Struct ClientBuilder 

pub struct ClientBuilder { /* private fields */ }

Builder for A2aClient.

Start with ClientBuilder::new (URL) or ClientBuilder::from_card (agent card auto-configuration).

Implementations

impl ClientBuilder

pub fn build(self) -> Result<A2aClient, ClientError>

Validates configuration and constructs the A2aClient.

Errors

• ClientError::InvalidEndpoint if the endpoint URL is malformed.
• ClientError::Transport if the selected transport cannot be initialized.

pub async fn build_grpc(self) -> Result<A2aClient, ClientError>

Validates configuration and constructs a gRPC-backed A2aClient.

Unlike build, this method is async because gRPC transport requires establishing a connection.

Errors

• ClientError::InvalidEndpoint if the endpoint URL is malformed.
• ClientError::Transport if the gRPC connection fails.

impl ClientBuilder

pub fn new(endpoint: impl Into<String>) -> ClientBuilder

Creates a builder targeting endpoint.

The endpoint is passed directly to the selected transport; it should be the full base URL of the agent (e.g. http://localhost:8080).

pub fn from_card(card: &AgentCard) -> Result<ClientBuilder, ClientError>

Creates a builder pre-configured from an AgentCard.

Selects the first supported interface from the card. Logs a warning (via tracing, if enabled) if the agent’s protocol version is not in the supported range.

Errors

Returns ClientError::InvalidEndpoint if the card has no interfaces.

pub const fn with_timeout(self, timeout: Duration) -> ClientBuilder

Sets the per-request timeout for non-streaming calls.

pub const fn with_stream_connect_timeout( self, timeout: Duration, ) -> ClientBuilder

Sets the timeout for establishing SSE stream connections.

Once the stream is established, this timeout no longer applies. Defaults to 30 seconds.

pub const fn with_connection_timeout(self, timeout: Duration) -> ClientBuilder

Sets the TCP connection timeout (DNS + handshake).

Defaults to 10 seconds. Prevents hanging for the OS default (~2 min) when the server is unreachable.

pub fn with_protocol_binding(self, binding: impl Into<String>) -> ClientBuilder

Sets the preferred protocol binding.

Overrides any binding derived from the agent card.

pub fn with_accepted_output_modes(self, modes: Vec<String>) -> ClientBuilder

Sets the accepted output modes sent in SendMessage configurations.

pub const fn with_history_length(self, length: u32) -> ClientBuilder

Sets the history length to request in task responses.

pub const fn with_return_immediately(self, val: bool) -> ClientBuilder

Sets return_immediately for SendMessage calls.

pub fn with_custom_transport(self, transport: impl Transport) -> ClientBuilder

Provides a fully custom transport implementation.

Overrides the transport that would normally be built from the endpoint URL and protocol preference.

pub const fn without_tls(self) -> ClientBuilder

Disables TLS (plain HTTP only).

pub const fn with_retry_policy(self, policy: RetryPolicy) -> ClientBuilder

Sets a retry policy for transient failures.

When set, the client automatically retries requests that fail with transient errors (connection errors, timeouts, HTTP 429/502/503/504) using exponential backoff.

Example

use a2a_protocol_client::{ClientBuilder, RetryPolicy};

let client = ClientBuilder::new("http://localhost:8080")
    .with_retry_policy(RetryPolicy::default())
    .build()?;

pub fn with_interceptor<I>(self, interceptor: I) -> ClientBuilder

where I: CallInterceptor,

Adds an interceptor to the chain.

Interceptors are run in the order they are added.

Trait Implementations

impl Debug for ClientBuilder

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.