agenticraft_foundation.mpst.patterns

4 communication patterns built from session types: request-response, pipeline, scatter-gather, consensus.

Common multi-agent session patterns.

This module provides reusable session type patterns for common multi-agent communication scenarios.

Patterns: - RequestResponse: Simple client-server request-response - ScatterGather: Coordinator sends to all, gathers responses - Pipeline: Sequential processing through stages - Consensus: Multi-party agreement protocol

Each pattern provides: - Global type constructor - Local type projections - Example usage

ConsensusPattern dataclass

Two-Phase Commit consensus pattern.

ATTRIBUTE	DESCRIPTION
coordinator	Coordinator participant ID TYPE: ParticipantId | str
participants	List of participant IDs TYPE: Sequence[ParticipantId | str]
prepare_label	Label for prepare messages TYPE: str
vote_yes_label	Label for affirmative vote TYPE: str
vote_no_label	Label for negative vote TYPE: str
commit_label	Label for commit decision TYPE: str
abort_label	Label for abort decision TYPE: str

global_type(with_choice=False)

Build the global session type.

PARAMETER	DESCRIPTION
with_choice	If True, include explicit choice branches (only practical for 1-2 participants) TYPE: bool DEFAULT: False

RETURNS	DESCRIPTION
SessionType	Global type for two-phase commit

participants_set()

Get all participants including coordinator.

PipelinePattern dataclass

Pipeline session pattern.

ATTRIBUTE	DESCRIPTION
stages	List of stage participant IDs in order TYPE: Sequence[ParticipantId | str]
data_label	Label for data messages between stages TYPE: str
repeatable	If True, pipeline can repeat TYPE: bool

global_type()

Build the global session type.

RETURNS	DESCRIPTION
SessionType	Global type for pipeline

The type is

Stage_1 → Stage_2 : Data. Stage_2 → Stage_3 : Data. ... Stage_{n-1} → Stage_n : Data. end (or X for repeatable)

participants()

Get all participants in the pipeline.

RETURNS	DESCRIPTION
set[ParticipantId]	Set of stage participant identifiers.

RequestResponsePattern dataclass

Request-Response session pattern.

ATTRIBUTE	DESCRIPTION
client	Client participant ID TYPE: ParticipantId | str
server	Server participant ID TYPE: ParticipantId | str
request_label	Label for request message TYPE: str
response_label	Label for response message TYPE: str
repeatable	If True, pattern can repeat TYPE: bool

global_type()

Build the global session type.

RETURNS	DESCRIPTION
SessionType	Global type for request-response

participants()

Get all participants in the request-response interaction.

RETURNS	DESCRIPTION
set[ParticipantId]	Set containing the client and server identifiers.

ScatterGatherPattern dataclass

Scatter-Gather session pattern.

ATTRIBUTE	DESCRIPTION
coordinator	Coordinator participant ID TYPE: ParticipantId | str
workers	List of worker participant IDs TYPE: Sequence[ParticipantId | str]
task_label	Label for task messages TYPE: str
result_label	Label for result messages TYPE: str

global_type()

Build the global session type.

RETURNS	DESCRIPTION
SessionType	Global type for scatter-gather

The type is

Coordinator → Worker_1 : Task. ... Coordinator → Worker_n : Task. Worker_1 → Coordinator : Result. ... Worker_n → Coordinator : Result. end

participants()

Get all participants in the scatter-gather pattern.

RETURNS	DESCRIPTION
set[ParticipantId]	Set containing the coordinator and all worker identifiers.

two_phase_commit(coordinator='coordinator', participants=None, with_choice=False)

Create a two-phase commit global type.

PARAMETER	DESCRIPTION
coordinator	Coordinator participant name TYPE: str DEFAULT: 'coordinator'
participants	List of participant names TYPE: Sequence[str] | None DEFAULT: None
with_choice	Include explicit choice branches (only for 1-2 participants) TYPE: bool DEFAULT: False

RETURNS	DESCRIPTION
SessionType	Global session type

Example

Simple 2PC with 2 participants

g = two_phase_commit()

Custom participants

g = two_phase_commit("leader", ["replica1", "replica2", "replica3"])

With explicit branching (for 2 participants)

g = two_phase_commit(with_choice=True)