feat(xmtp_api_grpc): bidi_stream transport primitive

[tylerhawkes]

Stack 2/4 of the XIP-83 bidi client lane: #3769 → #3770 → #3771 → #3772.

Adds one primitive to the protocol-agnostic Client trait: bidi_stream(request, path, BoxDynStream<Bytes>) -> http::Response<BytesStream> — outbound stream of encoded protobuf messages in, inbound message stream out. Default implementation errors ("not supported by this transport"), so gRPC-Web/wasm and mocks are untouched; forwarded through the &T/Box/Arc/boxed-client impls. GrpcClient overrides it natively via tonic Grpc::streaming + the existing TransparentCodec, reusing the NonBlocking stream machinery verbatim. build_tonic_request made generic over the body type.

🤖 Generated with Claude Code

Note

Add bidi_stream bidirectional streaming transport primitive to xmtp_api_grpc

• Adds a bidi_stream method to the Client trait in traits.rs that accepts an outbound BoxDynStream<'static, Bytes> and returns an inbound BytesStream; the default implementation returns an unsupported-transport error.
• Implements bidi_stream for non-wasm GrpcClient in client.rs using TransparentCodec and NonBlockingStreamRequest over HTTP/2.
• Delegates bidi_stream through BoxedClient and all blanket forwarding impls (&T, &mut T, Arc<T>).
• Updates generated protobuf code with new Subscribe bidirectional RPC and associated SubscribeRequest/SubscribeResponse message types including serde impls.
• Makes build_tonic_request generic over the request body type to support streaming use cases.

^{Macroscope summarized af6ab11.}

[claude]

Claude finished @tylerhawkes's task —— View job

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Code Review Completed

Review checklist:

• Read changed files (traits.rs, client.rs, boxed_client.rs)
• Analyze implementation for issues
• Provide review feedback

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Review Feedback

Reviewed: 2026-06-16 21:05 UTC

The implementation is well-structured and follows existing patterns. One observation and minor suggestion:

Correctness & Pattern Consistency

client.rs:194-219 - The bidi_stream implementation follows the same pattern as stream (lines 164-189), which is good for consistency. However, note that build_tonic_request was made generic (line 84) specifically to accept BoxDynStream<'static, Bytes> as the body type. This works because tonic's streaming method accepts this type, but it creates a subtle coupling: if the signature of body in bidi_stream changes, the generic bound on build_tonic_request might need adjustment.

Documentation

Consider adding a brief doc comment on build_tonic_request to clarify that it's generic over body type to support both Bytes (unary/server-streaming) and BoxDynStream (bidirectional) use cases. This would help future maintainers understand why it's generic.

traits.rs:150-160 - Default implementation correctly returns an unsupported-transport error. The parameter suppression via let _ = (request, path, body) is idiomatic.

Coverage: The 14% patch coverage reported by Codecov is expected for this primitive-level infrastructure. Testing will naturally come in stack 3/4 when higher-level subscription logic consumes this transport.

Overall: LGTM - solid foundation for XIP-83 bidi streaming.

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[codecov]

Codecov Report

❌ Patch coverage is 14.28571% with 24 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (tyler/xip83-1-subscribe-protos@21b315c). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
crates/xmtp_api_grpc/src/grpc_client/client.rs	22.22%	14 Missing ⚠️
crates/xmtp_proto/src/traits.rs	0.00%	8 Missing ⚠️
crates/xmtp_proto/src/traits/boxed_client.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@                        Coverage Diff                        @@
##             tyler/xip83-1-subscribe-protos    #3770   +/-   ##
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  Coverage                                  ?   84.41%           
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  Files                                     ?      408           
  Lines                                     ?    59796           
  Branches                                  ?        0           
=================================================================
  Hits                                      ?    50477           
  Misses                                    ?     9319           
  Partials                                  ?        0           

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