feat: extract agent-bus scheduling kernel

README.md

@@ -41,8 +41,12 @@ Version `0.1.x` contains the converged foundation layer:
   stream-repetition detection;
 - portable loop observers for budget/context/wall-clock guards, finalization,
   repetition detection, SSE events, task boards, and bounded trajectories;
-- shared agent-bus stop signals/pools, filesystem skill loaders, session
-  history, renewable wall-time leases, and language helpers.
+- complete agent-bus communication, spawn control, reusable sessions,
+  result recovery, fan-in policy, shared pools and stop signals;
+- portable tools, task/finalization budgets, role-scoped resource management,
+  and backend-injected DAG scheduling;
+- filesystem skill loaders, session history, renewable wall-time leases, and
+  language helpers.
 
 The initial extraction is based on the already-merged integration branches:
 
@@ -68,9 +72,10 @@ Code belongs in AgentCore when it:
 - accepts product behavior through typed inputs or explicit hooks;
 - has tests that run without either product repository installed.
 
-Provider clients, session affinity, user/session retention policy, checkpoint
-association, workflow node implementations, sandbox mounting/authorization,
-UI history, and product-specific observers remain in their product.
+Provider clients, session affinity, durable process/event-store implementations,
+user/session retention policy, checkpoint association, workflow node
+implementations, sandbox mounting/authorization, UI history, and
+product-specific observers remain in their product.
 
 ## Development
 
@@ -147,10 +152,15 @@ edit both products' core copies, that is evidence it belongs here.
    MiniDAG/graph construction, middleware/observers, agent-bus coordination
    primitives (shared pools and stop signals), skills, session history, models,
    and scoped registries.
-8. **Agent-bus scheduling** (next): extract the shared communication models,
-   runtime, spawn guard, bus, and fan-in orchestration behind explicit product
-   hooks. Product tool assembly and workflow-specific policy remain downstream.
-9. Remove product compatibility facades after downstream imports have moved to
+8. **Agent-bus scheduling** (complete in AgentCore): communication models,
+   durable result-message recovery, runtime, spawn guard, reusable sessions,
+   bus/fan-in orchestration, resource management, task budgets, and the
+   backend-injected DAG scheduler. Product tool assembly, persistence backends,
+   and workflow policy remain downstream.
+9. **Provider substrate** (next): converge the shared provider transports,
+   fallback engine, prompt cache, usage metering, and non-blocking streaming
+   behind product configuration and session-affinity adapters.
+10. Remove product compatibility facades after downstream imports have moved to
    `agent_core`.
 
 Each slice must leave product CI green and must not depend on a floating branch.

agent_core/components/agent_bus/__init__.py

@@ -1 +1,103 @@
-"""Portable agent coordination primitives."""
+"""AgentBus — multi-agent dispatch, communication, and spawn control.
+
+Also serves as the back-compat entry point for ``agent_core.components.agent_bus``
+(the former flat-file module). Re-exports the public API from submodules.
+"""
+
+from agent_core.components.agent_bus.agent_comm import (
+    AgentComm,
+    DeliveryMode,
+    EventStoreContractError,
+    event_ordinal,
+)
+from agent_core.components.agent_bus.bus import (
+    AgentBus,
+    configure_default_event_sink_resolver,
+    configure_default_pause_check_factory,
+    configure_default_session_activity,
+)
+from agent_core.components.agent_bus.fan_in import (
+    COMPLETE_STOP_REASONS,
+    INCOMPLETE_STOP_REASONS,
+    ORCHESTRATOR_AGENT_NAME,
+    CompletionInfo,
+    CompletionPolicy,
+    FanInBatch,
+    classify_completion,
+    format_report_block,
+    format_status_line,
+    format_status_report_block,
+    process_collected,
+    session_state,
+)
+from agent_core.components.agent_bus.models import (
+    CollectResult,
+    DepthLimitExceeded,
+    JobEntry,
+    PendingSessionTask,
+    SessionWaitOutcome,
+    SubAgentResult,
+    SubAgentRuntimeSpec,
+    SubAgentSession,
+    SubTask,
+)
+from agent_core.components.agent_bus.runtime import (
+    adapt_default_session_result,
+    adapt_default_subagent_result,
+    build_default_subagent_loop_config,
+    build_default_subagent_observers,
+    build_session_loop_config,
+    close_session_boundary_aborted,
+    resolve_session_observers,
+)
+from agent_core.components.agent_bus.shared_pool import SharedArtifactPool
+from agent_core.components.agent_bus.spawn_guard import (
+    BudgetExhausted,
+    SpawnDepthExceeded,
+    SpawnGuard,
+    SpawnReservation,
+)
+
+__all__ = [
+    "COMPLETE_STOP_REASONS",
+    "INCOMPLETE_STOP_REASONS",
+    "ORCHESTRATOR_AGENT_NAME",
+    "AgentBus",
+    "AgentComm",
+    "BudgetExhausted",
+    "CollectResult",
+    "CompletionInfo",
+    "CompletionPolicy",
+    "DeliveryMode",
+    "DepthLimitExceeded",
+    "EventStoreContractError",
+    "FanInBatch",
+    "JobEntry",
+    "PendingSessionTask",
+    "SessionWaitOutcome",
+    "SharedArtifactPool",
+    "SpawnDepthExceeded",
+    "SpawnGuard",
+    "SpawnReservation",
+    "SubAgentResult",
+    "SubAgentRuntimeSpec",
+    "SubAgentSession",
+    "SubTask",
+    "adapt_default_session_result",
+    "adapt_default_subagent_result",
+    "build_default_subagent_loop_config",
+    "build_default_subagent_observers",
+    "build_session_loop_config",
+    "classify_completion",
+    "close_session_boundary_aborted",
+    "configure_default_event_sink_resolver",
+    "configure_default_pause_check_factory",
+    "configure_default_session_activity",
+    "event_ordinal",
+    "format_report_block",
+    "format_status_line",
+    "format_status_report_block",
+    "process_collected",
+    "resolve_session_observers",
+    "session_state",
+]