ag2-network-discussion

name	ag2-network-discussion
description	Open an AG2 network `discussion` channel — N-party (2+) round-robin where each participant speaks in fixed order, cycling until explicit close or TTL. Use when the user wants a brainstorm with a fixed cast, a panel discussion, or round-robin reviewers. Covers `agent_client.open(type="discussion", target=[...], knobs={"ordering": ORDERING_ROUND_ROBIN})`, the `expected_next_speaker` rotation, the `hc.can_send(...)` probe pattern (default handlers skip LLM calls when it isn't their turn), `DiscussionState`, the `turn_within` expectation defaults (`warn` at 120s / `hide` at 600s), view-window sizing for N participants, and the four close patterns that work with this adapter. Load this after `ag2-network-quickstart`. For conditional handoffs or declarative orchestration, see `ag2-network-workflow` instead.
license	Apache-2.0

AG2 Network — Discussion Adapter

discussion is an N-party round-robin channel. Participants speak in a fixed order, cycling indefinitely until you close it. The adapter enforces "wait your turn" via validate_send; the hub's can_send probe lets each agent's default handler skip wasted LLM calls when it isn't that agent's turn.

Prerequisite: read ag2-network-quickstart first. This skill assumes you already know Hub.open, HubClient.register, the channel lifecycle, and Envelope basics.

When to use

• "Three agents debating in turn"
• "A panel discussion / brainstorm with a fixed cast"
• "Round-robin reviewers commenting on a draft"
• Any fixed-order N-party turn-taking where each participant gets a slot per cycle

Don't use discussion for:

• Conditional handoffs ("if alice mentions security, hand to the security expert") → use ag2-network-workflow.
• Pipelines where each step happens once → use ag2-network-workflow with TransitionGraph.sequence([...]).
• Two participants with no fixed order → use conversation (covered in ag2-network-quickstart).
• Strict 1Q1R → use consulting (covered in ag2-network-quickstart).

Shape

Participants	2+
Turn order	Round-robin (creator first, then participants in registration order)
Auto-close	No
Termination	Explicit channel.close() or TTL (see "Closing" below)
Default view	WindowedSummary(recent_n=N*2) where N is the participant count
Default expectations	turn_within(120s, warn), turn_within(600s, hide)
Knob	{"ordering": ORDERING_ROUND_ROBIN} (only ordering shipped today)

The view recent-window is sized to N*2 so each agent's projection covers roughly the last two full cycles — enough context for a coherent reply without ballooning the prompt as the discussion grows.

Discussion agents, the NetworkPlugin, and say

HubClient.register(...) attaches NetworkPlugin by default — that adds peers / channels / tasks / context / delegate, the identity-level verbs. The say tool is not a plugin tool; it's offered per turn by the DiscussionAdapter itself (tools_for(...)), and only to expected_next_speaker — so a participant only sees say on the turn it's allowed to speak.

You normally don't need say: the default handler already posts the round-end EV_TEXT(reply.body) from the agent's plain reply, which is that turn's contribution. The hazard is an agent that calls say(content="…") and then also returns a non-empty body — two EV_TEXTs in one turn; the DiscussionAdapter folds the first, advances expected_next_speaker, and the round-end one fails validate_send (expects <other> to speak). attach_plugin=False does not suppress say (it's adapter-owned), so it isn't the fix here; use it only if you want a bare agent without the five plugin verbs.

Prompting alone isn't always enough: capable models will call say unprompted just because it's present in the per-turn tool surface. If you see the double-send in practice, swap the notify handler for one that calls agent.ask(...) without tools= (so the adapter-injected say isn't offered to the LLM) — see ag2-network-tools-and-views → "Bypassing adapter tools".

# Bare discussion participant (no plugin verbs) — still gets `say` from the adapter on its turn:
alice = await alice_hc.register(alice_agent, Passport(name="alice"), Resume(), attach_plugin=False)

The examples below pass attach_plugin=False for compactness; drop it if your participants need delegate / peers / etc. Full detail: ag2-network-tools-and-views → "Adapter-owned tools (tools_for)".

