId": "abc123",
+    "resourcePath": "/story",
+    "httpMethod": "GET",
+    "requestId": "test-request-id",
+    "accountId": "123456789012",
+    "stage": "prod",
+    "identity": {
+      "sourceIp": "127.0.0.1",
+      "userAgent": "curl/8.0"
+    },
+    "apiId": "abc123"
+  },
+  "body": null,
+  "isBase64Encoded": false
+}
diff --git a/sam-dotnet-responsestreaming-bedrock/sam-dotnet-responsestreaming-bedrock.json b/sam-dotnet-responsestreaming-bedrock/sam-dotnet-responsestreaming-bedrock.json
@@ -0,0 +1,64 @@
+{
+  "title": "Lambda Response Streaming with Amazon Bedrock — Story Generator (.NET)",
+  "description": "Stream LLM-generated story text token-by-token from Amazon Bedrock through Lambda response streaming and API Gateway to the client.",
+  "language": ".NET",
+  "level": "200",
+  "framework": "SAM",
+  "introBox": {
+    "headline": "How it works",
+    "text": [
+      "This pattern deploys a Lambda function that invokes Amazon Bedrock (Claude Sonnet) via the ConverseStream API and pipes generated tokens directly through API Gateway response streaming to the client.",
+      "The user specifies a genre, setting, and theme via query parameters, and the story appears word-by-word in the terminal. First tokens arrive within seconds — no waiting for the full generation to complete.",
+      "This demonstrates end-to-end streaming from Bedrock through Lambda to the client using the .NET response streaming SDK (LambdaResponseStreamFactory.CreateHttpStream)."
+    ]
+  },
+  "gitHub": {
+    "template": {
+      "repoURL": "https://github.com/aws-samples/serverless-patterns/tree/main/sam-dotnet-responsestreaming-bedrock",
+      "templateURL": "serverless-patterns/sam-dotnet-responsestreaming-bedrock",
+      "projectFolder": "sam-dotnet-responsestreaming-bedrock",
+      "templateFile": "template.yaml"
+    }
+  },
+  "resources": {
+    "bullets": [
+      {
+        "text": "Lambda Response Streaming Documentation",
+        "link": "https://docs.aws.amazon.com/lambda/latest/dg/response-streaming.html"
+      },
+      {
+        "text": "Amazon Bedrock ConverseStream API",
+        "link": "https://docs.aws.amazon.com/bedrock/latest/userguide/conversation-inference-call.html"
+      },
+      {
+        "text": "Amazon Bedrock",
+        "link": "https://aws.amazon.com/bedrock/"
+      }
+    ]
+  },
+  "deploy": {
+    "text": [
+      "sam build",
+      "sam deploy --guided"
+    ]
+  },
+  "testing": {
+    "text": [
+      "See the GitHub repo for detailed testing instructions."
+    ]
+  },
+  "cleanup": {
+    "text": [
+      "Delete the stack: <code>sam delete</code>."
+    ]
+  },
+  "authors": [
+    {
+      "name": "Doug Perkes",
+      "image": "",
+      "bio": "Senior Solutions Architect at AWS, focused on .NET and serverless.",
+      "linkedin": "dougperkes",
+      "twitter": ""
+    }
+  ]
+}