Enum A2aError 

#[non_exhaustive]
pub enum A2aError {
    Http(Error),
    Json(Error),
    JsonRpc {
        code: i32,
        message: String,
    },
    Discovery {
        url: String,
        reason: String,
    },
    Stream(String),
    Server(String),
    Security(String),
    Timeout(Duration),
}

All errors that can occur in A2A client and server operations.

The variants map to distinct failure modes so callers can recover appropriately:

• Retry on Http (transient network issues).
• Inspect the code on JsonRpc — -32001 is task-not-found, -32002 is not-cancelable.
• Abort on Security — endpoint rejected by TLS or SSRF policy.

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 reqwest HTTP transport error (connection refused, timeout, TLS, etc.).

Json(Error)

JSON serialization or deserialization failure.

JsonRpc

The remote agent returned a JSON-RPC error object.

Well-known codes defined by the A2A spec:

• -32001: task not found
• -32002: task not in a cancelable state

Fields

code: i32

message: String

Discovery

AgentRegistry could not retrieve a valid AgentCard from the remote agent’s well-known URL.

Fields

url: String

reason: String

Stream(String)

An error occurred while reading the SSE event stream from a streaming call.

Server(String)

An internal server-side error (binding failure, task processing panic, etc.).

Security(String)

A request was rejected by the client’s security policy.

Triggered when A2aClient is configured with require_tls = true and an http:// endpoint is used, or when ssrf_protection = true and DNS resolves to a private/loopback address.

Timeout(Duration)

A request or task processing operation exceeded its deadline.

Trait Implementations

impl Debug for A2aError

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

Formats the value using the given formatter.

impl Display for A2aError

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

Formats the value using the given formatter.

impl Error for A2aError

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<Error> for A2aError

fn from(source: Error) -> Self

Converts to this type from the input type.

impl From<Error> for A2aError

fn from(source: Error) -> Self

Converts to this type from the input type.

impl From<JsonRpcError> for A2aError

fn from(e: JsonRpcError) -> Self

Converts to this type from the input type.