Smallest example

import asyncio

from autogen.beta import Agent
from autogen.beta.config import AnthropicConfig
from autogen.beta.knowledge import MemoryKnowledgeStore
from autogen.beta.network import (
    EV_CHANNEL_CLOSED,
    EV_TEXT,
    ORDERING_ROUND_ROBIN,
    Hub,
    HubClient,
    LocalLink,
    Passport,
    Resume,
)


async def main() -> None:
    config = AnthropicConfig(model="claude-sonnet-4-6")
    hub = await Hub.open(MemoryKnowledgeStore(), ttl_sweep_interval=0)
    link = LocalLink(hub)

    alice_hc, bob_hc, carol_hc = (HubClient(link, hub=hub) for _ in range(3))

    alice = await alice_hc.register(
        Agent("alice", prompt="The optimist. One short sentence.", config=config),
        Passport(name="alice"), Resume(), attach_plugin=False,
    )
    bob = await bob_hc.register(
        Agent("bob", prompt="The realist. One short sentence.", config=config),
        Passport(name="bob"), Resume(), attach_plugin=False,
    )
    carol = await carol_hc.register(
        Agent("carol", prompt="The skeptic. One short sentence.", config=config),
        Passport(name="carol"), Resume(), attach_plugin=False,
    )

    channel = await alice.open(
        type="discussion",
        target=[bob.agent_id, carol.agent_id],
        knobs={"ordering": ORDERING_ROUND_ROBIN},
    )
    await channel.send("Topic: should every developer learn Rust?")

    # Halt after 6 EV_TEXT envelopes (= 2 full alice→bob→carol cycles).
    await wait_for_text_count(hub, channel.channel_id, expected=6)
    await channel.close(reason="cap_reached")

    for hc in (alice_hc, bob_hc, carol_hc):
        await hc.close()
    await hub.close()


async def wait_for_text_count(hub, channel_id, expected, *, timeout=180.0):
    deadline = asyncio.get_event_loop().time() + timeout
    while asyncio.get_event_loop().time() < deadline:
        wal = await hub.read_wal(channel_id)
        if sum(1 for e in wal if e.event_type == EV_TEXT) >= expected:
            return
        await asyncio.sleep(0.05)
    raise asyncio.TimeoutError("did not reach expected count")


asyncio.run(main())

The order in target=[bob.agent_id, carol.agent_id] is significant — it becomes the rotation order after the creator. The cycle is therefore alice → bob → carol → alice → bob → carol → … until the cap fires.

How turn skipping works (the can_send probe)

When alice sends her first envelope, the hub fans EV_TEXT out to bob and carol. Both default handlers fire in parallel:

• bob's handler — calls hc.can_send(channel_id, bob.agent_id). The adapter says "yes, bob is expected_next_speaker." Handler runs Agent.ask, sends bob's reply.
• carol's handler — calls hc.can_send(channel_id, carol.agent_id). The adapter says "no, expected_next_speaker is bob." Handler returns without engaging the LLM.

When bob's reply lands, the same fan-out repeats. Now expected_next_speaker = carol, so carol's handler engages and bob's skips. No wasted LLM calls anywhere.

If you write a custom handler for a discussion channel, mirror this pattern — and delegate non-text envelopes to default_handler so you keep the auto-ack of EV_CHANNEL_INVITE (otherwise the channel sits in INVITED until invite_ack_timeout and the hub closes it on you):

from autogen.beta.network import Envelope, EV_TEXT, default_handler


async def my_handler(envelope: Envelope) -> None:
    if envelope.event_type != EV_TEXT:
        await default_handler(envelope, client)   # invite-ack + lifecycle bookkeeping
        return
    if not hc.can_send(envelope.channel_id, my_agent_id):    # sync — not awaitable
        return  # not our turn — skip the LLM call
    # ... read WAL, project view, run Agent.ask, send reply ...

A HumanClient in the round-robin

A discussion participant doesn't have to be an Agent. Register a HumanClient (hc.register_human(Passport(name="user", kind="human")) — see ag2-network-quickstart → "HumanClient") and add it to the participant order like any other. It has no notify handler that auto-responds, so the application drives its turn: subscribe with on_envelope(...) (or pull with next_envelope(...)) and, when an envelope lands, check hc.can_send(channel_id, user.agent_id) (sync, not awaitable) — if it's the human's turn, prompt the person and await user.send(channel_id, text); otherwise wait. (The framework's own discussion tests do exactly this — a human gating on adapter state for its slot in the rotation.)

