@computeragent/session-store-mongo

MongoDB-backed SessionStore for the ComputerAgent harness. Plug-in implementation of the Claude Agent SDK's native SessionStore contract — enables cross-process conversation continuation when sessions live in a shared database instead of on local disk.

Install

pnpm add @computeragent/session-store-mongo

Use

Register the store with the harness server at boot:

import { createHarnessServer } from "@computeragent/harness-server";
import { MongoSessionStore } from "@computeragent/session-store-mongo";

const app = createHarnessServer({
  engines: { /* ... */ },
  identityLoaders: { /* ... */ },
  sessionStores: {
    mongo: (options) => new MongoSessionStore({
      url: process.env.MONGO_URL!,
      database: "computeragent_sessions",
      ...(options as object ?? {}),
    }),
  },
});

Then have any client request the store by kind:

const agent = new ComputerAgent({
  source: "...",
  harness: "claude-agent-sdk",
  sessionStore: { kind: "mongo" },
  sessionId: previousSessionId,  // for resume
  envs: { ANTHROPIC_API_KEY: "..." },
});

The server-side builder receives the wire-side options field; the SDK never carries connection credentials over the wire — keep them server-side.

Storage layout

One document per session under the sessions collection of the configured database (default: computeragent_sessions):

{
  "_id": "<sessionId>",
  "projectKey": "<engine-derived>",
  "entries": [ /* SessionStoreEntry */ ],
  "updatedAt": <Date>
}

entries[] follows the Claude Agent SDK's SessionStoreEntry shape — JSONL-equivalent records the SDK appends per turn (user messages, assistant responses, tool calls, system events).

Architecture notes

• Two engines, one port. The SessionStore interface is engine-agnostic. The Claude Agent engine consumes it natively (the SDK reads/writes through it). The gitagent engine currently manages its own filesystem session format and ignores ctx.sessionStore; a future GitclawSessionStoreAdapter can mirror gitclaw's session dir into any SessionStore for symmetric resume across engines.
• Idempotency. Entries are deduplicated by uuid. Re-appends of an entry already present are no-ops — safe for SDK retries and importSessionToStore replays.
• Single-writer. A simple load → filter → write cycle. Concurrent writes against the same sessionId from different harness processes can interleave; the SDK's flow is single-writer per session, which makes this correct in practice. Multi-writer parallelism (e.g., a fan-out farm against one logical session) would require a transactional update pipeline — captured as future work.

Configuration

new MongoSessionStore({
  url: "mongodb://user:pass@host:port/admin",  // required
  database: "computeragent_sessions",          // default
  collection: "sessions",                      // default
  clientOptions: { /* MongoClientOptions */ }, // optional, forwarded to driver
});

close() releases the underlying MongoClient cleanly. The store auto-connects on first append/load/size/listSessions call; explicit connect() is offered for callers that want to surface connection errors at boot.

Tests

MONGO_URL="mongodb://..." pnpm --filter @computeragent/session-store-mongo test

Live integration tests use ephemeral ca_test_<random> databases that are dropped on teardown — safe to run against shared clusters without polluting other apps' data. With MONGO_URL unset the live suite is skipped automatically.