Ag2 Knowledge And Memory

Knowledge, memory, and context assembly

This skill covers three related primitives that work together:

| Primitive | Lives in | Role | |---|---|---| | KnowledgeStore | ag2.knowledge | Path-based persistent storage (memory / sqlite / disk / redis) | | Assembly policies | ag2.policies | Shape (prompts, events) per turn before the LLM call | | Aggregation / Compaction | ag2.aggregate / .compact | Write structured knowledge to the store / trim event history |

KnowledgeConfig wires all three onto an Agent via the knowledge= constructor parameter; assembly policies go via assembly=.

When to use what

| User intent | Reach for | |---|---| | Remember user preferences / state between conversations | WorkingMemoryAggregate + WorkingMemoryPolicy (and a persistent store) | | Summarise each session for next time | ConversationSummaryAggregate + EpisodicMemoryPolicy | | Hard-cap event history sent to the LLM | SlidingWindowPolicy(max_events=N) | | Cap by approximate token count | TokenBudgetPolicy(max_tokens=N) | | Drop lifecycle / observer events from the LLM's view | ConversationPolicy() | | Trim stream history (not just LLM view) | TailWindowCompact or SummarizeCompact | | Route observer alerts to the LLM | AlertPolicy() |

60-second recipe — persistent working memory

from ag2 import Agent, KnowledgeConfig
from ag2.aggregate import AggregateTrigger, WorkingMemoryAggregate
from ag2.config import OpenAIConfig
from ag2.knowledge import DiskKnowledgeStore
from ag2.policies import ConversationPolicy, WorkingMemoryPolicy

store = DiskKnowledgeStore("./journal-state")
config = OpenAIConfig(model="gpt-5")

agent = Agent(
    "journal",
    prompt="You are a daily journal companion.",
    config=config,
    knowledge=KnowledgeConfig(
        store=store,
        aggregate=WorkingMemoryAggregate(config=config),
        aggregate_trigger=AggregateTrigger(on_end=True),
    ),
    assembly=[
        WorkingMemoryPolicy(),  # injects /memory/working.md on every LLM call
        ConversationPolicy(),
    ],
)

After each conversation the aggregate writes /memory/working.md. The next time you build an Agent against the same store, WorkingMemoryPolicy reads that file in and injects it as prompt context. The agent "remembers" without replaying chat history. Full runnable example: assets/journal_companion.py.

> Heads-up: knowledge=KnowledgeConfig(store=...) also hands the LLM a knowledge tool, seeds SKILL.md files into the store (which tell the model to use that tool), and dumps each turn's events to /log/. Fine for a journal companion that manages its own memory — but if you want the store available to policies without exposing it to the model, pass expose_tool=False, write_event_log=False. See "KnowledgeConfig(store=...) does four things — and three of them are now opt-out" under Wiring it all on the Agent.

KnowledgeStore implementations

| Implementation | Use when | |---|---| | MemoryKnowledgeStore() | Tests, ephemeral sessions | | SqliteKnowledgeStore(path) | Single-process durability — pragmatic default | | DiskKnowledgeStore(root) | Files should be human-readable on disk — first arg is root; requires the watchdog extra (the on_change watcher uses it). Without watchdog installed, importing the class raises a missing-dependency error. | | RedisKnowledgeStore(url_or_client) | Multi-process / cross-host sharing — first arg is url_or_client: pass a Redis URL string or an already-built redis.asyncio client. A URL string also needs the redis package. | | LockedKnowledgeStore(store, lock) | Wrap any store to serialize concurrent writers — first arg is store, second is the lock (both positional). Reads pass through unlocked; only write / delete / append acquire the lock. |

API (all async):

await store.write("/artifacts/report.md", "# Q3...")
text = await store.read("/artifacts/report.md")
children = await store.list("/")            # immediate children, dirs end in '/'
await store.delete("/artifacts/old.md")
exists = await store.exists("/artifacts/report.md")

off = await store.append("/log/events.jsonl", '{"t":1}\n')   # WAL-style
new_slice = await store.read_range("/log/events.jsonl", off)  # only new bytes
sub = await store.on_change("/log/", on_change_callback)

Assembly chain — what the LLM actually sees

Pass AssemblyPolicy instances via assembly=[...]. The Agent wires an internal AssemblerMiddleware at the outermost middleware position. Each policy transforms (prompts, events) and pipes into the next.

