Memory Configuration Reference

Memory types in AgentEnsemble are provided by the agentensemble-memory module, which is a separate optional dependency from agentensemble-core.

Module Coordinates

// Gradle (Kotlin DSL)
implementation("net.agentensemble:agentensemble-memory:2.0.0")

<!-- Maven -->
<dependency>
    <groupId>net.agentensemble</groupId>
    <artifactId>agentensemble-memory</artifactId>
    <version>2.0.0</version>
</dependency>

agentensemble-core declares a compileOnly dependency on agentensemble-memory, meaning agentensemble-memory is not included transitively. Add it explicitly when you use any memory feature.

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MemoryStore (v2.0.0 primary API)

MemoryStore is the v2.0.0 SPI for task-scoped cross-execution memory. Set it on the ensemble and declare scopes on tasks:

MemoryStore store = MemoryStore.inMemory();

Ensemble.builder()
    .memoryStore(store)
    .task(Task.builder()
        .description("Research AI trends")
        .memory("research")   // declares the scope
        .build())
    .build()
    .run();

Interface

public interface MemoryStore {
    void store(String scope, MemoryEntry entry);
    List<MemoryEntry> retrieve(String scope, String query, int maxResults);
    void evict(String scope, EvictionPolicy policy);

    static MemoryStore inMemory() { ... }
    static MemoryStore embeddings(EmbeddingModel model, EmbeddingStore<TextSegment> store) { ... }
}

Factories

Factory	Description
MemoryStore.inMemory()	Lightweight in-memory implementation. Entries stored in insertion order; retrieval returns most recent (no semantic search). For dev/testing.
MemoryStore.embeddings(EmbeddingModel, EmbeddingStore)	Production implementation using LangChain4j embeddings for semantic similarity retrieval.

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MemoryScope

Declares a named scope with optional eviction configuration.

// Simple -- no eviction
MemoryScope.of("research")

// Keep last N entries
MemoryScope.builder()
    .name("research")
    .keepLastEntries(10)
    .build()

// Keep entries within a time window
MemoryScope.builder()
    .name("research")
    .keepEntriesWithin(Duration.ofDays(30))
    .build()

Builder Field	Type	Description
name	String	Scope identifier; must not be blank
keepLastEntries	int	Eviction: retain only the N most recent entries after storage
keepEntriesWithin	Duration	Eviction: retain only entries stored within this window

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EvictionPolicy

Applied after each storage operation on a scope with a configured eviction policy.

Factory	Description
EvictionPolicy.keepLastEntries(int n)	Retains the n most recent entries; evicts oldest first. n must be positive.
EvictionPolicy.keepEntriesWithin(Duration d)	Retains entries whose storedAt is within the given duration. d must be positive.

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MemoryEntry (v2.0.0)

Immutable record of a single stored entry.

Field	Type	Description
content	String	Raw text content (typically the agent’s task output)
structuredContent	Object	Parsed structured output (nullable)
storedAt	Instant	When the entry was stored
metadata	Map<String, String>	Metadata; standard keys: "agentRole", "taskDescription"

Use entry.getMeta("agentRole") to read metadata values.

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MemoryTool

Gives agents explicit mid-task access to a named scope:

MemoryStore store = MemoryStore.inMemory();

Agent agent = Agent.builder()
    .role("Researcher")
    .tools(MemoryTool.of("research", store))
    .build();

The LLM can call storeMemory(key, value) and retrieveMemory(query) during its ReAct loop.

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EnsembleMemory

Configured via EnsembleMemory.builder(). At least one memory type must be enabled.

Field	Type	Required	Default	Description
shortTerm	boolean	One of these must be set	false	Accumulate all task outputs within a run and inject into subsequent agents
longTerm	LongTermMemory	One of these must be set	null	Cross-run vector-store persistence
entityMemory	EntityMemory	One of these must be set	null	Named entity fact store
longTermMaxResults	int	No	5	Maximum number of long-term memories retrieved per task. Must be greater than zero.

