MCP server opencode-mem

opencode-mem

Persistent memory infrastructure for AI coding agents.

A Rust MCP server combining PostgreSQL full-text search, optional vector retrieval, and hierarchical summaries.

---

opencode-mem is a Rust MCP (Model Context Protocol) server for storing and retrieving agent observations. PostgreSQL is the canonical store; pgvector-backed embeddings and hierarchical summaries provide additional retrieval paths when configured.

Inspired by claude-mem, with a PostgreSQL-first architecture for OpenCode and MCP clients.

Core design

Area	Current implementation
Runtime	Rust workspace with MCP stdio, HTTP, and CLI entrypoints
Storage	PostgreSQL, with pgvector used for vector retrieval
Retrieval	Full-text, keyword, semantic, and hybrid search paths
Memory pipeline	Queued observations, structured summaries, and drill-down
Privacy boundary	<private> filtering before persistence and model calls
Recovery	Visibility timeouts, dead-letter handling, and degraded-mode responses

Implemented paths

• Hierarchical summaries can be expanded back to their stored source events.
• Hybrid retrieval combines PostgreSQL full-text results with vector similarity when embeddings are enabled.
• Structured metadata extraction records files, functions, libraries, errors, and decisions from model output.
• Context-aware compression can create a new observation, update a supplied candidate, or skip a low-value result.
• MCP, HTTP, and CLI entrypoints share the same PostgreSQL-backed service layer.
• Database connection failures are surfaced through circuit-breaker and degraded-mode paths.

Architecture

graph LR
    A[AI Agent / IDE] -->|MCP stdio| B[opencode-mem]
    A -->|HTTP :37777| B
    B --> C[Queue Processor]
    C --> D[LLM Compression]
    D --> E[(PostgreSQL)]
    E -->|pgvector| F[Semantic Search]
    E -->|tsvector / GIN| G[Full-Text Search]
    F & G --> H[Hybrid Results]

Crate Structure

crates/
├── core/              # Domain types (Observation, Session, Knowledge, etc.)
├── storage/           # PostgreSQL + pgvector + migrations + circuit breaker
├── embeddings/        # Vector embeddings (fastembed BGE-M3, 1024d, multilingual)
├── search/            # Hybrid search (FTS + keyword + semantic)
├── llm/               # LLM compression (OpenAI-compatible API)
├── service/           # Business logic (ObservationService, SessionService, QueueService)
├── http/              # HTTP API (Axum)
├── mcp/               # MCP server (stdio)
├── infinite-memory/   # Hierarchical infinite memory backend
└── cli/               # CLI binary

Installation

From source

git clone https://github.com/Stranmor/opencode-mem.git
cd opencode-mem
cargo build --release
# Binary: target/release/opencode-mem-cli

Quick Start

Prerequisites: latest stable Rust · PostgreSQL with pgvector extension

1. Configure

export DATABASE_URL="postgresql://localhost/opencode_mem"
read -rsp "Provider API key: " OPENCODE_MEM_API_KEY && printf '\n'
export OPENCODE_MEM_API_KEY
export OPENCODE_MEM_API_URL="https://api.openai.com"  # or any compatible endpoint

Use a credential manager or protected environment file for persistent secrets; do not commit database passwords or provider keys to opencode.json.

Migrations run automatically on first start.

2. Run

# MCP server (for IDE integration):
opencode-mem-cli mcp

# HTTP server (for dashboards and external integrations):
opencode-mem-cli serve

3. Integrate with OpenCode

Add to your opencode.json. OpenCode substitutes the already exported environment variables at runtime, so the config remains safe to commit:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "memory": {
      "type": "local",
      "command": ["/path/to/opencode-mem-cli", "mcp"],
      "environment": {
        "DATABASE_URL": "{env:DATABASE_URL}",
        "OPENCODE_MEM_API_KEY": "{env:OPENCODE_MEM_API_KEY}",
        "OPENCODE_MEM_API_URL": "{env:OPENCODE_MEM_API_URL}"
      }
    }
  }
}

MCP Tools

The server exposes MCP tools for search, retrieval, knowledge, and summary drill-down. The recommended workflow is Search → Timeline → Get Observations so clients fetch full records only when needed.

Tool	Description
search	Search memory with semantic understanding. Returns index with IDs.
timeline	Get chronological context within a time range.
get_observations	Fetch full details for specific observation IDs.
memory_get	Get a single observation by ID.
memory_recent	Get the most recent observations.
memory_hybrid_search	Combined FTS + keyword search.
memory_semantic_search	Pure semantic search with hybrid fallback.
save_memory	Save memory directly (bypasses LLM compression).
knowledge_search	Search the global knowledge base.
knowledge_save	Save a new knowledge entry (skill, pattern, gotcha).
knowledge_get	Get a knowledge entry by ID.
knowledge_list	List knowledge entries by type.
knowledge_delete	Delete a knowledge entry.
infinite_expand	Expand a summary to see child events.
infinite_time_range	Get events within a time range.
infinite_drill_hour	Drill from day summary to hour summaries.
infinite_drill_minute	Drill from hour summary to 5-minute summaries.
__IMPORTANT	Workflow documentation (3-Layer Pattern).