Two kinds of policy — order matters: injection before reduction.

| Kind | Purpose | Built-ins | |---|---|---| | Injection | Add to prompts | WorkingMemoryPolicy, EpisodicMemoryPolicy, AlertPolicy | | Reduction | Trim events | ConversationPolicy, SlidingWindowPolicy, TokenBudgetPolicy |

Validate ordering manually:

from ag2.assembly import AssemblerMiddleware
warnings = AssemblerMiddleware.validate_order(policies)  # returns list of warnings on known bad orderings

(AssemblerMiddleware and the AssemblyPolicy protocol live in ag2.assembly for advanced/manual harness wiring; you don't need to import them when just passing built-in policies via assembly=[...].)

Built-in policies

from ag2.policies import (
    AlertPolicy,
    ConversationPolicy,
    EpisodicMemoryPolicy,
    SlidingWindowPolicy,
    TokenBudgetPolicy,
    WorkingMemoryPolicy,
)

# Injection
WorkingMemoryPolicy()                                 # reads /memory/working.md
EpisodicMemoryPolicy(max_episodes=5, transparent=True) # reads recent /memory/conversations/
AlertPolicy()                                          # delivers ObserverAlerts to LLM, halts on FATAL

# Reduction
ConversationPolicy()                                  # drops non-conversation events
SlidingWindowPolicy(max_events=50, transparent=True)  # last N events
TokenBudgetPolicy(max_tokens=32_000, chars_per_token=4, transparent=True)

transparent=True appends a [policy_name] Showing X of Y events. note to the prompt — useful while tuning. Realistic chain:

assembly=[
    WorkingMemoryPolicy(),
    EpisodicMemoryPolicy(max_episodes=3),
    AlertPolicy(),
    SlidingWindowPolicy(max_events=80),
]

Aggregation — writing knowledge to the store

AggregateStrategy.aggregate(events, ctx, store) → None extracts and persists. Two built-ins, both take a ModelConfig for a summarisation call (use a cheaper model than the agent's main one):

| Strategy | Writes | Pairs with | |---|---|---| | WorkingMemoryAggregate(config=..., prompt="…") | /memory/working.md (single rolling file) — prompt= overrides the merge template ({existing} / {events} placeholders) | WorkingMemoryPolicy | | ConversationSummaryAggregate(config=...) | /memory/conversations/{ts}_{stream_id}.md | EpisodicMemoryPolicy |

AggregateTrigger controls cadence — every_n_turns, every_n_events, on_end. AggregateTrigger() alone fires nothing; opt in to at least one. on_end=True defaults off because each fire is an LLM call.

Compaction — trimming stream history

CompactStrategy.compact(events, ctx, store) → list[BaseEvent]. Replaces the stream's history. Two built-ins:

| Strategy | Behaviour | Cost | |---|---|---| | TailWindowCompact(target=N) | Keep last N events; drop the rest (optionally persist to /log/) | Zero LLM calls | | SummarizeCompact(target=N, config=...) | Summarise dropped events into one CompactionSummary; insert at head | One LLM call per fire |

CompactTrigger(max_events=N, max_tokens=M, chars_per_token=4) — fires when any threshold is crossed.

from ag2.compact import CompactTrigger, TailWindowCompact, SummarizeCompact

SummarizeCompact inserts a CompactionSummary event at the head; ConversationPolicy allows it through so the LLM still gets that context.