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LongTermMemory Interface

public interface LongTermMemory {
    void store(MemoryEntry entry);
    List<MemoryEntry> retrieve(String query, int maxResults);
}

EmbeddingStoreLongTermMemory

The built-in implementation. Uses a LangChain4j EmbeddingStore<TextSegment> and EmbeddingModel.

Constructor:

new EmbeddingStoreLongTermMemory(
    EmbeddingStore<TextSegment> embeddingStore,
    EmbeddingModel embeddingModel
)

Both arguments must be non-null.

LangChain4j Embedding Stores: InMemoryEmbeddingStore (development), Chroma, Qdrant, Pinecone, Weaviate, Milvus, PostgreSQL pgvector, Redis, and more.

LangChain4j Embedding Models: OpenAI text-embedding-3-small / text-embedding-3-large, Ollama embeddings, Azure OpenAI embeddings, and more.

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EntityMemory Interface

public interface EntityMemory {
    void put(String entityName, String fact);
    Optional<String> get(String entityName);
    Map<String, String> getAll();
    boolean isEmpty();
}

InMemoryEntityMemory

The built-in implementation backed by a ConcurrentHashMap.

EntityMemory entities = new InMemoryEntityMemory();
entities.put("Acme Corp", "A B2B SaaS company with 15,000 enterprise customers");
entities.put("Alice Chen", "Head of Product, background in NLP research");

Entity names are trimmed when stored and looked up. put() replaces any existing fact for the same entity name.

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MemoryEntry

Each recorded task output produces a MemoryEntry with:

Field	Type	Description
content	String	The raw output from the task
agentRole	String	The role of the agent that produced it
taskDescription	String	The task description
timestamp	Instant	When the output was recorded

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Custom Implementations

Custom Long-Term Memory

public class PostgresLongTermMemory implements LongTermMemory {
    @Override
    public void store(MemoryEntry entry) {
        db.insert("memories", entry.getContent(), entry.getAgentRole(),
                  entry.getTaskDescription(), entry.getTimestamp());
    }

    @Override
    public List<MemoryEntry> retrieve(String query, int maxResults) {
        return db.vectorSearch(query, maxResults).stream()
            .map(row -> MemoryEntry.builder()
                .content(row.content())
                .agentRole(row.agentRole())
                .taskDescription(row.taskDescription())
                .timestamp(row.timestamp())
                .build())
            .toList();
    }
}

Custom Entity Memory

public class ConfiguredEntityMemory implements EntityMemory {
    private final Map<String, String> facts;

    public ConfiguredEntityMemory(Map<String, String> facts) {
        this.facts = new HashMap<>(facts);
    }

    @Override
    public void put(String entityName, String fact) { facts.put(entityName.trim(), fact); }

    @Override
    public Optional<String> get(String entityName) {
        return Optional.ofNullable(facts.get(entityName == null ? null : entityName.trim()));
    }

    @Override
    public Map<String, String> getAll() { return Collections.unmodifiableMap(facts); }

    @Override
    public boolean isEmpty() { return facts.isEmpty(); }
}

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Example: All Memory Types

EmbeddingStore<TextSegment> store = ChromaEmbeddingStore.builder()
    .baseUrl("http://localhost:8000")
    .collectionName("agentensemble-memories")
    .build();

EmbeddingModel embeddingModel = OpenAiEmbeddingModel.builder()
    .apiKey(System.getenv("OPENAI_API_KEY"))
    .modelName("text-embedding-3-small")
    .build();

EntityMemory entities = new InMemoryEntityMemory();
entities.put("Project Horizon", "Q4 initiative to expand into the APAC market");

EnsembleMemory memory = EnsembleMemory.builder()
    .shortTerm(true)
    .longTerm(new EmbeddingStoreLongTermMemory(store, embeddingModel))
    .entityMemory(entities)
    .longTermMaxResults(3)
    .build();