package a2a-client

0.3.0

• Pull-based streaming: open_streaming_message and open_task_subscription return an Event_stream.t read with Event_stream.next. They return once the agent has accepted the request and sent its first event, so refusals, HTTP errors and agent errors (also in-band ones) are known before anything is relayed. Events are read only as the caller takes them; Event_stream.close or leaving the switch releases the connection. Reconnection works as for the push form, which is unchanged.
• ?accumulate:false on streaming calls tracks only the task's id, context, status and metadata, so memory stays constant on long streams.
• Folding stream events is linear: 0.2.2 copied the task history on every status update and the parts of an artifact on every appended chunk, which was quadratic in the number of events.
• connect and of_agent_card take ?rewrite_endpoint to use another URL than the one the Agent Card advertises, and rebase_endpoint ~onto moves it onto the host the card was fetched from (agents in containers often advertise their bind address).
• New library a2a-client.testing: a scripted agent behind a Transport.t, with typed replies encoded for any protocol version and binding.
• Error.Code.to_reason, the inverse of of_reason.

Breaking changes, so that decoded values carry their meaning in the type instead of being checked later:

• Protocol.t (V1_0 Jsonrpc, V1_0 Http_json, V0_3) replaces create ?protocol_version ?binding; 0.3 over HTTP+JSON can no longer be written. protocol client returns it; connect keeps ?protocol_version and ?bindings as preferences.
• Agent_interface.protocol_binding and protocol_version are Known _ | Unknown of string instead of strings, parsed when the card is decoded.
• Absent values are options instead of "": Message.message_id, the context_id of status and artifact update events, and next_page_token.
• Agent capabilities are bool (absent means false).
• Push notification configs are split into Push_notification_config.t (url, token, authentication, id), as sent with a message, and Task_push_notification_config.t (task_id and that config). A config whose taskId is missing no longer decodes.
• URLs are Uri.t: interface and push config URLs, URL parts, and the URLs of an Agent Card (provider, documentation, icon, OAuth and OpenID Connect).
• wait_for_task and send_message_and_wait take ?poll:Poll.t instead of ?interval ?max_interval ?backoff.
• A2a_client_testing.agent takes ?protocol.
• The opam file carries the version, so pins and lock files show which release is used.
• The package is on the opam repository: opam install a2a-client.

0.2.2

• The HTTP and connection pool tests run over an in-memory Eio network instead of loopback TCP sockets, so they pass where binding a socket is not permitted (e.g. in the opam sandbox on macOS).

0.2.1

• Require cohttp-eio, cohttp and http >= 6.2.1. Earlier versions have a different Cohttp_eio.Client.make ~https type and do not compile.

0.2.0

• HTTP+JSON (REST) binding for protocol 1.0, selected from the Agent Card (~bindings) or with create ~binding:Http_json. REST errors (google.rpc.Status with an ErrorInfo reason) become Rpc_errors with the same codes as JSON-RPC errors. New module Protocol_binding, new binding accessor, and Error.Code.of_reason.
• list_tasks (ListTasks) with filters and cursor pagination.
• Push notification configs: create_task_push_notification_config, get_…, list_…, delete_…, and push_notification_config in Send_message_configuration (also with protocol 0.3).
• get_extended_agent_card (GetExtendedAgentCard, 0.3 agent/getAuthenticatedExtendedCard) and with_agent_card.
• Stream resumption: ~reconnect:(Reconnect.make ()) re-attaches a broken stream with SubscribeToTask (with Last-Event-ID and backoff), and falls back to GetTask if the task ended meanwhile. Off by default.
• Transport.pooled: HTTP/1.1 keep-alive connection pool scoped to a Switch, with a retry on stale connections. Responses not read to the end are drained in the background so their connections can be reused.
• Transport.meth gains `DELETE; Transport has an interface file.
• Capability checks against the Agent Card also cover push notifications and the extended Agent Card.
• Error.Code.to_string (Other n) is now "error n", as it also covers REST errors.
• Behaviour change: connect, of_agent_card and select_interface now also pick HTTP+JSON interfaces, in the card's order. Pass ~bindings:[ Jsonrpc ] to keep JSON-RPC only.
• Breaking: Send_message_configuration.t has a new field push_notification_config; build the record with make.
• Backward compatibility with A2A v0.3. The protocol version is negotiated from the Agent Card (1.x preferred, then 0.3.x) or set with ~protocol_version. Existing code needs no changes.
• Agent Cards in the v0.3 layout (url, preferredTransport, additionalInterfaces, security, type-tagged security schemes, supportsAuthenticatedExtendedCard) are decoded.
• New modules Protocol_version and Codec_v0_3; new version accessor.
• select_interface falls back to a v0.3 JSON-RPC interface instead of failing with No_compatible_interface.
• Breaking: the public API is narrowed to what applications use. Jsonrpc and Sse are no longer exported, and Codec exposes only the protocol conversions (internal helpers and Codec.to_string are gone; use Codec.decode_json / decode_string). Lifecycle exposes Outcome and apply.

0.1.0

Initial release.

• A2A protocol v1.0 client over the JSON-RPC binding (cohttp-eio, Eio).
• Agent Card discovery and JSON-RPC interface selection.
• SendMessage, GetTask, CancelTask, SendStreamingMessage, SubscribeToTask.
• Incremental Server-Sent Events parser.
• Task lifecycle helpers: Outcome, wait_for_task, send_message_and_wait.