[Bug]: gRPC errors do not include google.rpc.ErrorInfo

[jmesnil]

What happened?

Summary

gRPC errors from the SUT do not include google.rpc.ErrorInfo in the status details, which is required by the A2A specification for all A2A-specific errors.

Requirement

• ID: GRPC-ERR-001
• Section: 10.6 — A2A errors include ErrorInfo in status details
• Level: MUST
• Spec: https://github.com/a2aproject/A2A/blob/0833a5f5fd1b715519c0aecf9e3055e3f9f38089/docs/specification.md#106-error-handling

Specification

For A2A-specific errors, implementations MUST include a google.rpc.ErrorInfo message in the status.details array with:

• reason: The A2A error type in UPPER_SNAKE_CASE without the "Error" suffix (e.g., TASK_NOT_FOUND)
• domain: Set to "a2a-protocol.org"
• metadata: Optional map of additional error context

Expected behavior

When the SUT returns an A2A-specific error (e.g., TaskNotFoundError), the gRPC response should include a google.rpc.Status with a google.rpc.ErrorInfo message in the details array, encoded in the grpc-status-details-bin trailing metadata. The ErrorInfo should have reason set to the error type in UPPER_SNAKE_CASE (e.g., TASK_NOT_FOUND) and domain set to "a2a-protocol.org".

Actual behavior

The SUT returns a plain gRPC NOT_FOUND status with a message string but does not include google.rpc.ErrorInfo in the status details. The grpc-status-details-bin trailing metadata is missing or does not contain an ErrorInfo entry.

Reproducer

# Trigger TaskNotFoundError by requesting a non-existent task
grpcurl -plaintext -d '{"id": "tck-nonexistent-task-001"}' \
  localhost:9999 lf.a2a.v1.A2AService/GetTask

# Expected: gRPC NOT_FOUND with google.rpc.ErrorInfo in status.details:
#   reason: "TASK_NOT_FOUND"
#   domain: "a2a-protocol.org"
#
# Actual: gRPC NOT_FOUND without ErrorInfo in grpc-status-details-bin

TCK test

• tests/compatibility/core_operations/test_error_handling.py::TestGrpcErrorStructure::test_grpc_error_for_nonexistent_task
• tests/compatibility/grpc/test_status_codes.py::TestGrpcErrorInfo::test_error_info_in_status_details

Relevant log output

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