Enum ClientError 

#[non_exhaustive]
pub enum ClientError {
    Http(Error),
    HttpClient(String),
    Serialization(Error),
    Protocol(A2aError),
    Transport(String),
    InvalidEndpoint(String),
    UnexpectedStatus {
        status: u16,
        body: String,
        retry_after: Option<Duration>,
    },
    AuthRequired {
        task_id: TaskId,
    },
    Timeout(String),
    ProtocolBindingMismatch(String),
}

Errors that can occur during A2A client operations.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Http(Error)

A transport-level HTTP error from hyper.

HttpClient(String)

An HTTP-level error from the hyper-util client (connection, redirect, etc.).

Serialization(Error)

JSON serialization or deserialization error.

Protocol(A2aError)

A protocol-level A2A error returned by the server.

Transport(String)

A transport configuration or connection error.

InvalidEndpoint(String)

The agent endpoint URL is invalid or could not be resolved.

UnexpectedStatus

The server returned an unexpected HTTP status code.

Fields

status: u16

The HTTP status code received.

body: String

The response body (truncated if large).

retry_after: Option<Duration>

Server-requested retry delay parsed from a Retry-After header (delta-seconds), when present on a 429/503. The retry layer honors this in preference to its own computed backoff so the client does not hammer a server that explicitly asked it to wait.

AuthRequired

The agent requires authentication for this task.

Fields

task_id: TaskId

The ID of the task requiring authentication.

Timeout(String)

A request or stream connection timed out.

ProtocolBindingMismatch(String)

The server appears to use a different protocol binding than the client.

For example, a JSON-RPC client connected to a REST-only server (or vice-versa). Check the agent card’s supported_interfaces to select the correct protocol binding.

Implementations

impl ClientError

pub const fn retry_after(&self) -> Option<Duration>

Server-requested retry delay, if this error carries one (a Retry-After header on a 429/503). The retry layer prefers this over its computed backoff.

pub fn is_stream_lagged(&self) -> bool

Returns true when this is the server’s recoverable consumer-lag signal on a streaming subscription rather than a real failure.

Do not stop reading when this is true. The stream continues, and a consumer that keeps polling still receives every later event including the terminal status. Treating it as fatal silently truncates the task:

while let Some(event) = stream.next().await {
    match event {
        Ok(ev) => { /* handle */ }
        // Recoverable: note the gap and keep going.
        Err(e) if e.is_stream_lagged() => {
            eprintln!("dropped {:?} events", e.dropped_event_count());
        }
        Err(e) => break, // genuinely fatal
    }
}

pub fn dropped_event_count(&self) -> Option<u64>

Number of events the server dropped, when this is a consumer-lag signal (see ClientError::is_stream_lagged); None otherwise.

impl ClientError

pub const fn is_retryable(&self) -> bool

Returns true if this error is transient and the request should be retried.

Retryable errors include:

• HTTP connection/transport errors
• Timeouts
• Server errors (HTTP 502, 503, 504, 429)

Trait Implementations

impl Debug for ClientError

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

Formats the value using the given formatter.

impl Display for ClientError

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

Formats the value using the given formatter.

impl Error for ClientError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl From<A2aError> for ClientError

fn from(e: A2aError) -> Self

Converts to this type from the input type.

impl From<Error> for ClientError

fn from(e: Error) -> Self

Converts to this type from the input type.

impl From<Error> for ClientError

fn from(e: Error) -> Self

Converts to this type from the input type.