Memory System

The memory system provides session management and event storage for agents. It tracks conversation history, tool calls, delegations, and provides a bridge between KAOS events and Pydantic AI message types.

Memory Implementations

Class	Description	Use Case
LocalMemory	In-memory storage with limits	Default, single-pod
RemoteMemory	Central memory-service client (short + long-term tiers)	MemoryStore-bound agents
NullMemory	No-op implementation	Disabled memory

Configuration

Via Environment Variables

Variable	Default	Description
MEMORY_ENABLED	true	Enable/disable all memory operations
MEMORY_CONTEXT_LIMIT	6	Max history events for context window
MEMORY_MAX_SESSIONS	1000	Max sessions (LocalMemory)
MEMORY_MAX_SESSION_EVENTS	500	Max events per session (LocalMemory)
MEMORY_STORE_ENDPOINT	-	Central memory-service URL (set by the operator when a MemoryStore is bound; selects RemoteMemory)

Via Agent CRD

spec:
  config:
    memory:
      enabled: true
      type: remote            # "remote" (bound MemoryStore) or "local" (pod-local)
      memoryStore: shared-memory
      scope: user             # private | user | shared | session
      tools: all              # all | read | write
      failureMode: soft       # soft | strict

See the Agent CRD and MemoryStore CRD references for the full memory surface (scopes, tools, client params, storage modes).

Memory tiers

A RemoteMemory agent layers three tiers behind one client:

• Short-term — a verbatim window of recent turns replayed for conversational continuity (also the local fallback when the store is degraded).
• Medium-term — a rolling summary/digest of evicted turns (clientParams.rollingSummary).
• Long-term — semantic, cross-session facts extracted into the bound MemoryStore and recalled by relevance.

LocalMemory keeps only the pod-local short-term window.

Memory-Enabled Gating

When memory_enabled=False (or MEMORY_ENABLED=false):

• NullMemory is used — all operations are no-ops
• No conversation history is maintained between requests
• Memory endpoints return empty results
• Useful for stateless agents or performance-critical paths

Pydantic AI Bridge

The memory system bridges KAOS MemoryEvent objects to Pydantic AI ModelMessage types (ModelRequest / ModelResponse). This enables conversation continuity:

Memory Events → _memory_events_to_messages() → Pydantic AI message_history
Pydantic AI run result → _extract_and_persist_events() → Memory Events

Event-to-Message Mapping

KAOS Event Type	Pydantic AI Type
user_message	ModelRequest with UserPromptPart
task_delegation_received	ModelRequest with UserPromptPart
agent_response	ModelResponse with TextPart
tool_call	ModelRequest with ToolReturnPart
tool_result	ModelRequest with ToolReturnPart

Context Window

The memory_context_limit controls how many recent events are included in the Pydantic AI message_history. This bounds context size for the LLM.

MemoryEvent Structure

@dataclass
class MemoryEvent:
    event_id: str
    timestamp: datetime
    event_type: str
    content: Any
    metadata: Dict[str, Any]

Event Types

Type	Description
user_message	User input
task_delegation_received	Delegation from parent agent
agent_response	Final agent output
tool_call	MCP tool invocation
tool_result	MCP tool result
delegation_request	Delegation to sub-agent
delegation_response	Sub-agent response
error	Error during processing

Session Management

# Create session
session_id = await memory.create_session(app_name="agent", user_id="user123")

# Get or create (idempotent)
session_id = await memory.get_or_create_session(session_id="id", app_name="agent")

# List sessions
sessions = await memory.list_sessions()

# Delete session
await memory.delete_session(session_id)

Event Management

# Create and add event
event = memory.create_event("user_message", "Hello!", metadata={"source": "api"})
await memory.add_event(session_id, event)

# Get events
all_events = await memory.get_session_events(session_id)
filtered = await memory.get_session_events(session_id, event_types=["user_message"])

Memory Endpoints

Always available (not behind a debug flag):

GET /memory/events

curl http://localhost:8000/memory/events
curl http://localhost:8000/memory/events?session_id=abc&limit=50

GET /memory/sessions

curl http://localhost:8000/memory/sessions

RemoteMemory

Central memory-service client used when an agent is bound to a MemoryStore. The operator injects MEMORY_STORE_ENDPOINT and the runtime routes short- and long-term memory through the service:

from pais.memory import RemoteMemory

memory = RemoteMemory("http://memory-service.namespace:8080")

Uses the same API as LocalMemory; persistence and cross-session recall are handled by the memory service.

Cleanup

LocalMemory uses deques for automatic eviction:

• Events evicted when max_events_per_session exceeded
• Sessions evicted (oldest 10%) when max_sessions exceeded