Wiring it all on the Agent

KnowledgeConfig is the bundle:

from dataclasses import dataclass

@dataclass
class KnowledgeConfig:
    store: KnowledgeStore
    expose_tool: bool = True               # auto-inject the `knowledge` LLM tool?
    write_event_log: bool = True           # dump each turn's events to /log/{stream_id}.jsonl?
    compact: CompactStrategy | None = None
    compact_trigger: CompactTrigger | None = None
    aggregate: AggregateStrategy | None = None
    aggregate_trigger: AggregateTrigger | None = None
    bootstrap: StoreBootstrap | None = None    # default: DefaultBootstrap(mention_tool=expose_tool)

KnowledgeConfig(store=...) does four things — and three of them are now opt-out

Passing knowledge=KnowledgeConfig(store=...) bundles four concerns. Defaults preserve the original behaviour, but expose_tool and write_event_log flags now turn most of it off:

1. Registers the store so assembly policies (WorkingMemoryPolicy, …) can context.dependencies.get(KnowledgeStore). (Usually the only thing you wanted — and the one piece with no flag, because it's the point.)
2. Auto-injects a knowledge action-group tool into the agent's tool list (knowledge(action="write"/"read"/"list"/...)). Disable with expose_tool=False.
3. Seeds SKILL.md files into the store on first ask — /SKILL.md, /artifacts/SKILL.md, /memory/SKILL.md, /log/SKILL.md — unless you pass an explicit bootstrap=. The default is DefaultBootstrap(mention_tool=expose_tool), so when you set expose_tool=False the seeded SKILL.md automatically stops telling the LLM to "use the knowledge tool" (it can't — there is no tool). For no seeding at all, pass bootstrap= your own no-op StoreBootstrap (a class with async def bootstrap(self, store, actor_name): pass); there's still no built-in NoBootstrap.
4. Persists turn events to /log/ — after every turn, the agent's full event history is dumped to /log/{stream_id}.jsonl. Disable with write_event_log=False. Persistence failures emit an EventLogFailed event on the stream (and also logger.exception).

So "store visible to policies, invisible to the LLM, no /log/ clutter, no SKILL.md files" is:

agent = Agent(
    "summarizer",
    config=config,
    knowledge=KnowledgeConfig(
        store=DiskKnowledgeStore("./agent-state"),
        expose_tool=False, write_event_log=False,   # no `knowledge` tool, no /log/ dump
        aggregate=WorkingMemoryAggregate(config=cheap_config),  # aggregation/compaction wiring still works
        aggregate_trigger=AggregateTrigger(on_end=True),
    ),
    assembly=[WorkingMemoryPolicy()],   # reads /memory/working.md from context.dependencies
)

If you also want zero SKILL.md seeding, add bootstrap=NoBootstrap() where NoBootstrap is your own no-op StoreBootstrap. The older alternative — skip KnowledgeConfig entirely and register the store as a plain Agent(..., dependencies={KnowledgeStore: store}) — still works and is the absolute minimum (no tool, no bootstrap, no /log/, and no aggregate/compact wiring); use it when you want to drive store.write("/memory/working.md", ...) yourself from, say, a separate "reflector" pass.

Full shape:

agent = Agent(
    "assistant",
    config=main_config,
    knowledge=KnowledgeConfig(
        store=DiskKnowledgeStore("./state"),
        compact=TailWindowCompact(target=100),
        compact_trigger=CompactTrigger(max_events=200),
        aggregate=ConversationSummaryAggregate(config=summarizer_config),
        aggregate_trigger=AggregateTrigger(every_n_turns=10, on_end=True),
        # expose_tool / write_event_log default True; bootstrap defaults to
        # DefaultBootstrap(mention_tool=expose_tool). Set explicitly only to opt out.
    ),
    assembly=[
        WorkingMemoryPolicy(),
        EpisodicMemoryPolicy(max_episodes=3),
        AlertPolicy(),
        SlidingWindowPolicy(max_events=80),
    ],
)

The harness wires internal middleware conditionally — _AssemblerMiddleware, _HaltCheckMiddleware, _CompactionMiddleware, _AggregationMiddleware. You only pay for what you turn on.

