Supabase REST Checkpointer for LangGraph

Problem

LangGraph's MemorySaver stores state in-process. Ephemeral deployments (Railway, Fly, etc.) kill processes on redeploy, losing all interrupted graph state. PostgresSaver needs a direct Postgres connection string, which may not be available.

Solution

A BaseCheckpointSaver implementation that stores checkpoints via Supabase's PostgREST API using the existing Supabase client. No direct Postgres connection needed.

Setup

1. Create Tables

Run scripts/create_tables.sql in Supabase (via SQL editor or exec_sql RPC):

CREATE TABLE langgraph_checkpoints (
    thread_id TEXT NOT NULL,
    checkpoint_ns TEXT NOT NULL DEFAULT '',
    checkpoint_id TEXT NOT NULL,
    parent_checkpoint_id TEXT,
    type TEXT,
    checkpoint JSONB NOT NULL,
    metadata JSONB DEFAULT '{}',
    created_at TIMESTAMPTZ DEFAULT now(),
    PRIMARY KEY (thread_id, checkpoint_ns, checkpoint_id)
);

CREATE TABLE langgraph_writes (
    thread_id TEXT NOT NULL,
    checkpoint_ns TEXT NOT NULL DEFAULT '',
    checkpoint_id TEXT NOT NULL,
    task_id TEXT NOT NULL,
    idx INTEGER NOT NULL,
    channel TEXT NOT NULL,
    type TEXT,
    blob JSONB,
    PRIMARY KEY (thread_id, checkpoint_ns, checkpoint_id, task_id, idx)
);

2. Use the Checkpointer

from supabase import create_client
from supabase_checkpointer import SupabaseCheckpointer

client = create_client(url, key)
checkpointer = SupabaseCheckpointer(client)
graph = builder.compile(checkpointer=checkpointer)

3. Fallback Chain (recommended)

def _create_checkpointer():
    # 1. Try Supabase (durable across redeploys)
    try:
        from supabase_checkpointer import SupabaseCheckpointer
        client = get_supabase_client()
        if client:
            return SupabaseCheckpointer(client)
    except Exception:
        pass

    # 2. Try SQLite (survives process restarts within same deploy)
    try:
        from langgraph.checkpoint.sqlite import SqliteSaver
        import sqlite3
        return SqliteSaver(sqlite3.connect("checkpoints.db", check_same_thread=False))
    except Exception:
        pass

    # 3. Fallback: in-memory (lost on restart)
    from langgraph.checkpoint.memory import MemorySaver
    return MemorySaver()

Implementation

The full implementation is in scripts/supabase_checkpointer.py. It implements all required BaseCheckpointSaver methods:

• put() — Upsert checkpoint to langgraph_checkpoints
• put_writes() — Upsert pending writes to langgraph_writes
• get_tuple() — Fetch latest checkpoint + pending writes for a thread
• list() — Iterate checkpoints for a thread (time-travel)

All data serialized as JSONB. Uses json.dumps(obj, default=str) for non-serializable types.

Key Details

• Thread isolation: Each graph run uses a unique thread_id in the config
• Checkpoint ordering: Uses created_at DESC for latest checkpoint lookup
• Write deduplication: Composite primary key prevents duplicate writes
• Error tolerance: All operations wrapped in try/except — logs errors but doesn't crash the graph
• No async required: Uses synchronous Supabase client (PostgREST over HTTP)