HTTP API

HTTP endpoints are organized across the following handler modules:

• observations — CRUD and bulk operations for observations
• sessions / sessions_api — Session lifecycle, summaries, retrieval
• session_ops — Advanced operations (merge, split, archive)
• infinite — Deep-zoom endpoints (expand_summary, time_range, drill_hour, drill_minute)
• search — Semantic, FTS, and hybrid search
• knowledge — Global knowledge base management
• queue — Pending queue and DLQ inspection
• context — Context compilation for agent injection
• admin — Health checks, configuration, diagnostics

CLI

# Server
opencode-mem-cli serve                 # HTTP API server (port 37777)
opencode-mem-cli mcp                   # MCP stdio server

# Maintenance
opencode-mem-cli backfill-embeddings   # Generate missing vector embeddings
opencode-mem-cli import-insights       # Import legacy JSON insights

# Data Access
opencode-mem-cli search <query>        # Search observations
opencode-mem-cli get <id>              # Get observation by UUID
opencode-mem-cli recent                # Recent observations
opencode-mem-cli projects              # List tracked projects
opencode-mem-cli stats                 # Database statistics and queue health

# IDE Hooks
opencode-mem-cli hook context          # Retrieve context for prompt injection
opencode-mem-cli hook session-init     # Initialize a new session
opencode-mem-cli hook observe          # Record an observation
opencode-mem-cli hook summarize        # Trigger session summarization

Configuration

All configuration is via environment variables:

Variable	Required	Default	Description
DATABASE_URL	Yes	—	PostgreSQL connection string
OPENCODE_MEM_API_KEY	Yes	—	API key for the LLM provider
OPENCODE_MEM_API_URL	No	https://api.openai.com	OpenAI-compatible API base URL
OPENCODE_MEM_MODEL	No	—	Model for compression (e.g., gpt-4o)
OPENCODE_MEM_DISABLE_EMBEDDINGS	No	false	Disable vector embeddings (1 or true)
INFINITE_MEMORY_URL	No	DATABASE_URL	Separate DB for infinite memory
OPENCODE_MEM_EXCLUDED_PROJECTS	No	—	Glob patterns for excluded projects
OPENCODE_MEM_FILTER_PATTERNS	No	—	Custom noise filter patterns (regex)
OPENCODE_MEM_DEDUP_THRESHOLD	No	0.85	Cosine similarity for dedup [0.0, 1.0]
OPENCODE_MEM_INJECTION_DEDUP_THRESHOLD	No	0.80	IDE injection loop detection [0.0, 1.0]
OPENCODE_MEM_EMBEDDING_THREADS	No	cores - 1	ONNX embedding threads
OPENCODE_MEM_MAX_RETRY	No	3	LLM compression retries
OPENCODE_MEM_VISIBILITY_TIMEOUT	No	300s	Queue visibility timeout
OPENCODE_MEM_QUEUE_WORKERS	No	10	Concurrent queue workers
OPENCODE_MEM_DLQ_TTL_DAYS	No	7	Dead letter queue retention
OPENCODE_MEM_MAX_CONTENT_CHARS	No	500	Max chars per observation field
OPENCODE_MEM_MAX_TOTAL_CHARS	No	8000	Max chars for LLM prompt
OPENCODE_MEM_MAX_EVENTS	No	200	Max raw events per memory chunk

Development

Prerequisites

• latest stable Rust
• PostgreSQL with pgvector extension
• An OpenAI-compatible LLM API (for compression features)

Running Tests

export DATABASE_URL="postgresql://localhost/opencode_mem_test"

# Unit tests (no DB required)
cargo test --workspace

# Integration tests (requires running PostgreSQL)
cargo test --workspace -- --ignored

Code Quality

cargo fmt --all
cargo clippy --workspace -- -D warnings

Development constraints

• PostgreSQL remains the canonical persistence path.
• Missing or invalid data returns an explicit error or absence, not a fabricated value.
• Schema changes use forward migrations and preserve existing data.
• Privacy filtering must remain ahead of persistence, queues, embeddings, summaries, logs, and external model calls.

Project Status

Active pre-release project. Core MCP, HTTP, PostgreSQL, queue, and search paths are implemented, but release readiness depends on the current CI result and validation against a real OpenCode consumer. IDE-specific hooks remain outside the current scope. Infinite memory and semantic search should be treated as experimental until their deployment requirements and failure modes are documented and exercised end to end.

Contributing

Contributions welcome! See CONTRIBUTING.md for development setup and guidelines.

License

MIT