agent-checkpoint-cas 0.1.0

Type-guided externalized state for LLM agent frameworks.

AgentRef

Agent checkpoints should not have to carry your entire data plane.

AgentRef externalizes large workflow state into content-addressed storage while keeping only compact references in LangGraph, LlamaIndex, AutoGen, and Deep Agents-style checkpoints. It gives state fields two explicit roles:

• Inline[T]: small control state kept directly in checkpoints
• Externalized[T]: large values stored externally; checkpoints keep only a ContentRef

The goal is to make checkpoint write amplification hard to represent in user code. Assigning an Externalized field stores the serialized payload in CAS and keeps only a content-addressed reference in state.

Memory Impact

Local RSS measurements show lower peak memory when large state values are stored outside framework checkpoints. The Deep Agents row is from a real Deep Agents-based complex workflow after obvious large-payload trimming was already in place; the other rows are deterministic complex workflow benchmarks that preserve final output hashes.

Workload	Scenario	Baseline peak RSS	AgentRef peak RSS	Peak RSS reduction
LangGraph	Quality-preserving complex benchmark, 3-run median	703.6 MiB	191.6 MiB	72.8%
LlamaIndex	Quality-preserving complex benchmark, 3-run median	902.5 MiB	229.8 MiB	74.5%
AutoGen	Quality-preserving complex benchmark, 3-run median	659.1 MiB	243.3 MiB	63.1%
Deep Agents-based complex workflow	Real workflow, 10 concurrent runs	1.056 GiB	803.4 MiB	25.7%

For the Deep Agents-based workflow, idle RSS for the application process was effectively unchanged (267.6 MiB baseline vs. 266.5 MiB with AgentRef). On an idle-adjusted basis, application RSS growth fell 34.0% (813.7 MiB -> 536.9 MiB). The companion Postgres process peak fell 35.6% (331.8 MiB -> 213.6 MiB), and its idle-adjusted RSS growth fell 41.0%. Both variants completed 10/10 runs.

These numbers are local benchmark results. They are intended to show memory behavior for comparable before/after workloads, not to claim universal absolute RSS values across machines.

Install

The PyPI distribution is agent-checkpoint-cas; the Python import package stays agentref.

With pip:

pip install agent-checkpoint-cas

Optional framework integrations are split by extra:

pip install "agent-checkpoint-cas[langgraph]"
pip install "agent-checkpoint-cas[llamaindex]"
pip install "agent-checkpoint-cas[autogen]"
pip install "agent-checkpoint-cas[postgres]"
pip install "agent-checkpoint-cas[all]"

With uv in a project:

uv add agent-checkpoint-cas
uv add "agent-checkpoint-cas[langgraph]"
uv add "agent-checkpoint-cas[llamaindex]"
uv add "agent-checkpoint-cas[autogen]"
uv add "agent-checkpoint-cas[postgres]"
uv add "agent-checkpoint-cas[all]"

With uv in the current environment:

uv pip install agent-checkpoint-cas

Usage

Declare State

from agentref import AgentRefState, Externalized, Inline


class ResearchState(AgentRefState):
    current_step: Inline[str]
    iteration: Inline[int]
    citations: Inline[list[str]]
    retrieved_docs: Externalized[list[dict]]
    raw_html: Externalized[str]

LangGraph

from langgraph.graph import StateGraph

from agentref import AgentRefState, Externalized, Inline
from agentref.adapters.langgraph import LangGraphAdapter
from agentref.storage import FilesystemCAS


class RAGState(AgentRefState):
    question: Inline[str]
    docs: Externalized[list[dict]]
    answer: Inline[str]


adapter = LangGraphAdapter(
    RAGState,
    backend=FilesystemCAS("./state_blobs"),
    inline_threshold_bytes=64 * 1024,
)


def retrieve(state):
    docs = [{"id": "doc-1", "text": "large retrieved text"}]
    return {"docs": docs}


def answer(state):
    return {"answer": f"Read {len(state['docs'])} document(s)."}


graph = StateGraph(adapter.schema())
graph.add_node("retrieve", adapter.wrap_node(retrieve))
graph.add_node("answer", adapter.wrap_node(answer))

