Letta

Letta (formerly MemGPT) is a framework for stateful agents with long-term memory. Its OpenAI provider accepts a custom base URL, so you can back Letta agents with Router9.

Setup

Point Letta's OpenAI provider at Router9 with two environment variables before starting the server:

export OPENAI_API_KEY=sk-r9k-your-key-here
export OPENAI_API_BASE=https://api.router9.com/v1

Then start the Letta server as usual (for example letta server). Any agent configured with an OpenAI model will route through Router9.

Choosing Models

When creating an agent, set its LLM to an OpenAI-handle model that Router9 routes on:

from letta_client import Letta

client = Letta(base_url="http://localhost:8283")

agent = client.agents.create(
    model="openai/gpt-4o",
    embedding="openai/text-embedding-3-small",
)

Swap openai/gpt-4o for any model Router9 supports, such as openai/claude-sonnet-4-20250514.

Tips

• Letta agents run long-lived, memory-heavy sessions — Router9's flat monthly pricing avoids per-token surprises.
• Set OPENAI_API_BASE and OPENAI_API_KEY in the environment the Letta server runs in, not in agent code.
• Point embeddings at Router9 too by using an openai/ embedding handle.