gRPC Error: 12 UNIMPLEMENTED: unknown service x / Method not found
The server doesn’t have the service or method the client called — proto mismatch, wrong package name, or calling the wrong server.
12 UNIMPLEMENTEDunknown serviceMethod not found Meaning
Fully qualified names (package.Service/Method) must match exactly. Outdated generated code, missing service registration on the server, or routing through a proxy to the wrong backend cause it.
Common causes
- Client and server proto definitions differ
- Service not registered on the server
- Wrong package/service name
- Proxy routing to another service
⚡ Quick fix
- List services with grpcurl (reflection)
- Regenerate client stubs from the same proto
- Register the service in the server setup
Detailed fix by platform
Shell
- bash
grpcurl -plaintext localhost:50051 list grpcurl -plaintext localhost:50051 describe orders.v1.OrderService
How to diagnose
- Services — Exposed list
- Protos — Same version?
- Routing — Correct backend?
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Last updated 15 Oct 2026