LlamaIndex Workflow

from agentref import AgentRefState, Externalized, Inline
from agentref.adapters.llamaindex import LlamaIndexAdapter
from agentref.storage import FilesystemCAS


class WorkflowState(AgentRefState):
    current_step: Inline[str]
    docs: Externalized[list[dict]]


adapter = LlamaIndexAdapter(
    WorkflowState,
    backend=FilesystemCAS("./state_blobs"),
)


async def retrieve_step(ctx):
    store = adapter.context_store(ctx.store)
    await store.set("current_step", "retrieve")
    await store.set("docs", [{"id": "doc-1", "text": "large retrieved text"}])

await store.get("docs") hydrates on read, while await store.to_checkpoint_dict() keeps only ContentRef values for externalized fields.

AutoGen

AutoGen does not expose one stable state schema across versions. AgentRef therefore provides explicit helpers for state dictionaries and message-history payloads instead of monkeypatching Agent classes.

from agentref.adapters.autogen import AutoGenAdapter
from agentref.storage import FilesystemCAS

adapter = AutoGenAdapter(backend=FilesystemCAS("./state_blobs"))

history = adapter.externalize_message_history(
    [{"role": "worker", "tool_result": "large tool output"}],
    threshold_bytes=1024,
)

hydrated = adapter.hydrate_message_history(history)

See docs/autogen_limitations.md for the integration boundary.

Storage Backends

Use FilesystemCAS for local runs, benchmarks, and run-scoped temporary storage. Use PostgresCAS when checkpoints need persistent storage, TTL metadata, or operational cleanup.

Backend	Best for	Lifetime model	Cleanup	Notes
InMemoryCAS	tests and ephemeral demos	process lifetime	process exit	fastest option, not durable
FilesystemCAS	local runs, benchmarks, run-scoped workflows	directory lifetime	delete the run directory or migrate/prune by hash	simple durable storage, no built-in TTL
PostgresCAS	production, persistent checkpoints, multi-worker apps	database-managed lifetime	expires_at plus prune_expired()	TTL metadata, operational visibility, migration aliases

All backends are passed directly to adapters:

from agentref.adapters.langgraph import LangGraphAdapter
from agentref.storage import FilesystemCAS, InMemoryCAS, PostgresCAS

memory_adapter = LangGraphAdapter(RAGState, backend=InMemoryCAS())
local_adapter = LangGraphAdapter(RAGState, backend=FilesystemCAS("./state_blobs"))
postgres_adapter = LangGraphAdapter(
    RAGState,
    backend=PostgresCAS(
        dsn="postgresql://user:pass@localhost:5432/app",
        backend_id="postgres:agentref",
        default_ttl_seconds=7 * 24 * 3600,
    ),
)

PostgresCAS stores created_at, last_accessed_at, and expires_at metadata. Expired payloads are removed explicitly with backend.prune_expired(); AgentRef does not delete referenced objects automatically.

Existing filesystem payloads can be copied into Postgres without rewriting old checkpoints by configuring the Postgres backend with the old backend id as an alias:

from agentref.storage import FilesystemCAS, PostgresCAS, migrate_cas

old = FilesystemCAS("./state_blobs")
new = PostgresCAS(
    dsn="postgresql://user:pass@localhost:5432/app",
    backend_id="postgres:agentref",
    backend_aliases=[old.backend_id],
)

migrate_cas(old, new)

Invariants

The test suite covers these core invariants:

• externalized payload bytes do not appear in checkpoint bytes
• identical payloads produce identical content hashes
• oversized inline values raise InlineSizeExceeded
• checkpoint round trips preserve hydrated values
• ambiguous framework auto-detection raises a clear error
• older checkpoints can hydrate externalized values while CAS content exists

Examples

• examples/langgraph_rag.py
• examples/llamaindex_research_workflow.py
• examples/autogen_multi_agent.py

Each example avoids importing optional framework packages at module import time, so the repository can be imported and tested without installing every framework.