State object

@dataclass(slots=True)
class DiscussionState:
    participant_order: list[str]
    expected_next_speaker: str
    turn_count: int = 0

participant_order is fixed at create time by sorting participants on Participant.order. Round-robin advances by (current_index + 1) % len(participant_order) after every accepted EV_TEXT. Read state for inspection or testing via hub._adapter_states[channel_id] (the underscore signals "operator API" — not for production agent logic).

Validation rules

DiscussionAdapter.validate_send rejects:

• EV_TEXT from anyone other than state.expected_next_speaker — raises ProtocolError.
• Sends from non-participants.
• Sends to a closed channel.

Protocol envelopes (EV_CHANNEL_*, ag2.task.*) bypass the turn check — they're bookkeeping, not turn-taking.

Customising the ordering

Today only ORDERING_ROUND_ROBIN ships:

from autogen.beta.network import ORDERING_ROUND_ROBIN

channel = await alice.open(
    type="discussion",
    target=[bob.agent_id, carol.agent_id],
    knobs={"ordering": ORDERING_ROUND_ROBIN},  # equivalent to "round_robin"
)

Passing any other ordering raises at create time. Future orderings (dynamic, weighted, priority) plug in here without breaking the round-robin contract.

If you need conditional turn-taking now, switch adapters to workflow — TransitionGraph.round_robin(participants, max_turns=N) gives you the same shape with the option to add conditions later. See ag2-network-workflow.

Closing

discussion never auto-closes. Four patterns work; pick by who decides:

Pattern	Who decides	When
App-side cap → channel.close()	Your orchestration code	Turn count, time, or any external predicate
Agent-side tool (via ChannelInject)	The LLM	A participant decides "we're done"
Custom adapter subclass	The framework	Content-based stop (rare for discussions)
TTL / turn_within expectations	The hub's sweepers	Safety net only

App-side cap (canonical)

await wait_for_text_count(hub, channel.channel_id, expected=6)
await channel.close(reason="cap_reached")

The reason flows on EV_CHANNEL_CLOSED.event_data["reason"] — pick something descriptive so observers can distinguish a clean cap from a TTL or expectation violation.

Agent-side tool

Same pattern as the other adapters — inject the active Channel, call close():

from autogen.beta.network.client.inject import ChannelInject


async def end_discussion(reason: str, channel: ChannelInject) -> str:
    if channel is None:
        return "no active channel"
    await channel.close(reason=f"agent_close:{reason}")
    return f"closed: {reason}"


for agent in (alice_agent, bob_agent, carol_agent):
    agent.tool(end_discussion)

Any participant can wrap up. See ag2-network-quickstart's "Five close routes" for the full picture.

When discussion isn't enough

The moment you need conditional turn-taking ("if bob mentions deadlines, jump to deadlines_expert"), discussion is the wrong adapter. Migrate to workflow — same N-party shape, but turn-taking lives in a TransitionGraph with FromSpeaker, ToolCalled, and ContextEquals conditions. See ag2-network-workflow for the migration recipe.

Default expectations

Expectation	Threshold	Handler	What it does
turn_within	120s	warn	Logs AUDIT_KIND_EXPECTATION_VIOLATED. Channel stays open.
turn_within	600s	hide	Marks the slow speaker as "skip" in the view projection for one cycle. Channel stays open.

Discussion deliberately never auto-closes from expectations — a slow speaker shouldn't kill the whole panel. If you want the channel to terminate on a stalled cycle, override the expectations to auto_close via ag2-network-governance.

Quick reference — imports

from autogen.beta.network import (
    DISCUSSION_TYPE,           # = "discussion"
    ORDERING_ROUND_ROBIN,      # = "round_robin"
    DiscussionAdapter,         # the adapter class itself (rarely instantiated directly)
    DiscussionState,           # state dataclass
    HumanClient,               # a non-LLM participant in the rotation — HubClient.register_human(...)
)

The string forms type="discussion" and ordering="round_robin" work too — the constants are equivalent and exist for type-safety in larger codebases.