Lifecycle events emitted on the agent's stream:

• CompactionStarted → CompactionCompleted (events_before / events_after / usage) or CompactionFailed (the exception)
• AggregationStarted → AggregationCompleted (strategy / usage) or AggregationFailed (the exception)
• EventLogFailed if persisting the /log/ event stream raised
• HaltEvent when AlertPolicy sees a FATAL alert

The *Failed ones are the durable, observable signal — the harness also logger.exceptions them, but you don't need to configure Python logging to see something went wrong: subscribe to the stream (see ag2-observers-and-alerts).

Going deeper

• assets/journal_companion.py — runnable end-to-end working-memory demo (mirrors code_examples/06).
• assets/long_doc_chat.py — assembly + compaction stress test (mirrors code_examples/07).
• Source docs:
• website/docs/user-guide/advanced/knowledge_store.mdx — store API, EventLogWriter, LockedKnowledgeStore.
• website/docs/user-guide/advanced/assembly.mdx — full policy reference and ordering rules.
• website/docs/user-guide/advanced/aggregation.mdx — aggregate strategies and custom strategies.
• website/docs/user-guide/advanced/compaction.mdx — compact strategies and custom strategies.
• website/docs/user-guide/agent_harness.mdx — KnowledgeConfig constructor reference, turn-lifecycle middleware order.

Common pitfalls

• Reduction before injection — SlidingWindowPolicy before WorkingMemoryPolicy means the working memory injection isn't counted against the budget. Always: injections first, then AlertPolicy, then reductions.
• Forgetting KnowledgeStore dependency for memory policies — WorkingMemoryPolicy and EpisodicMemoryPolicy look up the store via context.dependencies.get(KnowledgeStore). KnowledgeConfig(store=...) registers it for you; if you wire the policy manually, register the store in dependencies too.
• Aggregation costs an LLM call per fire — on_end=True on every conversation can add up. Pair WorkingMemoryAggregate and ConversationSummaryAggregate thoughtfully; consider every_n_turns=N for high-volume agents.
• Mixing HistoryLimiter middleware with assembly reduction policies — they both trim. Pick one mechanism. Assembly is more flexible (rich shaping, transparency notes); HistoryLimiter is simpler.
• read_range operates on byte offsets, not character offsets — multi-byte UTF-8 sequences need careful alignment.
• Forgetting that WorkingMemoryAggregate is destructive — it overwrites /memory/working.md each fire. That's intentional (rolling state, not log) but expect prior content to merge or disappear.
• Expecting AlertPolicy to render alerts to the LLM without being in assembly= — alerts sit on the stream as ObserverAlert events but only reach the LLM when AlertPolicy injects them.
• KnowledgeConfig(store=...) ≠ "just a storage handle" — it also auto-injects a knowledge LLM tool, seeds SKILL.md files into the store, and dumps every turn's events to /log/. Turn those off with KnowledgeConfig(store=..., expose_tool=False, write_event_log=False) (the default bootstrap then also stops mentioning the tool, since mention_tool defaults to expose_tool); or skip KnowledgeConfig and use Agent(..., dependencies={KnowledgeStore: store}) for the bare minimum. See "KnowledgeConfig(store=...) does four things — and three of them are now opt-out" above.
• WorkingMemoryAggregate's default prompt is content-oriented — out of the box it preserves what the conversation was about ("preserve important existing context, remove outdated information"), not strategy; a research agent that wants memory to track tactics (which phrasings/domains worked) ge

…

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: ag2ai
• Source: ag2ai/ag2-skills
• License: Apache-2.0

Install and usage instructions live in the source repository linked above.