grpc
This Claude Code skill builds and reviews gRPC services and clients in .NET, covering protobuf contracts, unary and streaming RPCs, client factories, interceptors, deadlines, and cancellation handling. Use it when designing backend-to-backend RPC communication, optimizing service-to-service integration in microservices, or deciding between gRPC, HTTP APIs, and SignalR. The skill invokes dotnet build and test commands with focused smoke checks when code changes occur.
git clone --depth 1 https://github.com/managedcode/dotnet-skills /tmp/grpc && cp -r /tmp/grpc/catalog/Frameworks/gRPC/skills/grpc ~/.claude/skills/grpcSKILL.md
# gRPC for .NET
## Trigger On
- building backend-to-backend RPC services or clients
- adding protobuf contracts, streaming calls, or interceptors
- deciding between gRPC, HTTP APIs, and SignalR
- optimizing gRPC performance, deadlines, cancellation, or connection reuse
- integrating service-to-service communication in microservices
## Do Not Use For
- public browser-first APIs unless gRPC-Web limitations are explicitly acceptable
- SignalR hub design, realtime UI fan-out, or websocket-style client collaboration
- generic ASP.NET Core minimal APIs or REST controllers with no protobuf/RPC requirement
- non-.NET gRPC work unless the user asks for cross-stack contract guidance
## Load References
- [references/patterns.md](references/patterns.md) for proto design, streaming implementations, interceptors, health checks, load balancing, and client factory setup.
- [references/anti-patterns.md](references/anti-patterns.md) for common channel, deadline, streaming, message-size, and exception-handling mistakes.
## Workflow
1. Validate the architecture fit before touching code.
- prefer gRPC for backend RPC, strong contracts, low-latency calls, or streaming
- prefer REST or minimal APIs for broad browser compatibility and loosely coupled public APIs
- prefer SignalR for browser/client realtime fan-out and UI collaboration
2. Treat `.proto` files as the source of truth.
- keep package names, `csharp_namespace`, service names, and versioning deliberate
- reserve removed field numbers and avoid reusing tags
- use wrapper types or explicit messages when optionality matters
3. Choose the RPC shape from the interaction model.
- unary for request/response
- server streaming for large or progressive result sets
- client streaming for uploads or batches
- bidirectional streaming for coordinated two-way flows
4. Wire server and client behavior together.
- register services with `AddGrpc`
- use `AddGrpcClient` or long-lived `GrpcChannel` reuse
- set deadlines and propagate cancellation
- convert domain failures to appropriate `RpcException` status codes
5. Add observability and resilience where the boundary justifies it.
- logging or exception interceptors
- OpenTelemetry traces and status-code metrics
- retry policy only for safe idempotent calls
6. Validate with the repo's normal build and tests, plus a focused smoke call when runnable.
```mermaid
flowchart LR
A["RPC requirement"] --> B["proto contract"]
B --> C["server implementation"]
B --> D["client factory or channel"]
C --> E["deadlines / cancellation / status codes"]
D --> E
E --> F["build, tests, smoke call"]
```
## Examples
Use client factory for normal app integration:
```csharp
builder.Services.AddGrpcClient<Greeter.GreeterClient>(options =>
{
options.Address = new Uri("https://localhost:5001");
});
```
Always set a deadline and pass cancellation:
```csharp
var response = await client.SayHelloAsync(
new HelloRequest { Name = name },
deadline: DateTime.UtcNow.AddSeconds(5),
cancellationToken: cancellationToken);
```
For streaming, check cancellation inside the read/write loop and keep message sizes bounded. Load [references/patterns.md](references/patterns.md) before writing detailed streaming code.
## Anti-Patterns
- creating a new `GrpcChannel` per call
- omitting deadlines and relying only on client-side cancellation
- ignoring `ServerCallContext.CancellationToken` in streaming handlers
- sending large single messages instead of chunking or streaming
- using gRPC as the default public browser API
- swallowing exceptions inside interceptors
- retrying non-idempotent calls without explicit policy
## Deliver
- stable protobuf contracts and generated-code ownership
- service and client code that match the RPC shape
- explicit deadline, cancellation, retry, and status-code behavior
- tests or smoke checks for serialization and call behavior
- documentation of browser, transport, or deployment constraints when relevant
## Validate
- `dotnet build` succeeds after contract or generated-code changes
- tests or smoke checks exercise at least one server/client call
- streaming methods respect cancellation and bounded message sizes
- channels are reused through client factory or a long-lived channel
- status-code handling is intentional and observable
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