Problem

The Mem0 memory plugin lets gateway-supplied user_id (passed in kwargs at session initialization) override the configured user_id in mem0.json. For single-user installs this silently fragments Mem0's namespace across gateways.

Concrete repro:

1. Configure ~/.hermes/mem0.json with "user_id": "matvey"
2. Send a message via the Telegram gateway from Telegram user ID 1370472126
3. In the Mem0 dashboard, observe that the Telegram-originated memory is scoped under user_id="1370472126", while messages from the local TUI are scoped under user_id="matvey"
4. mem0_search from the TUI cannot find Telegram-originated facts; the namespaces are siblings, not unified

Why this matters: every gateway path with a different user_id source (Telegram numeric IDs, Discord IDs, web chat session IDs) creates its own Mem0 namespace. Searches scoped to matvey silently miss memories tagged with 1370472126. hermes doctor doesn't surface the fragmentation.

Current code: plugins/memory/mem0/__init__.py:208

self._user_id = kwargs.get("user_id") or self._config.get("user_id", "hermes-user")

The comment at L206–207 says this is intentional — "Prefer gateway-provided user_id for per-user memory scoping" — which is correct for multi-tenant deployments but counter-productive for single-user installs.

Proposed solution

Add a force_user_id boolean config option to mem0.json. Default false (preserves current behavior). When true, ignore gateway kwargs:

{
  "user_id": "matvey",
  "agent_id": "echo",
  "rerank": true,
  "force_user_id": true
}

if self._config.get("force_user_id"):
    self._user_id = self._config.get("user_id", "hermes-user")
else:
    self._user_id = kwargs.get("user_id") or self._config.get("user_id", "hermes-user")

Backward compat

Default to false — existing multi-user/multi-tenant setups continue to behave identically.

Documentation

plugins/memory/mem0/README.md already documents user_id, agent_id, rerank. Add force_user_id to that table.

Doctor check

hermes doctor could flag detected Mem0 namespace fragmentation (multiple user_ids in the same Mem0 account) and suggest setting force_user_id if the account is meant to be single-user.

Affected versions

Hermes 0.8.0+ (confirmed reproducing).

Working local patch

I'm running a config-first patch in production (self._user_id = self._config.get("user_id") or kwargs.get("user_id") or "hermes-user") — works fine for the single-user case but isn't what should ship. The config flag is the right shape.

Happy to send a PR if there's interest.